Energy generation. Primarily solar, wind and other clean energy

Can you (legally) unplug from the electric utility?





In California:





We’d love to hear your stories in your location or jurisdiction.



Free Money for Schools

Did your school miss out on the Prop 39 gravy train? Here’s the next best thing. 3fficient has secured access to federally backed, ZERO interest loans for energy saving upgrades engineered and implemented by 3fficient. Each district is eligible for a cap of $3 million dollars for energy projects. Here’s the catch:

  1. Applications must be submitted by May 31, 2019. Late or incomplete applications will not be considered.
  2. Half of the ranking is based on % of students on free and reduced meals. The higher the better. That’s where you shine!
  3. The other half of the ranking is based on total energy savings as provided by a professional energy audit* originated or peer reviewed by 3fficient. The higher the cost savings, the better. That’s where we shine!

*An energy audit requires review and compilation of utility meter data, engineering site visits to verify existing conditions and then professional calculations to accurately calculate energy and cost savings.

Eligible energy upgrades are as follows:

  • Interior and exterior lighting systems.
  • Energy management systems and equipment controls.
  • Pumps and motors.
  • Building envelope and insulation.
  • Energy generation including renewable energy (e.g., photovoltaic systems (PV)), ground-source heat pumps, and combined heat and power projects (co-generation) with renewable fuel.
  • Load shifting projects, such as thermal energy storage or batteries.

This is a great opportunity for schools to upgrade their district risk free. At 3fficient, we specialize in engineering energy efficiency projects that are specific to winning such competitive loans through our SmartZero Program. By crafting a project for highly qualified school’s we can help apply, win and implement the renovations and upgrades your school buildings need at zero cost and zero risk to the district with potential for zero net energy.

Application deadline is May 31st, 2019. So don’t delay? Let us do the heavy lifting! We’ll conduct the audit, complete the paperwork, and work diligently to ensure you are implementing quality solutions that will help make your district more efficient, resilient, and competitive amongst its peers. All paid from savings.

Are micro grids the answer to climate change?

Wildfires in California are tragic and incredibly expensive.  Many lives lost.  Property and homes lost.  Livelihoods lost.  Sensitive habitat and wildlife lost. At well over $9 Billion, damages from the 2018 wildfires in Northern California were financially devastating. The cause for many, as it turns out, traces directly to the largest utility in the country, PG&E.  Lawsuits held PG&E fully liable which then caused an almost immediate bankruptcy filing to avoid billions in payouts, more than the company was worth.  As in 2001, the utility may come back even stronger and more profitable for shareholders.  As utility solar prices have plummeted, the bankruptcy will allow PG&E to renegotiate their (now) overpriced early stage large solar supply contracts.  Certainly a prudent financial move for PG&E to take advantage of.

Meanwhile, towns like Paradise, CA were literally wiped off the map from fast moving wildfires sparked by PG&E’s power lines running through densely wooded communities.  Will those livelihoods come back stronger?  Doubtful.  As most disasters go, many will simply leave as they have no jobs or income to return to.  Others will rebuild with insurance funds.  But, is that even a good idea?

Environmental, weather and fire experts are quick to point out that forest fires will continue to increase in frequency and ferocity as climate change continues to warm the planet and dry out many of earth’s forests.  So what can be done to avoid future calamity? There are 3 obvious choices:

  1. Build fire resistant homes and buildings.  When you light a match and hold on long enough, you will certainly get burned since the match stick is flammable.  So how can we not expect a wood frame home to burn down from a nearby forest fire.  Most of the trees are left standing after a fast moving fire since the wood is wet and protected by bark.  Meanwhile, nearby dry wood structures almost always burn to the ground.  In reality, wood stick construction really has no business in any alpine forest.  The easy solution lies with the Counties to only permit fire resistant construction in forests.  Insurance companies will likely catch on and assign more equitable risk (and cost) to fire prone properties as well.  While that may sting (a lot) for homeowners who want to rebuild, it’s more equitable for all as having ANY grid lines running through the forest is likely to cause future fires.
  2. Hold counties accountable for lax enforcement of fire protection codes around buildings.  The results from the fires going through Paradise and other towns seem to illustrate lax code enforcement.
  3. Require utilities to reroute transmission lines around forests and new buildings or communities in forests to be off grid with 100% self generation.  Until transmission lines are removed from forests, it is simply a matter of time before the next horrific and incredibly expensive fire will happen.  For the $9 billion price tag, there would be an army of developers lining up to build off grid communities for Paradise and many other towns.  Policy makers and insurance companies should come together to assign risk to the grid, instead of looking for a bailout that so often happens.

