Heat loss through skylight

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I have 6 skylights in my house (12 year old house). In trying to lower my heating bills, I am looking at all possible ideas to save.
I have noticed that the rooms with skylights are MUCH cooler than other rooms, making me conclude that heat is being lost through the skylights.
How do I minimize this heat loss?
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You might get some improvement by adding ceiling fans or a ducted circulation fan to move the warm air at the ceiling back to near floor level.
If your skylights are at the top of a shaft you can close off the shaft at celing level with a plastic panel.
The skylight is a window which is less insulated that the ceiling and since warm air rises it is even worse than a standard window.
I have seen installations where the skylight is covered with an insulated panel during winter.
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snipped-for-privacy@yahoo.com wrote:

In my last house I had 4 huge sky lights in the loft. It was a kind of bubbly looking double pane one with lots of air gap in between. I definitely thought I was gaining heat into the room rather than losing it in sunny days. You can install shutter I guess. Tony
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snipped-for-privacy@yahoo.com wrote:

Yes, moveable insulation is the answer. I saw a Book just on this.
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Impeach Bush ! a noble cause
Operation Iraqi Liberation = O.I.L.
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My code for ceilings is R 35 mimimun, a single pane glass is R 1, dual pane lowEargon R 3.3. Seal it up with R 7.2" foamboard glued together for R 30+ for winter, or put it on hinges to open only in daylight, use a rope or some sort of device. Or get fancy and motorise it and use x10 controllers. I use Foamboard the R 7.2" type to seal a few windows and fireplace. On my fireplace I screwed in steel L channel and glued magnetic tape to the foamboard, 3 sheets glued together to seal to the steel L channel, its a removable Plug, it made a big difference in warmth in the living room and furnace cycles less.
Skylights are like a hole in your ceiling letting out heat. Since heat rises no glass made is considered energy efficient enough for ceilings in high heat Zones.
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m Ransley errs again:

Nonsense. InsUlation only slows heat loss. If each layer of glazing blocks 10% sun and adds R1, the net loss for an N layer skylight on an average Dec day in Chicago is 0.9^Nx460-24h(65-26.7)/N Btu/ft^2, ie any skylight with more than 2 layers will have a net gain, vs a loss for mere insulation.
Nick
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Nick you are an idiot, there is to little sunshine in winter to give a net gain, the days are to short, the suns angle to low at Chicago latitudes. I replaced a 6ftx9ft single pane S facing window with Tri pane and insulating curtains, That alone cut my utilities in winter 10 %. You also Assume its always sunny in chicago.
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You are wrong on all counts. Try numbers :-)
Nick
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Nick you are wrong on all accounts try experiance with windows. Your numbers dont account for real life weather.
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If what you stated was in fact true it would be the single biggest selling point manufacturers of skylights could wish for. So look for your self, find the claims and post all the net energy gains from manufacturers of Chicago lattitude. You can`t because they don`t exist. Your numbers and theory are flawed. I see neighbors go to double pane, and many more remove them. Skylights cost energy in the real world. You are like a bad computer program.
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m Ransley Dec 27, 4:20 pm
"Skylights cost energy in the real world. You are like a bad computer program. "
So does any window and last time I checked most houses have lots of those. I'm unconvinced that a skylight is so much worse than a similar size double pane window in a wall. Both have inside air against the glass, don't they? Sure, the air may be a few degrees warmer at the ceiling surface than at a window located in a wall, but in the big picture, I don't think it amounts to much.
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Today and this time of year 6 hr of radiant energy from the sun is all you get, if it isnt cloudy out. 18 hrs is your time frame to loose energy, 3 times the period of gain. A dual pane lowEargon window is no better than R 3.5. Minimum chicago code is R 35 ceilings R 60 being optimal. Heat rises and is proportionatly lost at a greater rate through the ceiling than walls. I still say if your numbers reflected real world weather you would see. Cloudy days are not in your numbers. If what you said was true it would be a true selling point manufacturers would take advantage of. But R 3.5 looses heat when there is no sun, and more than it gains over 18 hrs darkness . Now you show me an R 35 skylight, that will save energy, but we have no such glass yet.
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Irrelevant. Simple physics and real weather data say a skylight with N glazing layers will gain 460x0.9^N Btu/ft^2 and lose 24h(65-26.7)/N on an average December day in Chicago. With more physics or calculus, you might figure dGain/dN = 0 makes N = e^(0.505N+1.47). N = 5 on the right makes N = 5.6 on the left, then 5.77, 5.82, and 5.84, so N = 6 maximizes the net gain, vs a ***LOSS*** for mere insulation.

