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lisatec
Joined: 02 Apr 2005
Posts: 3
Location: Viginia
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 Posted: Sun Apr 03, 2005 1:24 pm Post subject: Low E |
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Can someone explain why low e coatings are (supposedly) more efficient whether your house is in a cold climate or a hot one?
In a cold climate you'd want the radiant heat of the sun to enter the house and then not be allowed back out. (Green house effect)
In a warm climate, you don't want the energy to enter through the glass in the first place. Either the glass should be reversed in a warm climate, (there is no evidence of that) or low e glass in a cold climate prevents as much heat gain as it contains heat loss. What would be the point of having it?
lisatec |
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rabadger
Joined: 22 Feb 2005
Posts: 24
Location: Valparaiso, IN
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| Posted: Tue Apr 05, 2005 2:54 pm Post subject: |
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I do not know much about manufactures claims on low-e glass. I do know about HVAC load calculations and system design. One can run a heating cooling load calculation on a home using good double pain windows and then change the factors to low-e and come up with different results but the actual size of the required unit may not change. Sometimes better windows will let you install a smaller A/C and sometimes not. Things like direction the window faces, shading and overhang also effect the results. When sizing heating and cooling there are no two buildings the same. It is the actual application that counts. I am getting ready to do several load calculations for a person living in SC. He would like to see the difference in cooling and heating requirments using 4"walls, 6" walls, standard double pain windows and low-e windows so he can determine if it will be worth the additional costs for more expensive model windows and other construction changes. For example I remember doing a load calculation for a person that was into energy eff. big time. I figured the best low-e glass 6" walls filled with insulation with
2" insul board. He had the home design so all the windows were on a east and north exposure, and the lot was wooded with large trees. the difference between low-e and good double pane really was not that great.
If he were to rotate the home and cut down the trees the difference was enough to think about it. Homes are getting bigger and you can only use the heating and cooling equipment that is available on the market. You also have to throw the duct design codes and standards into the formula. There is such a thing as over kill.
Some day I will find the time to research the way window manufacturers test the products and maybe that will shed more light on the subject. If you talk to the window salesperson they will all tell you that they have the best product and the more expensive model is worth the price.
_________________
Richard
Learn what you need before you shop!
A comfortable home is a happy home!
www.HVAC-consult.com |
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lisatec
Joined: 02 Apr 2005
Posts: 3
Location: Viginia
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| Posted: Fri Apr 08, 2005 2:27 pm Post subject: Low E |
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Forgive me, I'm not yet familiar enough with the functions of this forum to know if you, (Richard) are receiving this reply. Assuming you are, I'd only like to say thank you for responding. From your reply it's obvious to me that you are someone who questions specifications and evaluates designs realistically. Does it work or not? Lets see the utility bills over an entire year.
Personally, I'm torn between building what I know the market will pay for and then competing with all the other builders or, doing what I enjoy. I enjoy experimenting and making changes to systems that need improvement. I also like really simple things that work well. Minimal moving parts etc.. My wife and I recently built a house in Alabama. Because of her career, we will be moving around a bit for the next year and a half or so, consequently the house we built for ourselves is now for sale.
If you're curious, look at www.lisatec.com
Next year we'll be in California for one year exactly. When we return to the South Eastern USA, we'll build again.
With luck, I'll run into people with your knowledge, experience and attitude.
Robert Pollock |
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