
Musings of an Energy Nerd

Stupid Energy-Saving Tips

Martin’s roundup of ill-conceived internet advice

Just for fun, I recently Googled the phrase “energy-saving tips.” I dove deep — all the way to page 7 of the Google results. My research was profoundly discouraging.

Back in 2011, I wrote two articles about bad energy-savings tips. (See More Energy Myths and A Plague of Bad Energy-Saving Tips.)

Since then, is there any possibility that the quality of online advice improved? Not a chance.

Evidently, there is a secret stupid tips network (or stupid tips underground) that shares bad advice. Every now and then, some utility executive or government employee comes up with a new stupid tip, and (worried that the idea might not get the recognition it deserves) immediately sends out a mass e-mail to every member of the stupid tips network, so that the tip can be published widely.

Virtually every list of energy-saving tips on the Web includes some bad advice. The bad advice is so pervasive that I have decided to catalog these tips by category — to create a taxonomy of stupid tips.

Here’s my top ten list — common tips that show up repeatedly.

1. Fill your half-empty refrigerator or freezer with plastic bottles filled with water. This stupid tip will never save you enough energy to show up on your electric bill. Nevertheless, the advice is provided by the California Energy Commission, an electric utility called NV Energy, Avista Utilities, Wisconsin Public Service, Georgia Natural Gas, an electric utility called National Grid, Connecticut Light & Power, EnergyRight Solutions, and many others.

2. Clean the dust off your refrigerator’s heat-exchange coils. As I’ve noted before, researchers haven’t been able to measure any energy savings resulting from this measure. But a lack of data hasn’t stopped the following sources from advising homeowners to get out the vacuum cleaner: NV Energy, Connecticut Light & Power, and EnergyRight Solutions.

GBA Prime

This article is only available to GBA Prime Members


Start Free Trial


  1. But Why? | | #1

    #1 Filling Frig with water bottles
    may not save energy but it will certainly extend the life of your persihable items in the event of a power loss such as has been going on across this country in the wake of last Friday/Saturdays ice storm. Adiitionally, homemade ice is cheaper for summer needs and more ecological than ice made in a central plant, trucked to a store and bought by someone who drove to a store to buy it.

  2. But Why? | | #2

    #3 Schedule an annual furnace tune up
    may not save you energy but it may save your life.....if that matters at all to anyone. and it also exposes problems that are, by Murphy's Law, bound to happen when least convenient.

  3. User avater GBA Editor
    Martin Holladay | | #3

    Response to B.W.
    You wrote, "Filling your fridge with water bottles may not save energy..." and "scheduling a annual furnace tuneup may not save you energy..."

    So we agree. The first tip doesn't belong on a list of energy-saving tips; it belongs on a list of things you can do to prepare for a power outage.

    And the second tip belongs on a list of things you can do to minimize the chance of carbon-monoxide poisoning.

  4. Sandra Heiser | | #4

    Follow up
    Good post! Will there be a 'profoundly ENcouraging' post of Brilliant Energy Saving Tips? Please? :)

  5. User avater GBA Editor
    Martin Holladay | | #5

    Response to Sandra Heiser
    My list of "Real Energy-Saving Tips" is included on this page. It is a sidebar on the left-hand side of the article. My list includes 11 tips.

    The GBA website has lots more information on the 11 topics I mention in my tips list. If you use the "search" box on our site, you'll find enough information to keep you reading for hours.

  6. Kevin Dickson, MSME | | #6

    Money saving tips
    From my experience in owning lots of rental units, I need to comment.
    I can't quibble with your lists, but here's my related list of money saving tips:

    1. Change the furnace filter at least yearly. A neglected furnace filter increases the odds that lint and pet hair will accumulate on the furnace motor. That will cause the motor to overheat, causing short cycling (which reduces furnace efficiency) and eventual motor failure. Motor replacement is $200-$600.

    2. The summertime use of ceiling fans in some climates may eliminate the need to spend money on installing or using air conditioning.

    3. Really dirty refrigerator coils can cause premature failure of the refrigerator, or inadequate cooling of the food inside. Lint can also cover the compressor, insulating it, causing it to short cycle.

    4. Storm windows may be more cost effective than new windows energy-wise, but keep in mind that they won't make a crappy old window operate better, or add any resale value to the house. New windows do both, and therefore can be a better investment in some situations.

  7. Sandra Heiser | | #7

    Thank you, missed

    Thank you, missed seeing that the first go-round. This might not be the place to say it, but I'd like to voice my appreciation for this site and the obvious dedication and effort you put into it. We reference it often in our practice. THANK YOU!

  8. But Why? | | #8

    Changing furnace filters more than yearly is advisable. I have seen them clogged to the point that the whole filter gets sucked into the blower locking it up which, without a belt to slip/burn/break in todays direct drive blowers, means a burnt up motor in short order. While you can debate the savings of energy versus the cost of the filters, there shouldn't be any debate that a dirty filter does use more energy and does pose a risk to the air handling system in a number of ways.

  9. User avater GBA Editor
    Martin Holladay | | #9

    Another response to B.W.
    It should go without saying, but it seems that every time I write an article debunking energy-saving myths, I have to repeat the following statement: it's perfectly OK to engage in many of the activities listed on this page.

    It's OK to clean your refrigerator coils. It's OK to change your furnace filter frequently. It's OK to clean the reflectors under your stove burners. It's OK to cook with lids on your pots.

    Just don't expect any of these actions to save a significant amount of energy.

  10. Robert Connor | | #10

    Ultimate energy saving tip that will get me flamed!
    One tip that will never happen in this country is: Do not have children. When a couple has one child they increase their carbon score by a factor of 6. Since most of the guys here have kids, I don't think anyone would say this idea.

  11. User avater
    Aaron Birkland | | #11

    Furnace filters and ECM blowers
    From Stuff [Michael Chandler] Learned at Joe Lstiburek's House, Part 2:

    The difference of the pressure curves of clean versus dirty filters is pretty shocking as well. In one example, an ECM system with a clean filter running at 0.2 inH20 at 1,100 CFM drawing 225 watts ran with a dirty filter at 0.5 inH20 at 1,100 cfm drawing 320 watts. If it had been a PSC motor on that air handler, the flow would have been reduced on the order of 40-50%."

    So while it may be unlikely that the filter will get that dirty in a month, and it's certainly unlikely that a yearly service tech visit is the most cost effective way to replace a filter, changing the filters on equipment with an ECM blower when they get noticeably dirty looks like it could save some energy

  12. User avater GBA Editor
    Martin Holladay | | #12

    Response to Aaron Birkland
    It makes sense to change furnace filters when they get dirty. Homes that are dusty will need more frequent filter changes than homes that are less dusty. Most homes will do just fine if the filter is changed once or twice a year -- but if you want to do it more often, that's fine too.

    Changing filters once a month won't save you any energy, and tips like this are a distraction from the important measures that can really reduce your annual energy bill.

  13. Dick Russell | | #13

    Humorous typo
    Martin, under "Suggestions that are never going to happen" you wrote:

    "The next tip reminds me of the advice given in the 1950s by parish priests about martial relations:"

    What's "martial relations?" Intimate karate? (I couldn't help that one)

  14. Brent Eubanks | | #14

    #9: A/C condensor
    You said that this one has been debunked, but I'd like to get more detail on that. We know that a refrigeration cycle performs more efficiently when rejecting heat to a lower temperature (all other things being equal), so it's hard for me to see how this tip could be wrong, thermodynamically speaking.

    I can see how this might be in the category of "real, but too small to matter". But even there, I'm skeptical. the temperature difference between a metal box in the sun vs in the shade (in a place where it matters, like Florida or Phoenix) can be 50+ degrees (which means you may nearly double your overall system delta-T). How can that NOT impact heat rejection efficiency?

  15. User avater GBA Editor
    Martin Holladay | | #15

    Response to Brent Eubanks
    The temperature of the metal box is irrelevant. The relevant material (fluid) for heat transfer is outdoor air. Outdoor air is at the same temperature on the sunny side of your house as it is on the shady side of your house.

    Once the outside fan comes on, a tremendous volume of outdoor air flows across the outdoor heat exchange coils.

    While it's true that a thin film of air near siding that has been warmed by the sun, or a thin film of air near a metal box that has been warmed by the sun, is at a somewhat higher temperature than the outdoor air, the volume of air in that film is insignificant compared to the large volumes of air pulled through the condenser.

  16. Nick T - 6A (MN) | | #16

    The outside air is not the same
    Outside air is the same everywhere? what?

    The south side of my last house landscaped with dark grey rock and tucked behind garage... was not the same air temperature as the north side of my house.

    And a 2ton condenser fan doesn't have enough umf to clear all that air and radiant heat off the rocks/house. If you put a temperature probe in the shade of the condenser it will be significantly warmer then the north side of the house.

    Yes if a house has a dirty filter it will increase the speed of the fan and also could reduce the efficiency of the cooling system due to lower airflows (if not variable fan speed) - however in both cases it would have to be a freakishly dirty filter! For 2-4$.... get a new filter regularly.

    The argument that stuff is hardly measurable so therefore a myth... Why isn't the passivehaus myth over PGH listed? lol

    But yes! It is funny how so many utilities and energy savings groups push these old out dated ideas. Yes i suppose if everyone cleaned their air intake of their fridge (older fridges maybe more important? with serious heat to reject) it would make an impact on the utility side of things (10000 customers....times a few watts....) lol.

  17. Aaron Vander Meulen | | #17

    Think I'm going to go suggest
    Think I'm going to go suggest to the wife we set the thermostat to the outdoor temperature...Its 36* so its not THAT cold...

  18. John Richards | | #18

    Extremely Unhelpful
    I signed up just to make this one post.

