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Clutchcargo 10-24-2008 12:30 PM

Low-E in the Northeast.
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I notice that HD is stocking Low-E windows on the floor now. In the Northeast where we the heating season is much longer than cooling season, does it make sense to use a Low-E window? During the winter wouldn't you want the benefit of solar gain? I think the warmer states would benefit more while in the northeast, solar gain is a good thing.

Lansing 10-26-2008 01:53 AM

I Always use a window with low E in it...What your likely wondering is where on the window they set the low E film...It can be set for the area north or south you live in...Just ask them where its set on the windows they are selling there...

Clutchcargo 10-26-2008 07:33 AM

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Originally Posted by Lansing (Post 176882)
I Always use a window with low E in it...What your likely wondering is where on the window they set the low E film...It can be set for the area north or south you live in...Just ask them where its set on the windows they are selling there...

This might be why I don't understand the Low-E usage in cold climates. What do you mean by this?

Lansing 10-26-2008 10:39 AM

Ok if you live where you get a lot of hot sun and run A/C units you want to keep the sun and its damaging effects out of your house right...So where the film is set on the glass will be important to get this result...

But If you want to keep the heat in your house as your running a heating system you want the film set on the glass in a different spot to bounce the heat back into your room...Where I'm living they want to keep the heat in as their is more winter than summer and the window people make that happen by where they set the low E film on the double window the inside edge or to the outside edge... in Canada has booklets with pictures on what I'm doing a poor job of explaining here that show where the film should be set to get what effect you want or need from the coating...Hope this helps ...

drewhart 10-26-2008 10:41 AM

i live in the northeast and i just bought 5 windows with low-e, not really knowing why. how does it work, you say it reduces solar heat transfer? do they not coat the whole window evenly, is there more of it near the bottom where the sun would hit?

Lansing 10-26-2008 11:08 AM

Yes they coat the hole window area on the side that they do the coating...If you want to bounce the suns rays out to keep your room cooler its set on the inside of the outside glass...If you want to bounce the room heat back into the room to keep it warmer and save your heat its set on the inside glass facing your room...We are talking a double insulated glass window here...The coating also stops the damage to floor materials and drapes from ultra-violet rays of the sun coming in your home...

wrangler 10-26-2008 11:22 AM

This link might help you to understand it a little better, as well as those hard to decipher ratings you often find on windows.

oberon 10-26-2008 07:26 PM

There are two primary types of LowE coatings available - pyrolitic or hard coat - and sputter or soft coat. Both types significantly out-perform clear glass in energy efficiency.

Pyrolitic or hardcoats are primarily tin oxide and are applied to the upper surface of the glass in a process called Chemical Vapor Deposition or CVD. In the CVD process, vapor directed to the hot glass surface reacts to form a ceramic coating while the glass is still semi-molten in the tin bath portion of the float process.

Sputter or softcoats, on the other hand, are applied to the glass surface as multiple layers of metals and metal oxides in a series of plasma-filled vacuum chambers in a process called Magnetron Sputtering Vacuum Deposition or MSVD.

While coatings are often referred to as simply LowE, in fact there are different coatings within the hard/soft coat arena often refered to as LowE, LowE2, LowE3; and while LowE is often used generically to indicate either a hardcoat or single-silver softcoat, LowE2 or LowE3 are often used generically to indicate the number of layers of silver in the coating.

Dual or triple silver sputter coats (low solar heat gain products) are generally built to surface #2 of a dual pane IG unit, while a single silver (high solar heat gain) or a pyrolitic coating is often built to surface #3.

In a heating dominated climate, the two reasons for placing the LowE coating on the #3 surface of the IGU is to allow for solar heat gain in the winter and to block the transference of the heat from inside the home to the outside.

High Solar Heat Gain (or HSHG) coatings and Low Solar Heat Gain (or LSHG) coatings are all designed to block far - or longwave - infrared energy. This is the range that includes typical household-produced heat. This is also the frequency range of heat that is produced when the sun warms an object – the heat you feel "reflected" from a hot wall or sidewalk on a hot, sunny summer day. While direct solar energy is shortwave IR, the heat released by a sun-warmed object is longwave IR…and hopefully that made sense.

A typical hardcoat or single-silver layer softcoat works in this application since all types of LowE coatings block the far infrared energy - thus keeping winter heat indoors - but neither is designed to be effective at blocking shortwave infrared - thus "allowing" solar heat access to the home - winter or summer.

Placing a high solar gain coating on surface #3 maximizes the level of solar heat gain thru the IG unit which can be an advantage in winter and can also be a disadvantage in summer.

A Low Solar Heat Gain product, on the other hand, is designed to block both near and far infrared energy. It will keep heat - including direct solar gain – from passing thru the window in both summer and winter.

These coatings are placed on surface #2 to maximize effectiveness against direct solar gain by blocking solar heat before it can pass into the airspace in the IG unit – and into the home.

Softcoats typically have lower (better) U-factor numbers than do hardcoats which confuses the issue as well since harcoats allow more solar gain, they also lose more heat.

About 80% of LowE coatings used in the US are softcoats.

Lansing 10-27-2008 12:04 AM

Very good...I couldn't say it as good...You got the facts down...Good stuff and true...:thumbsup:

Marvin Gardens 10-27-2008 10:42 AM

Low E is wonderful, and a curse at the same time.

While it reduces cooling costs and cuts down UV transmission which will fade just about anything, it will also keep nice radiant heat out in the winter time.

To me the answer is something like Tucson Rolling Shutters. These are expensive and not realistic for most.

I use non low E in my vacation home. It is in the desert and temperatures range from 120 in summer to -10 in winter. It's just designed to shade the summer sun from hitting the windows yet allows the winter sun to shine in. Lots of thermal heating that way. But it was designed that way and when replacing windows most can't just redesign the house.

I am also building a sun room out of non low E windows so that I can heat the place in the winter. It has vents on the sides at the top that will open and allow the heat to escape in the summer.

oberon 10-27-2008 07:59 PM

A high solar gain LowE coating is the best of both worlds if you want to take advantage of free heat from the sun.

Although it is true that the LowE will cut down on solar heat gain versus clear glass - depending on the actual glass area and on the window framing material, a clear glass window will pass about 60-70% of available solar heat gain while a high solar heat gain LowE coating, in the same circumstance, will pass about 50-60% of available solar heat gain - the LowE coating also cuts down on the heat loss thru the glass to the outside whenever the window isn't benefitting from direct solar exposure - something that clear glass doesn't do very well.

You will save energy and money using a high solar gain LowE coating versus clear glass. How much depends on where you live and how you live, but in in the right circumstances field performance studies have demonstrated savings that could be as high as 35% versus clear glass.

Clutchcargo 10-28-2008 07:34 AM

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Excellant information, thanks guys.

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