In the likely event that status quo utility power is restored and towns like Paradise are rebuilt like before, who will be responsible for the next destructive fire?  The utility for providing power or the county for allowing it or the residents for using (and paying for) that electricity?  In brutally honest terms, the drug pusher, the cop who looked the other way or the addict?

Is the risk worth the reward?  When nuclear power or any generation source is developed, the development is never 100% risk free.  When parents let their kids drive a car, they always know there is risk – and accept that.  So, why do we mandate near 100% reliability for electrical power?  In the future, utilities will be compelled to shut off power at the distribution level during high risk wind events.  Larger transmission lines will likely stay energized.  Will that eliminate all the risk?  Not at all.  The Camp Fire that roared through Paradise was caused by a transmission line (not local distribution lines). With that in mind, perhaps the electric grid could be de-risked by allowing even lower reliability or accessibility?  Transmission lines get shut off during wind events, or power lines are removed entirely from alpine forests.  That would certainly make way for more reliance on standalone distributed energy like many in Joshua Tree, CA or smart micro grids in larger communities like Borrego Springs after the Southern California wildfires of 2007?

With massive and deadly wildfires becoming an annual event in California, will PG&E simply cut down a bunch of trees and reinstall utility poles like before, or will the local governments demand better energy architecture going forward?  As of the writing of this post, the former seems to be playing out.  PG&E crews are (understandably) busily restoring power so homeowners and business owners have electricity to rebuild with and move on.  I believe a potentially faster and more resilient solution would be for builders to be required to build off grid homes or building-integrated microgrids while requisitioning developers to build community-scale microgrids that backup or augment distributed rooftop solar and wind on the buildings and carports.  This would simply be accelerating upcoming building codes in California.  Smart energy storage would be included in all new, energy efficient homes and buildings just like an appliance is today.  That energy storage could then be interconnected as the key component of a resilient community micro-grid.  Imagine that.  A town without unsightly and dangerous power lines that has long lasting, clean, self sufficient and resilient power!  What a simple and SAFE concept.

Author’s note:  When I introduced this concept just ten years ago it was commented as heresy in online blogs.  Today, probably “meh” or “wow, why aren’t we doing that?”

Tax Depreciation

The printed IRS tax manual is literally more than 73,000 pages.  IRS agents and their teams can’t even keep up with tax changes let alone the volumes of code.  That’s why CPAs are more like general practitioners and need to rely on specialists to help maximize savings.

One such opportunity for maximizing savings is with depreciation for your buildings.  When purchasing, refinancing or remodeling a building, your depreciation schedule is affected – or should be.  Even though buildings have a typical 39 year depreciation basis, all the materials, wiring, insulation, fans lights and other components affixed to the structure need not have that looooong basis.  As you can imagine, there are a lot of materials in a building that can (and should) have a much shorter depreciation period. Segregating or quantifying and adjusting those costs can result in substantial and immediate tax savings.

How much is this worth?
Say you remodeled or refinanced your half million dollar building 5 years ago, you might be eligible for a refund of $30k – $40k right now!  Let’s say your building’s book value was $10M, you might expect to save $600k – $800k.  Would that pay off debt?  Fuel your next expansion?  Buy a competitor?  Kick start your retirment?

Is that it?
For many of our customers, we find 5x those amounts by combining other tax and utility savings!  What if your profit margins went up 30% or 50% or doubled, sustainably?  Would it change the valuation of your company?  For most, that helps vault them to “top dog” status.

What if I delay?
Unfortunately, the ability to reclassify costs from past renovations will end with the 2018 tax year.  While this method will not go way anytime soon, the ability to reach back in time will.  So, if you remodeled or even had a small upgrade in the past, you must act now BEFORE filing your 2018 returns.  Miss that window and you’ll throw away thousands in potential savings.