    I found this blog entry supremely frustrating. The reason is because it is just a rant. You provide links to the so-called bad tips - but no regular home-owner cares where the bad tips came from. We care WHY they are bad tips, but your explanations are profoundly lacking. At best you make off-hand comments and mention uncited studies but most of the time you just write as if the problems with the tips are self-evident. They are not! If we had the expertise to understand what is wrong with the tips then we would not need to read the blog post in the first place because we would already know that the tips are poor ones.

    I will give examples:

    Caulking around windows "The big leaks are in your attic and basement" - OK, but that doesn't address how useful it is to do the windows if the big leaks are taken care of.

    AC Condenser in the shade: "debunked many years ago by researches at the FSEC" - where is the report?

    Close off heating registers: So the advice is contradictory - how about an explanation from an HVAC expert about what is the right advice?

    Water in the fridge / freezer: No explanation as to why they make the tip nor why it is wrong - if you have the space for a big block of ice in your freezer what is the downside?

    Install a fireplace: What is wrong with that? Is it because of air leakage? Is it because burning wood is not a cost-effective way to heat a room? What about a fireplace with a lot of thermal mass like a stone hearth?

    If your goal is to rant, mission accomplished. If your goal is to educate, you need to start over from the beginning and provide much better explanations of just why each tip is unhelpful or at least link to a comprehensive explanation. Otherwise you aren't helping anyone to better understand the issues.

  19. User avater GBA Editor
    Martin Holladay | | #19

    Response to Nick T
    Q. "Outside air is the same [temperature] everywhere? what?"

    A. I stand by my answer. It is. This can easily be verified by the use of a thermometer. (Of course, the bulb of a traditional glass thermometer should not be in the sun, or the sunlight will cause the fluid in the thermometer to give a false reading of the air temperature; the thermometer must be shaded.)

    The reason that you feel warmer on the south side of your house is because of radiation from the sun striking your skin and clothing -- not because the air temperature is different.

    The volume of the thin film of air adjacent to sun-warmed surfaces is quite tiny. It represents a tiny percentage of the air that is forced by the fan through the condenser coils.

  20. User avater GBA Editor
    Martin Holladay | | #20

    Response to John Richards
    Your criticisms are fair, and I'll do my best to answer your questions.

    Q. "Caulking around windows ... The big leaks are in your attic and basement. OK, but that doesn't address how useful it is to do the windows if the big leaks are taken care of."

    A. There are many articles on this website that discuss blower-door-directed air sealing. Here are a few of them:

    Questions and Answers About Air Barriers

    Blower Door Basics

    Getting the Biggest Bang for Your Air-Sealing Buck

    Navigating Energy Star’s Thermal Bypass Checklist

    Air Sealing an Attic

    A Home-Energy Audit

    By now, weatherization contractors who are trying to reduce the air infiltration number shown on a blower door have learned where to look for leaks, and which leaks to address first. In most homes, the leaks that matter are in the attic and basement. Windows tend to be located near the home's neutral pressure plane, and are therefore much less affected by the stack effect.

    To reduce air leaks near a window, you might need to perform some of the following work: (a) Add weatherstripping or replace the existing weatherstripping; (b) carefully remove the casing and seal the gap between the window rough opening and the window frame with low-expanding canned spray foam, and then replace the casing. Although this work is unlikely to make a significant difference if you are trying to reduce the rate of air leakage in your home, it's perfectly sensible to do it, and it can often improve occupant comfort. But remember: the first places to begin your air sealing efforts are your attic, basement, and crawl space.

    Q. "AC Condenser in the shade was debunked many years ago by researchers at the FSEC. Where is the report?"

    A. One of the best articles on this topic, "The Nonbenefit of Shading Air Conditioners," was published in the July 1995 issue of Energy Design Update. While it is not available on the web, you may be able to find it in a good academic library.

    You might also look at "Air Conditioner Shading Shows Minimal Savings," in the Sept/Oct 1995 issue of Home Energy.

    Q. "Close off heating registers: So the advice is contradictory - how about an explanation from an HVAC expert about what is the right advice?"

    A. Don't close off your heat or air conditioner registers in unused rooms. Studies show that this practice increases leaks through leaky ductwork, wasting energy.

    In a previous article (More Energy Myths), I provided more information on this topic. In that article, I wrote, "[Michael] Blasnik quotes a study performed by Iain Walker, a staff scientist at LBNL: 'The results of this study showed that register closing led to increased energy use for a typical California house over a wide combination of climate, duct leakage, and number of closed registers. The reduction in building thermal loads due to conditioning only part of the house was offset by increased duct system losses, mostly due to increased duct leakage.' ”


    A. I'm not sure why this tip is offered -- the logic behind bad advice is often lost in the mists of time. I would guess that someone was trying to reduce the volume of air that spills out of a refrigerator every time the door is opened. The energy savings resulting from making this volume of air smaller would be insignificant. There is no downside to keeping a big block of ice in your freezer, so go right ahead and do that if you want to.


    A. You guessed correctly: fireplaces are responsible for huge levels of air leakage, even when they aren't operating. When they are operating, they often remove more heated air from your house than they provide, resulting in a net loss of heat. If you want to use firewood as a fuel to heat your house, install a wood stove. For more information on this topic, see All About Wood Stoves.

    GBA has many articles that are written for homeowners who are just beginning to examine energy-related issues; you might be interested in browsing through our encyclopedia (available by clicking on the "Green Basics" tab at the top of every page). We also have a few articles (like this one) geared toward energy geeks. In any case, whether your are a beginner or an energy geek, we welcome your feedback, and we also welcome questions on our Q&A page.

    Finally, if you use the "search" box on the GBA website, you can find thousands of articles on many topics.

  21. Jonathan Teller-Elsberg | | #21

    Save energy by being a hippie
    In particular, I'm thinking of the classic energy saving habit of showering infrequently. It worked wonders for me in my feckless youth until a coworker asked me to shower more often. I decided I liked my coworker more than I liked saving a smidge of energy. But for the misanthropes in the audience, reducing consumption of hot water has got to be a genuine energy saver. (Right?) I compromise by taking short showers and using a low-flow shower head.

  22. Lastman Ever | | #22

    I think your views on curtains, also noted in previous articles, need a little more evidentual backing. While the theory seems sound, I have always found that closing curtains, whether well sealed at the top or not has a significant effect on both comfort and the measureable temperature of the room for a constant heat source. These effects would be less significant with insulated glazing, of course.

  23. User avater GBA Editor
    Martin Holladay | | #23

    Response to Lastman Ever
    Like many of the tips discussed on this page, there is nothing wrong with pulling your curtains shut on a cold winter night. This measure will usually improve occupant comfort, by reducing the chilling effect (radiational cooling) that occurs when heat radiates from a person's skin or clothing to a cold window pane.

    Pulling curtains shut on cold winter nights isn't stupid. But I called it an "incomplete tip" for three reasons:

    1. There isn't any evidence that this measure will lead to significant energy savings.

    2. The discussion failed to address the characteristics of an effective window quilt, thereby wasting an opportunity to explain what a good window quilt would look like. (A window quilt differs from curtains in several ways. A window quilt has an airtight assembly at the top that seals the gap between the window quilt and the wall; it also has relatively airtight tracks at the sides; and it seals against the window stool with weatherstripping and Velcro. Without these features, curtains set up convective currents that can actually raise your energy bill slightly.)

    3. The discussion failed to address the fact that effective window quilts aren't a cost-effective energy savings measure, because any savings attributable to the use of a window quilt aren't enough to justify the high cost of a window quilt.

    By the way, I have a window quilt in my bathroom, and use it regularly during the winter. It is effective, and I'm glad I have it. But I am under no illusions that it will save enough energy to justify its high cost.

  24. Nick T - 6A (MN) | | #24

    Diffuser followup

    Regarding the studies (in Cal) were these results scewed by the HVAC being located in the attic and or primarily cooling data?

    Curious because duct losses (leak or temp) inside a conditioned space (floor, wall, basement) aren't completely lost or wasted. They are essentially the same as heating/cooling an unused room.... but really in the case of leakage in walls/floor space.. it serves to cool/heat a somewhat desired location (keep wood floors warmer, walls of interior space,etc).

    When it comes to the cost of conditioning a space; the higher the dT between space and outside the worse the heating/cooling load. So as is often the case you can close a guest bedroom keeping it 15-10°F below thermostat Temp - resulting in ::slightly:: lower costs of that 100-150sqft. In the summer similar conditions can be seen on a very hot sunny day with west facing windows.... as high as 15-20°F (shaded air temp).

    And yes the higher impact measure ... don't have wasted spare space... don't have unshaded west facing windows.... insulate more so as to not have a dT or neeed heat/cooling... but that isn't a low cost/no cost energy measure (which most people are looking for unfortunately)

    As always thank you for your insight and time! great blog.

  25. User avater GBA Editor
    Martin Holladay | | #25

    Response to Nick T
    I think it's safe to assume that (a) most of the homes in the California study had ductwork that was partially outside of the thermal envelope of the house, and (b) most of the homes in the California study had leaky ductwork.

    One reason why it's safe to assume these conditions is that they are typical. We'd all love to see builders start putting ducts indoors, and we'd all love to see well-sealed ductwork. But in most areas of the country, it hasn't happened yet.

    I recently heard a presentation (at the December 2013 Buildings 12 conference in Florida) by Iain Walker of LBNL on “Building Envelope and Duct Airtightness of New U.S. Dwellings.” According to Walker, "Duct leakage is low in Washington and high in New Mexico and Florida. ... Just over 1/3 of duct leakage in Florida is duct leakage to outside."

    In regions of the country with basements, ducts are more likely to be indoors than in regions of the country with slab-on-grade homes.

