Tuesday, March 13, 2007

Suburban Solar Retrofit










JBC said...

Be careful when cooling in summer to not drop the temperature of your thermal mass below the dew point. If you do water from the atmosphere will start condensing on it.

This is not a significant problem out west where the summer dew point could be tens of degrees below the ambient temperature.

In the southeast, however, the dewpoint, due to high humidity, is often only a few degrees below the ambient temperature.

This is why subfloor radiant heating systems are relatively common but subfloor radiant cooling systems are not. Any surfaces cooled below the dewpoint start weeping due to condensation. Not what you want inside your house.

rich said...

Hi Jeff

A significant portion of your winter heating would also be attributable to solar gain through windows (I hope, anyway) Blinds on those windows, or planting deciduous vines to block them in summer, can do a lot towards cooling the interior of the house.

From a hassle-to-benefit ratio standpoint, I think closing off your interior radiator loop in the summer would reduce your installation and maintenance costs, and reduce the overall system headaches that could result from perfecting the radiator.

That's assuming you don't want to spend a lot of time jacking around with it. It'd be great if someone out there would, but I know it doesn't suit my temperment.

There's lots of good info on passive solar retrofits at

JCamasto said...

Cool. JBC and I share the same three initials...
Jeff: We spoke on the Ishthink conference call - here's a peek showing retrofits I've done.

(click to enlarge)

Or, read the whole story: [url=http://ishthink.org/our_solar_home]Our Solar Home[/url]

I dig your idea of using the ST panels as a radiator at night - I'd have to add some electronically controlled valving, and a second cold water storage tank, but it's intriguing none-the-less. An atmospheric-based heat pump, essentially...

Instead of radiant piping and a dedicated thermal mass - I use a water/air heat exchanger placed upstream of the forced-air furnace blower, and utilize the thermal mass of the house & furnature. The blower motor is very efficient (as is the furnace), and it is set to circulate air 24/7. Of course, the tighter and better insulated the house, the better this strategy works, but it's what I got at the moment... A btu is btu...

Check out [url=http://www.solarserviceinc.com/]Solar Service Inc[/url] - One of the premier solar thermal designer/installers in the country (predominately in IL). For decades, Brandon Leavitt has installed 1000's of systems, residential to commercial. He's a friend and colleague - please feel free to drop my name if you'd like to speak with him.


JCamasto said...

Ah.. sorry I blew the tag formatting above - but the ol' cut & paste still flies...


After some more thought on using a typical ST panel as a radiator - I don't think you'll get the same evaporative effect with typical closed-loop ST panel (as the below-ground ice-maker you've blogged previously). It would simply be utilizing the ambient nighttime temperature. However, if you used a pond...

then you might already be half way to geo-thermal heating/cooling heat pump...


Anonymous said...

Jeff, this problem has been well-addressed, I think, by OM Solar of Japan:




Paula said...

Enertia Homes has developed a solution to this issue that I find very smart. The house is a passive-solar/geothermal hybrid. It has a wide open basement area to provide temperature stabilization; the walls of the house constitute the thermal mass, and are enclosed in an "envelope" -- with the south-facing side almost entirely made of glass -- that circulates either sun-warmed or ground-cooled air around the interior mass walls.

I have wondered if such a solution couldn't be somehow ported to existing homes by essentially building a south-facing "sunroom" addition that also happens to envelope the whole house. I don't see how it would work with homes that don't have basements, though.

Anyway, Enertia is here: http://enertia.com/Science/HowItWorks/tabid/68/Default.aspx

Jeff Vail said...

As usual, blogger is having some difficulties with comments. Here is a comment received via email from "Energy Lens":