What if I do nothing?
If you get an email and don’t read it now or don’t reply right away, what are the chances you ever will?  In the competitive business world, delaying and doing nothing are the same thing.  Competitors are always looking for advantages to eliminate competition.  This happens every day.  One competitor quietly grows profits while others who don’t simply fade away into the sunset, never to be heard of again.

So don’t seal up the entrance to your “gold mine”.  Let our engineering and construction experts find your hidden tax savings.  For a free, no cost assessment that could change your business dramatically,

Click here to see if you qualify.

Section 179D

Do you own or plan to build or remodel 50,000 or more square feet of real estate? Are you looking for additional tax deductions? If so, you could likely benefit from energy efficiency deductions available under IRS Section 179D. Here are some common questions about the deduction.

What is the 179D energy efficiency deduction?
In an effort to reduce the energy consumption by buildings within the United States, Congress passed legislation allowing for a tax deduction for building owners who have either increased their building’s energy efficiency or have constructed energy efficient facilities. This provision is commonly referred to as 179D.

How much is the deduction worth? 
The maximum deduction allowable under 179D is $1.80 per square foot of building space. As an example, a 100,000 square foot building may qualify for up to a $180,000 deduction under 179D. The deduction is most beneficial for projects of 50,000 square feet or more.

Who is eligible to receive the deduction? 
For privately owned buildings, the building owner is generally eligible for the deduction.

For government-owned property, the governmental entity may assign the deduction to a qualifying party, typically the architect, contractor, engineer or consultant with significant involvement in the design or construction of the property. The assignment of the deduction is made on a first-come, first-serve basis.

Which buildings qualify? 
Commercial and residential buildings taller than three stories that are located in the U.S. and placed in service after Dec. 31, 2005, and prior to Dec. 31, 2017, potentially qualify.  The deduction is taken the year the building was placed into service.

How is the deduction obtained? 
To claim the 179D deduction, energy savings must be certified by an unrelated “qualified individual” who is a contractor or engineer licensed in the same jurisdiction as the building. A site visit of the property is generally required, followed by energy modeling using engineering software approved by the IRS.

Click here to see if you qualify.

Grid (un)reliability








For a free assessment of your buildings, Click here


Solar Lease vs PPA

What’s the difference between a solar lease and a solar PPA?

In short.  Not much.  These days it’s mostly just the name, but here’s the skinny.

Solar PPA:

In a Power purchase agreement, you are agreeing to buy the power – whether you need it or not.  A third party is financing and building the power plant on your site with the deserved expectation that you will buy the commodity it produces so they can pay off the investment and make a profit.  This is basically what electric utilities have been doing for over a hundred years.

  • Solar PPA stands for solar “Power Purchase Agreement.”
  • PPA gives you a low up front cost.
  • You’re locked in for 10, 15 or perhaps 20 years to this agreement, which is transferable to a new owner.
  • They charge you a set electrical rate that is sometimes flat, and sometimes calculated to rise over the term of your agreement. So instead of paying for coal or gas fired electricity rates, you’re paying for PPA rates generated through your “local” solar panels.
  • The PPA company takes care of the maintenance and any needed repairs and monitors your system.
  • You don’t get any tax benefits or State rebates or Renewable Energy Credits (RECs).
  • You usually have some kind of option to buy later or at the end of the agreement for a set price per watt. Sometimes this is negotiable (and you should at least try since used solar panels aren’t worth much.)
  • You need to have an excellent credit rating to qualify.
  • You’re tied to the grid, so any residual electricity needs that your solar panels don’t produce is covered by your utility.

Solar Lease:

In a lease, you are leasing equipment.  A third party is financing and building the equipment (e.g. solar power plant) on your site with the deserved expectation that you will pay off the hardware over time.  When the lease is paid off you can usually “turn it back in”, buy it out at a predetermined residual value, or extend the lease term.