    Homes with forced-air distribution systems are much harder to zone than systems with hydronic distribution systems. Shutting off registers isn't good for the system, because the furnace or air handler needs a minimum air flow over the heat exchanger or over the indoor coil to operate properly. Shutting off registers causes more air to escape from leaks -- and most duct systems have leaks.

  26. Bob Coleman | | #26

    "It's perfectly OK..."
    That reminds of Scott Adams' - Dilbert creator - acronym: (BOCTAOE) But of Course There Are Obvious Exceptions when presenting an argument or issue.

  27. Bob Coleman | | #27

    Measured Impacts of Air Conditioner Condenser Shading
    Reading FSEC one report, it doesn't look like any striking conclusion can be made that it doesn't work, it just doesn't provide miracles, and may not be worth the cost.

    If you can take advantage of free site planning and placement, it might be worth the time for the few % point gains. Also important to note that some shading attempts like that in the third experiment can have a negative affect.

    Would be nice to see them or someone do a more controlled study; identical units located in the same environment at the same time with controlled output, one shaded, one not.

  28. User avater GBA Editor
    Martin Holladay | | #28

    Response to Bob Coleman
    Anyone choosing to compile an "energy-savings tips" list needs to prioritize. Ideally, these lists would start with tips that either result in significant energy savings, or which fall into the "big bang for your buck" category. Tips that result in only very small levels of energy savings, or which aren't particularly cost-effective, wouldn't make the list.

    I'll quote from the July 1995 article from Energy Design Update, "The Nonbenefit of Shading Air Conditioners":

    "The results of two-year field study by the Florida Solar Energy Center (FSEC) show that energy savings [resulting from shading air conditioners] are minuscule at best. ... The problem is that a typical 3-ton unit moves about 2,800 cubic feet of air per minute or 170,000 cubic feet per hour. In order for a shading device to be effective, it would have to shade the entire area in which that air is contained. ... Shading just the air conditioner does almost nothing, says [researcher Danny] Parker. Even at peak sunlight (1,000 watts per square meter), shading two-thirds of the sunlight form a 3-ton air conditioner would theoretically reduce the cooling air temperature by only 0.3 degrees F and thereby increase the air conditioner efficiency by less than half a percent. ...

    "The results [of the study] show that the house with a trellis saved only 3% in energy and the house with plantings actually showed an increase of 18% in energy use after the shading was installed. Parker hypothesizes that the reason for the increased energy consumption was that the plantings caused some of the exhaust air to recirculate back into the air conditioner."

  29. But Why? | | #29

    You would never see the AMA or the CDC
    write an article telling you washing your hands won't prevent cancer WITHOUT them also telling you that washing your hands will prevent many other diseases and should be done DESPITE not preventing cancer.

    You would never see mechanics write an article telling you that changing your oil won't save you significantly at the pump without telling you that you still need to change your oil to prevent costly damage to you car.

  30. User avater GBA Editor
    Martin Holladay | | #30

    Response to B.W.
    The focus of my article was to warn readers about energy-saving tips that are unsupported by data, so that readers who are interested in saving energy aren't waylaid by bad advice. The article was certainly too long; at 2,600 words, it violates all of the rules of blogging.

    In spite of the article's length, many readers wish it were longer. I have tried to fill in the gaps in the Comments section by providing more documentation to support the statements made in the article.

    You suggest that I should have included a section in my article explaining some of the useful characteristics and benefits of the measures that don't save energy.

    Objection noted. In my defense, I assume that readers have common sense.

    I will once again repeat what I wrote before: It's perfectly OK to engage in many of the activities listed on this page. It's OK to clean your refrigerator coils. It's OK to change your furnace filter frequently. It's OK to clean the reflectors under your stove burners. It's OK to cook with lids on your pots. Just don't expect any of these actions to save a significant amount of energy.

  31. Robert Connor | | #31

    But why has no one taken my
    But why has no one taken my advice about thinking about and limiting family size? That would help most of all. Or do you guys all have large families? Oh, let me guess, Jim Bob Duggar is a member of the GBA.

  32. greenhouse437 | | #32

    hot water heaters
    Missing from the list is the advice I see alot from utilities: save fuel by lowering setting of the hot water heater. As far as I understand, heating the water to 140 deg can prevent Legionnaire's disease and when you use a fairly inexpensive mixing valve --which is required to prevent scalding--which mixes the outgoing house hot water temp down to 120 deg or less, then you increase the supply of hot water/output of the tank.

  33. Douglas Horgan | | #33

    Warmth through Alcoholic Fish
    Great job as usual Martin! (Guess I'm in the intended demographic for your post.)
    I'm definitely trying that fish tip!

  34. User avater GBA Editor
    Martin Holladay | | #34

    Response to Mark Johnson
    After I deleted your second post, you deleted your first. That was unfortunate. Any chance you can recreate your excellent comments? I hope you can.

    [The gist of Mark Johnson's accidentally deleted comments, which I hope he will soon recreate, was that he used a manometer to measure whether accumulating dust on his furnace filter would cause a reduction in airflow across the filter. After 5 years of continuous measurements, the original filter had still not caused a reduction in airflow, even though the filter was fuzzy and gray.]

  35. Mark Johnson | | #35

    HVAC Air Filters / Reliant Energy advice
    I can hardly believe I am defending Reliant Energy, but their advice to cook with a lid might be relevant to humidity in the house. As it is in hot-humid South Texas (mainly Houston), outdoor dewpoint may be 72F much of the summer and indoor humidity is often poorly controlled too. Something which reduces indoor humidity would indeed reduce the felt need for AC a bit, and there might actually be some energy savings. I bet too small to measure though.

    I have something to say about HVAC filters too, the advice to change every 30 days reminds me of oil-change businesses' advice to change your car's motor oil every 3000 miles. As I write this it is New Years Day and some social and family matters call right now. I will post in 24-48 hours on the subject of filters.

    Best wishes -- M. Johnson

  36. Zolton Cohen | | #36

    Furnace filters..

    Geez, no good deed goes unpunished, eh? I LIKED the article and understood it. As far as I could discern, it wasn't designed to be a complete treatment or explanation of why those recommended practices aren't helpful in saving energy. Just a list...

    On the subject of furnace filters though, I have a modest money-saving (though not necessarily energy-saving) tip. I virtually never change my filter. The one in my forced air gas system is probably 7-8 years old. But every month or so I remove it briefly and vacuum it off.

    That takes just a few minutes and the filter works perfectly after the cleaning. If there are energy savings to be calculated, it could be that doing so removes from the equation driving to a store and buying a new filter. Or reducing the amount of trucking and packaging used to transport and protect a new filter.

    It's a small thing. But we of the frugal persuasion take some pride in being, well, frugal.

    Zolton Cohen

  37. Edward Krause | | #37

    saving energy in the aggregate
    I agree some of these practices are stupid by any means of measurement, but others save energy in the aggregate even if they may not save significant money; simple little tasks or habits can have a significant impact on the overall energy usage when done by millions. The utilities may be implying individual households will see it on their monthly bill, when the utility is more concerned with the capacity of power plants, and, I would hope, the size of a carbon footprint over years. They may only save a household a few dimes. I agree there may be smarter ways -- more bang for the buck, or watts for the work -- to save both energy and money.

  38. Roger Williams | | #38

    Shading , wall plugs, and light bulbs.
    I have a problem with saying that sealing wall plugs does not save significant energy. It cost us ten dollars to buy the sealing foam kits to do the outside plugs. We noticed that the cold air was coming in the sockets. We took the foam removed from the kits and put them on the back of baby safety plugs from the dollar store. Reduced drafts were a great benefit. Maybe it only saved $5 a year, but that is a 50% ROI.

    Shading a heat pump with deciduous trees cools the summer heat by a minimum of 10F and lets the sun shine into the area in winter. I see this as an advantage.

    I replaced my light bulbs with CFL bulbs and got complaints from my wife on the quality of the light. I saw no difference in my power bill. In the summer we have 15 hours of daylight and in the winter the heat replaced some of the baseboard load. We now have LED bulbs and they are far superior light sources. We now heat with a heat pump and we may see a small difference in power consumption. 7.5% ROI, for the power to the lights is way better than the bank.

    I know that if I had access to seal the attic the ROI would be great, but access would involve major holes in gables.

  39. John Walls | | #39

    Ducts in conditioned space with Recycle duct
    Martin, as a followup to Nick T's post and your response:
    If you assume that all HVAC ducts in a forced-air system are in the conditioned space, then your concern was that the air handling system might not provide enough flow across the indoor coil for proper operation if you closed off a few rooms.
    My question---If you have a GSHP (with all ducts in conditioned space) with a recycle duct/damper at the AHU to address low-flow zones, is that an energy hog, or is it efficient?

  40. R Hunt | | #40

    Curtains and air conditioners.
    Happy holidays, great list. Funny stuff.
    How about this one,, I don't think its been printed on any list, but I've certainly heard it often. "After using your oven in the winter, leave the door open to help heat the room" Or "keep the oven door closed to keep the heat in during the summer"
    On the curtains, NOT Quilts. I suppose the possible small increase in energy consumption due to the minor convection currents that a curtain could set up is due to the very thin film of air on the colder surface of the window being drawn into the room at a faster rate than if the curtains were left open and there was no air movement across the window.. That statement kinda makes the case of keeping your AC condenser in the shade?? At least until the fan comes on and instantly removes all the slightly cooler air.... In that case, would wind chill have an effect on the condenser? Technically not, if its -10 out, and you measure the surface temp of a rock on the windy side of your house, it will be the same temp as a rock on the protected side. Of course, however, the condensation that forms on the fins of the condenser evaporate quicker when assisted with air movement, thereby increasing the evaporative cooling effect, or wind chill.
    What about using curtains during the cooling season?
    Well,, argument for the sake of arguing I guess. Like I said, Funny stuff...

