Energy efficient windows??

Not exactly sure if foam board would look so nice or bring in light? I have Pella's (low-e double pane with argon) which I would NEVER buy or recommend. I was told that they were great but have found that they are no different than any other company who is making it on their previously good name. I won't even get started on the rampage of why all these companies are selling out their future for short term gains (I guess the ceo's NEED bonus' on top of their inflated salaries for making such great decisions). Anyway, I have heard that in our area Martin triple panes (although more $) are the best. When I built my house 4 years ago, they were about $200 more per window whiched seemed like too much back then (I have 21 windows in my house). Now wishing I would have gone with them. The other thing I have heard of but never seen is using 2 "cheaper" windows per opening. This works for deep framed or double framed houses with deep jambs. I like the concept but am not sure how that looks? Just my 2 cents that is probably worth less than 2 cents.

Had all of our windows done this year - learned that in Canada, windows have a rating system for various factors:

http://www.cmhc-schl.gc.ca/en/co/renoho/refash/refash_021.cfm

Unfortunately, I learned that after we bought the windows. Not sure if US has a similar system.

We have ratings here in the US as well. No need to follow some brand, I used certainteed windows and they have been great. The windows are all easily highly efficient compared to your current ones. Consider latch styles too. Bang for the inulating buck isn't good with windows unless you had grossly leaking windows before. Better to insulate ceiling/floor/and walls.

In large measure, it's all a matter of what you want to pay and the bang you want for your buck. Ceiling/attic insulation, sealing cracks (caulking) come before any windows. In general, double pane/gas filled has a U factor of 0.4-0.5 (the lower the U factor, the greater the resistance to loss of heat; U factor is the inverse of R rating). But you can get triple pane and more. U factors of 0.08-0.12 are available; quite pricey.

We live in N MN, winter temps this winter reached -36F, had about 44 days in Dec-Jan with below 0F temps. Our windows are rated U-0.12 (probably center of glass rating), and they are warm to the touch inside with way below 0 outside. No frost, no condensation; trap heat inside in the winter and block heat from the outside in summer.

Do some serious research, this can be a big investment. Shortcut advice, even from the great participants on this forum, will not substitute for proper research on your own.

Also, there have been a number of threads on windows, search those out and you will get all kinds of advice without starting a thread to do this all over again.

start with insullation unless you have windows that flap in the breeze like I did. I had to wedge a comb into the space between them so I could sleep at night from all the banging in the wind, that was with storm windows. I got some windows installed by Home Despot, I am not happy with them in any way except that they stop the drafts. They are single hung (the top doesn't move) and have child latches that fall out if you raise the window to fast. (complaining to HD got me a handful of extra latches that fall out after they get hit the first time) They also cost almost $500 a piece.
If you are going to do windows look for your window world dealer, I got ten of them a few years later and they are great, back then they were $189 a window, now I think they are $250 or so. they are double hung, tilt wash, have two latches, a security lip that locks them together in the middle when they are latched, and double child latches that I don't think you could break unless you used a hammer. (if you see the commercial on TV the guy stands on the window glass to show how strong it is) I have had them for 4 years and they are still great and don't warp, stick, or leak. Window world has a different price structure, the basic window is the advertised price, a screen is $10 more, a storm window is more, dividers (mounted between the panes) are more, argon gas inbetween is more, low E coating is more, etc. Mine just have a vacuum inbetween the panes and that is enough for me. ( I did buy the screens also) I cut my oil usage by a good amount after doing the whole house, but I already had blown in insulation, so windows were the next big heat loss, now I am looking at getting three plain wood doors replaced.

I agree on the the previous comment on doing your own research. Windows for a house can cost as much as a new car, so spend the time and understand what you are getting for your money.

A few comments - I found that argon and other inert gas fillings have an insanely long payback period. You pay a lot more for the addition of the gas, and you don't get much more insulating value. Your money is better spent on triple pane instead. If you need to replace windows with something that looks similar to what you already have, then the style of window is pre-determined. However, if you have flexibility on the window style, go with a casement or other type that has a press to fit seal and not a sliding seal (like a double hung). A press fit seal will have less infiltration and will make a big difference in comfort and savings. Low E coatings can be worth the cost in comfort if you will be sitting near the windows, or if they are very large windows. If the windows will face south and you get good sun exposure, pay attention to the solar heat gain coefficient - the higher the better. This will ensure that you continue to get solar heat through the windows. Not all new windows excel at this. In fact, many have very low solar heat gain coefficient due to low E coatings that block solar gain. Not what you want if your southern exposure is good, and you have overhangs to block the worst of the summer sun during mid day.