  • There is usually no down payment, so $0 down.
  • You’re locked into 15 years or more years, which is transferable to a new owner or home.
  • In a solar lease, vs. PPA, you do NOT pay for any power that your solar panels generate.
  • Instead, you pay a lease payment plus any extra power you need to buy from your electric company. So, solar panel power is technically free, but you have a set lease payment that rises 3 to 4% a year. That’s typically less than the 5% rate increases by your electric company. Some programs have a flat rate, so no yearly increases.  You usually have flexibility on the payment model.
  • Like a PPA, they usually take care of maintenance and repairs and monitor your system, but that’s not always the case.
  • Similarly, you don’t get tax benefits or rebates or Renewable Energy Credits (RECs).
  • Like PPA’s, you have an option to buy later or at the end of your term for a set residual price. You should try to negotiate the Fair Market Value (FMV) at the end of the lease, as used panels aren’t worth much more than the cost of taking them off your roof.
  • You need to have a good to excellent credit rating also, depending on the program.
  • Also like a PPA, you’re tied to the grid, so any residual electricity needs are covered by your utility.

So, bottom line for a solar lease vs. PPA:

  • PPA, you pay for power generated by solar panels with some money down and flat or yearly increases on your PPA electric rate. You also benefit from tiered rates.
  • Lease, you have no money down (typically) and pay a flat leasing fee that rises every year by a certain percent, plus left over utility bill. You also benefit from tiered rates.

While both these options are good for low cost financing, there’s not a huge difference when it comes to a solar Lease vs. PPA. If it saves you money and you like what you see, go for it.

Now 3fficient is offering a new option.  It’s called an energy services agreement (ESA).  This new financial model is similar to a PPA or Lease, but instead of just solar, you can get various efficiency upgrades too.  Basically, by agreeing to host our smart microgrid on site and buying power at a lower cost than the utility, you’ll also get a myriad of building and process upgrades included.   Like a PPA, you will not own the energy equipment so it will not impact your credit rating or borrowing power.  You’ll be free to use your credit for important purposes like say, growing your business.  You’ll get resilient, clean energy that will “keep the lights on” even when the grid is down.

Either way, you have nothing to lose by getting a quote from and comparing the financial pros and cons. Upon request, we’ll even give you both options, so you can compare an energy services agreement with outright purchasing.

How to Make Your Multi Tenant Buildings More Valuable

Most apartment complex owners are very limited in what they can do to stay competitive with newer properties. Lower rents, remodel or tear down and replace?  But, what if there was a better option?  An option that actually reduced the tenant’s monthly expenses while increasing rental revenues AND property values for the owner?

Well now there is.  3fficient’s Smart Zero program is now available for multi-family building owners, like apartment communities.  This comprehensive green building program provides the capital and turnkey EPC contracting for efficient holistic modernizations coupled with on-site renewable energy generation and storage.  Owners get smart energy upgrades and substantially improved property values while tenants get more comfortable and modern spaces with really low utility bills.  A true win-win!

Here’s how it works:

Step 1.  Analyze

  • Property Owner completes the Quicklook survey to see if they qualify for this unique upgrade program.
  • 3fficient Customer specialist will contact the Owner to confirm their online application and compile some additional property details, e.g. number of apartments and SF for each (typically size per floor plan and qty of each).
  • 3fficient will provide a preliminary energy assessment of indicative savings and property value impacts.

Step 2. Engineer

  • Upon engagement, 3fficient will provide engineering and a detailed, bankable engineering estimate of costs and savings.
  • Owner can use that to decide on desired rent adjustments in advance – based on projected savings per metered dwelling unit.

Step 3.  Integrate

  • Upon funding approval, 3fficient will procure necessary permits and materials, then manage implementation and commissioning of desired upgrades.

Step 4.  Enjoy

  • Tenants will enjoy lower monthly expenses and tell their friends how sustainable and great their community is.
  • Owner will enjoy the many low and zero carbon accolades, the increased rental demand, the increased revenues, profits and property values that effectively cost the owner nothing.

Energy Efficiency Upgrades Get Even Sweeter

On December 15, 2017, the unified version of the Tax Cuts and Jobs Act was put into law. Among other goals, the Tax Cuts and Jobs Act was designed to simplify tax codes, reduce the tax on wages and lower tax on business income. Section 179 of the new IRS tax code allows businesses to deduct the full purchase price of qualifying equipment from gross income.

What Is Section 179?
Section 179 of the Tax Cuts and Jobs Act of 2017 allows for qualifying products to be expensed immediately, including “heating, ventilation and air-conditioning.” This means that a system can be expensed in its first year rather than depreciated over a 39-year period.  As a proponent of Section 179, 3fficient is ready to help building owners better benefit from the opportunities this bill creates.