    Best wishes...

  41. Curt Kinder | | #41

    Some random thoughts
    1) adding thermal mass (water jugs) to unused volume in fridge or freezer might help by lengthening compressor cycle times - more time in steady state operation. Likely savings, a few pennies, not worth navigating round the jugs while using the fridge.

    2) Furnace filters - HVAC systems, to work efficiently, need plenty of the third letter "A", as in air flow. Reduced air flow reduces efficiency. Greatly reduced air flow endangers system compressor whose failure has little to do with energy but improves my (as an HVAC contractor) bottom line. That's not in my clients' best interests, though, so we do our best to always install systems with big, low pressure drop filters requiring less frequent changes.

    Fouled air filters allow dust to foul evaporator coils and blower wheels. Say what you want, but when those components are fouled, system efficiency drops.

    3) Curtains and blinds on windows in summer somewhat reduce solar gain. In winter they reduce radiated heat loss and increase occupant comfort. In both cases, relaxed thermostat settings provide similar comfort at some energy savings.

    4) We very often close off air flow to some rooms via an interesting automatic process called zoning. It allows use of smaller systems and often keeps those smaller systems operating at lower capacities providing increased comfort and significant energy savings.

    5) It is intuitive that a dirty refrigerator condenser coil will impede airflow and heat transfer. Just because researchers, whoever they may or may not be, have failed to construct a study or test apparatus in support of the relevant physics doesn't change them.

  42. Charles Campbell | | #42

    air filters
    Kevin Dickson, MSME wrote, "A neglected furnace filter increases the odds that lint and pet hair will accumulate on the furnace motor. That will cause the motor to overheat, causing short cycling (which reduces furnace efficiency) and eventual motor failure."

    Curt Kinder wrote, "Fouled air filters allow dust to foul evaporator coils and blower wheels."

    It seems to me that the more clogged a filter is, the better it filters, because the larger pores become smaller and smaller. Therefore it seems more likely to me that the motor overheating is due to reduced airflow, not dust, lint and pet hair. However, as the filter clogs, the negative pressure in the return plenum rises, possibly causing the junk on the filter to be sucked into the plenum.

    I guess I'm just asking whether we really know what contributes most to equipment failure, dust or lack of airflow?

  43. User avater GBA Editor
    Martin Holladay | | #43

    Response to Roger Williams (Comment #38)
    I'm glad that you were pleased at the performance of the foam gaskets that you installed behind the electrical cover plates on your outlets. I doubt that this measure saved you $5 a year, however. In any case, here is a better way to seal electrical outlets:

    (a) Turn off the circuit breaker.

    (b) Remove the cover plate.

    (c) Carefully remove the screws holding the receptacle or switch in the box, and pull the receptacle or switch out into the room as much as possible.

    (d) Seal the holes at the back of the box where the cables enter the box with caulk. Don't fill the box with canned spray foam.

    (e) Caulk the gap between the drywall and the electrical box.

    (f) Put everything back together.

    This method will be more effective than using a foam gasket.

    The outdoor air temperature is not reduced by shade, but hot people feel more comfortable in the shade than they do in the sun, because of the reduction in radiation.

    I'm glad you like your LED lamps. You wrote that switching from incandescents to CFLs didn't lower your energy bill. This really isn't a matter of your impression; I'm not sure what happened in your house. The reduction in energy use is easy to measure in a lab (and in your home, if you have a meter). Swapping incandescents for CFLs is the single most cost-effective energy saving measure you can take.

  44. User avater GBA Editor
    Martin Holladay | | #44

    Response to John Walls (Comment #39)

    A. I'm not sure, because I don't know what a "recycle duct/damper" is. Perhaps a GBA reader who is familiar with this type of system can respond.

  45. User avater GBA Editor
    Martin Holladay | | #45

    Response to R. Hunt (Comment #40)
    R. Hunt,
    Q. "What about using curtains during the cooling season?"

    A. Closing your curtains can reduce solar heat gain during the summer, but the measure isn't anywhere near as effective as exterior shading. When you pull your curtains shut, the sun enters the home and heats up the curtains. On the other hand, if you have an exterior awning, the solar heat will never enter your house in the first place.

  46. User avater GBA Editor
    Martin Holladay | | #46

    Response to Charles Campbell (Comment #42)
    Q. "I'm just asking whether we really know what contributes most to equipment failure, dust or lack of airflow?"

    A. I imagine that either phenomenon could cause equipment failure. To clarify:

    (a) I recommend that duct systems be well designed. Oversized ducts are always preferable to undersized ducts. High static pressure makes your air handler fan work harder and raises your energy bills. Big ducts and big filters are good.

    (b) I don't recommend that anyone run their equipment with a dirty filter. By all means, when your filter is dirty, change it.

    (c) It's true that a dirty filter makes a more effective filter than a clean filter. But it also makes your fan motor work harder, so it is undesirable.

  47. User avater GBA Editor
    Martin Holladay | | #47

    A comment from Steve Easley
    I just received an e-mail from Steve Easley. The subject line of his e-mail read, "What happens when you close your blinds to save energy..."

    Steve wrote, "Per Item 10 on your 'Stupid Tips to Save Energy.' I took this photo in an Indiana home a few years back. The folks closed their blinds to save energy and could not figure why their windows were growing mold. I think it speaks for itself…."


  48. Mark Johnson | | #48

    HVAC Air Filters
    I would like to question the thinking behind the HVAC advice "change your filter every 30 days". My theory this comes from two sources: 1) the desire to assume conditions rather than measure them, and 2) selling more filters with a short estimate of lifetime.

    Directly this matter would be expected to save little energy, but energy is wasted whenever you consume more stuff than you actually need. Usually the issue with HVAC filters is whether it would tip a forced air system into one which actually malfunctions.

    Over 5 years ago, I heard about a Carrier high end control system which I understood to measure air flow and tell the homeowner to change the filter when the back pressure (called External Static Pressure, or ESP) rose by a measured amount. Some Dwyer liquid manometers were being sold cheaply, so I bought one and attached it to my HVAC system in order to mimic this. Although I watched the system ESP frequently, decided to wait until I saw some measurable ESP rise before I changed the filter. And waited, and waited, until 5+ years had passed and I finally decided there must be other reasons to change the filters.

    Dust had accumulated on the filter face until extremely dirty, they looked like grey felt, yet there was no measurable rise in ESP and therefore no meaningful drop in airflow. Probably a factor in this is very generous filter area, with the 3.5 ton system 1400 cfm system I have and TWO 20*30 filters, this is perhaps twice the average. For that reason I would never advise another person to repeat this experiment unless they could closely monitor its progress, if a filter significantly reduces air flow then it can cause malfunctions and possible costly repairs, as well as people discomfort in the house.

    You often hear HVAC technicians admonishing one not to buy 3M Filtrete brand filters, on the assumption that they are "too restrictive". A variation on this advice I have heard is, 3M Filtretes are okay at first but load up quicker than other filters and are then more restrictive. When dust loads up on the filter, it actually improves its ability to screen out particles, but also it is said to increase back pressure. I am sure the stories about a filter being bowed in its frame due to air pressure, are not made up. But I submit the theory that problems actually stem from a poor design with a very small filter area compared to the air flow needed. Again, let me remind you my experiment was with a very large filter area.

    When professionals measure filter performance, they take into account the air speed at the filter face. This is an inverse number vs. filter area. One tester I saw, used air speeds of 300, 400, and 500 fpm (feet per minute) when testing 20 different filters. This is consistent with the rule of thumb "one sqft per ton of AC" -- 400 cfm through 1 square foot = 400 fpm. This rule of thumb is much spoken about , sometimes violated for convenience, so there are many houses putting more stress on their filters. On my own system, I calculated filter face speed and it is well under 200 fpm which might explain much of my observations.

    The advice to change filters once/month is often said and I understand people rarely honor it. Rather than monthly filter changes, I believe most people would be better off to add return capacity (and filter) area until they are above average -- I have been consistently advised by professionals there is no real downside to this, so go big if you can. The energy savings will be not in your electric bill, but in the reduced manufacturing where you can forego buying a $20 filter every month.

  49. User avater GBA Editor
    Martin Holladay | | #49

    Response to Mark Johnson
    Thanks for your comments, and your account of an interesting experiment.

  50. Gordon Clements | | #50

    Proper Window Coverings Do Save Energy -
    We have focussed our Vermont based window coverings business on the practical side of comfort and energy savings for the last 28 years - including weighted thermal lined drapes, Warm Window, Window Quilt etc. About 10 years ago we concluded the most attractive, durable, easy to install, cost effective product to be insulating double cell honeycomb shades made from bonded polyester fabric. About 10 years ago we added side tracks and fuzz bar to reduce air circulation and branded them EcoSmart Insulating Shades. They have been tested by your own organization (GBA-Peter Yost), Harvard Properties, Carb (Winters, Aldrich), EnergyBalance (Andy Shapiro) and found effective. Doing thousands of homes a year, and surveying every one, I can also say anecdotally and emphatically that customers agree - and return to make repeated purchases. (Our repeat customer base 65%.) In essence there is less draft or radiant heat loss so less impulse to turn up the thermostat. We also encourage their use to take advantage of solar heat gain when available with the shades open, then close them to block heat loss. And the reverse in summer - I also find personally that using our ceiling fans, and following this regime allows us to get away without A/C in summer - and it does get hot in VT in summer! Some of our customer comments are sometimes almost too dramatic to believe, but may be attributable to the fact they have a tool that works to make them warmer and more comfortable - along with many other benefits. I believe that compared to alternatives insulating cellular shades with 4-sided seals, are cost effective and therefore warrant an "Energy Saving Tip".

