# reducing skylight heat loss...



## longshanks (Jul 23, 2009)

Hi all...

I have a love-hate relationship with our skylights. We love the natural light that they provide, but I'm going bananas dealing with winter roof leaks, and trying to make a decision on what to do with this mess. My wife doesn't mind a bit of wet drywall, and I think she thinks I'm OCD:laughing:

The previous owner of the house had the same problem, so we replaced the roof last year, including 2 new Velux skylights and continuous ridge and soffit venting. I also spent more hours than I care to think, up in the attic insulating around the skylight tunnels. They extend up to 7' through the attic and terminate in openings in the ceiling above our bathroom and living room. Roof is 5/12 pitch.

We live in northern Canada in an area that gets extreme cold winters and deep snow. It's common to have 3-4' of snow on the roof all winter, and temperatures of -20C. Due to these conditions we get ice damming around/below the skylights, due to the fact that they melt the snow that falls on them. In 2 of the 3 winters we've lived here, during a mid-winter thaw, water backed up through the shingles and we get a @#$%^ roof leak. 

I shelled out $7K for a new roof last year and the roofer told me that he did I+W shield under both skylights, but last winter there was some leaking under one of them. I'm at my wits end, trying to get roofer to come back and fix areas that leaked, but he hasn't shown up yet and we're getting quite close to winter. Other roofers won't come and fix due to their fear of liability. Although I'm not the type of person that wants to resort to this I am considering taking the guy to small claims court for all the damages if he doesn't fix it before winter.

Here are my options:

1) remove the skylights completely
2) replace the skylights with sun tunnels
3) further diy work on reducing skylight heat loss
4) electric de-icing cables
5) shovel roof before winter thaws

More than one person has suggested that I should block off the bottom of the skylight tunnels with plexiglass/acrylic/plastic. Theoretically this would let the light through, but reduce the amount of heat going up the tunnel in the winter. I could frame these up fairly easily, and make them so that they could be cracked open a little if condensation ever became an issue...

I'm interested in hearing your opinions on what I should do. Also would like to hear from anybody with experience in framing in the bottom of the tunnels with acrylic. 

thanks for your thoughts...


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## Wood_Smith (Jun 21, 2009)

*plexiglass..*

I had an older home and couldn't afford to replace the windows so I bought kits (this was about 30 years ago, don't know if they still sell them) to make frames to put plexiglass on the window openings (the openings were deep, about 12").
One side of the frame had a magnet and a channel the plexi went in. The other side was metal and attached to the window opening. You cut the plexi to fit, pushed it in the channel, attaced the metal strips and bingo! a second layer of window. They lasted for years, when I sold the house.


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## oh'mike (Sep 18, 2009)

I tacked 1x2 ledger boards about a foot below the skylights and simply set a sheet of plexiglass on top of the ledger boards-----cut down on the condensation---

The skylights were single pane vintage 1928.


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## Ron6519 (Mar 28, 2007)

Sounds like you have 2 issues. Roof leaks and condensation. It also sounds like the house moisture level is high if you have condensation on your skylights.
Get the roof fixed and maybe the condensation will disappear, maybe not.
The moisture from the leaks will linger a few weeks if the area isn't open and dried. Once you're sure the roof is fixed and the building materials are dry, measure the houses' humidity level to see if it's too high. If it is, find out why and reduce it.


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## longshanks (Jul 23, 2009)

those are some great ideas. The suggestion for simply placing a plate of heavy acrylic on top of a frame in the skylight tunnel is something that I can manage. I am hopeful that this will give some additional R-value and reduce much of the heat that goes up the tunnel. thanks for that Mike. 

Condensation is not an issue in our house. The humidity where we live is pretty high, but we only rarely have condensation on the skylights. 

The roof still needs to be fixed. Any suggestions on motivating a roofing contractor to come back and fix this? I paid top dollar and the guy gave me a one-year warranty.


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## Ron6519 (Mar 28, 2007)

longshanks said:


> The roof still needs to be fixed. Any suggestions on motivating a roofing contractor to come back and fix this? I paid top dollar and the guy gave me a one-year warranty.


Write him a certified letter with a time frame fix. If he doesn't respond, get the roof fixed by someone else. Then take him to small claims court for the cost of the repair.
The comment of, "Other roofers won't come and fix due to their fear of liability.", makes no sense. Roofers fix leaks all the time. When they take on any job, they take on the responsibility of doing the job correctly.
Contractors take on jobs all the time and every time they do, they take on responsibility for the job. And the liability if they do it incorrectly.
Call a roofer up and say you need a roof leak fixed around some skylights.
Don't tell them the issue with the old contractor, it's not relevant. The only thing relevant is the leak.
Keeping water from leaking around a skylight isn't rocket science.
A caveat.
You do not fix a leaking skylight with tar or roofing cement. Any clown who say that's how he fixes them is not competant to own tools.
The roof around the whole skylight needs to be removed and the curb reflashed. If they're not willing to that, it won't get fixed and you're wasting your money.


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## longshanks (Jul 23, 2009)

Thanks Ron, what you say makes sense and that's a good plan of action if he doesn't show. He finally called back today and said he is going to re-shingle and re-do the I+W shield. He also said that he recommends putting up de-icing cable. how on that?