What Equipment Qualifies?
Virtually every solution we offer qualifies.  3fficient can help you explore options for updating, upgrading and retrofitting your building’s systems that result in immediate and often long term tax benefits. So, if you are contemplating or have already upgraded any of the following systems, contact us right away:

  • HVAC Equipment
  • Roofing Upgrades
  • Skylights and Daylighting
  • Window improvements
  • Connected Lighting
  • Building Controls and Automation Systems
  • Security and Access Control

Businesses that purchase, finance or lease less than $2.5 million in the above business equipment during the 2018 tax year typically qualify for deductions through Section 179. Since the deduction begins to phase out if more than $2.5 million of equipment is purchased, it is most useful for small- to medium-size businesses. The markets that 3fficient specializes in!

Act Now!
Section 179 can change each year without notice (Section 179 has even changed mid-year), so it benefits you to take advantage of this generous tax code while it’s available.  Take advantage now before congress changes their mind.

How to Apply
Contact 3fficient for a free green building assessment to see if you qualify to take advantage of these hidden gems.  Our experts can help with strategies to properly segregate costs and maximize tax savings for these qualifying improvements.

To learn more about how 3fficient can help, contact us.

Great Parks Need Great Public Safety

Urban planners and architects go to great effort and expense to design fun and interesting parks.  But is your urban park safe and secure for visitors?  Pretty easy to find tragic headlines that say no.  But how do you really know for sure?  Cameras, sensors, other smart tech?  Nice to have, but without electricity, that’s been pretty much impossible.  Until now!

Check out these cool new self-powered devices that are sure to bring attractive design, modern features and public safety to any park or urban space.  In fact, they double as cost effective furniture, community art and smart tech all in one.  A virtual 3-for-1.

Civic planners, architects, landscapers and public safety officers take notice.  You now have some great new tools to activate and energize your parks and open spaces.  Learn more.

Urban Wind Making a Comeback?










GAO: Climate change now costing U.S. billions

Webster’s defines addiction as, “compulsive need for and use of a habit-forming substance”.  “Persistent compulsive use of a substance known by the user to be harmful“.  Americans, strike that, Humans are easily addicted.  We know deep down that our addiction is very costly. Yet we keep at it.  Often hoping someone else will deal with our problem and just make it go away.  But, the problem is, it usually doesn’t.  In fact, it typically gets worse.  Much worse.  According to, it starts with denial, then anger, bargaining, depression and acceptance.

In the United States and much of the developed world, we have many addictions, but one that is now showing great harm to all of humanity is our addiction to fossil fuels.  While nearly every climate scientist in the world and most natural scientists are in firm agreement, it really doesn’t take a science degree to observe what is happening over time and deduce the root cause.  Our natural world is drastically changing before our eyes.  As a species on top of the food chain, we are in clear denial.  Most business and regulatory decisions are still being made on short term economic impacts without regard to long term economics and jobs or for that matter, resources.

With the Trump administration in firm denial of our fossil folly, the implications of our addictions are swelling rapidly.  Unfortunately, Mother Nature is doing her thing and seems to be ignoring social media.  Disasters from man made global warming are continuing to worsen and become more frequent.  But finally, the major re-insurers and even the GAO are assigning economic impacts to these disasters and THAT will change business decisions in capital markets. No doubt the addicts will try to squelch the scientists and doctors trying to fix the addiction (to fossil fuels), but in the end we all have to own up to our own addictions and take actions.

We can cost effectively make our buildings incredibly efficient and smarter, especially the existing ones.  We can choose renewable energy on our buildings.  We can adding storage to eliminate “the middle man” (utilities).  We can choose to buy electric vehicles and easily charge them at home, work or on the go like we do our cell phones. Above all, we MUST defend our right to choose to end the fossil folly that is driving our planet to extinction like the dinosaurs.  In the end, actions speak louder than words.  Do more with less!  Be 3fficient.