    Re Steve Early's picture - I hear about mold issues from building professionals all the time - but not from hundred's of thousands of customers who actually live with the shades. Two points to the comment:
    1. The Harvard study found that mini blinds, as shown in this picture, actually increased energy consumption with the average inside/outside temperature differential 26 degrees with minis, 33 degrees bare glass, and 37 degrees with EcoSmart shades. Gas consumption on average was 48 therms with EcoSmart Shades verses 68 therms with minis. Unfortunately this is the largest selling window covering in the US.

    As for mold, insulating a window between exterior cold air and warm, moist indoor air will make it colder and therefore condense out some of that moisture. There are ways to reduce this - by reducing the humidity, which may be a good idea for any number of reasons, and/or reduce the glass temperature difference. The latter, by definition, will also reduce the shade's effectiveness. Bottom line, if we get 2 or 3 complaints about condensation a year it is a lot - and as a % fewer complaints from any other product for any other reason. Those customers who do have a condensation problem feel it is worth it to wipe up the moisture in the morning because the shade is working. That there are many other things they do to save energy and stay warm that take a lot more effort.
    In conclusion I wish GBA would say more emphatically that homes in cold climate with conventional single or double pane windows, which represent the majority in the US, would benefit from insulating cellular shades that provide a 4 sided seal if they are used appropriately - which your own study shows they would be. That homes would be more comfortable and would consume a lot less energy. After all, conservation is the best route to our energy problem.

  51. User avater GBA Editor
    Martin Holladay | | #51

    Response to Gordon Clements
    You are in the business of selling cellular window shades, so of course you are in favor of them. They're a good product. GBA has published glowing reports of this type of window quilt before; if you want to read what's been published here, start with these two links:

    Insulating Window Shades

    EcoSmart Double Honeycomb Cellular Shades


    It's hard to imagine how I could have written my advice in a way that would have been clearer. I wrote, "When this advice ('close your curtains at night') is repeated, the authors usually fail to mention that you need a way to stop air from flowing between the curtain and the window — or else convection currents will sabotage your efforts to save energy."

    It seems that you agree with my advice, since you advocate the use of "shades that provide a four-sided seal" -- in other words, a type of shade that "stops air from flowing between the curtain and the window." I'm glad that we agree, and I'm glad that you sell shades that work.

    In general, I think that GBA has presented a balanced view of your product. Cellular window shades are effective, but they aren't cheap. For cold-climate readers who can afford them, they can save energy and improve occupant comfort.

    I think the jury is still out on whether this product is cost-effective.

  52. John Walls | | #52

    Response to Martin Holladay (comment #44)
    This GSHP air handler unit has several zones (ducts going to various places that are individually thermostatically controlled). Each zone has it's own control damper. So, at any one time, the system may be conditioning a different quantity of zones. At some point, there may be only one zone being conditioned, and that zone may have relatively small needs---in fact, possibly so small that there would be insufficient flow across the coil for proper operation. To address this problem, one solution is to install an additional "zone" that "recycles" from the discharge plenum of the air handler unit back to the suction plenum. This "recycle zone" damper would open up only when needed to maintain adequate flow across the coil for proper operation, and to avoid high duct pressures, or any other issues associated with air-handler-unit low flow or restricted flow.
    There are other control features to help the situation, like a multi-speed compressor and fan motor, but at some point, the recycle damper will have to engage.
    So, the question is----in general, is there a significant efficiency impact (aka wasted energy) when in "recycle" mode? (i.e. one "regular zone" in operation with the "recycle zone" simultaneously in operation). Is the energy hickey simply the extra fan motor usage (higher air flow than needed for the one zone) or are there other factors at play?

  53. User avater GBA Editor
    Martin Holladay | | #53

    Response to John Walls
    My knowledge of zoned forced-air systems is imperfect, and is based mostly on this article by Gary Bailey: Zoning Forced-Air Heating Systems.

    Bailey wrote:

    "If a furnace was designed to deliver air to 12 duct runs, but only two dampers are open in one zone that’s calling for heat, the furnace would be at risk of damage from heat stress. The ideal way to cure this problem would be to use a multi-stage furnace, where the burner can fire at different rates, but that only makes sense if you’re replacing the furnace.

    "When adding zoning to an existing system, the best way to get rid of excess heat is to create a separate “dump zone,” which throws extra heat into an unused part of the house — a basement workshop, for instance, or an upstairs storage room or insulated garage. If the furnace sits in an unfinished basement, there’s no harm in dumping the heat directly to the surrounding air.

    "Another way to get rid of excess heat with a Carrier multi-stage furnace is to use a bypass loop between the supply and return trunks. If the airflow falls below a certain level, the difference in pressure opens a simple barometric damper and sends air back to the furnace.

    "Many times, we have to combine bypass loops and dump zones to get an acceptable result. Neither of these methods is energy-efficient, but most clients are willing to waste a little heat to gain the comfort a zoned system provides."

  54. Jonathan Teller-Elsberg | | #54

    Response to Robert Connor's comment 31
    Robert, I don't think asking "why has no one taken my advice about thinking about and limiting family size?" is the right question. Silence in the comments does not mean that people think you necessarily wrong, only that there is no need to say anything in response. Your comments that people can reduce energy consumption through having fewer children is not controversial. No one is going to rebut your argument and claim, "I reduced my utility bills by having another child." Also, the focus of Martin's blog has been primarily on cost-effective energy savings. Whatever their impact on utility bills, kids are definitely money sinks.

  55. Seth Romme | | #55

    Tips that save energy but cost too much: Not one-size-fits-all
    Martin: I like the article, nice job. We've done energy myth buster seminars similar to some of these one-liners for quite some time now. The "Tips that save energy but cost way too much to implement" section is something I think is worth a little questioning. As an example, a ground-source heat pump can absolutely be the the smartest financial decision & save energy (here in Wisconsin). Whether or not that is the case is completely dependent on the heat loads, fuel source you're replacing, and the install cost. As energy advisors, we've financially justified numerous ground-source heat pumps given those 3 home-specific factors.

    On top of that, whether or not it costs too much now and going forward is heavily reliant on what predicted energy inflation rate is being used as well as the interest rate of financing. The same principle applies to replacement windows. Sure, replacing windows solely to save energy dollars is an impossible money-saving scenario. However, many many people are replacing windows because they have to (mold, rot, etc) or simply want to (aesthetics). In that case, you definitely can get a return on the incremental cost of energy efficient windows depending on the the other variables of the home: structure, fuel source, loads, etc.

    The need for custom analysis on a home-by-home basis is why we started doing independent home energy advising. Each home is unique, which has proven to yield different smart, energy efficient recommendations. We've seen the best financial options be ground-source, while others are typical gas-fired furnaces, or some triple pane windows, others double pane. It truly rarely is a one-size-fits-all situation, but every home has a perfect size with upfront modeling and optimization!!

  56. User avater GBA Editor
    Martin Holladay | | #56

    Response to Seth Romme
    It seems that you agree with me about window replacement, since you wrote, "replacing windows solely to save energy dollars is an impossible money-saving scenario." The fact that people do it for other reasons is irrelevant to the topic of my article.

    When it comes to ground-source heat pumps, I simply disagree. Ground-source heat pumps are almost never a good investment for owners of single-family homes. For more information on the background of my views, you might want to read Are Affordable Ground-Source Heat Pumps On the Horizon?

  57. Seth Romme | | #57

    Response to Martin Holladay
    I read your article on GSHPs including a handful of the comments and your responses to them. I enjoy the added perspectives from all around. As an independent energy advisor for both homeowners and builders, I am far from a die-hard GSHP advocate, but I'm weary of using generalities regarding its positive or negative financial impact without the exact home's specifics (fuel source availability, rates, loads, etc). That being said, I don't think the $20k range is that few and far between for an installed GSHP system, at least here in WI. Two different projects that I've consulted on recently have come back with $20k and $21k GSHP quotes from separate installers (before any credits/rebates). The $21k was for an in-floor system on a 1500 conditioned square foot home, while the $20k was for a forced-air system on a ~4,800 conditioned square foot home. In the case of the $20k, my alternative for a LP furnace+AC was about $15k. That $5k cost increase and about 3.1 CoP meant the homeowners would save about $29 the very first year (mortgage increase less energy bill savings) and about $4.5k over 20 years (4.25% interest, 5% energy inflation) with the GSHP.
    As close to a generality as I can get at this point, given all the homes I've looked at in WI over the last couple years is that a GSHP cannot be financially justified when the home has access to natural gas, and thus can go with a NG furnace+AC. Reason being, with our current fuel rates the $/mmBTU is: $38 electricity and $7.90 NG. For round number's sake say $40 and $8. That means the GSHP would have to have a COP of 5 to even match the operating cost of the NG furnace throughout heating season...not happening (as you've alluded to). In this case, install cost makes no difference at this point because GSHP is not less than a forced air + AC. Even with this "close to generality," I continue to automatically model the financial viability of it on every NG project to ensure the builder or homeowner sees the facts, specific to their home.
    Perhaps these GSHP install costs are a WI thing? Or our fuel rates (elec, LP, NG) are that different than other parts of the country? Very interesting!!

  58. User avater GBA Editor
    Martin Holladay | | #58

    Response to Seth Romme
    You are comparing the cost of a ground-source heat pump to a $15,000 forced air furnace. But for some reason, you aren't comparing the cost of a ground-source heat pump with one or more ductless minisplits, two of which can cost $5,500 or $6,000 installed.

