The u-factor of a window is defined by the resistance to heat transfer via conduction. A 33% reduction in window u-value results in a 33% reduction in heat transfer via conduction. For example, imagine a double-pane window u-factor at .30, and a triple pane window u-factor of .20. The change in resistance to heat conduction is .10, or 33% of the original u-factor of .30. We can't jump to dollar savings from here, because it is difficult to know how much of a home's total heat loss is due to heat conduction through the windows, and also because u-factor is only one part in a window's energy performance (that also includes air leakage, SHGC, and durability over time). As I said, we do know the savings of going from double to triple will be much less than 33%, and for most people much less than 10%. If you want to calculate dollar savings due only to u-factor reduction (which as Window4U said is not the only factor in choosing triple pane), you can do it using the BTU formulas in the thread I linked to, but the calculations are not trivial.
windowrep, if you disagree, it would be helpful to describe why rather than just saying I'm wrong. It is difficult to respond and clarify otherwise.
Shucco Corona 4000's
Agreed
I agree 100% with FenEx as I happen to know that he is dead on with his numbers in regards to U Value.
My original point was for the price you are paying, you will get a better return on investment (ROI) with the triple glass.
Another ancellary benefit is your house will be quieter with triple glass as it reduces outside noise better than double as well as sound proofing your home.
So go for the triple glass and with the money you save throw yourself a big LOUD party without fears of disturbing your neighbors.
My original point was for the price you are paying, you will get a better return on investment (ROI) with the triple glass.
Another ancellary benefit is your house will be quieter with triple glass as it reduces outside noise better than double as well as sound proofing your home.
So go for the triple glass and with the money you save throw yourself a big LOUD party without fears of disturbing your neighbors.
to figure out a percentage of heat loss or energy savings for each house you will need to know too many variables. as discussed here before you need to know the u-factor of the windows you are replacing. for instance, single pane with aluminum frames=u factor of 1.00, (i am using round numbers for simplicity. now you put in a double pane with argon low-e at a u-factor of .30. in this situation are you saying that a triple will decrease heat loss by another 33%? i think that is too many percents. 33% per .1 u-factor is 252%. anyway enough with the numbers, w4u is right if you rerplace your windows for energy effeciency only, then 90% of the people replacing windows would not do it. then there would be no need for this board and alot of us would be looking for different careers. sorry guys did not want to turn this into a big thread on percents and formulas. from my experience i have found that asthetics plays 3 times the role of any other variable anyway. if you have an ugly window at .00001 u-factor, you are not going to sell many windows. imho
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windowrep, I think I finally see the reason for the misunderstanding we have here. The % decrease in conduction is relative to the referenced starting point. Starting from single pane aluminum and starting from double pane argon vinyl are different reference points. I can see why it is confusing, but the percentages can't be calculated on in the way you are suggesting to get the 252%.
A good way to illustrate this is that starting with 4 gallons of gas using one gallon reduces your tank by 25%. With 3 gallons, using one removes 33% of your tank. In effect, the % decrease (% heat conduction decrease) is not a linear relationship to the number of gallons used (absolute reduction in u-value), when the starting # of gallons (starting u-value) changes between the comparisons.
So I definitely agree with you that triple pane won't "decrease heat loss by another 33%" if your reference/starting u-factor is 1, but it will if your starting/reference u-factor is double pane argon. What is hiding here is that a percent is a percent of some reference value, not an absolute number. Hopefully this is a clearer explanation.
A good way to illustrate this is that starting with 4 gallons of gas using one gallon reduces your tank by 25%. With 3 gallons, using one removes 33% of your tank. In effect, the % decrease (% heat conduction decrease) is not a linear relationship to the number of gallons used (absolute reduction in u-value), when the starting # of gallons (starting u-value) changes between the comparisons.
So I definitely agree with you that triple pane won't "decrease heat loss by another 33%" if your reference/starting u-factor is 1, but it will if your starting/reference u-factor is double pane argon. What is hiding here is that a percent is a percent of some reference value, not an absolute number. Hopefully this is a clearer explanation.
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FenEx
I have been living in this house now for 17 years which is a 1900 sq. ft. ranch with a 1/2 basement in the center and 1/4 craw space on both ends.
The heating system is an oil fired hot water heat with base board registers. This house is southern MI., almost in OH. I have been keeping heating cost records for the post 5 years.
2001/2002...burnt 592 gals. cost for the heating season $592
2002/2003... " 625 gals. " $828
2003/2004... 598 gals. $878
2004/2005... 609 gals. $1287
2005/2006... 433 gal. $1042
I have no idea how much electricity the is used to run the water pump motor or the oil injector motor, but I say maybe it could add 10% to the cost. But I really do not know.
Now look at how many gals. was used in last years heating season. That is the first year with the new windows with a U-Factor of .32. Those new windows replaced a wood framed, double pain, with no Low-E and I think no Argon. I also think that last winter was milder than average. I forgot what the U-Factor is on the old windows.
I have been living in this house now for 17 years which is a 1900 sq. ft. ranch with a 1/2 basement in the center and 1/4 craw space on both ends.
The heating system is an oil fired hot water heat with base board registers. This house is southern MI., almost in OH. I have been keeping heating cost records for the post 5 years.
2001/2002...burnt 592 gals. cost for the heating season $592
2002/2003... " 625 gals. " $828
2003/2004... 598 gals. $878
2004/2005... 609 gals. $1287
2005/2006... 433 gal. $1042
I have no idea how much electricity the is used to run the water pump motor or the oil injector motor, but I say maybe it could add 10% to the cost. But I really do not know.
Now look at how many gals. was used in last years heating season. That is the first year with the new windows with a U-Factor of .32. Those new windows replaced a wood framed, double pain, with no Low-E and I think no Argon. I also think that last winter was milder than average. I forgot what the U-Factor is on the old windows.
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- Joined: Wed Oct 05, 2005 9:11 am
You could look at it this way. If you go with these U-Factors from 0 to 1... 0 could theoretically mean, aluminum foil for a window which may get fairly close to 0, and 1 meaning no heat lose what so ever.
-.1 - .2 - .3 - .4 - .5 - .6 -.7 - .8 - .9 - 1
Then .1 is 10% more efficient then 0 and .2 is 10% more efficient then .3 and so forth. This makes more sense to me. But that's me.
-.1 - .2 - .3 - .4 - .5 - .6 -.7 - .8 - .9 - 1
Then .1 is 10% more efficient then 0 and .2 is 10% more efficient then .3 and so forth. This makes more sense to me. But that's me.
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