Managing Energy Costs in Grocery Stores

[vc_row][vc_column][vc_column_text css=”.vc_custom_1507823430100{margin-bottom: 0px !important;}”]Energy costs can account for up to 15 percent of a grocery store’s operating budget.  The US average was roughly $4/SF in 2015.  For example, a 40,000 square foot store might spend $160,000 a year just for electricity.  Because grocery stores’ profit margins are so thin—on the order of 1 percent—every dollar in energy savings is equivalent to increasing sales by around $59.  In this example, let’s say energy costs are cut 20%, that would equal $32,000 in savings the first year.  That’s equivalent to ($32,000/.01) $3.2M in sales.  Kind of a BIG deal!

Grocery stores in the US use an average of 52.5 kilowatt-hours (kWh) of electricity and 38,000 Btu of natural gas per square foot annually. In a typical grocery, refrigeration and lighting represent about 65 percent of total use (Figure 1), making these systems the best targets for energy savings.[/vc_column_text][vc_row_inner][vc_column_inner width=”1/2″][vc_column_text css=”.vc_custom_1507823360409{margin-bottom: 0px !important;}”][/vc_column_text][/vc_column_inner][vc_column_inner width=”1/2″][vc_column_text css=”.vc_custom_1507823336638{margin-bottom: 0px !important;}”][/vc_column_text][/vc_column_inner][/vc_row_inner][vc_column_text css=”.vc_custom_1507912524423{margin-bottom: 0px !important;}”]

Figure 1: Energy consumption by end use
In grocery stores, refrigeration and lighting are the bulk end uses for electricity; space heating and cooking dominate natural gas use, albeit a much smaller pie than electricity.


You’ll be better able to manage your store’s energy costs if you understand how you’re charged for energy. Most utilities charge commercial buildings for their natural gas based on the amount of energy (therms) delivered. Electricity, on the other hand, can be charged based on two measures—consumption (kWh) and demand (kW). The consumption component of the bill is based on how much electricity, in kWh, the building consumes during a month. The demand component is the peak demand, in kilowatts (kW), occurring within the month or, for some utilities, during the previous 12 months. Monthly demand charges can range from a few dollars per kW to upwards of $20/kW. Peak demand can be a considerable percentage of your bill, so care should be taken to reduce it whenever possible. As you read these energy cost management recommendations, keep in mind how each one will affect both your consumption and your demand.

Here are some fixes you can do:

Read more

How to plug those (energy) holes in your building

Taking an infrared thermograph of an air conditioned building in the daytime, can be quite alarming. Infrared thermography is the same technology in night vision goggles used by military special forces. It reveals the infrared light spectrum or “heat signature” of objects. On buildings, it reveals variations in heat flow.  The more heat flow the brighter the image.  Windows and skylights, being the least insulated are usually the biggest culprits of energy waste.  For the last 100+ years, heating and air conditioning systems have compensated or covered up the wasted energy flowing through windows and skylights.  But with high energy costs and power plant pollution, that veil is starting to be removed.

Over the last 30 years of my career, I’ve assessed energy efficiency at hundreds of buildings – schools, offices, hospitals, industrials, you name it.  The one thing they all have in common – “energy holes”.   Heat pouring into or out of “closed” windows and skylights.  That heat flow, seen through infrared thermography, translates to wasted energy and unnecessarily BIG electric bills for cooling and increased gas bills for heating.   It also means wasted capital on oversized air conditioning units.  With energy costs the first or second largest expense in most every organization’s budget, why is this still so?  Here’s the typical answers:

  1. “My windows are too expensive to replace.”
  2. “Window tint darkens the room so I’m forced to turn the lights on during the day.”
  3. “Adding tint makes my “window” a mirror at night – I can’t see out but everyone else can see in.”

Before responding, let’s first take stock in what a window is supposed to do:

  1. Let visible light through, so “free” natural light can come in and people can see outside.
  2. Insulate the building, i.e. block heat flow in or out.
  3. Block outside noise.
  4. Block UV rays to protect your carpet, furnishings and skin.
  5. Minimize glare from direct sunlight.

So, again, why are windows not more efficient?

New buildings are usually designed to meet minimum code requirements to keeps costs down.  So, “expensive” products like triple pane, low-emissivity, gas filled windows are rarely considered.  And until construction techniques change dramatically, window replacement will remain costly due to the time and labor required to replace them.  As a result, the energy savings payback for window replacements is usually way too long compared to other options or priorities.