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## Ron6519 (Mar 28, 2007)

longshanks said:


> Thanks Ron, what you say makes sense and that's a good plan of action if he doesn't show. He finally called back today and said he is going to re-shingle and re-do the I+W shield. He also said that he recommends putting up de-icing cable. how on that?


A properly flashed skylight would not need heating cables.
I've been putting skylights in since the early 80's, I've never had one leak and never put heat cables around skylights.
With the proper installation of membrane and the flashing package that came with the unit should be all you need.
The instructions back in the 80's didn't even require tarpaper up the sides of the curb. All you used was the aluminum flashing package and it worked fine. Over the years the instructions have changed, along with the building materials. But, the bottom line is, if you don't install it correctly, it will leak.


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## Wildie (Jul 23, 2008)

With 4 feet of snow on the roof, there will be little or no light coming from the sky-light.

I would suggest that its the heat loss through the glass thats causing the snow to melt. The snow melt runs down and forms a dam. Then more snow melt runs up through the flashing.
As long as heat from the house can contact the glass, snow will melt.
I would make a removable plug that will close off the tunnel. The plug would have an R value of about R40.
Next, make a vent in the side of the tunnel that would be closed off in the summer. This vent will allow cold air to cool the glass and stop the snow from melting.


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## longshanks (Jul 23, 2009)

Well, the skylights are not leaking and neither are the curbs. I worked with the roofer on the skylight/curbs and I know that they are done right. What is happening is as Wildie says; the heat on the glass melts the snow, and it re-freezes downslope of the skylights. Given some time, there is enough heat loss through the skylights to melt away 3-4' of snow, and then it freezes downslope on the roof. Our roof is relatively low-pitched, and during a mid-winter thaw these ice dams collect melt water and it pools up long enough to drain through the shingles/I+W and into the attic...

what I am trying to do now is reduce the amount of heat loss. I've done all the attic ventilation I possibly can. I think the next step might be to put some acrylic over the bottom of the tunnels. I'd like to get by without the heat cables, but I am thinking that these are pretty challenging conditions for skylights to function without the ice-dam problems that we're having. thoughts?

Still crossing my fingers for the roofer to show and hopefully shed some light on it...


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## Ron6519 (Mar 28, 2007)

It would help if you stated the roof pitch slope and not a generalization of, "relatively low pitched".
I would have installed ice and water shield up the entire "low sloped roof". I do it now on any slate roof I do, regardless of the slope.


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## Wildie (Jul 23, 2008)

Snow is an insulator and if the attic temperature is above freezing because the venting is blocked from deep snow, perhaps a cupola would vent off the warm air .

http://www.familyhandyman.com/DIY-P...ttics/Attic-Ventilation/how-to-build-a-cupola


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## longshanks (Jul 23, 2009)

Ron, it is a 5/12 pitch. According to the roofer, he put continuous I+W up the valleys, and around/downslope of both skylights. The odd thing is that one of them leaked in 3 locations last winter. About 2' below the skylight, and again near the bottom of a valley that is situated down from the skylight. 

The question in my mind is, given the deep snow and extreme cold temperatures we get here, can I trust this roofing system to not leak when it ice dams, or would it be wise to put the heater wires back up there in the event of a mid-winter thaw? There were heat cables on the roof when we bought the house but initially I didn't want to be bothered with them... 

I did a lot of work last year opening up the soffits, and installed continuous ridge vent. It is as well ventilated as it can be in the attic, and I'd estimate only a couple degrees difference from outside temperatures.

attached are a couple photos of the roof last winter when it leaked. I dug out the skylights to have a look, and you can see the ice below them in these shots. I was surprised that it leaked...


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## Ron6519 (Mar 28, 2007)

A few questions.
How much of an overhang do you have?
How far up the roof was the ice and water shield installed?
In the house, what sort and how much insulation do you have just inside the overhang?


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## picflight (Aug 25, 2011)

I am curious to know where in N. Canada are you?


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## longshanks (Jul 23, 2009)

to answer your questions...

overhangs are 24", and I+W goes all the way up the valleys, 22" to each side of the valleys. The insulation is blown in, and I'd estimate about 20+ inches of it all over the attic floor. Just inside the overhangs, it is filled to within about 2" of the roof sheathing, where I have baffles around the entire soffit. I've checked the roof after a heavy frost and the only spots I can see any heat loss/frost melt is immediately around the skylights.

We are located in Prince George, BC. Let me guess, you saw all the snow and you want to move here from California? 

Roofer did show up today and he thinks the water got in at the bottom of a valley where a dutch gable joins the roof. He thinks that ice build up around the bottom of this valley forced water up under the roof overhang at the end of the gable, and leaked in (if that makes sense). He did a bunch of caulking around the flashing and shingles and thinks that should fix it...


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## Ron6519 (Mar 28, 2007)

If the overhangs are 24", the I&W shield should run along the gutter line by at least 2 rows(66"). If it doesn't, you'll need those cables again.
But like I said, with that climate and that roof pitch, I would have run it up the whole roof.


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## picflight (Aug 25, 2011)

longshanks said:


> We are located in Prince George, BC. Let me guess, you saw all the snow and you want to move here from California?
> ..


it's nice to live in the snow sometimes.


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