Lastly, there is a lot of marketing b.s. about how customers should replace their windows to save money. Unless your windows are really old and in really poor shape, the payback period for the new windows may be very long (15+ years or more). If you haven't already done more basic energy efficiency upgrades, such as insulating the attic and walls, stopping obvious infiltration, etc. then I would do that first before you replace the windows.

A little math goes a long way in making the payback calculations. Its well worth the time to do the calculations. The more money you save on the right investments, the quicker you can make more investments, and save more.

Unless your windows leak as much air when closed as when open (almost just kidding), I frankly don't think payback through energy savings should be the primary criterion for window replacement. I think window aesthetics, viewing and comfort are primary. And, if you're putting in expensive windows, I think it is foolish to have shades and drapes so you can't see out of your windows. Why pay big $ just to cover the window up? Build a wall instead - cheaper too.

Our situation likely is extreme: we live in the woods on a lake, we wanted great views on all sides of our house, we needed winter comfort (freedom from drafts, no condensation or frost, and we wanted the ability to sit in comfort by the widows in the dead cold of winter). Our walls are only 8', and to get what we wanted we installed 5'H casements and picture windows on three sides, plus large awning syle in the bedrooms mounted high enough to prevent outside viewing in of my wife's beautiful body. We have no window coverings at all. Total is about 43' of 5'H window, plus the awning windows. Window replacement started in 1992 and ended in 2000. We paid about $45K. The windows are 4-pane equivalent (2 glass + 2 plastic film, exotic gas filled and coated glass and film, alum clad for maintenance free, wood inside), and as mentioned above U=0.12. These windows perform better insulation-wise than some of our walls.

Energy payback I compute to be after the end of the world. Comfort and viewing until that time are priceless.

As unappreciated pluses these windows retain inside heat in the winter, allow direct solar heat gain in winter, reject outside heat in the summer, and reject indirect solar heat gain in summer. On sunny winter days, -10F outside and howling winds whipping snow across the lake, the direct solar heat gain heats the entire house for a couple of hours. The wood stove in the living room heats the house the rest of the time. On sunny summer days, leafed out trees plus 4' eaves block the summer sun, and the house stays comfortable.

For my cost payoff, I save the equal or greater of one window each year in fuel savings.
I burned almost 600 gal of oil before the first windows, they were the upstairs windows I got my fuel used down closer to 400 gal the next year. The rest of windows in the house (window world) saved me another 100 gal, I burned 300 gal or so after that.

Payback on windows are almost as long as the window will last unless they are really bad.

Windows may vary from company to company, but they all subscribe to the same theories. What can really make a difference is the installation. Once a window is closed it should not leak, but all around it is the problem. House wrap, exterior foam baoards spray in insulation can even make a low end window installation worth it.

I maintain that sealing air leaks, whether they occur at windows or elsewhere, is the first thing you should address. If you end up replacing your windows, consider using casements as they generally seal better than double-hungs because they have compressed seals instead of sliding ones. I think a standard double-glazed casement window might give you the most value for your dollar. However, I'm not sure that a well-sealed single-glazed window used with a well-sealed storm window wouldn't provide the same level of insulation though.

Semipro said:

I maintain that sealing air leaks, whether they occur at windows or elsewhere, is the first thing you should address. If you end up replacing your windows, consider using casements as they generally seal better than double-hungs because they have compressed seals instead of sliding ones. I think a standard double-glazed casement window might give you the most value for your dollar. However, I'm not sure that a well-sealed single-glazed window used with a well-sealed storm window wouldn't provide the same level of insulation though.

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I agree - our windows were a huge air seal improvement - used to see the curtains move on a windy day. The biggest improvement we saw was the day we swapped the old leaky basement windows with new sealed units - humidity jumped 10 percent in the house just from the lack of infiltration. Beyond the sealing factor, the functionality of new windows - opening and closing - versus the old units that needed sticks of wood to hold them open, assuming they would open, was the other deciding factor.

www.energystar.gov
Windows are not a mystery, they are a science. Frame construction, glass packs.
With the new tax credit. It clearly states that a window has to a have a maximum U factor of .30 (lower the number the better)
and a solar heat gain of .30 or better.
Krypton gas is 30% more effective than argon. Avoid metallic type spacers between the glass. Look for a TPS or a Super Spacer premium.These seals are non heat/cold conductive and will flex with the glass and their seal failure rates are very very minimal.
Ok I always hear people say that gas will leak out with time.Ok Think about a tubeless tire on a wheel.It will hold 35-90 psi for years without going flat.,. This glass pack has a filling of inert gas that is just full. not even under pressure.
What ever company the OP chooses just make sure that their windows are eligible for the tax credit of up to 1500$ or 30% of the cost of the product. Not the install.
I would never put my family at risk by having any sort of foam board in my living space. Windows are there to look through.
Good windows have an R value of R-10. That would take a piece of rigid foam 2 inches thick..That is a whole bunch of nasty fumes in the event of a fire. Not counting the immediate fuel source you are adding.

