I just had a bathroom redesign completed by a very competent/professional builder. We removed the only window and added an operable roof skylight with a good-sized light well (5 to 6 ft.) Used a nice Velux skylight with low e glass.
Now I have condensation forming on the four walls of the light well after running the shower. The builder came back and re-insulated with a second layer of bat insulation in the attic, but the problem remains. The room is small, and we have an exhaust fan, but it’s located in the flat section of ceiling, not in the light chase. My simple mind is telling me to just add a second fan, or a remote fan, that would draw moist air from the top of the skylight well. My limited understanding of condensation also tells me there’s some air infiltration, which means I should re-caulk all the joints.
Can someone run through the fundamentals of good skylight installation (aside from don’t do it?) Your expertise is appreciated.
Replies
where are you? What's the outside temp? fill out yer profile.
>a second layer of bat insulation in the attic
is the insulation around the light well or on the attic floor? The insulation needs to keep the walls of the light well warm which will prevent the condensation.
Once that's done the steam will reach the skylight. Kinda hard to insulate that though. I read a fair number of posts about dripping condensation off of skylights.
The good news is that Velux seems to be the best skylight by far.
splat
Sorry, I don't see any spots to add additional information beyond my log-in credentials, but I'll keep looking.
I'm in New Jersey. The problem first surfaced in the winter, which was understandable (warm moist air and cold attic). After the builder came back and made some changes, I washed down the walls and painted. I thought the problem was resolved, but the drips have come back slowly but surely through the spring and continue now (outside temperatures up to 75 F)
The attic floor has one layer of insulation and the light well itself has at least two layers of insulation.
As for the skylight itself, it doesn't appear that it's causing any condensation. The moisture appears to be forming on the walls themselves, fairly high up.
Thanks for your help.
"Sorry, I don't see any spots to add additional information beyond my log-in credentials, but I'll keep looking."click on My Forums
should see your name and underneath it says "My Prifile", click on that, then change profile.
bobl Volo, non valeo
Baloney detecter
I don't see any spots to add additional information beyond my log-in credentials, but I'll keep looking
Top center of the screen, ought to be "UPDATE PROFILE" in a medium-dark grey.
Or, you can click on your own screenname in blue, which should then show your profile.
Might be easier to move your existing fan to the side of the skylight well, rather than add another. The warm (and presumably moist) air is going to collect there, anyway.
In my hugely humid climate, a skylight well does much better with a rougher texture (to hide spots or spotting), or with a defined texture, like grooves, T&G (real or simulated) to channel the drips.Occupational hazard of my occupation not being around (sorry Bubba)
"V"That is up in the curb area where the unit ties in with the roof. It is almost impossible to insulte perfectly there. I use spray foam in a can when installing a skylight there to reduce the problem.
It is possible too thqat cold air spilling off the glass is keeping the wall surface cool up there so the mopisture condenses. changing the air flow patterns would probably help. you could have the fan vent location changed so it is sucking the exhaust out near the source of the problem, or try adding a minifan( like on the back of your PC - you want quiet low amperage, and small) way up in the skylight pocket to move the air around. Experiment with different angles to get the right exchange vortex.From experience, I would never have introduced a skylight to a small bathroom. A romance like that is doomed to end in divorce.if you are looking for something offbeat, you could ring a cove light or rope light all the way around that position, to be left on much of the time. The heatr would disperse the problem, maybe - and at night it would function as a nightlight.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
I'm inexperienced with skylites, so forgive my stupid Q..
Can one hook a return air vent into that space the OP describes? Since he's complaining about condensation in cool weather, maybe redirecting it to another part of the house could be good?
OT, those solar cell companies keep getting weaker...
I would expcet a setup like that to draw that moisture a short distance into the duct and let it condense right there, possibly dripping through a seam to act like a leak in the roof.Everything is weak this week, and I have not been home at the PC to react timely. Things turning today though.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
I cured a skylight which used to drip icy water on the head of whoever was in the shower. I installed a sheet of polycarbonate at ceiling level, preventing the moist air from getting up to the glass in the first place. There is no other way to fix this problem and still leave a skylight in place.
This problem has two parts: low glass temperature and warm humid air. You have to remove one part or the other or keep them separate. If you don't accomplish one of these things, you will still have the same problem.