...like you I spend a great deal of time thinking about the ideal envelope for weathering the future. We currently live in a 5000 sq. ft. "green" off-grid solar-hot water heated (radiant flooring) home that was built around an existing structure. We milled as much of the lumber as possible from our own property & etc. And we're well under way on the edible forest garden, raised beds, chickens & etc. My next project will be an electricity free cabin that utilizes passive solar design & solar tube lighting & gravity fed spring water & etc. Like you I've thought about embedding a large water reservoir within the building to radiate heat throughout the night... we're at 4000 feet in the Appalachian mountains, so we don't really need to worry (yet, anyway ;-) about summer cooling. Fans suffice. But on to my real point, my experience with solar hot water: We began by heating our (rather large) home entirely with an outdoor wood boiler. It proved to be quite a lot of work hauling wood to the boiler at midnight in the snow in the middle of winter. (not to mention processing the wood - thankfully a lot was left from the milling of our house lumber) And we had to keep it going in the summer as well for domestic hot water and the cool nights. And we hated the fact that we were burning so much wood. Really gave us a tangible sense of what we had been getting from "conventional" systems in the past. So when we decided to build a barn I bought a used 5000 gallon stainless steel tank (formerly used for syrup) and super-insulated it and buried it within the barn. I then had the south facing roof pitched properly for about 1200 sq. feet of solar hot water panels. Net net, the tank stays above 130F and we're heating our house and all our domestic hot water practically year-round. I run the wood boiler only when we have a string of cloudy days in the winter, or a string of days below 20F. It's pretty awesome. The loft above the super-insulated tank in the barn has a small service door which easily heats the loft passively. All of our electric is PV, and we've only had to run our generator 3 or 4 times this winter. With LED lighting and a DC freezer with it's own panels we should be generator free next winter. But it is all too extravagant. Hence my obsessing about an electricity-free home...

Jeff Vail said...


Good point with the condensation issue. In Denver, the humidity is ususually under 20%, so it wouldn't be an issue, except that when we have our frequent summer thunderstorms it can spike up to 90% in less than an hour. Of course, that usually happens in the late afternoon such that--if the mass is sized properly--it should be approaching equillibrium with indoor air temperature (and thunderstorms also tend to drop the temperature into the 70s...)

This is potentially an advantage of large, compact banks of cool water (such as a single, central wall), because condensation can more easily be addressed and collected than it can from sub-floor cooling, or other solutions that are highly dispersed throughout the house.

Jeff Vail said...


My house does OK when it comes to maximizing solar gain from winter sun, and shading from summer sun. I definitely need to put up a trellis to shade my west-facing windows in the summer. However, suburbia (at least suburban Denver) seems to have been designed with absolutely no awareness of solar orientaton. Most builders seem to take the exact same home plan and orient them purely based on street frontage. Everywhere I look, the exact same house plan is sited with a huge wall of two-story windows facing alternately due south (on one side of the street) or due north (on the other side). This is, I think, the key issue: as a nation we have invested a huge percentage of our wealth in suburbia. We can discuss all day long how that was a stupid idea (it probably made short-term economic sense due to various subsidies), but it is also a done deal. Some suburban houses are blessed with good orientation (like mine, for the most part), but many, many others have nothing but garage on the south side, and a huge bank of windows on the north.

Anyway, like you, I probably don't want to spend a lot of time and money experimenting with making the perfect solar-heater/radiative-cooler concept work, at least not on my existing suburban home. It's something that I'm more likely to work on with enthusiasm in designing and building my "long-term solution."

Jeff Vail said...


That's a pretty impressive set of solar collectors & PV on the side of your house! Do you use the flat-plate water heaters just for hot water, or also for radiant space heating?

I agree that the system seems pretty close to a geothermal heat exchange... I have a basement that is always a nice 60 degrees, I guess I should leverage the existing blower that is part of my furnace/AC (which is located in the basement)...

Jeff Vail said...

Re: Energy Lens' comment-

Your set up sounds pretty nice! I'll probably post in the next few days about my "ideal" home design--something that I've been pondering for quite some time. It will be unique from most "sustainable home designs" as it is designed for the environment of southern Arizona (not a guarantee that's where I'll end up, but I like it, and I like the challenge such an environment poses). So it will be much more focused on cooling and water collection for both house and gardden, with the ability to use the copious sunshine to power virtually everthing via passive solar...

Dryki said...

I've got a superinsulated active/passive home with slab on grade and radiant floor in Maine. Made that mistake of running cool water through the slab once. Once.

I no longer heat the slab, but instead put on long underwear and run a small fire in wood stove now and then. Of the 1400 sq ft only about 600 gets heated and I'm aiming to reduce that a bit next year. Depending on the surfaces the comfort level will vary; you want to pay attention to average radiant temperatures to feel warm, regardless of air temperatures. In other words, try to heat yourself, not the house.

