Photo from Department of Energy.
Note: See the updated information about DOE’s Triple Pane program: 12/9/2011
I bet you just got used to hearing about double pane, Low-E glass, Argon filled windows. You know the ones. The ones labeled as ENERGY STAR? Now, there is a new babe in town getting a lot of attention from the Department of Energy. The R-5 window has all the right curves and significant energy savings compared to its distant cousin, the ENERGY STAR window. Yep, this R-5 is energy efficient beauty with triple panes of either high solar-gain, Low-E Glass, Argon/Krpton Gas or high solar-gain, Low-E Glass, Argon/Krpton Gas, depending on your area of the country. According to the DOE,
“Common ENERGY STAR windows only have an R-value of 3. Increasing the R-value from 3 to 5 reduces average heat loss through the windows by 40% and saves consumer money on energy bills.”
But why are the R-5 windows the darlings of the DOE?
“Windows in the U.S. account for 30% loss of building heating and cooling energy, representing an annual impact of 4.1 quadrillion Btu (quads) of primary energy. Windows have an even larger impact on peak energy demand and on occupant comfort.”
So are these babes for everyone? They are best suited for cold and mixed climate areas. So, why isn’t everyone jumping on the R-5 bandwagon? Cost versus energy efficiency. That energy type rope. (Isn’t that always the problem?)
Well, never fear; the DOE developed an affordable volume purchase program. How affordable? Prior to the development of the program, the DOE estimated a price premium of $4/ft² compared to today’s typical ENERGY STAR windows. To find out the volume pricing for specific types of windows in various climates, see here. To compare costs versus savings for highly insulated windows in different climates, see here.
What make the R-5 windows so special?
According to the Efficient Window Collaborative,
“Triple-Glazed** with High-Solar-Gain Low-E Glass, Argon/Krypton Gas
This figure illustrates the performance of a window with a very low heat loss rate (low U-factor). In this case there are three glazing layers and two Low-E coatings, 1/2″ argon gas or 1/4″ krypton gas fill between glazings, and low-conductance edge spacers. The middle glazing layer can be glass or plastic film. Some windows use four glazing layers (two glass layers and two suspended plastic films). With this window, both Low-E coatings are spectrally selective in order to minimize solar heat gain. This window is best suited for climates with both significant heating and cooling loads.
Triple-Glazed** with Low-Solar-Gain Low-E* Glass, Argon/Krypton Gas
This figure illustrates the performance of a window with a very low heat loss rate (low U-factor). In this case there are three glazing layers and two Low-E coatings, 1/2″ argon gas or 1/4″ krypton gas fill between glazings, and low-conductance edge spacers. The middle glazing layer can be glass or plastic film. Some windows use four glazing layers (two glass layers and two suspended plastic films). Both Low-E coatings in this product have high visible light transmittance. The use of three layers, however, reduces the beneficial solar heat gain. This product is suited for buildings located in very cold climates, although Double-Glazed with High Solar Gain Low-E should be considered if passive solar heat gain is desired.”
For more detailed information about different glazing area of windows, see here.
If you are like me, you probably still have questions. The DOE created an informational presentation about the program.
Residential Case Study
Sometimes it is hard to understand the cost savings without seeing an actual cost case study. The DOE cites various studies ranging from residential to commercial applications. The agency used the Wisdom Way Solar Village retrofit job as an example of residential cost savings associated with the installation of triple pane windows.
“One successful example is Wisdom Way Solar Village, a small residential development comprised of 10 duplexes in western Massachusetts. These homes were designed and built to showcase energy-efficient building performance at affordable price points. Duplexes of this project range in size from 2-bedroom units at 1,137ft² to 4-bedroom units totaling 1,773ft². Successful use of triple-pane high performance windows in concert with an improved overall building envelope allowed for the scale-down from a conventionally sized heating system to a 12,000 Btu natural gas unit. This heating unit reduction represented a $4,500 savings in the total cost of the system. Additionally, due to the superior insulating properties of the windows and overall envelope, occupants can expect to save over $1,000 annually on energy. Despite a $7,000 incremental cost for an enhanced building envelope—$3,500 of which was spent on window upgrades—achieving building performance that allows for a more compact heating system can offset much of this incremental cost and significantly reduce the payback period.”