  59. Seth Romme | | #59

    Response to Martin Holladay
    We've looked at minisplits and in WI, not only have we seen that they aren't as cost effective, but the market is also saying that. Even the lowest cost homes (the ones who are willing to save a couple hundred bucks by installing elec DHW rather than gas) aren't installing minisplits. The budget systems are always forced air furnace with ACs.
    To get the right comfort level in our basements and all other levels and rooms of the home, the minisplits become too expensive. To try and improve comfort, we've looked at ducted minisplits but we then start getting into additional cost issues with the ducting in order to really move the air properly.
    The fact is, every home needs its own unique analysis to identify which energy component is the best return. Whether it be the HVAC, the amount of attic insulation, or the performance specs of the windows.
    In regards to GSHP and their true CoPs, you may find this home tracker interesting. To stay true to our independent roots and continue to learn from real data, we've been tracking this home that we provided energy advising on for several years now (room by room temps, GSHP incoming/outgoing temps, etc):
    Thanks for the great discussion!

  60. David Profitt | | #60

    Interesting article
    Still not sure if you wrote this just to get responses or if you're serious. About 10% is valid, the rest is, well, varying degrees of not-so-much. As Seth Romme pointed out, every house is different, just like the people who live in them. What is hard fact in one instance is fantasy in another. The Florida based test that determined shading the AC compressor did not increase it's efficiency was, I'm sure, true - in Florida where the humidity is near 100% all summer long. Do that same study in a low humidity climate like Arizona and you'll get starkly different results. Same goes for the ground coupled heat pump. It may not make financial sense in a cold climate line MN, but what about taking that to a humid heating climate like Florida, as ambient humidity is a major factor in an AC compressor's ability to get rid of the heat it's collected inside the dwelling.

    The window leakage part was particularly amusing, as old single pane windows (or poorly installed new ones) can be a major source of air infiltration. R-value doesn't matter much if you've got a 5 mph breeze blowing thru on a windy day. Insulation slows the transfer of heat - it provides neither heating or cooling effects. This is not to say it isn't important - it's just only part of the story.

    As it's a cold day and I"m stuck inside, just for fun I'll address them briefly:
    1. The water bottles in the freeze. Run that one by a physics professional. If he has a sense of humor (not common in that profession, I admit) , he (or she) will find it amusing.

    2. The refrigerator coils. These coils sweat in the performance of their job. In a typical house, this will collect dust. The job of these coils is to be a radiator. Dust buildup becomes an insulator. The physics guy can explain this one also.

    3. Schedule a furnace tune-up. Furnace burners get very hot, then cold. They sweat. They rust. Then they leak. This is bad. This can happen fairly quickly.

    4. Change your filters monthly. Not valid, especially if you still have those leaky windows and other air leaks. A month may be tool long. Change them when they look dirty.

    5. Caulking around your windows. If you have a draft coming around your windows, caulk them. Storm windows won't fix this. When you can afford it, get new windows. Complete units, not the "pocket" replacements all the window companies want to sell you. They won't stop air leaks around the window jambs. Especially if you live in an older home. And have had the walls insulated. The space around the window jambs didn't get any.

    6. Foam gaskets under outlet covers. If you can feel air coming out of these locations, the gaskets won't fix the problem but will definitely help. You may need longer screws to re-attach the covers. Better still get over size cover plates (and the gaskets) as the the area under the cover plate is frequently cracked or crumbling.

    7. Run your ceiling fans backwards. Only if you want the heat down where your body is (that pesky physics thing again).

    8. Run ;your AC and ceiling fans simultaneously. This one is iffy on energy savings, but it's big on comfort level. It keeps the air moving, encouraging uniform temperatures. At my house, if my wife feels cold in her sewing room, the thermostat goes up even if I"m warm & cozy in my sun-filled office. Keeping the fans going helps keep the thermostat setting down (or up, depending on the season). There is a cost to running these fans, both in short term electrical costs and long-term wear and tear, but my experience thru the years has proven it to be a wise move.

    9. Locate your AC unit in the shade. You probably don't have a choice in this, as the location was determined by many factors that didn't have anything to do with energy efficiency. If you are in an area of high humidity, it won't matter (like Fl). If you are in a low humidity area, shading the unit has been proven to help. Don't take my word for it, do a little poking around on the DOE website.

    10. Closing the curtains in the winter. Depends on your windows, the way the window is facing and the weather. On a bright sunny day the solar gain thru a (caulked) 50 yr old window may still be advantageous.

    Tips that cost too much. The GSHP and windows will typically increase the re-sale value and the saleability (two different factors) of your home. A well designed SWHS can also help with space heating. Saving energy and increasing comfort are also a plus. Don't understand why that $30k UV array was missing from this list.

    Real energy tips:
    1. I'm good with that one.
    2. Good, but how much is too thin?
    3. Good again, but skip the cellulose if you live in one of those high-humidity areas (like FL). Paper, I mean cellulose, is a porous materiel, no matter what it's treated with.
    4. Good. Better yet, have a professional do it.
    5. Good, maybe. Don't count on energy savings with the LED's just yet, especially in recessed fixtures. They can actually produce more heat at the socket than the incandescent they are replacing.
    6. Good idea on the fridge, not so much on the furnace blower.
    7. Depends on the house, the climate.
    8. A good one-room comfort solution but not in a cold climate. Air coupled heat pumps are better than they used to be but when the temps drop into the 20's they kick in resistance heaters and the meter starts spinning. Good in warmer climates though.
    9. Depends on the climate, exposure, cost, rebates and whether the electric companies follow the trend of Hawaii and stop requiring the power companies to buy back the power. Other states are considering this as the resulting power regulation of the grid is a nightmare.
    10. Depends on whether you will be home during the day or not. It's that physics thing again....
    11. Ok this time of year, put your beer outside.

    Contradicting advice:
    Close off registers in unheated room. Remember that thing about what insulation does? When you close off these rooms they gradually become outside temp, Now you have an UN-insulated wall between you and whatever the outside temperature is.

    Wild Exaggerations
    Window replacement. Varies with individual application.

    Caulk and weatherstrip. If you have on the best cold weather coat that money can by and you turn your uncovered face into a 10 mph wind does your nose get cold? Anything you can do to stop air infiltration (U value in modern building lingo) will increase comfort and decrease heating and AC costs.

    Open crawl space vents in the summertime. Guess what? If you live in a humid area like the south, there will be humidity under your house, vents open or closed, all year round. In the Southern states, many code models prohibits all the vents from being closeable. The best solution is a properly and permanently sealed crawlspace (also permitted under those codes). Or leave the vents open. Air movement (even humid air) will help prevent excessive moisture accumulation.

    More attic vents. Improperly placed and sized attic vents do more harm than good. Soffit venting and corresponding ridge venting will promote airflow (physics again), though the reversal of this airflow at night as temperatures cool will allow the moisture laden air to condense on the attic insulation, reducing it's effectiveness. Better alternative: seal the attic space from the outside air with a combination radiant and moisture barrier. Works great! Keeps the insulation dry and keeps the attic space significantly cooler in the summer, prevents heat loss thru convection in the winter.

    Instal a fireplace: But they look nice.....

    Thanks for the article. It provided some entertainment on a cold boring day stuck in the office. But come on, you weren't really serious, were you???

    Engineer-turned-Builder (28 yrs ago). You didn't really think we were all carpenters or MBA's, did you?

  61. User avater GBA Editor
    Martin Holladay | | #61

    Response to David Profitt

    Q. I'm not sure I understand your point. How many kWh per year will the trick save? Without data, your point is lost. We're looking for tips to save homeowners money on their energy bills. If you replace a volume of air with cold water, you limit the amount of air that spills out of the refrigerator when you open the door. I get it. So what? It's not worth the trouble.


    Yup. Coils get dusty. So hook up your handy watt-hour meter and tell me how many kWh per month your trick saves.


    So if you are worried about a rusting heat exchanger, by all means schedule a furnace tuneup. Just don't expect that you will recoup your $200 annual payment to the HVAC tech in energy savings, because you won't.

    You wrote, "4. Change your filters monthly. Not valid, especially if you still have those leaky windows and other air leaks. A month may be too long. Change them when they look dirty."

    You seem to agree with me: change them when they're dirty. So, in your house, is "a month too long"? Are you on the every-two-weeks schedule? Heavens, your house is dusty.


    You and I agree: if you know where to caulk, by all means caulk. But caulking windows is not a definition of "weatherizing." Weatherizing starts in the attic and basement; windows are way down the list. Any if you want to replace your windows, go ahead. You'll never save enough energy to pay for your new windows, however.

    You wrote, "6. Foam gaskets under outlet covers. If you can feel air coming out of these locations, the gaskets won't fix the problem but will definitely help."

    So we agree.

    You wrote, "7. Run your ceiling fans backwards. Only if you want the heat down where your body is (that pesky physics thing again)."

    There is absolutely no evidence that this improves comfort. And it certainly won't lower your energy bills. I believe in physics, like you, but I also believe in comparing pre-retrofit to post-retrofit energy bills. Running ceiling fans backwards during the winter will raise your electricity bills without lowering your space heating bills.

    You wrote, "8. Run your AC and ceiling fans simultaneously. This one is iffy on energy savings."

    Right. As in, there is absolutely no data to support it.


    Cite me the study. Website tips don't count.

    You wrote, "10. Closing the curtains in the winter. Depends on your windows, the way the window is facing and the weather."

    I'm not sure what your point is. Show me the study that documents energy savings.

    You wrote, "The GSHP and windows will typically increase the re-sale value and the saleability (two different factors) of your home."

    Show me the study.

    You wrote, "Saving energy and increasing comfort are also a plus."

    I wrote that these tips save energy; they just aren't cost-effective.