Anonymous said...


I highly doubt that the system you proprose will do much at all to heat and cool your house. Do you realize how hot the surface temperature of a wood-fired stove needs to get in order to heat a 2300 SF space by an additional 10 degrees in the winter?

You'll do better with the following:

1) First of all, create more efficiency: lower energy usage by replacing lighting with CF or LCD units. Weatherstrip and insulate. Replace old appliances. Install thermal window treatments (shades/curtains).

2) Enhance your home's passive solar gain by adding/retrofitting south-facing windows for additional winter warmth.

3) Install a high-efficiency wood stove with catalytic converter in a centralized area of your home to heat the areas least served by passive solar heat.

4) Evaporative (swamp) coolers use a quarter of the power used by AC systems. Dump the AC and strategically locate 1 or 2 evap coolers instead. Turn these areas/zones on and off as needed

5) Solar hot water is the best investment you can make, but it won't heat your living spaces too well. Consider also the energy required to pump the water to and from sotrage tanks.

6) Strategic placement of deciduous shade trees, vines and trellises on the west and south side of your home will do wonders to cool it during the hot season.

Overall, the first consideration is conservation -- after you've got that buttoned down, your cost of heating and cooling with eco-groovy solutions will be greatly diminished.

Many Blessings,

Anonymous said...

You mention that the initial investment of the solar system is $3000 and that it will pay itself back in 8 years so it is a good investment. This is something that I don't like. Why do people who take important steps to live more ecologically and responsably have to justify their actions in economic terms? The investment is good because it will shrink the size of your ecological footprint and reduce your CO2 emissions. Those, in my mind are good enough reasons for the investment. People who buy tv's for $1500 don't ever have to justify the economic rationale of their investment. The tv will never pay itself back!

Living ecologically, atleast for now, might sometimes be more expensive, but its a choice that ecologically minded people are willing to make. I see this as a kind of hobby. Some people spend tens of thousands on hobbies, like cars for example. This solar waterheater is your ecological hobby, you're allowed to spend money on it. I, personally, applaud the steps you are taking and wish that there would be more people like you (and like the people who visit your blog).


Jeff Vail said...


I agree that we should want to live in a more ecologically sound manner for its own sake, and personally I look forward to pursuing it as a hobby. However, I think that there are two important reasons why we should be concerned with the "return on investment" or the "payback period" for environmenatlly beneficial retrofits. First, it is a means of identifying what are the most efficient (froma $ perspective) means of reducing my personal consumption and CO2 emissions. I have limited money (as we all do), and by prioritizing by "return on investment," I can best allocate that money within my hobby to achieve the desired result. Second, most people don't share this hobby... and while they may not take these steps for the sake of the environment and societal sustainability, they WILL likely take these steps if it can be shown that investing in a solar hot water heater will provide them a better return on their money than putting that same capital in a mutual fund. That's the door to broad implementation, and that's something that can only help.

JCamasto said...

Thanks, Jeff. The flat-plate ST collectors heat water (120gal storage) which is also used to supplement space heating, via a water/air coil placed upstream of the furnace blower (forced air, not radiant heating).

Pictures are available in the detailed link I provided above.

I absolutely require the furnace for 3-4 months of the year (the original model ('76) was replaced with a high efficiency unit the at same time I installed the ST). The two improvements combined to cut my annual gas use 50%.

The PV array is on pace to cut electrical use 60-65%.


Ken Neal said...

You need to increase your insulation & thermal mass levels considerably, by the sound of things. With the sort of temperature swings and sunlight levels you are talking about, a fossil fuelled heating and AC system should be entirely redundant. Using passive solar heating and night time cooling you should be able to guarantee comfort temperatures throughout the year without any heating or AC plant. Try using an evacuated tube solar thermal system to give yuo better winter efficiency.

Jeff Vail said...


I agree that in this climate, insulation and thermal mass would be 95% sufficient for a well designed house. The problem is that my home is part of the typical American institution of suburbia--Lots of windows placed for looks, not function, poor insulation, and orientation that didn't account for solar (not to mention the neighbors block much of the lower, winter sun.

