# Calculating window heat loss

• posted on February 20, 2004, 1:35 am
So I just put all new Harvey windows in my house, thinking that it would cause a noticeable improvement in my heating. I'm disappointed. Specifically I have this one small room with three windows (corner room) and despite the fact that the thermostat is 6ft outside this room reading 71, the room itself reads about 67-68. Worse, I walked my thermometer over to a window and it dropped to 62.
So my natural question is, is there a way that I can tell my windows have been installed properly and working as efficiently as they're supposed to? Is that much of a degree change expected? We've had some cold weather up here (Massachusetts) lately, but I wouldn't call it extreme -- 20's to 30's mostly.
I think it's gotta be a heat loss thing (as opposed to not heating the room enough, for instance) beacuse on a warmer day the thermostat read 72 and the room also read 72. So the differential seems to go up on cold days.
I do get condensation on the windows sometimes, but it's a baby's nursery and we often have a humidifier running so I'm assuming that's normal. There is no condensation between the panes in the window.

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• posted on February 20, 2004, 1:56 am
Duane Morin wrote:

I am not sure what you were expecting. First, what were those number before the new windows? Second I would not really expect much if any difference. If the windows are working, they will let less heat escape. With less heat escaping from your home, the thermostat will call for less heat, and your home will stay at the SAME temperature as before, but you will use less energy keeping it that way.
--
Joseph E. Meehan

26 + 6 = 1 It's Irish Math

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• posted on February 20, 2004, 2:55 am

That's a good thought. The new windows could reduce drafts as well, but he made no mention of drafts.

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• posted on February 20, 2004, 4:09 pm

I"m happy to say I'm not feeling any drafts. It's just colder than I expected. I will track down some U and R values (what's the difference?) and report back.
DUane

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• posted on February 21, 2004, 2:50 am

he
R- insulation value of the ONE item U-Insulation value of more than one item, like a wall...the combination of R values....IE: air space, drywall, insulation, outer wall insulation, wall material like brick, or other, and outdoor air envelope.

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• posted on February 20, 2004, 2:11 pm

My daughter's room is the coldest room in the house. At the other end of the upstairs is the master bedroom, also a corner room with three windows, but it has much more baseboard for heat and pretty much bakes us. So I am unable to heat the upstairs adequately -- in order to keep her room at around 68 I would need to set the thermostat to about 72 which would in turn make our bedroom around 73+. Yuck.
We moved the thermostat from the master bedroom out into a more central location at the top of the stairs, reasoning that formerly it was in the room that heated fastest, therefore not leaving any time for the other rooms to heat. But it has not helped - if anything it has made the problem worse by causing the master bedroom to heat longer and hotter.
I recognize that her room is probably getting the least heat, being way at the end of the pipes and not having a huge amount of baseboard. So I am overly paranoid about keeping as much of that heat in there as possible. I am concerned that her room is losing heat more rapidly than some of the others and not able to get it back.
Hope that clarifies my goals. I realize that by replacing all the windows in the house I (at least theoretically) improved the heating efficiency of the house across the board, and thus would not actually solve the problem :). My question came from the surprising discovery that the temperature dropped so significantly over by the windows, and I guess I just wasn't sure what to expect, so I asked.
I will look up the constants people are asking me for when I get home, and post again with that info.
Thanks!
Duane

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• posted on February 20, 2004, 7:46 pm
Duane Morin wrote:

You did a good think, but it was the wrong thing. Improved windows will save you energy and are likely to make you home more comfortable, but they will not help make the temperature more even.
Designing a system to efficiently, effectively and evenly is not rocket science, it's harder. It's heating science and is as much an art as a science. (Believe me, my son is a rocket scientist and could not design a good heating system if his life depended on it. He does a great job on satellites however.)
I suggest you find a professional familiar with the type of heat you are using and have them take a look. This can't be done on-line it takes a on site inspection.
In the long run it will not only make you more comfortable, but save you the cost of the work as well in energy savings.
Good Luck
-- Joseph E. Meehan
26 + 6 = 1 It's Irish Math

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• posted on February 21, 2004, 2:17 pm

will
rocket
are
you
If the OP has baseboard radiators, he may be able to shut the flaps on them in the room that is too hot and open them in the room that is too cool.

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• posted on February 21, 2004, 3:42 pm
snipped-for-privacy@morinfamily.com (Duane Morin) wrote:
-snip-

Your problem isn't necessarily heat loss, it is heat gain- from your furnace. Balance the heat and you're comfortable all over.
What kind of heating system do you have? While the easy way would be to hire a pro- you live there so you can tweak things on a daily basis until you're happy.

If all of the rooms had exactly the same heat loss & gain that might help. I hope you didn't take the wires out of the master bedroom-- If this is zoned heat & the upstairs is open to the downstairs, then I think you just went downhill in trying to control your heat.

So you have 3 choices-- cut down on the amount of heat reaching the other rooms so they all cycle longer-- or add supplemental heat to that room. Or you might be able to go with window quilts which can get your windows up to an R value in line with walls.
-snip-

Wait until you see the difference of R values between a window and a wall -- and if that isn't dramatic enough, figure the heat loss of that room against one of the bigger, less windowed rooms. -snip-
Jim

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• posted on February 20, 2004, 5:24 am

What type of window did you have before (single or double pane)? What is the U value of the new windows (should be a label on it somewhere)? Are they low-E?
-- Mark Kent, WA