Wet fiberglass insulation in attic
We just bought our first house, a 1958 3 story cape, in December. I was poking around in the attic after reading Insulate and Weatherize by Bruce Harley, looking for air leaks when I discovered that the fiberglass insulation, the bottom of the roof deck and rafters are all pretty wet. The 2nd floor has a about 4 feet of sloped ceiling (cathedral?) and the previous owner finished most of the 3rd floor, leaving small triangular attic spaces behind the kneewall and at the ridge. The original insulation runs above the 2nd floor ceiling; up the sloped section and under the new 3rd floor. The previous owner added fiberglass insulation between the roof rafters from 3rd floor presumable to the peak, although there is no access there.
The moisture is only on the north side of the roof, the south side is dry, so I don’t think this is general moist air from the house. The wet side also had two bathroom vent fan ducts running through it and out the gable wall. One of the ducts had some gaps in it which may be where the moisture came from but I don’t know how much the previous owner used it. I have since replaced all the ducts with 4″ rigid steel and sealed everything. There are no soffit vents, only a continuous ridge vent.
From the crawl space on the 3rd floor, I can pull down some insulation and see there is about a 2″ air gap between it and the roof. I wanted to have cellulose insulation blown in, in which case I didn’t care if there were no soffit vents.
But now what do I do? How can I get the roof to dry out? I can pull out some of the insulation, but not all. I don’t want to rip out all the sloped ceilings on the 2nd and 3rd floor. I don’t want to install soffit vents just to dry it this once only to plug them up again but that seems to me the simplest way to get it to dry. If I get it dry and then get dense pack cellulose blown in, is it just going to get wet again? I sure would appreciate any suggestions?
Replies
First figure out where the water is coming from. If it's cold where you are then it is likely wafting up into the cold attic from your warm living space and condensing on the cold roof plywood and getting everything wet.
Go into the spaces where the condensation is occurring and start examining the ceiling and blocking at the knee walls to find the leaks.
Plug the leaks up with blocks of Styrofoam and great stuff spray foam and then run a simple dehumidifier in the area to dry it out. (or wait 'til summer and let it dry out naturally - or both) Then have a blower door test done by an energy auditor to look for the leaks you missed on the first go-round and plug them up too.
If you have a roof leak, then call a roofer.
m
------------------
"You cannot work hard enough to make up for a sloppy estimate."
You don't say where you live. Very important. How cold does it get where you live?
> the previous owner finished most of the 3rd floor, leaving small triangular attic spaces behind the kneewall and at the ridge.
This setup is a frequent cause of problems.
> The moisture is only on the north side of the roof, the south side is dry, so I don't think this is general moist air from the house.
That doesn't eliminate moist air as a cause -- the sun shines on the south side, preventing condensation, but the condensation occurs on the cold north side. Of course, there could also be a roof leak, or problems with those bathroom vents. Or simply a major air leak from below in the area where there's the most moisture.
> I wanted to have cellulose insulation blown in, in which case I didn't care if there were no soffit vents.
I don't understand your point here. If you're implementing a "cold" roof, you need soffit vents. And you need to not block them with insulation, be it fiberglass or cellulose.
Dan's right, your location is a critical bit of info before any serious guessing from us 12 year old girls can commence.
Joe H
What's your foundation like? Slab? Basement? Crawl with a dirt floor? Most houses I've been in with wet attics had wet foundations.
Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein (or maybe Mark Twain)
"Get off your dead #### and on your dying feet." Mom
"Everything not forbidden is compulsory." T.H. White, The Once and Future King
I live in northern Connecticut (I meant to put that in the first post) and it has been about 0-30°F for the last few months. I have looked for air leaks into the attic but the only penetrations are two pull chain lights in the sloped part of the 2nd floor ceiling, the two bathroom vents and one drain vent, all of which are sealed. There are no ceiling fixtures and all the electrical lines come up where I can get to them. There is no heat in the attic and the only door up there is weatherstripped and insulated. I did have a blower door test done and the numbers were close to the minimum ventilation guidelines. I don't think they even sealed anything in the attic.