Fortunately, repairs and upgrades of existing windows is very cost effective.  Air infiltration and to a lesser extent noise infiltration can be reduced with simple caulking and weatherstripping repairs.  But, if your window frame is in poor shape or your building is next to a noisy airport or street,  heavy shutters, blinds, double or triple pane windows may be your only option.  When it comes to the main part of the fenestration, the glass or plastic (in the case of skylights), recent material breakthroughs in nanotechnology are revealing some very promising results to reduce solar heat gains.

Before explaining, it’s helpful to understand some physics.

The first law of thermodynamics states, “energy is neither created nor destroyed, it simply changes form”, e.g. heat, light, sound.  In simple terms, the sun is a hot ball that radiates energy (in the form of light) to the earth which then heats up the earth.  After being filtered through the atmosphere, sunlight reaches the earth’s surface as ultraviolet light, visible light and infrared light.  See image below.  Ultraviolet (UV) light is invisible but we see the damaging effects in faded carpets and furnishings or worse – skin cancer.  Visible light (daylight) is the rainbow of colors we see with our eyes.  Infrared light is the intense heat we feel when directly exposed to the sun, e.g. when we come out of the shade or a cloud suddenly moves away.

When it comes to windows, the goal is to block all the UV light, let most or all of the visible light through and block or selectively control the infrared light.  Here’s why.

When the sun’s light hits a window, some is reflected off and some is absorbed by the glass (which can then be directed into, or away from, the interior space) and some passes directly through.  For plastic windows and skylights, much of the UV is blocked, little is absorbed by the material, but most of the infrared light passes right through into the space as heat.

Heat is transferred in three ways: conduction, convection and radiation:

  • Conduction is heat transferred between two objects when they touch – such as when you touch a hot skillet or a warm window.
  • Convection is the flow of a fluid like warm or hot air rising as it is heated up, e.g. when you lean down and open the door of a hot oven and feel the rush of hot air hit your face or sit next to a hot window and feel the heat. Likewise, a large window or door can feel “drafty” as air rises up even though it’s not “leaking from outside.  So, take this into consideration if this is causing you to consider replacement windows.
  • Radiation is light energy heating up an object.  For example, when you step into the sunlight you can feel the sun’s radiant energy on your skin as your skin cells absorb the sun’s radiance.

For cooler climates (i.e. far northern or far southern hemisphere), it is ideal to allow the infrared heat in during the winter, but block as much as possible the rest of the year to reduce cooling loads.   For warmer climates, where most buildings are located, cooling costs usually dominate, so reducing solar heat gain usually dominates decision making.  But, maximizing natural light (without glare) is almost always desired.

So, how do we better manage or reduce solar heat gain?

Overhangs, awnings, light shelves and best of all, deciduous shade trees can help let in the winter sun and block the summer sun.  Unfortunately, they aren’t always practical and were not considered in the vast majority of buildings in existence today.  Clerestories are usually better than traditional skylights, but they are significantly more expensive and rarely used as well.  Then, there are interior window treatments and window coatings.  Interior treatments like shade screens and blinds can help stop the heat, but isn’t the whole purpose of a window to be able to see through it or let the natural light in?  That leaves coatings and tints.

Aftermarket coatings.

  • If your goal is to block out the visible light, then any dark tint will do.
  • If your goal is to block out the light and the heat, then a broad spectrum dark tint will help.  But even that is limited.  Dark curtains, shades or even plywood will actually work better.
  • However, If your goal is to block out just the UV light and the most or all of the infrared heat while letting the VISIBLE light come through, then new nano technologies, are your best bet.

A couple notable options:

Traditional glue-on window films.  Eastman V-Kool 70, Enerlogic 70 and Hi-Lite 70 are high quality plastic films that preform very well. They each block 99% of UV rays and up to 94% of infrared heat while only allowing about 60% of visible light in.  Unfortunately, blocking 30-40% of light still means the interior lights will need to be turned on to compensate.  The materials are relatively expensive and worse yet, they all tend to crack, chip or peel over time.  If applied poorly they will bubble.

Now the game changer…

Liquid window insulation is a spectrally selective paint-on, high performance nanotechnology coating. Nano coatings are a breakthrough because the particles are so small they are invisible to the human eye while adding the desired properties to the coating.  With the small size, the molecules won’t change the optics of the visible light, but are arranged to selectively block out other desired wavelengths.  Due to its application method, it is virtually impossible for liquid nano-tech coatings to bubble, chip, crack or peel.

