Heat loss through skylight

m Ransley errs again:

You are wrong on all counts. Try numbers :-)

Nick

Nick you are wrong on all accounts try experiance with windows. Your numbers dont account for real life weather.

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.

m Ransley errs again:

You are wrong on all counts. Try numbers :-)

One more time: 460 Btu/ft^2 of sun falls on the ground on an average 26.7 F December day in Chicago. Unlike insulation, any skylight with more than 2 layers of glazing will gain more solar heat than it loses... 6 is optimal:

layers net gain

A skylight with a south tilt or a shutter or a reflector can gain more.

Insulation can only LOSE heat.

Nick

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.

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.

m Ransley errs again:

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

"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 75-20=55 deg and at the side windows it's 70-20=50 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.

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

"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

Here's a good link that has some real data:

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.

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

By contrast, insulation just loses heat. An R100 ceiling would just lose

Would you rather gain 29 or lose 9 Btu of heat per day in December?

Nick

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.

I disagree. Where are your numbers?

Nick

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.

Again, YOU made the claims. It's your job to prove them. And again, where were you when they handed out Logic :-)

Proving "No skylight is good enough to gain heat on an average December day in Chicago" would seem to require that you have a list of every skylight on earth, including those yet unbuilt :-) I've already shown how to build a net heat gainer with multiple layers.

Nick

"I've already shown how to build a net heat gainer with multiple layers. Nick "

I don't know what planet you;re living on, but here on earth people in this newsgroup buy skylights, we don't build them based on hypothetical ramblings.

Some do, some don't, based on 300-year-old high-school physics, eg Newton.

Do you have a list with the physical characteristics of every commercially-available skylight on earth to prove your claim? :-)

If so, post it.

Nick

Nicks "Net gainer" , every day is a sunny one.

Nicks famous ideas, " Keep basement floor wet for humidity" " Remove steam radiator air vents for added humidity" Nicks theory, caulk will solve all lack of humidity issues.

Nicks hero, the hubble telescope engineers, "But the numbers were right, we just forgot a few equations."

There ya go nicko ol boy misquote me, Can you prove your " net gain" theory, no you cant, go take your alzheimers pill, the pink one, or is it the blue one you must ask yourself.