Make sure of the tax credit, I have missed every tax credit whenever upgrading my house!
when I did the windows the first time I didn't know about the tax credit, the second set of windows I missed the tax credit by 1 year, when I did my tankless water heater I missed another one by a few months, I did my pellet boiler in oct '08 so no luck there.
The other issue with vynil windows is the "box" construction, the frame around the window, the more baffles inside the box the better, this makes the window stiffer (why the window world guy can stand on his glass) and stops the flow of air from the top to the bottom (the biggest way heat transfers internaly).

Check out this site. www.alpeninc.com They use krypton gas instead of argon. Quite expensive if i remember right.

This is the company we used over 11 years ago. http://www.castlewindows.com/home.htm . They have a very good warranty. We just had them out last year to replace the screens because our cat decided to cut her way through to get to a bug. Replaced them for no charge.

Glass with a LowE coating will always outperform clear glass. As Ericjeeper pointed out, in order to qualify for the tax credit you need both U-factor and SHGC need to be below .30. This is not possible unless you have LowE windows. There are LowE coatings designed to allow solar heat into your home while blocking the heat in your home from going outside. There are also coatings that block solar gain as well.

Thermal or heat transfer thru a window is going to be both radiant and conductive. LowE coatings are designed to limit radiant heat transfer thru the glass while argon or krypton are intended to limit conductive heat transfer.

In the everyday world, we directly experience ultraviolet, visible, and infrared light. Different LowE coatings will block different portions of each "type" of light depending on the type of coating.

While UV will fade your carpeting, give you a tan (UVA), cause a "sunburn" (UVB), or may even lead to skin cancer (UVA again), it really doesn't add any appreciable heat to your home although sometimes people will talk about LowE coatings blocking UV as part of "heat" entering your home.

Visible light can also fade your carpeting and it does add heat to your home, but a window that blocks 100% of visible light wouldn't be of much value, so some folks will suggest tinted glass which does help to keep a home cooler by limiting the amount of light into the home. While LowE coatings perform a similar function, they just do it a lot better than tinted.

Infrared is the primary contributor to heat gain or heat loss thru a window. Infrared is divided into near, mid-range, and far (and it has a number of subdivisions depending on whether you want to change the channel on your TV using a remote, or if you want to spy on an enemy at night, or if you want to study the spectral distribution of a star...and more).

Anyway, direct solar heat gain is "near infrared". High solar heat gain LowE coatings will pass near infrared or direct solar heat gain allowing the solar heat into a home, while low and moderate solar heat gain coatings block percentages of near infrared or direct solar gain.

When you are out in the sun and you get that nice warm feeling on a bright sunny day (appreciated in winter, less appreciated in summer unless you are lying on a beach somewhere), you are experiencing radiant heat gain in the near infrared.

On the other hand, if you are standing next to a concrete wall and you can feel the sun's heat being "reflected" off the wall, you are now experiencing far infrared. It is still heat, and still radiant, and it is going to warm you, but the wavelength (frequency) of the radiation has changed from near infrared to far infrared when the near infrared was absorbed and then reradiated by the wall.

All LowE coatings block far infrared, but as mentioned different coatings allow different levels of near infrared to pass thru them.

If a homeowner wants direct solar gain, they can get a high solar heat gain coating that would allow near infrared to pass thru the window, and that near infrared heat will warm the furniture, the floor, the walls, anything that it penetrates. The near infrared will be absorbed and then reradiated in the far infrared spectrum – which is blocked by the coating and results in solar heat gain in – and heat stays in.

When the temperature outside is 0 and the inside temperature is 70, a clear glass dual pane window will allow about 21 btu/hr/ft² of radiant energy to escape to the outside thru the glass (assuming the window isn’t in direct sunlight). Adding a high solar heat gain coating lowers that number to 5 btu/hr/ft².
A moderate solar heat gain coating will lower radiant heat loss thru the glass to 2 btu/hr/ft² and a low solar gain coating will come in at 1 btu/hr/ft².
Given that these are ideal conditions and that there are slight variations in coatings depending on manufacturer.

On the other hand, if you are back on that beach and you are walking barefoot in the sand and you are just short of tears because your feet are being slowly roasted, you are experiencing conductive heat gain. In an IG window, this is where the advantage of adding an inert gas in the airspace since the gas limits the passage of conductive heat transfer thru the IG unit.