Any kind of air exhaust from the skylight well will simply draw more air past the glass on its way out, making more condensation. An air supply in the well might work, in that it might force the humid air down and away from the glass, but around here they are not usually installed in bathrooms.
Insulating the well is good, but does not change the temperature of the glass.
It might reduce the amount of condensation in the drywall in the light well, though. In my experience, skylight wells don't have a very long life in a heating climate. They get damp. The drywall gets brittle and crumbly. Things fall apart. When I am forced to install one, I use MR drywall.
Ron
I had a skylight in my last house that was in the bathroom up in Northern Maine. Loved the light, hated the problems.
The new house had alot of areas that would have been great for skylights. Didn't install a one. 35 year shingles with flashing kits that may last 15 years at best just don't cut it with me.
Had I kept the old house, we were planning on filling in the skylight.
I don't really understand the talk about insulation. If you don't have good ventilation in a bathroom, walls get wet from steam. It really seems like your vent fan is misplaced or underpowered. Anything that gets past it will end up in the skylight well. What about putting another fan up in the well, as close to the top as possible?
Frankly, I agree with you about the insulation but wanted to see if the science backed up my belief. During my investigations, I stood atop a ladder in the skylight chase while the shower was running. It was absolutely humid. It seemed like it might start raining if it didn't condense on the walls.
I have easy access to all sides of the skylight and can easily put a fan at the very top. Seemed like the most effective thing to do, but there are obvious cost implications so I thought I'd check with this group first. I can't possibly be the only person to have a skylight in a bathroom.
Thanks.
"I can't possibly be the only person to have a skylight in a bathroom."you aren't. Lots of designers make impractical mistakes like this
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
An operable skylight? You could open it a bit when you shower but then you may have a different problem in the winter...
Billy
Seriously consider the airtight clear glass cover at the bottom of the well. This stops the moist air from getting up to the cool areas and improves/reduces overall heat loss.
I have seen situations where people have installed small propeller type fans at the bottom of the well to blow heated room air continuously up into the well. This increases heat loss from the low R glass but usually stops the problem. Not the best solution though.
In my home inspections, I see the $17 Broan 50 cfm "monster" fan 95% of the time. This fan should be banned as it is a fan in name only. It is usually poorly ducted so that in the end it may only be moving 20 cfm or less. One I saw on Monday would probably be moving 5-6 cfm due to using a 3" "undereave" vent as the duct outlet!!! Another I saw with a drier type vent outlet could barely open the hinged vent cover!! Could this be your fan installation?? If so, get a real fan and install it properly.
Note: The stated cfm volume on fans is when tested with no duct, etc installed, like if it was sitting on your kitchen table. This is misleading since the cheap "paddle wheel" fans have no real power to move air against a small diameter (3") spiral type plastic duct plus exterior hood. To get any decent volume with bath fans, you must buy a "squirrel cage" type fan (70-110 cfm) and duct it with 4" smooth metal duct. Reduce the # of elbows through good design (An elbow has as much resistance to air flow as 10' of straight pipe) Slope the pipe downward near the outlet so that condensation, if any, will drain outwards. Do not have the fan wired with the light switch (now illegal in Canada); use a separate hand crank or electronic timer.
Thanks for all your comments and ideas. I was wondering how long it would be before someone told me that the skylight was a bad idea. I've been around enough to know it wasn't the smartest thing to do, but counted on the tremendous improvements in skylight technology to make the thing work. That's why I bought a good unit with the upgraded glass and a matching curb kit. My main concern was leaks though. Now I see there was something else to consider.
The bathroom isn't even 6 months old, so I'm committed to try and make this work.
I'll take a good hard look this weekend at the installation details and spray in some low-expansion foam wherever I can.
My belief is the glass shouldn't be the problem since it's insulated, but I'll try to contact Velux' tech service group to see if they have any insight.
The skylight is operable and even has a timed remote, so it can be opened and will automatically close after 1-5-15 minutes. But the bathroom is used primarily by my 11 and 16 year old daughters. Need I say more?
We used green board for all the walls, so I hopefully can get a few years out of this before I start seeing wall decomposition.
The observation that moving the exhaust fan might actually exacerbate the problem is disturbing, but something I'll need to consider before making holes. Not exactly sure how to analyze this one. The warm moist air is there already, so I'm not sure how much worse it can be.