I've attached a simple drawing of a cross section of the house. The pink was the original insulation, the blue is new, added when the the 3rd floor was finished. The only unfinished areas I have access to are the two triangular areas behind the kneewalls on the third floor, so I don't have a lot to go by, but I checked the insulation in four rafter bays across the whole roof and all are wet, so I'm pretty sure it's not a leaky roof.
The basement is half finished and very dry, no evidence of prior water leakage.
I have two main concerns. One is how do I dry out the insulation? Will adding soffit vents speed this up? Should I try to put a fan and or dehumidifier in behind the kneewall to force room air up through the ridge vent? Should I rip out as much of the wet roof insulation (blue in the picture) as I can? Or should I just wait till the middle of summer and check again? Second is once the insulation is dry, can I have cellulose blown in or will that not prevent them moisture problem? I thought dense pack cellulose acted as a vapor barrier.
My gut feeling is that the moisture is from the poorly plumbed bathroom vents that were on the north side. Since I've replaced those no new moisture should be getting up to the attic (or not much, at least). The moisture can't evaporate because there is not good air flow (ridge vent only) and the low temperatures. But I don't know how to proceed.
I'm in Litchfield County, so I'm familiar with your climate. How deep is your mud?Assuming no roof leak, I'd take a wait and see approach. You can add fans and dehumidifiers, but odds are things will dry out over the summer. I think at this time of the year, you probably shouldn't add anything new up there until next winter so you have a chance to verify that the problem has been fixed.If you're hiring the insulation work done, call Tony at R&M Insulation in Winsted. He's about the only conscientious insulation contractor I've ever encountered. He actually gets how insulation and air sealing work hand in hand. He'll probably be more expensive, but you'll get what you pay for. Tell him I sent you.BTW, without soffit vents, the ridge vent is pretty much worthless.Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein (or maybe Mark Twain)
"Get off your dead #### and on your dying feet." Mom
"Everything not forbidden is compulsory." T.H. White, The Once and Future King
"without soffit vents, the ridge vent is pretty much worthless."Can be more harmfull, depending...Sounds like he has most things sealed fairly well, but a house this old with a DIY finish up there is not as tight as it needs to be for an unvented attic space.Good that you could recommend a guy who understands this situation to actually be there to see and deal with it. Too many potential variables But while a roof leak is always possible, what he describes is consistent with what I have seen numerous times when condensation and improper venting are the root causes.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Places to look for for air leaks:Electrical penetrations, both wires and ceiling fixtures.
Plumbing vent penetrations.
Flue chases.
Ceiling soffits, such as those above kitchen cabinets.
Drop ceilings, often found in bathrooms.
The tops of stud walls, where wall drywall may not be tight against the top plate of the wall.Fans would be a good idea to accelerate the drying of the fiberglass. You want to get it dry before it has a chance to promote mildew and rot.Any situation similar to yours has a problem in that it's hard to assure good airflow from soffit vents to ridge vent, through the area where the top floor ceiling is tight against the roof rafters.
The modern conservative is engaged in one of man's oldest exercises in moral philosophy; that is, the search for a superior moral justification for selfishness. -John Kenneth Galbraith
"Fans would be a good idea to accelerate the drying of the fiberglass. "NOT if he is using them as he said - to blow room air into the attic space. That just adds to the amt of moisture condensing on the roof sheathing. I've seen it time and time again. People think they are solving the problem, but they make it worse, assume it is a roof leak, call me, then I fix the venting problem and it solves the moisture trouble all by itself.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Based on his drawing he has no "attic space", except in the kneewall.
The modern conservative is engaged in one of man's oldest exercises in moral philosophy; that is, the search for a superior moral justification for selfishness. -John Kenneth Galbraith
"Should I try to put a fan and or dehumidifier in behind the kneewall to force room air up through the ridge vent?"Whoa!Dehumidifier will help, but forcing more warm wet room air into the attic will make this worse. I have seen the same assumption tried many times and always with disastrous results.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Thanks everyone for all your input! I really appreciate it! It seems the general consensus is to just leave things be and monitor the situation. Since I don't have a dehumidifier, that's easy not to set up. The third floor is unheated, sealed off from the 2nd floor and I would have opened the windows before putting in the fans but that was a marginal idea at best anyway. I think making sure it drys out over the summer is a priority to rule out leaks and then wait until next winter to make sure it doesn't happen again.