Conductive is direct contact thermal transfer. Touch that warm wall from the earlier example and you will experience conductive heat thru your fingertips. And to get a little more technical, the heat that you feel from that wall even when not touching it is going to be a combination of radiative and conductive. Conduction because the air molecules near the wall are transferring heat between them. If you are close enough to the wall you will experience that as well.

In the IG unit, air molecules will transfer heat energy from the warmer glass pane to the colder glass pane – conductive transfer. Argon or krypton or xenon or whatever else they come up with will affect conductive heat transfer thus improving the energy performance of the unit.

Given the same 70F inside and 0 outside that I mentioned earlier, conductive heat loss thru the clear glass dual pane IGU is going to be about 13 btu/hr/ft² but add a LowE coating and conductive heat loss will increase to about 15-16 btu/hr/ft² (depending on coating). Seems like a LowE coating might actually be a bad idea in sme conditions???

Nope, since in the given scenario the coating lowers long wave infrared radiant heat loss from 21 btu/hr/ft² down to 5 btu/hr/ft² or better (again depending on the coating), thus the overall heat loss thru the IGU is improved significantly when using a LowE coating.

In the real world, a dual pane clear is going to lose in the neighborhood of 34 btu/hr/ft², but a dual pane with a low solar gain coating in the same conditions cuts that loss in half – down to 17 btu/hr/ft². A dual pane IGU with a high solar heat gain coating will cut total heat loss thru the IGU over 41%.

There are LowE coatings that are designed for folks who want winter solar heat gain, but unless people know to ask for a high solar heat gain coating then they are almost always going to end up with either a moderate or low solar gain coating which is more of an industry standard.

But again, in all conditions a window with LowE will outperform a window that doesn't have the coating.

Ericjeeper,

I work in the glass/window industry. This stuff is what I do in my day job and while I liked your posts and the entire thread, I am going to try to clarify a few things about windows and in the process it may appear that I am nit-picking your answers (NOT my intent). I hope that you see my comments as elaborating on your information - rather than contradicting it - which is my intention.

ericjeeper said:

www.energystar.gov
Windows are not a mystery, they are a science. Frame construction, glass packs.

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Good comment! Absolutely true.

Krypton gas is 30% more effective than argon. Avoid metallic type spacers between the glass. Look for a TPS or a Super Spacer premium.These seals are non heat/cold conductive and will flex with the glass and their seal failure rates are very very minimal.

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Krypton is at its energy performance best in a narrow airspace of approximately 1/4" or less which is why krypton is often used in triples with narrow airspaces. In wider airspaces - anything wider than 3/8" or so - krypton becomes much less attractive because of increased cost (about 100 times argon) and performance loss. Although krypton is still slightly more effective than argon even at 1/2" space, argon is a significantly better investment than is krypton.

Some of the best windows available use "metallic" spacer systems. While the choice of spacer will affect edge temperature of the glazing, the differences between spacer systems as installed in windows are signifiicantly less than certain marketing efforts would have you believe. In fact, identical windows with IG's using foamed silicone (Super Spacer), TPS, stainless steel, or Duraseal spacer systems will have identical overall energy performance (U-factors). Again, the choice of spacer has much less to do with overall performance of the window than does the choice of glass make-up, coating, or sash and frame material. Even edge temperature performance is less significant than some folks might believe. SuperSpacer is currently the industry leader, with TPS about 1/2 degree behind and Duraseal and stainless steel about 2 1/2 degrees "colder" than SuperSpacer. These numbers are based on the IG and not on the finished window.

Ok I always hear people say that gas will leak out with time.Ok Think about a tubeless tire on a wheel.It will hold 35-90 psi for years without going flat.,. This glass pack has a filling of inert gas that is just full. not even under pressure.

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In the best systems, argon will dissipate thru the spacer system at about 1% per year. This is negligible and really not worth worrying about. Krypton is a bit more of an uncertainty since there currently is no way to measure krypton in the field. Some folks suggest that containing krypton in the IG space is actually more difficult than keeping argon inside, but again currently there is no way to determine the actual level of krypton in windows in the field.

Good windows have an R value of R-10. .

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That would be a really good window! Windows with that level of performance are out there, but they are often prohibitively expensive. I would suggest that windows with R-values in the 5 to 7 range are also available and are going to be much more affordable. And I agree 100% that windows are to look thru and that options other than foam in the living room are available.

Also, from an earlier post, no current IG / window system uses a vacuum between the glass. That is a fairly common misconception.