    Q. "Real energy tips. ...Good, but how much is too thin?"

    A. If you have good access to your attic, blow in enough cellulose on the attic floor to meet the minimum R-value requirements specified in the International Residential Code for your climate zone.

    You wrote, "Good idea on the fridge, not so much on the furnace blower."

    I disagree. Running a furnace blower, which can draw 600 watts, 24/7 can add significantly to your electric bill. Switch it to "auto."

    You wrote, "Window replacement. Varies with individual application."

    The fact is, it's never cost-effective.

    You wrote, "Anything you can do to stop air infiltration (U value in modern building lingo) will increase comfort and decrease heating and AC costs."

    I'm a big fan of blower-door-directed air sealing. The work is mostly done in the attic and basement. And by the way, U-value (more accurately known as "U-factor") has nothing to do with air infiltration. U-factor is the mathematical inverse of R-value.


    You are correct on the first point, but wrong on the second. If the outdoor air is warm and humid, the more air movement, the wetter your crawl space becomes.

  62. Muriel Strand | | #62

    some comments not already raised...
    very interesting discussion.
    i don't understand why a ceiling fan would use significantly more energy in one direction than the other?
    i think putting lids on pots makes them heat faster, and it's wise to keep the flame (or coil) UNDER the pot not escaping up the sides.
    i think my relatively new and wonderful bottom-freezer fridge has the coils covered in back. presumably the mfr. found that keeping the dust off ensured ongoing energy efficiency.

    my uncle built a supplementary solar air heater that worked very well for him when the sun was shining. 12-oz cans painted black and fixed to the inside of a plenum with a transparent top, with the plenum slanted up toward the house and a vent at the top of the wall that he closed when it wasn't sunny.

    i think ducts are the work of the devil.
    fortunately my cottage came with a double-wall gas heater which i replaced with a gas fireplace-stove that's surrounded by some bricks for thermal mass and shielding in back for passers-by in the hall. the stove uses rather less gas than the old furnace, and the same thermostat which i mostly just turn on and off for comfort. and i have ceiling fans in every room tho generally just use the one near the stove. if i had a larger house i would just add more such stoves than install ducts. and of course i can close off a room and save some energy, depending on diurnal timing.

    when i had the old gas furnace, i got a lot more condensate from the combustion water getting out into the room air, and i had some humidity problems. but no way could i find a humidifier that would work in cold weather which was what i needed - they were all designed for louisiana summers.

    i also find that in my dotage i can forgo bathing longer than in my salad days, when i was green and oily. it's also not that hard to just wash the stinky bits to tide yourself over. and i hope that i'm not shortening the lifespan of my water heater thermostat by turning it up only when i actually want a nice hot shower. or bath.

    and i had the foresight to buy a house with large southwest shade trees, so i can get by with a whole house fan. and a wet t-shirt on really hot days, since i live in a mediterranean climate. (i live alone, not an energy saving measure.)

    at one point i looked into zoned heat pumps and air-air heat exchanger. they seemed like they would make life a little more complicated, and the latter also uses energy.

    about cost-effectiveness: it's dangerous to just look at the money, because money can never be the independent variable. given our fossil fuel addiction, energy conservation is the real independent value. how valuable? it would take a healthy adult a good 100 hours of continuous effort to generate the amount of energy available in a gallon of gas. if memory serves, we're good for about 75 watt. so can we afford ourselves? here are some considerations:

    soon i expect to install one or 2 light tubes, and i would be very interested in your assessment of those.

    thanks, muriel strand, p.e.

  63. User avater GBA Editor
    Martin Holladay | | #63

    Response to Muriel Strand
    You wrote, "When I had the old gas furnace, I got a lot more condensate from the combustion water getting out into the room air, and I had some humidity problems."

    If the moisture from the flues gases produced by your furnace were entering your living space, that means that you either had a cracked heat exchanger or a blocked flue. Both conditions are dangerous. Normally, all of the combustion gases (and their associated moisture) should leave your house through the flue.

    You wrote, "No way could I find a humidifier that would work in cold weather which was what I needed."

    It's a good thing that you couldn't find a humidifier, because humidifiers cause lots of problems. It's usually dangerous to operate a humidifier. Humidifiers can cause wall sheathing and roof sheathing to rot.

    I'm not sure what you mean by "light tubes," but if you are talking about linear fluorescent lamps, they are a good choice. The best fluorescent lamps (T-5 or T-8 lamps) have an efficiency of 98 to 105 lumens per watt. For more information, see Martin’s 10 Rules of Lighting.

  64. Linda Foss | | #64

    Hot climate resident that saves energy by using ceiling fans
    Just because some people might not adjust their thermostats when they use ceiling fans does not mean that they are better off not using the fan. The better advice is for them to turn the thermostat up and turn on a fan. And of course to turn off fans in rooms not in use.

    I keep my AC set around 80 and am comfortable with the use of a fan in the rooms in use. And of course, I dress right for the climate. That's another thing few people know how to do anymore. The loss of common sense over the last few decades is astounding. I know someone who is a green builder & director of a green building resource center. We toured his home where he has been doing a number of energy & water saving projects. The ceiling fan on his porch was going the whole time, with no one out there. And he was thrilled to share his astounding rediscovery of opening doors and windows on nice days. Saying we all forgot. I never forgot and can't imagine ever having forgotten. The days we can have the house open are the best days of the year.

  65. Muriel Strand | | #65

    other energy conservation measures include wooden or other solid floor coverings. carpeting requires vacuuming, but throw rugs are easily shaken outdoors. also, manual lawnmowers and rakes offer great exercise. and of course, nobody needs an electric can opener. plus which, canning is not as energy efficient as food preservation by drying.

    and there is also the tiny house movement...

  66. Muriel Strand | | #66

    light tubes
    light tubes are slightly specialized skylights:

    as for the old gas furnace, i'm quite sure the flue was working. i don't know about the heat exchanger, but the heater seemed to be designed in such a way that the flame was somewhat visible, so i had to be getting some of the combustion exhaust water tho by no means all. it was a standard item, like the sears "Empire Comfort Gravity MV 25000 BTU Wall Furnace - Natural Gas" but dating probably from the 1970s at the latest.

    but if a de-humidifier actually worked, there should be no mold hazard?

  67. User avater GBA Editor
    Martin Holladay | | #67

    Response to Linda Foss
    I agree with you about ceiling fans -- and so does Carl Seville, another writer here at GBA. For more information, see:

    Using Ceiling Fans To Keep Cool Without AC

    Ceiling Fans Are Evil

  68. User avater GBA Editor
    Martin Holladay | | #68

    Response to Muriel Strand
    Tubular skylights are a mixed bag. They punch a big hole in your thermal envelope (your insulation layer), so they will raise your energy bills. Some people like the light they produce, however. If you work outside of the home, and you aren't home during daylight hours, you won't be able to take advantage of the light. However, if you work at home, they may slightly lower your electricity bill (while raising your heating and cooling bills).

    In Comment #63, you said that you wanted a humidifier. In Comment #67, you said you wanted a dehumidifier. Big difference.

  69. Muriel Strand | | #69

    oops i meant de-humidifier
    does the de-humidifier exist that will work in the winter?

  70. User avater GBA Editor
    Martin Holladay | | #70

    Respose to Muriel Strand
    Many people install dehumidifiers in their basements, which are often cool. So, yes, dehumidifiers should work just fine indoors, in rooms that range from 50 degrees F to 80 degrees F.

    However, if you want to lower your indoor relative humidity during the winter, you don't want to use a dehumidifier (which is an energy hog). You want to use a ventilation fan.

    If you don't have a ventilation system in your house, leaving your bathroom exhaust fan(s) operating for 24/7 will lower your indoor humidity levels pretty quickly -- and will use less energy than a dehumidifier.

  71. W D | | #71

    Another tip
    It's refreshing to read a sober and factual assessment of energy saving tips and the amounts that may be saved.

    We've reduced our gas and electricity usage by 50% over the last 10 years or so. Numerous projects were involved. Of these, the greatest electricity savings came from installing solar grates. These savings occur when the Utility also benefits because peak demand is reduced. The Utility informs us we are now using 41% less electricity than the 20% most efficient homes of like size in our area. No windmills or PV are in use.

    Solar screens and solar grates are similar in their savings effect. Solar screens darken the room some and are recommended for permanent installation to avoid damage in handling. A view is maintained even though the screen is 80% closed. The curb appearance is changed some.

    Solar grates are three dimensional and operate to largely absorb infrared while mostly reflecting visible light. This selective reflectivity saves a/c electricity while illuminating the interior (think cool and bright). Maintenance is nil and the grates are designed for seasonal use. The curb appearance is changed. The grate is 80% open and the interior view head-on is good while curtailed at large angles. The view is maintained at night. In winter the grates are stored, allowing the sun to heat the home.

    It simply makes no sense to allow the summer sun to heat the home (or other building) and then use the air conditioner to overcome the solar heat gain. Better to absorb the infrared before it passes the window into the building interior (becoming part of the a/c load) and to smile when you get your next utility bill.

  72. Mark Woodruff | | #73

    Best energy saving tip ever!
    Explode a 100+ megaton thermonuclear warhead in any old volcano. The resulting dust in the atmosphere will not only greatly reduce the global temperature, but the potential extinction of mankind could lead to the largest energy savings ever!

    I asked Dr. Evil for most specific figures. He said he didn't have them yet, but was working on it...and would have results soon. Bwa ha ha ha....