Improving insulation in the attic is very possible, but the attic in my house only covers 1/3 of the home, as the rest has vaulted ceilings. Improving the insulation between the vaulted ceilings and roof, and in the 2x4 framed walls, is more difficult (actually, I don't know if it's economically possible--any insight, anyone?). Replacing the windows would help, though they are already double pane, and that's an expensive prospect for a marginal gain in insulation... I'm more likely to get bubble-wrap to insulate the windows while letting light in, and then to put honeycomb insualting blinds in place.

There are several problems with using thermal mass to "retrofit suburbia." First, suburban homes are generally built with very low thermal mass because that meant lower initial construction costs, and it also means that air-heating/cooling systems work better. So there's a long ways to go to make a home "high mass." Second, it can be difficult to increase mass without a major remodel. Replacing carpet or linoleum with tile or stone is probably the simplest (though not cheapest) solution. Creating a large water wall or adobe mass is often impossible given that the basic structure of most of wood-framed suburbia may not be sufficient, not to mention that this is also a major project.

For my home, the chief problem is that I need thermal mass in different locations in summer and winter. In winter, I *might* have enough direct solar gain through my south windows to heat a good size solar mass (my neighbors block some of the sun, and I haven't done the math to see if what remains is sufficient given size, insulation, etc.). But in the summer I need that thermal mass in a different location where night cross breezes and my fan can effectively cool it--because of the design of my house, the summer and winter locations can't be the same (I can keep the mass in the winter location from overheating in the summer by shading the windows, but because I can't adequately cool it off at night it will still be a drag on the whole system). So, I'm considering a mobile mass solution. Don't have specifics in mind yet, maybe drainable water benches, maybe a water bench on coasters?

Basically, my plan in order of perceived return on investment is:

1. Plant some deciduous trees to help control summer solar gain (already ordered... tasty cherries and european plums).
2. Bubble wrap on north-facing windows in winter (small return, but on a very small investment...supposedly improves the R-value of windows by 1 or 2, but costs pennies).
3. Install a high-efficiency wood-burning insert with catalytic converter in my existing (and unused) "gas show fireplace." Firewood is relatively cheap in Colorado, and it has the added (and critical) benefit of providing me guaranteed heating in winter--right now if I lose either electricity or gas at the wrong time I'm screwed...
4. Install a solar hot water system.

My existing forced-air AC/Heater has a "fan only" mode that allows me to essentially recirculate air from the top of my house through the basement, which is uninsulated concrete block, so acts as a sort of geothermal heat exchanger (probably pretty poor efficiency, but...). I may try to increase the effectiveness of this system, and may try to implement something along the lines of Jim's system where heat from thet hot water system is integrated into the forced air heating...

Ken Neal said...

Hi! Jeff

Can you sink a long pipe, 4 or 6 inch diameter, in your garden about 5ft down and 30ft long open to the air at one end and through the basement wall at the other. If you draw your ventilation air through this it will warm the air in winter and cool it in the summer. In the UK the ground temperature is about 50 to 55 F throughout the year at that depth. I don't know what it would be where you are.

Dave said...

Hi Jeff,
Came accross your blog while doing some surfing re solar space heating. I too am a denizen of suburbia and have been recently thinking about how to reduce the size of my footprint. Here in the NE we don't get as many sunny days in the coldest months but I feel a properly designed system can significantly decrease my carbon burden. With respect to thermal mass I think the key maybe to think a bit outside the box(ie building envelope)in terms of materials and placement.Many years ago I read an article about a solar engineer by the name of Norman Saunders. He designed a rather conventional suburban-looking house(New England saltbox style)in Shrewsbury Mass that obtained all space heat from solar gain. Despite the fact that the house was purpose-designed(very tight with a unique all roof collection system)I feel that his solution is worth looking into. He used a massive insulated rock bin under the house(upwards of 40 tons as I recall)and moved the heat around by forced air-calling on the stored heat in the rock bin during times of no solar gain-which can be upwards of 7 days in a row here in the winter months! Now, obviously we can't go digging out our basements but I have been considering the idea of using the same concept to store heat under a new sun room addition I am considering. I have enough basement now so the entire area under the addition could be converted to thermal mass storage. Saunders was noted for his use of simple, reasonable cost materials and techniques and this may translate into a way to retrofit my little cookie-cutter dwelling.

Jay Draiman said...