Available “tints” are 4%, 10% and 16% opacities.  The 4% version is virtually invisible and so clear that it can legally be used on automotive windshields*.  The 16% version has better thermal properties and a slight visible tint to help reduce glare.  The new 10% opacity is a popular “blend of the two which helps cut glare a bit, although not as much as traditional plastic window films. Like the expensive films above, liquid window insulation can block 99% of UV radiation.  But unlike the (now) old tech, liquid window insulation allows 84% – 96% of visible light in while blocking 85% – 97% of infrared heat.  The more opaque, the more infrared heat is blocked.

Liquid window insulation has outstanding performance for most applications.  Perhaps the most important metric for window films in modern “green” building design is the light to solar heat gain ratio (LSG), the LSG ratio provides a gauge of the relative efficiency of different glazing systems in transmitting daylight while blocking solar heat gains.  The higher the ratio, the brighter the room is without adding excessive amounts of heat.

The following chart is a compilation of (lab and NFRC) spectrometer test data. For a spectrally selective solar control film or coating, the LSG ratio will typically be higher than 1.2, while for other films, the LSG ratio will be smaller than 1.0.  The LSG ratio for liquid window insulation is superior to other high end films.

How to read the chart above:

  • Tint.  The opacity or percentage of natural (visible) daylight being blocked.  The lower the percentage the better, unless your goal is to darken the space. Keep in mind, dark plastic films tend to be reflective at night, blocking the view out at night.
  • Visible light Transmission is directly related to tint.  The higher the percentage the better.
  • UV rejection is the % of damaging UltraViolet rays being blocked.  The higher the percentage the better.
  • IR rejection is the % of infrared heat from the sun being blocked.  For warmer climates that need cooling, the higher the percentage better.
  • SHGC is the % of solar heat entering the space. For warmer climates that need cooling, the lower the percentage better.
  • LSG is the ratio of Visible Light Transmission over Solar Heat Gain (VT/SHGC) which measure overall efficiency of a window or skylight coating.  The higher the percentage the better.

The Solar Heat Gain Coefficient (solar efficiency) of new (dual pane low-e) assemblies ranges from 0.41 – 0.60.  However, with daily thermal and UV aging, the soft rubber seals harden and decay, allowing the inert gas between the panes to leak out over time.  As a result, the thermal efficiency is dramatically reduced, leaving the SHGC higher (less efficient) than the even the single pane NanoTint coated alternative.

To take this analysis a step further, we made up our own field test boxes with the front face all glass and faced them directly into the sun.  The results below show the mostly transparent (16%) coating matching dark “limo” tint with solar incidence at 90 degrees, but as time passed and the sun angle became less direct, the nano coating far outperformed even the darkest of traditional tints.  Since the sun is rarely at a right angle to any glass surface, one would expect the liquid window insulation to lead the pack in cumulative energy savings and comfort, such as in a vehicle or next to a window.

I think one of the most compelling applications for liquid window insulation is on skylights.  Skylights are great at bringing in natural light deep inside a building, but the side effect is a lot of unwanted solar heat gain.  Most are plastic, curved and very difficult to apply plastic films to.  This is where liquid window insulation really shines (pun intended).  Getting traditional film on an overhead skylight is very challenging.  If it’s curved plastic, it’s almost impossible.  Liquid window insulation, on the other hand, just rolls on with a special paint roller.  For opaque skylights, it can even be sprayed on.  UV rays will be blocked out and direct infrared heat dramatically reduced.

With better durability, longevity and costs at or below cheaper dark films, the liquid window insulation is a far superior value in comfort, durability, aesthetics, thermal performance, first cost and lifecycle cost.  In terms of  window “upgrades” any of the above films are good, but the liquid window insulation seems to be a consistently better in all areas.

For a more information on installation, click here.


  1. LBNL Fenestration Heat Transfer Basics
  2. DOE Energy Performance Ratings for Windows, Doors and Skylights
  3. Nano particle coatings and applications in window film, DeMeyer

*Note.  Always confirm with local vehicle code and/or enforcement authorities to ensure code compliance.