  73. Julie Tolliver | | #74

    Put a Shine on Lightbulbs - Add to the Keep You Busy List!
    This Old House - 28 Small Steps to Big Savings - "Dirty bulbs emit 30 percent less light than clean ones, according to the U.S. Department of Energy (DOE). If the room is dimmer, you might get the urge to turn on more fixtures. Instead, dust bulbs in lamps and other open fixtures regularly with a clean, dry cloth; just be sure to switch off the lights and let the bulbs cool thoroughly first, as heated bulbs can shatter.

    The Payoff: Every additional LED lightbulb you don't turn on for, say, 5 hours a day, saves about $3 a year. Don't switch on seven extra light sources for that amount of time and save about $21 a year."

    By the way, as a Home Performance Contractor, I really appreciate this "Stupid Tips" article and all of it's comments. Clients ask me all the time "I heard that...will save me energy'' and this has been a great source to be already familiar with...such things and have ready-rebuttals! Not to mention, it's always amusing!

    I turned my LED bulbs off when I started writing this - they should now be cool enough for me to spend the rest of the afternoon dusting! I'm gonna rake in the savings!!

  74. Jonathan Beers | | #75

    More questionable energy tips
    Gotta love this one: " 3. Redecorate with more carpeting. More carpet means more heat insulation – and also an opportunity for more homey decor. The rugs are made of heat-absorption material that collects the heat that is normally lost on hardwood floors."

    From Arcadia Power's blog, “10 Easy Ways to Save Energy at Home,” posted On 22 Sep 2015.

  75. User avater GBA Editor
    Martin Holladay | | #76

    Response to Jonathan Beers
    Classic gibberish! "Heat-absorption material" has a nice ring to it.

    How about Tip #7? "Move around some furniture." Now that's got to save oodles of energy. I'm going to try it today.

  76. User avater
    Dana Dorsett | | #77

    Love the cookies too! :-)

    "We know it is tempting to look at the deliciousness – but patience is much more than a virtue here. If you keep your oven door closed you can save a large amount of energy in such a simple way. The oven already takes a large amount of time to heat up, so imagine the amount of energy you release when opening up the oven even once – let alone the five times you already do when baked good are inside."

    Don't "....imagine the amount of energy you release when opening up the oven even once..." - calculate it!

    Assuming even a very large 8 cubic foot oven at 350F in a 70F room, and assuming that 100% of the air is replaced when you open up the door...

    (350F-70F) x 0.018 BTU/degree-ft^3 x 8 = 40.3 BTU, or about 0.01kwh.

    Almost all residential range ovens are between 4-5 cubic feet, and, the actual air exchange is probably only ~50-75%, not 100% so you're really looking at about 15 BTU, or 0.004 kwh.

    If you check the cookies 5 times with a fully open door for a good gulp of air exchange that's about 0.02 kwh. Even in high priced electricity areas (which is usually WELL over the energy cost of gas-fired oven) where retail electricity costs 25 cents/kwh, that's about 1/2 of one cent.

    If you turn the 40 watt oven light for the 10 minutes of baking time (as shown in the picture on that site) it uses 0.040 x 10min/60min= 0.007kwh, so you've saved maybe 0.013kwh. At 25 cents/kwh you've saved maybe 1/3 of one cent.

    You'd have to bake one batch of cookies a day for a full year (checking it 5 times every time, with a fully open door each peek not just a crack) for that to add to a buck. At the national average price of electricity it's maybe 50 cents, and if it's a gas oven, less. That's the order of magnitude of the "....large amount of energy..." you'd be saving by not opening the oven 5 times every time you bake a batch of cookies.

    If you then calculated the reduction in heat load on the heating system or increased load on the cooling system the net energy use would be even lower still, in most climates.

  77. User avater GBA Editor
    Martin Holladay | | #78

    Darn it, Dana
    There you go again, Dana -- puncturing the balloon of a blogger who wants to "just imagine" by suggestion calculations.

    Hmmm... maybe if our schools weren't arresting 9th graders for bringing their science projects to school, we might have more bloggers who knew how to calculate.

  78. User avater
    Dana Dorsett | | #79

    Bloggin's a 'ritin' exercise...' calculatin' is 'rithmetic.

    Some go to Harvard, others M.I.T., but this one doesn't take hard-math. A smart 5th grader good at "word problems" might have been able to come up with the correct order of magnitude with only a small amount of guidance.

    Maybe I just don't have a good enough imagination to play in the blogger leagues! :-)

    The kid in TX wasn't the first (and probably not the last) case of paranoia over breadboarded electronics- an M.I.T. sophomore was arrested for wearing a home made blinky-blinky-LED pin on her sweatshirt at Logan Airport in Boston several years ago:

    D'ya think that if it was part of a weapon she might have hid it UNDER the hoodie?

    One has to wonder if the TX kid's name had been Alex instead of Ahmed the local school & legal authorities' presumptions / perceptions of what the thing was might have been different. I don't blame him for not going back to that school.

  79. Sherwood Botsford | | #80

    Stuffing the fridge.
    1. Fridge/Freezer.
    Whether it will make a difference depends on how often you go to the fridge, and how long the door is open. A fridge or upright freezer that is opened twice at breakfast and 3 times at supper, you are probably right.

    A typical north American fridge is 18-22 cubic feet. Call it 18. Let's suppose that it normally has 6 cuft of stuff in it, and that clever use of water bottles, rectangular milk jugs can get it up to 12. So there is 6 cuft of air inside. Let's suppose that 5 cuft of this changes with every door open and shut operation.

    With the unstuffed fridge these numbers are 12 and 10.

    5 cuft is roughly 1/7 cubic meter. A cubic meter is 1.25 kg. Air has close to the same specific heat as water per kg. So to cool a cubic meter of air from 70 F to 40 F will take 1.25 * 2.2 * 30 BTU = about 80 BTU. And since this is BoE math, we'll call a BTU a kJ. So 80 kJ. A kWh is 3600 kJ So opening the reefer door 7 times a day for 45 days = 1 kWh. So we're talking 8 kWh/year.

    Except 7 times? Really. Me:
    Morning coffee: open fridge, grab creamer, shut fridge. Pour creamer. Open fridge replace creamer close fridge. I typically do 5 cups of coffee a day.
    That's 10
    Breakfast cereal. Often two separate operations for milk and for creamer again.
    Now we are at 14.
    Lunch: Cheese, mayo, mustard. Often 2 openings each.
    Now we are at 20.
    My wife isn't much different, so we are at 40 before we get to supper.

    I don't think that 60 is an unrealistic count. I suspect that families with kids are worse. Now we are talking about 64 kWh per year. At 8 c/kWh (My differential rate -- I have a $60 month line charge) this is close to 5 bucks. For people paying 16 c/kWh this could be as much as $10/year!

    The upright freezer isn't opened as often, but the air exchange is more thorough (You often have to look for something.) and the delta T is twice as large.

    On the flip side of this: A crowded fridge is open longer to get anything not in front. And maybe my 83% air change on opening is too high.

  80. Sherwood Botsford | | #81

    Ceiling Fans
    In a cathedral ceiling we run a ceiling fan 24/7/365 on low. 12 w. We heat with two wood stoves, and the heat tends to stratify.

    In the the den where the other stove is, we do reverse the fan in winter. (Sucking up, not blowing down) I don't see it as making any difference in terms of heat distribution, but the perception of 'drying eyes' for people near the fan is far less. In summer when I come in from the field, I will often stand under it and switch it to high for a few minutes.

    The backup heating system is hot water baseboards.

  81. Sherwood Botsford | | #82

    Unplug your second freezer?
    If I did that, the meat would spoil!

    Unplug the second freezer if it's empty, or only used to keep beer cool.

    We have two freezers, one upright, used for anything that stacks (wire basket at the bottom for bags of veg) and one chest freezer. The latter is 75% full on average for the year, hitting a minimum before the fall fractional cow comes home. The former is typically about half full. It's fullness is adjusted by things like bags of whole wheat flour which don't require freezer space, but which go rancid if stored for long periods at room temp.

    Two freezers for only two people? It's 75 km to the nearest good grocery store. I figure that the Subaru costs us $30 for a round trip. $30 is 375 kWh. A storage unit that saves us 3 trips a year to town (based on an average of 100 kWh/month) is a win. This also allows us to get groceries once a month on First Tuesday (15% off) with a more local trip between for milk and fruit.

    One good tip: Put your freezer collection on the porch. While fridges act erratic in unheated spaces, I've had 4 different freezers that lived on the breezeway or on a covered deck. Here we have a strongly net heating climate. The house is cooler than the porch only in afternoons on a warm sunny day. And in winter, the freezer may not come on for days at a time.

  82. User avater GBA Editor
    Martin Holladay | | #83

    Response to Sherwood Botsford
    Good for you for doing the math to show that the energy needed to run your freezers is less than the energy that would have been used for extra shopping trips with your Subaru. That's the kind of calculation that more homeowners should be performing when making energy decisions.

  83. Sherwood Botsford | | #84

    Closing curtains at night.
    While this will not stop convection on the inside of the glass, I would expect it to make a difference to radiation. This assumes that the curtains are close to opaque. If the temp on the window side of the curtains is the average of the window glass temp and the room temp, the radiation looses will be cut by somewhat more than half. (Radiation is proportional to the 4th power of absolute temperature.) Drapes with a back side of aluminum coated mylar should do even better.

    With a 100 F differential, a window acting like a black body cavity has a net radiation outward of about 75 w/m2 or about 25 BTU/ft2/hr. Given that an R2 window in this same situation will fllush 50 BTU/ft2/hr, cutting your radiation loss in half isn't that big a deal. Even cutting ALL of it is still only saving 1/3 of your losses. And even here 100 degree differentials aren't THAT common. Because of that 4th power law, at a 50 degree delta T you don't have nearly the loss.

Log in or become a member to post a comment.



Recent Questions and Replies

  • |
  • |
  • |
  • |