# Can Skylights be energy efficient



## SPS-1 (Oct 21, 2008)

Skylights are not the most thermally efficient. You can see HERE the U-value of their skylights. By comparison, a pretty good new window will have a U-value of less than .3 (lower is better). You will see that some glass configurations are more efficient than others, but in reality, only a couple of those glass types are readily going to be available. Plus, you likely will have a tunnel to insulate too, and will have some heat loss through it as well.

But just the same, I wanted the light and to see the sky, and was going to have two skylights regardless of loosing a little heat. If your roof slope faces South, you will also need shades on it. At my last house, I had two skylights on the South roof, and simply kept the shades closed from May to October, and open the rest of the year.


----------



## Bud9051 (Nov 11, 2015)

Not real energy efficient but not a total disaster if you do a careful job of insulating and air sealing.

Consider, there are probably other places that could be improved more than enough to offset whatever loss/gain the new skylight represents.

Modern reality is, LEDs and other form of efficient lighting can provide 365 light at probably less expanse. I now leave several night lights on all the time. Calculated cost is very minimal and the added security for this old goat (living alone) is a must.

Bud


----------



## Randy Bush (Dec 9, 2020)

They can be just as efficient as a good quality window you install in your home. Velux is a good one, themo glass argon filled can buy light filter shades for them . Conpare to the old plexiglass bubble ones miles different.


----------



## Domo (Nov 9, 2018)

bobdown said:


> I live in Vancouver and I want to put Skylights in to get more light in the winter months. So I was wondering. from an efficiency point of view, can Skylights be energy efficient?
> I am concerned I will lose heat in winter and get too much heat in summer (especially during a heatwave)
> 
> I look forward to your opinions.


LOL - skylights give you light as well as unwanted heat in the summer and a chimney effect that promotes water condensation in the winter. They also provide a challenge for insulating when the skylight is in a full (close to roof) cathedral/vaulted ceilings since any bays that are blocked by the skylight will not be able to breathe - thus capturing moisture where it should be dry. Some are better than others - think way ahead regarding water dripping down the sides of the recess, under any trim boards and onto floor/furniture below. 

Could I suggest tubular skylights? They introduce light and avoid most of the problems.


----------



## chandler48 (Jun 5, 2017)

I just can't see the lucidity of cutting a large hole in an otherwise non leaking roof. I agree that LED lighting is a better choice.


----------



## A. Danger Powers (Aug 13, 2021)

We inherited an octagon house built in the 1960s with a lot of skylights that were replaced in the 1970s, and 80s, and 90s due to failure and/or water damage. I would not install skylights someplace that I could not easily inspect for water damage or failure. Whether it's the product, installation or both, when they fail they let water in. If you don't catch it right away, it's a bad spot. All skylights fail eventually...

I would try some LED full spectrum light bulbs and see if you like those. My neighbor has those in his basement and it feels like real daylight. Just an option before you tear open a watertight roof...


----------



## Jean4now (Jul 6, 2021)

I made the mistake of putting a large skylight in a South roof. Sun was brutal and faded the wood floor where it wasn't covered by area rugs and faded the hand woven rugs where it was. UV film wasn't much help. Heat gain in the summer was significant as was heat loss in the winter even though it was double pane. Had it been on the North side there would have been more than enough brightness even on somewhat overcast days.

My biggest mistake however was not having the walls (or whatever the space between the skylight frame and the ceiling is called) angled. Maybe everyone already know this but I didn't. If you lok at windows (or window spaces 'cause I don't know that there was glass) on thick stone walled castles, the window space is much smaller than the interior space in which the window is set. It is angled to enlarge from the outside opening to the larger inside opening in the wall/ceiling. Because light (other than LEDs) spreads outward. My 10" depth from the roof to the ceiling interior was straight. I guess the builder didn't know either. I could have had a much smaller skylight with just as much light coming into the room. Because it would have been diffused I wouldn't have had as much fading. Because it would have been smaller I would not have had as much heat gain/loss.

I think tubular skylights are a waste. Only a small amount of sunlight because it can't "spread" and a hole in your roof.


----------



## Old Thomas (Nov 28, 2019)

No skylights for me. Cutting a hole in my R50 ceiling and installing something in it that is a fraction of that doesn’t make sense to me. And it is only a matter of time before they leak. Anything you can do to reduce roof penetrations is beneficial.


----------



## Deja-vue (Mar 24, 2013)

I installed 3 Solar Tubes back in the 90's, they work well, bring natural light into the House and won't leak.








The Pros and Cons of Solar Tubes - Home Reference


Solar tubes offer free lighting and are more affordable than skylights, but what about their downsides? Read up on solar tube pros and cons today.




homereference.net


----------



## SW Dweller (Jan 6, 2021)

I installed 2 Solar Tubes in my ranch style hall way in Phoenix. Could have gotten away with one. Asphalt roofing. Since there are covers in the ceiling the heat in the summer was not so bad. 
It really depends on how much light you want and what your willing to sacrifice.
I had a tree near by and eventually a storm broke the globe on the roof. I had a bucket over the hole for 4 months while i waited for the MFG to send me a new one. 

I know there are skylights made for european energy standards, that open and close and have shades


----------



## snic (Sep 16, 2018)

LED lighting is very efficient and my guess is that you wouldn't come out ahead with skylights. That said, nothing quite beats natural light. I put in a solar tube in a very dark hallway, and it's completely transformed that area. Yes, we could have just left the lights on all the time, but the reality is we didn't and wouldn't do that. (One tip re solar tubes: the light can seem blue and harsh. That can be solved by putting a sheet of color correction film at the ceiling end of the tube, right on top of the diffusing cover. Photographers and cinematographers use that to change the color of the light coming in through windows or other sources. I chose a yellowish/orangish one that changes the light from 6000 kelvins to something like 4500, with about 10% loss of light intensity. The light is much softer and more pleasant now.)


----------



## viper (Jul 30, 2009)

I'd suggest you go find what it is you would like to install and bring those in here so we can run calcs. I would agree that a likely more 'efficient' path is a solar panel or two, and LED lights on the interior. However, it is very well known that it is hard to beat natural lighting!!!! Why do you think 7 figure homes are stacked with windows? I'd say sometimes you have to take an energy hit to increase your happy. Natural light light includes light spectrums that artificial light struggles with. 

After all, once you understand the efficiency difference between an insulated wall and a window, you would quickly conclude that an 'efficient' home should not have windows........but they do....


----------

