Cold Air from 25 Year Old Velux Roof Windows & Wells
I read Martin Holladay’s article in the January 2014 FHB on proper insulation of skylight shafts with great interest. I have a master bath that has a pair of Velux motorized roof windows going back nearly 25 years, and that bath has always been plagued with being much colder than it should. Despite being heated with in-floor radiant heat that gets wonderfully warm to the touch, when I sit on the throne I’m always aware of cold air on my head during the winter. Reading that article made something click, and I tried an experiment.
I bought some 2″ rigid foam and, using my table saw, ripped it to the proper width for the window wells. Then I used a skill saw to cut the proper angle to match the well flare, inserted the foam, and taped it into place temporarily with blue painters tape. The difference was astounding! Clearly the improperly insulated walls of the window well were acting as a cold air source, cooling off the rising, heated air and having it drop back down as a cold breeze. I’d always suspected the wells as a source of the problem, but now what to do?
My questions are, in no particular order:
1. Is a 25 year old Velux a candidate for total replacement due to its’ age and the technological improvements since it was produced? I already have had most of the low voltage motors fail, so don’t get me started on that topic!
2. Are the newer products appreciably better, or is an open-able roof window always going to be a heat leak?
3. If I were to engineer a solution where, in the winter, I mounted a weather-stripped, fixed window with at least dual pane insulated glass in the opening at ceiling level, would that likely be nearly as good as my 2″ foam insert or am I wasting my time?
4. Unfortunately, this bathroom is an attic area that is isolated, meaning that because of scissor trusses in the adjacent vaulted master bedroom ceiling, there is literally no way to get into the attic of the bathroom. And I don’t want to open up the gable end from the outside to get it, which is covered with fairly new Hardie Plank siding now. The only way to get in there is to open up the ceiling, with all of the hassle involved in ultimately patching the opening in a way that doesn’t show. No easy solution there, but I’m open to ideas on the best way to improve this pesky problem. Thanks very much!
-Mike R
Replies
Like you, I had a similar situation. early 80s Velux, openng, skylight window in an attic bedroom. The additional light that the skylight gave was great. When I renovated the bedroom last year, I replaced the old Velux with a new "fixed" velux window. I also had the sloping ceiling/roof sprayed with 5" of closed cell foam. Made a BIG difference.
But, the skylight will always put a big hole in my roof! My solution was similar to yours. I made a removable insulated panel. I glued together two, 2" closed cell foam panels for a R value of 14. The foam panel has a gasket around it's edge and with some small wedges forms a tight compression fit in the skylight well. A ceiling colored fabric was glued to the good side so that it blends in with the ceiling.
Where I live in Central NY we have LOT"S of snow so my skylight is partially covered most of the winter anyway. So I install the insulated panels into the skylight well every November and remove it around the middle of March. After a few days , I forget that it's even there.
That way I can have my cake and eat it to! Light during the milder season and insulation during the dead of winter.
Great minds must think alike!
Oh good, glad you've already done this and it worked! I hadn't considered adding a second piece of foam but actually it makes perfect sense to do so. And I figured painting it with the same paint as the ceiling would suffice for the couple or three months I'm likely to use it. I like that wedge idea too, way better than my blue painters tape! It's already made a difference in there, but quite a bit darker in the morning. :)
If you fit a window to the bottom of the opening you're pretty likely to get condensation above it. How serious is hard to say.
Have you determined whether the cold is coming through the windows proper, or the sidewalls? Can you simply insulate the sidewalls?
Condensation above the lower window
You're probably right, it's what I was afraid of.
As to insulating the shaft, see my earlier problem about attic access. And no way to add insulation inside the shaft since it's essentially the same size as the window. I can't tell if the problem is the shaft or the window itself but I suspect it's probably both.
Can't you wedge foamboard on the inside of the shaft?
I know that every home and situation is different and your home may not perform the same as mine. But, I get no condensation on my skylight or well. In the spring when I remove the foam board everything is fine with no mold or water staining. Fortunately, in my situation everything is well insulated and there's no air movement thru the ceiling. The weatherstriping around the edge of the foam also helps in keeping a tight seal.
I would check for air leakage first. Get a smoke pencil and get up there on a windy day. If the skylight is truly leaky, you'll find out. Then you will know the answer to replacement or not. I've got two Velex fixed skylights that do not leak.
Then, get an infrared thermometer to check the temperature of the side walls in the window well. Those surfaces ought to be nearly the same as the horizontal ceiling in the bathroom. If the sidewall temp is very low then adding insulation is necessary. So, hope that you HAVE to replace the window units, then you can get slightly smaller ones that will fit the slightly smaller wells that you will have after adding 2" of xps foam. Or, tear out some drywall. Fixing that isn't really all that difficult.
Your situation is a lot different than the other guy's. His skylight is in a bedroom, your's in a bath. Your moisture/condensation issue is vastly magnified. But, you can leave your blue foam plug in place for a spell and check for yourself. Nothing replaces actual field experimentation.
foam = no light
Howdy dead air space is good at not transmitting heat. So on our sky lites instead of foam i had plexiglass cut to fit in & trimmed out the shaft opening a bit narrior with casing. The pleiglass rests on it. To midigate air leakage added a foam tape on the casing. Worked great much warmer in our room and still light and simply take out the plexiglass in the seasons that i wish to open the sky lites.