Top Ten Reasons to Restore or Repair Wood Windows
1. Because your windows fit your house.
• Quirky as they might be, your older windows fit your house. Care was taken to match the weight and
style of window to the building, the trim, etc. They have expanded and contracted with the seasons.
With proper weather stripping they can be made to fit and seal even better. Replacement windows have
a rigid structure that fits within your window openings. Old houses move and shift over time and
frequently the gaps that open up around replacement windows and the window openings result in more
drafts that the original windows.
2. Because you appreciate good craftsmanship
• The true mortise and tenon construction of antique windows is incredibly strong and even when it begins
to weaken is easily repaired. Many unique window shapes were created because of the craftsmanship
with wood joinery. Antique windows were built to last and not land in landfill.
3. Because you value good materials.
• Antique wood windows are constructed of old growth timber. The wood is much denser and more
weather resistant than today’s tree farmed softwoods. Delicate profiles are possible because of the
density of the wood. The reason these windows are still around, even with years of neglect, is because
the wood is of very high quality requiring no cladding or additional materials to give them weather
resistance. Minus all the ugly paint your wood windows are usually quite beautiful, graceful, and strong.
4. Because you love the character of antique glass.
• Even the glass in antique windows tells a story. It may be roundel or cylinder glass, each indicating a
certain era of manufacturing. Old glass has varieties of color and texture that are a delight to the eye.
Two layers of glass are better than one, and in an antique home that second layer of glass should be the
storm window that protects the original window.
5. Because you think a warranty should be more than 20 years.
• Chances are your windows have done their job for fifty or more years already. Sure, they may be a little
creaky and may not be as attractive as they once were, but it’s a far better investment to repair a proven
performer than to sink money into a new window that only has a 20 year warranty at best. With proper
maintenance your antique windows should last another 100 years. Heck, even without maintenance they
may last that long!
6. Because you want to avoid vinyl.
• Poly vinyl chloride (PVC) is becoming one of the greatest concerns in the building industry. Not only
does the production of it create an environmental nightmare, but the gases it emits over time are
becoming a concern. Heaven forbid your house catches fire, and PVC burned will release toxic amounts
of dioxin. If you are concerned about lead, please understand that it is used as a stabilizer in the
manufacture of PVC. If you are concerned about our planet’s health you should read up on efforts to
reduce the use of vinyl.
7. Because you want more light.
• Replacement windows are set into the window opening, and the sash is smaller than the originals. You
get less viewing area and less light. Who wants less light?
8. Because windows are a functional part of your house.
• Weights and pulleys are the best balance systems every invented. There is a prevalent myth that a lot of
cold air comes in through the weight pocket. If there is cold air in the weight pocket it’s generally
because there is a gap between the outside trim of the house and the siding. It may also indicate a poor
seal at the floor joists. Replacing easily serviceable weights and pulleys with vinyl jamb liners or
invisible balance systems means installing a system that has a maximum life span of 10-20 years but
generally fails in less time. You can’t believe how joyful it is to open and close windows easily with one
hand when everything is restored to the way it was designed to work!
9. Because you really can save 30-40% on heating costs.
• According to the Field Study of Energy Impacts of Window Rehab Choices conducted by the Vermont
Energy Investment Corporation, the University of Vermont School of Civil and Environmental
Engineering and the U.S. Army Cold Regions Research and Engineering laboratory the estimate first
year energy savings between a restored wooden window with a good storm window vs. a replacement
window was $0.60. Yup, less than a buck. In their conclusions section they noted “The decision to
renovate or replace a window should not be based solely on energy considerations, as the difference in
estimate first year savings between the upgrade options are small.” Broken glass, failed glazing, no
weather stripping – these small and repairable items are what really effect energy efficiency in windows.
10. Because the greenest building is one that is already built.
• Replacement windows are touted as a way to save energy. But when evaluated from the perspective of
the entire production, shipping, installation and removal process replacing windows consumes a whole
lot of energy, or viewed the other way an older building has a great deal of embodied energy. If the total
energy expenditure to manufacture replacement windows is considered the break even period stretches
to 40-60 years. In the words of Richard Moe, President of the National Trust for Historic Preservation
“We can’t build our way out of the global warming crisis. We have to conserve our way out. That means
we have to make better, wiser use of what we have already built.” Repairs and restoration work are done
by local craftspeople paying local taxes. The use a minimum of materials and resources and a maximum
of labor. Restoring windows is the best use of existing materials and the best way to support the local
economy.

BeGreen said:

Oberon, thanks for taking the time to share your knowledge on this subject. It's great to hear the straight and skinny on window construction.

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Thanks BeGreen.