To help that along, I'll have to dig through the insulation between the floors and look for breaks in the drywall, something I didn't do. The chimney flue is another problem I'm not sure how to tackle. The previous owner framed and put up drywall around three sides of it on the 3rd floor, leaving only about 4" between the studs and the chimney. There is a 2" gap that runs all the way to the basement. I can seal off the open side easily enough but would it be worth it to rip out some the drywall on the other three sides in order to seal those? Is there some easier way to seal them up besides flashing and fireproof caulk, such as expanding spray foam that could be shot in a few, smaller holes? Would just sealing the gap in the basement be enough?
Thanks also to you, Andy Engel, for the insulation guy. I was neutral about the guys I got my first quote from and would have liked someone a bit more respectable. I'll be sure to give him a call when this all clears up.
Fire code - Use sheet metal and fire caulk next to the chimney. You're welcome. Good luck, and let us know how it all works out.Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein (or maybe Mark Twain)
"Get off your dead #### and on your dying feet." Mom
"Everything not forbidden is compulsory." T.H. White, The Once and Future King
>>What's your foundation like? Slab? Basement? Crawl with a dirt floor? Most houses I've been in with wet attics had wet foundations.
Worth repeating.
I do crawls last, and will have a pretty good idea of how wet/dry after traversing the attic!
"Ask not what the world needs. Ask what makes you come alive... then go do it. Because what the world needs is people who have come alive."
Howard Thurman
Bob, I find a nearly 100% correlation between wet attics and wet basements. This fellow sounds like there's something else going on though. And Piffin is right about the lack of soffit venting potentially worsening the problem.Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein (or maybe Mark Twain)
"Get off your dead #### and on your dying feet." Mom
"Everything not forbidden is compulsory." T.H. White, The Once and Future King
In one of my first inspections, when I opened the attic hatch, I first thought they'd put the roof felt under the sheathing. Worst I've ever seen.
I have seen "wet" attics from other problems, although rare.
Did an inspection for a middle eastern client who didn't pay the slightest bit of attention. Got a call back in really cold weather because of condensation on interior walls and even mold.
They were keeping the temp in the 80's and had the humidifier set at its highest setting!The attic reflected that "moisture problem!"
"Ask not what the world needs. Ask what makes you come alive... then go do it. Because what the world needs is people who have come alive."
Howard Thurman
Edited 3/11/2009 5:18 pm ET by rjw
I wonder how many moisture problems are culturally driven? That's a fun one.Did I tell you about the consultation I did earlier this winter where I noticed a dirty patch of insulation at the end of an attic duct run? Turned out the HVAC hack hadn't capped the end of a supply trunk. That might 'splain the $600/month heating bills that client was enjoying. BTW, I like your quote.Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein (or maybe Mark Twain)
"Get off your dead #### and on your dying feet." Mom
"Everything not forbidden is compulsory." T.H. White, The Once and Future King
Did I tell you about the consultation I did earlier this winter where I noticed a dirty patch of insulation at the end of an attic duct run? Turned out the HVAC hack hadn't capped the end of a supply trunk. That might 'splain the $600/month heating bills that client was enjoying
That does it, I going looking for supply lines open !>G<
It is very common to have more condensation on a north sloping roof than on a south, and the leaky ducting could have aggravated the problem.
The biggest cause is no soffit vents. A ridge vent in place with no soffit vents and no air channel can make a condensation problem worse, because it creates negative pressure in the attic space it is trying to vent. if there is no replacement air from soffit vents, the suction just pulls warm moist air from the house into the attic before venting it out again. Meanwhile it hits that cold north surface and leaves some wet behind.
Welcome to the
Taunton University of Knowledge FHB Campus at Breaktime.
where ...
Excellence is its own reward!
>>The moisture is only on the north side of the roof, the south side is dry, so I don't think this is general moist air from the house.
FWIW, In my area, NW Ohio, it is not uncommon to see signs of condensation on the north slope and not on the south - difference in temps during daylight hours and, I believe, more radiation out at night.
"Ask not what the world needs. Ask what makes you come alive... then go do it. Because what the world needs is people who have come alive."
Howard Thurman