My fan is definitely not a bargain-basement model. I'm particular enough that I specified an upgraded model, and it cost considerably more than $20. It's located right next to the shower and is controlled by it's own switch. I'll check the exhaust ductwork this weekend. I know it's rigid pipe and there's no flap on the exhaust port
Thanks again for your thoughts. I'll check back after I get into the attic.
One other option that would work if you don't mind the configuration is to install a small fan to blow air across the skylight. I have used an outdoor-rated ceiling fan to do this. The fan can be left on continuously. It cured my mildew problems immediately in a custom shower. You will have to locate it a code-approved distance from the shower, of course.
I've read thru most but not all responses.
I too, have a velux skylight(fixed) in a bathroom. Insulation, leakage etc are not the problem. Think of it as putting a mixed drink or soda with ice on a coffee table- soon that condensation will show up. It's not really a problem if your skylight is placed over the bath or a drain. Your best bet is good paint on greenrock, eggshell or glossier finish to promote runoff when moisture builds up.
A bath fan will do little in this situation, but venting the skylight helps.
Cage,
The R-value of your glazing is probably not more than R-4. It's the glass.
Ron
As others have stated, this would be the simplest fix, might run you $20 & 1 1/2hrs of your time . This one is in a 3/4 Bath that teenagers use, 5years & problem free.
View Image
Orange ceilings?
I would have used Photoshop to change the color of that pic first!
Where big on the Broncos, here in Denver!
Oh! I forgot. When the Broncs lost early this year, we seem to have forgotten...
OT, come on down to the Belmar Optimist Club's Pancake Breakfast being held each Sunday from 10am til 2pm at the Belmar Farmer's Market.
We've set up a pretty decent partnership with Whole Foods and Belmar management to run a great fundraiser for the student activities at Alameda High School.
Betwixt you and me, you can get a free coupon for our breakfast from Whole Foods in Belmar this week only. Of course, you gotta buy something from them! But in doing so, you get this free "Customer Appreciation" coupon that actually pays us full price for our kid's programs.
I'm told by our customers these pancakes are the best ever!
Edited 6/15/2006 7:04 pm ET by peteshlagor
Do you have a ventilation fan in the bathroom? If you don't, you need one ASAP. Adding insulation isn't going to help. You need to use the fan when someone is in the shower and let it run for a while after they're done.
There are several really good (and quiet) exhaust fans available. I put in a Broan fan last year that was so quiet that I thought I had forgotten to connect the wiring. You'll pay more for quiet fans, but it's worth it.
Since you have a skylight, it may need to be installed as high in the "chimney" as possible since that's where that warm, moist, air is going to accumulate.
P.S. Did you notice that I got thru that without once saying that skylights in bathrooms aren't really good ideas?? - lol
I do have a fan in the bathroom, it's just not located in the skylight well. And it is a nice one. In fact, if I may get off topic a bit, I asked for an upgraded Broan model that would be quiet. It's surprisingly noisey even though I recall it was a sub-1 sone model. I wonder if it doesn't meet my expectations or if the installation details/connections are causing excess noise.
Another thing to check this weekend. It shouldn't be too bad crawling around my attic on a 90 degree day.
Panasonic makes the best and quietest bath fans for in ceiling installations.
For those clients wishing skylights for their bathroom renovation, I try to steer them to Velux Suntube (or whatever their trade name is.) They provide light provided by an accordian-type expandable tube. They're a fairly straight-forward install, with no condensation problems, that I know about. It means giving up the ventilated well (the roof-mounted fixture is fixed and transparent,) and the lens at the end of the tube in the bathroom ceiling is opaque, so you have no clear view of the sky, but they provide enough light that you think someone left a light on during the day.
"I am the master of my fate, I am the captain of my soul." Invictus, by Henley.
perhaps the problem is caused by the gap between the skylight flashing above and its frame below. Seems some have problems insulating that so-called rough-opening gap between the rafter framing and the skylight frame. Just a thought as I have heard some homeowners complain on drafts through skylight though there are no apparent holes.
Cage, I'm in NJ too. We've had a Velux skylight in our master bath since we remodeled 5 years ago. We've had zero problems with it. Our situation is slightly different since we have a cathedral ceiling, so the "whole wall" is insulated.
What's great is that this time of year (or at least when the A/C isn't on), we leave the skylight open and get lots of ventilation in the bathroom.