Light Commercial Case Study
In addition, to the above case study, the DOE cites the 34,500 square foot Cambria Office Facility retrofit in Ebensburg, PA, as an example of energy cost savings to support the installation of R-5 windows:
“This facility incorporates highly insulating, triple glazed windows at an incremental cost of $15,000 compared to traditional double glazed windows. These windows permitted the complete elimination of the perimeter heating system priced at $25,000.The air conditioning system was also downsized from 120 to 60 tons, saving $40,000 of which 15 tons or $10,000 was directly attributable to the triple glazed windows. Operating energy costs for this facility are less than a similar-sized office building in PA with traditional double-glazed windows.”
So, readers, what are your thought about the new IT kid on the block, the R-5 window? Is its premium cost worth the energy savings? Let me know your thoughts.
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Luc J says
That’s great, first time I hear of those. I have LOTS of glass surfaces in my house, I think I’ll do the math to see if it’s worthwhile. In my case, it’s double glass already, I might not replace it immediately. But last year, one window was broken (6ftx6ft) and I’d definitely replace that with these new ones if it happens again.
.-= Luc J´s last blog ..Secure USB Flash Drive – Personal Pocket Safe =-.
Condo Blues says
I heard about these windows a couple of years ago and got positively giddy about the energy efficiency. The fact that the price is significantly higher and that I have double paned windows that are energy efficient made me remind myself that the greenest thing is what you already own. But if I was in a situation where I had to replace old inefficient windows in my house, I’d give them a good hard look. I admit it’s strange to be giddy about windows and building supplies but I am.
.-= Condo Blues´s last blog ..6 DIY Recycling Ideas for Non DIYres =-.
Cypress Lumber says
I believe that eventually this will be the norm of all mid-level to high-end home and office construction. Although the cost is much higher per unit, but over time the energy savings will more than pay for the windows themselves. I assist my customers day in and day out with their cypress lumber needs as well as other specialty wood and I can tell you that almost all of them want to save money in their future energy costs. You have to figure that a house is an investment and you need to prepare for the future by choosing these windows as the price of everything is rising, so will the cost of electricity. Think of this as buying a hybrid vehicle versus a gas guzzlers, you will expect to pay more up front but it will pay off over time.
David Williams
Kosh says
I seem to recall that triple pane windows were all rage, at least in the colder climates (Denver) back in the 80’s. Then they fell out of favor.
In fact, when starting the passive solar straw bale house that we just completed, I asked about them and was told common wisdom decided they weren’t necessary. As I was VERY busy with all the other details, I never followed it up.
But the bottom line is, I don’t think this is a new concept.
Green Talk says
Kosh, you are probably right. I think the new concept is that the Government is trying to negotiate a lower price for the windows so more people will use them. Anna
Tell us more about your straw bale house? Have any pictures?
CW says
The volume purchasing program will help increase demand for these energy saving R-5 windows, just like the renewable energy tax incentives have increased the installation of residential photovoltaic solar electric systems. If it pencils out financially, people will eventually want them.
Crystite says
The main reason why one would not switch from double pane to triple pane even though triple pane can be much more energy efficient, is the cost factor. Triple panes cost considerably more than double. But if the price is now going to come down, then it would make it easier for folks to decide to go with triple panes, I think.
.-= Crystite´s last blog ..Triple Pane Windows -What To Know =-.
Frank says
We are providing consumers with triple pane windows from $399. Check us out!
Jerry says
A SPECIAL THANKS TOO:
I would like to extend a Special Thanks to all the brave owners of retail window companies across America that have had the courage to sell and install these highly energy efficient windows for more then two decades. These men and women have paved the way in a direction America should have always been on and now that we as a country with the support of the Department of Energy should never be forgotten as more new retail companies begin selling R-5 or better windows. Along with the also brave and confident manufacturer’s that spent their money on the expensive machinery with the hopes that through hard work, outstanding marketing, new technologies, excellent installation this adventure would prevail, and it has. We like to say these retail window companies were “Green long before it was popular”. Marc LaFrance with the DOE is also owed a special thanks for spearheading this R-5 Volume Window Program which with good public awareness campaigns will change the window landscape forever and for better. The day of the cheap hollow vinyl double glass window is over.
Window Film says
Window manufacturers can really effect the environment in a positive way with this technology. All new houses can be built with very economically friendly windows thus saving energy.
lh_newbie says
Just keep in mind that R-value is not linear (i.e. going from R-1 to R2 will halve the heat transfer, but going from R-2 to R-3 does not). U-Factor is the rating we should pay attention to. U-Factor is the inverse of R-Factor. Lower is better. R-Value of 2 = 1/2, or a u-factor of 0.50; R-value of 3 = u-factor of 0.33. Even more imporant is that u-factor is the about of BTUs per hour per square foot per degree (F) that will pass through the window.