Jay Draiman, Energy Consultant
Northridge, CA. 91325
Mar. 21, 2007









"The goverment should serve as an example to its citizens"

Jay Draiman, Energy Consultant
Northridge, CA 91325
Email: renewableenergy2@msn.com

JCamasto said...

Best of luck leveraging all those "shoulds", Jay.

Seth Wagoner said...

Re: photovoltaics, I'm really hoping Nanosolar can deliver on their hype/buzz...

Gryphon said...

"...the attic in my house only covers 1/3 of the home, as the rest has vaulted ceilings. "

Jeff, you could easily build a drop ceiling in each of these vaulted rooms that could then be heavily insulated.

"...suburban homes are generally built with very low thermal mass.."

Rather than increase mass, increase heat gain. Build a sunroom or solarium on the southside of your house, then open and close your existing southside winows to control the amount of heat you let into the living space. Similar to the set-up here: http://en.wikipedia.org/wiki/Image:Illust_passive_solar_d2_319pxW.gif but without the massive trombe wall.

I've been thinking of how "standard" suburban houses with all their flaws can be retrofitted for years. Some solutions are obviously cheaper than others.

~ Gryphon

JCamasto said...

Precisely my plan, Gryphon. And when the siding needs to go, stud-out and insulate, wrap, windows, and seal/rerun/insulate all hvac/pluming running up my exterior walls.

Maybe add vestibules/air-locks around the doors, inside or out... If the house is really tight, a heat recovery ventilator.


Jeff Vail said...


All good points. In my particular case (as in much of suburbia), the south side of my house is exactly at the set-back line from my property line, so no structure can go there, plus south sun is blocked by my neighbor's house, which is equally close to the line. Fortunately, I have copious amounts of gain on the West side of my house--my priority there is to build seasonal shade, and one of the fruit trees that I just planted should go a long way in that regard. As for the drop-ceiling, I have angled windows that go right to the vaulted ceiling, so that isn't really an option for me without major redesign. I'm going to look into some kind of high R-value foam that can perhaps be sprayed into the narrow space that does exist between the drywall and the sub-roof? Who knows...

Susana said...

Gain Independence from your Utility Company.
Imagine your electric bill being as low as your cable bill. You could also be eligible for generous government rebates when you decide to convert to solar. When your system generates more electricity than you’re consuming, your utility meter will actually spin backwards. You accrue credit with your utility company at the same rate they are charging you. This allows you to reduce your electric bill and drive it toward zero. By using solar power, you can also reduce the amount of electricity you have to buy. Once the equipment has been installed, the electricity generated is free! In addition, PV panels typically have a long life and with no moving parts, they require minimal maintenance. See Link below for some awesome solar energy products! Save yourself money and the environment!
Sunlight Can Make Your Meter Spin Backwards. Sunlight is a renewable energy source and the conversion of sunlight into electricity via photovoltaic (PV) panels is an environmentally friendly process. It is one that is silent and produces no greenhouse gas emissions or other polluting by-products. You are actually helping the environment! Generating electricity from solar energy reduces your consumption of fossil fuels, which decreases pollution and greenhouse gas emission. By switching to solar power, you will combat global warming and reduce our nation’s dependence of foreign energy sources. Even a small solar electric system has a significant environmental impact. Did you ever leave a hose spread out on your ground in the summer and then hours later squirted it only to find out that the water is very hot? This is the same concept of how solar energy works. GO NATURAL!

Anonymous said...

I think what you may want is a LOW thermal mass sunspace (isolated gain) that is outside the insulated area of the house which will then overheat VERY quickly and then you have a thermostat run fan which blows the hot air in. And in the summer, you don't use it.

Google for "Norman Saunders" solar
to learn more. His houses are 100% solar in freezing cold new england.


Jay Draiman said...


That would be the best marketing approach I can think off.
This will instill confidence in the public to purchase the product.

Jay Draiman, Energy Analyst


fdg said...


fdg said...

Some new style Puma Speed is in fashion this year.


.thank you .


polo shirts

ralph lauren polo shirts
chaussure puma

chaussure sport

chaussures puma

puma CAT

ed hardy clothing

ed hardy clothes

ed hardy womens

ed hardy sunglasses

Gabriella Bannister said...

That would be cool if everyone can buy solar-water system. You are fortunate for the reason that you are saving a lot of money because of that.