Those numbers are NREL's 30-year measured weather data for Chicago.
Why not give up your excellent imitation of a nitwit? :-)
Nick
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"m Ransley Dec 27, 5:43 pm
Heat rises and is proportionatly lost at a greater rate through the ceiling than walls."
So let's say the air temp near the ceiling is 75 deg and it's 70 in the middle of the room where the windows are. If it's 20 degrees outside, the temp differential at the skylight is 75-20U deg and at the side windows it's 70-20P deg. So assuming the construction and size of the windows is the same, the skylight will be losing about 10% more heat than the side window. Hardly anything to get your shorts in a knot over or worrying about doing anything special as opposed to any other window.
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Is it 10% more, optimal wall insulation is well below ceiling ratings, from what I have read at different sites even SIP construction by near 50%. Alot is construction techniques but still retings are much lower in walls.I know it doesnt mean 50% goes up and out, but heat rises, and it could. Ive never read or seen skylights in optimaly insulated or solar designs. If it could automaticly close with a foam insulating plug when shaded it could be a net gain.
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"m Ransley Dec 27, 8:58 p
Is it 10% more, optimal wall insulation is well below ceiling ratings, from what I have read at different sites even SIP construction by near 50%. Alot is construction techniques but still retings are much lower in walls."
Here's a good link that has some real data:
http://homeenergy.org/archive/hem.dis.anl.gov/eehem/93/931109.html
It looks like a skylight has roughly 2X the heat loss of a similar vertical window, so you are right. They also explain why. It seems the main effect is that with a skylight being installed close to flat, the gas between panes circulates bottom to top, carrying heat from the inner pane to the outer. With a vertical window, the gas between panes doesn't move directly from pane to pane, so less energy is transferred. Kind of strange, as I would think that would be a second order kind of effect, but apparently it makes a big difference.
I'm sure there is some heat gain from the sun during winter that helps offset some of this. It might even offset all of the difference in some climates. Of course in the summer you have the opposite effect, where now the heat is working against you. Still, if the differential is 2X, it's still not all that bad.
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That's better, but any skylight is a net gain if more solar energy enters during a day than heat energy leaves during a day, which can happen with several layers of glazing. For instance, 3 layers of R1 glazing with 90% solar transmission would gain 0.9x0.9x0.9x460 = 335 Btu/ft^2 and lose 24h(65-26.7)1ft^2/R3 = 306, for a net gain of 29 Btu/ft^2 on an average December day in Chicago.
By contrast, insulation just loses heat. An R100 ceiling would just lose 24h(65-26.7)1ft^2/R100 = 9 Btu/ft^2.
Would you rather gain 29 or lose 9 Btu of heat per day in December?
Nick
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Nick no skylight I see offered has high SHG, this rating, a 50% lower R value, cloudy days and heat loss make your statements of net gain untrue. Now figure in extra heat load through summer, and you have a major net energy looser. But of course you do have independant results you can post to verify your energy saving claims. Please post them.
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I disagree. Where are your numbers?
Nick
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Nick wake up and read other links mentioned, and post some facts, not your usual unsubstantiated ramblings. You have proven nothing, you can`t back up your claims, so you don`t.
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