We just upgraded 10 windows in our home. That is 127.5 sq ft of windows. They were single-pane aluminum, which has a u-factor of ~ 1.15. The new dual-pane, low-e, argon filled windows have a u-factor of 0.27. When we have our heat set to 72 degrees and it’s 32 degrees outside, heat gains/losses from the insulation value of the windows went from 6,762 BTU/hr to 1,764 BTU/hr. this is with a u-factor of 0.27 (R-value of 3.7). That was a decrease of 4,998!
If we were to instead go with a R-value of 5 (u-factor of 0.20), the heat loss would decrease to 1,176 BTU/hr – for an incremental gain of 588 BTU/hr. Not a bad change, but not earth shattering either.
I guess what I’m saying is that financially, if people have dual pane windows, they probably won’t be able to justify upgrading them to triple if its purely a financial decision. But if a person has single pane, this does increase the encouragement of them to replace those old windows. We still have 9 more windows to replace (saving money for them). It will be interesting to see what happens!
Green Talk says
Lh, thanks so much for a wonderful explanation. Is there a basic formula that anyone can use their u factor to find out the btu loss or gain? Anna
lh_newbie says
Calculation for BTU/hr loss or gain:
(U-Factor) x (Sq Ft of window) x (Outside temp – inside temp [in degrees F]) = BTU/hr
Example 1: Heat Loss in winter through a 10 sq ft window
(0.30) x (10) x (30 degrees outside – 72 degrees inside) = BTU/hr
0.30 x 10 x -42 = -126 BTU/hr (since it’s negative, you’re losing heat to the outside)
Example 2: Heat Gain in summer through a 10 sq ft window
(0.30) x (10) x (100 degrees outside – 75 degrees inside) = BTU/hr
0.30 x 10 x 25 = 75 BTU/hr (positive number, therefore house is gaining heat)
As you can see, if an old single pane window with aluminum frames has a U-Factor of 1.15, it will have almost four times the heat gain or loss.
Summary: Old windows bad, new windows good. 🙂
Green Talk says
lh newbie, is there a site that generically tells you what your windows’ u factor could be if you don’t know? How does the type of framing around the window get taken into account? Or does it matter for your BTU formula?
Also, is there a formula to use that tells you what you would be saving per year if you do change your windows? Anna
Steve@Solar Window Film says
Serious windows use solar window film between the panes to act as the middle pane. This reduces the risk of thermal fracture and reduces the weight of the system.
What this means is that as well as being better at managing solar gain, the framing can be less expensive because there is less weight in the glass.
.-= Steve@Solar Window Film´s last blog ..GP Window Films – Solar Window Films – Insulating Window Films =-.
Robert Nemoyer says
I moved from double pane to triple pane with Krypton a few years ago. It cost me 14,000 dollars and I would really advise against it.
From single pane to triple pane makes sense but there wasn’t a significant increase in utility savings. I would check into indoor storm windows with a film. It is a much better payback. Also there are a number of movable insulations you can buy that add about R5 to your existing windows. My plan for next year is to put in carefully cut polyurathane into the windows of rooms which no one uses during the day when you don’t need daylighting and also during the night.
Green Talk says
Robert, would there be a condensation problem with the indoor storm windows? Also would it matter if the DOE brings about competitive pricing of the R-5? Someone told me of a house who had a Styrofoam fill the windows at night via a vacuum. In the morning the vacuum would suck the fill away to return the following night. Anna
upvc doors says
I do believe these will become standard for both hot and cold climates. With household becoming more aware and building standards reaching a minimum requirement we, the consumer will demand greater insulation.
Robert says
That is a good question about the condensation, but I think “no” I haven’t heard anything about condensation and usually it is the contrast between the cold outside and the warm inside. If you aren’t having problems with condensation with your double panes, you shouldn’t have problems with interior storms. Think about when you use shrink fit on your windows. It doesn’t cause condensation so an interior storm shouldn’t either. Google inside storm windows. You can make them or spend more money and and buy professional windows.
Anna@Green Talk says
Robert, good point. What do you think about interior storms? Anna
Richard Best says
I think that with the cost of heating and energy in this modern age, that these could well become the norm in households around the world. They may be expensive to install, but in the long run could save you a lot of money.
George Pepper says
I agree, Richard, I think that these windows could definitely be seen as a worthwhile investment.