Heat loss through sky lights?

[Chuckca]

How much heat is actually lost through sky lights....?  

I was in Home Depot and Lowe's last night...they didn't offer much info....what they did give was so so?

Wouldn't it make more sense to keep the roof closed and tight....use larger windows....?

Thanks

 

[Jimmy C.]

This link might help.
I worked at American Sky Lights for 10 years.
I can't answer your question, I never got into the selling side of it. Only fabrication.
I know they can tell you the amount of heat loss to expect.


We used to test the strength of the skylights by shooting a 2x4 at 150mph with an air cannon!
Dade County Approved! Not an easy thing to do.

This link has the line of highly insulated double domed skylight.

http://www.americanskylites.com/residential.html

[Shelley]

Big time.  Windows and sky lights are the weakest link and since heat rises, sky lights are the worst.

Velux is one of the better and higher priced ones.  Don't know for sure, but think the best you can do is around R7.  A homemade diffuser will help.

You might check on the tube ones.  I never have.  Hole is a lot smaller and they really put out some light.

[Amanda_931]

Humph!

Ms Grumpy is tired of reading about how r-values and u-values differ in important ways.   For instance, as a measure of how the wall as a whole is operating.

And two paragraphs later the author says that a u-value is 1/r-value, and vice versa.

Susan Susanka's latest column (Inspired House, maybe--one of them Taunton periodicals) mentions skylights.  She thinks that for the most part they are an admission that one hasn't designed the window system very well.  But sometimes there's no help for them.  Lofts and attics, for instance.  She recommends putting windows as close as possible to (white) walls to try to boost the light that actually gets into the room.  Maybe even going so far as to use very deep window wells as reflectors.

One could always run an insulating curtain (in channels would be nice) to help keep the heat from going bye-bye.  Somebody probably even sells a system made for the purpose.

[Amanda_931]

Oh, yes, and sometimes losing heat through the skylight is the whole point.

Not often getting water in through them, though.

[John Raabe]

The reason you go to the trouble of putting in a skylight is for the light and views - and sometimes for the ventilation. It's the same reason you put in windows. Yes, walls and ceilings are much better insulated than windows and skylights. But aren't we blessed to be able to have light holes that don't let ALL the heat out?

In a cold climate you will generally get the best price/performance from a dual glazed system 1/2" to 5/8" thick, low-E coated and filled with argon (unless you are at a high altitude in which case forget the argon - it won't stick around anyway). The frames can be vinyl or wood. Cladding is for lower maintenance. Low-e is done as much for comfort at night as for control of heat loss.

A well insulated wall is R-21, a well insulated roof R-30 a good window/skylight like above is about R-3 or 4.

Oh, one more thing. Walls and ceilings don't help much with solar gain - which you want in the winter and don't like in the summer. That's why south facing windows and skylights usually gain more heat than they loose over the year. Trouble is the timing isn't always perfect.

[Amanda_931]

John wrote:

 But aren't we blessed to be able to have light holes that don't let ALL the heat out?

Back in my (not all that wild  :'( ) Music Row days I knew a guy who wrote a song called "What would you do if all of the holes in your body healed up."

[glenn kangiser]

Amanda, I couldn't have put that better myself.

[DavidLeBlanc]

My parents used to put rigid white foam panels in their skylights in the summer. Otherwise, far too hot!

Great solar gain from them in winter! I don't recall them covering them at night, but I could be wrong about that!

How about panels built into the ceiling/roof that slide down (manual or motorized) to cover? Sort of like those found in some cars. Sealing a large part of the cavity the skylight is in should have some excellent insulation properties. Still air is excellent insulation.

[Amanda_931]

Back in the old days when Zomeworks was touting breadbox water heaters, no-freeze watering holes, and Zomes--and not just tracking mounts for solar panels--seems like they had something in the way of either motorized or easy to get from twenty feet below insulated skylight curtains.

[Shelley]

Even the cheapie skylights are double paned now.

So, you build a diffuser.  Some kind of trim around the ceiling opening.  Then a piece of plastic from HD cut to fit.  Then you have a dead air space some # of inches deep depending upon where in the pitch it's placed.

Works at 5000' in the intense NM sun.  Without a diffuser, you can feel the heat even if you get tinted skylights.  With a diffuser, pretty much a non-issue.  

If you're using the SL for solar gain as well as light, remove it in the winter.

Think I kinda tend to agree with Susanka.  If one is using them for light, probably a design issue.  Solar gain's a whole nuther thing.