The house I bought has attic insulation between the roof rafters with paper facing exposed. I know that this presents a fire hazard and I am planning to remove the paper facing.
I would prefer to not have the insulation exposed.
What do people do in this situation?
I was thinking of stapling tyvek over the insulation which would do the same job as paper facing but not be as flammable(flame spread rating of 25 and smoke developed rating of 450 for the tyvek)
any comments or suggestions on this?
thanks
Adrian
Replies
Its a bad idea to have the paper facing up because it is a moisture barrier and may trap moisture from house inside the insulation.
Why do you want to cover the insulation?
You get out of life what you put into it......minus taxes.
Marv
i read it as insulation is between RAFTERS, not the ceiling JOISTSso, attic is insulated/conditioned spaceif so, have you checked for spacer/air channel behind insulation -- up against sheathing? will this ever be finished area/bonus room or whatever??
Edited 5/5/2005 7:35 pm ET by ProBozo
The fire hazard of paper facing isn't that great, but if you want to remove it and if this is the only insulation in the roof (none in the ceiling) then you need some sort of barrier to prevent air circulation through the FG (which pretty much destroys it's insulating ability). Tyvek would work, though it doesn't provide a vapor barrier.
(It would help if you entered some profile data so we know where you live.)
Off-topic, sort of, but that's what Tyvek was originally designed to be...a covering for insulation.
Idea was to prevent air washing over the surface of FG insulation from reducing the effective R-value of the insulation.
Personally? I wouldn't worry about the paper facing. Although it's not the best VB, code-wise it keeps you covered.
If you want to cover the paper, leave it in place and just staple the Tyvek over it. The Tyvel won't count as a VB so you can leave the paper intact without the system being considered as two VBs.
If you REALLY want to remove the paper, then staple poly over the exposed FG to give you a VB. If you;re antsy about the poly, then you could cover it with Tyvek.
Still, big picture? I wouldn't worry about the paper being a fire hazard. By the time a fire got into your attic, it'd sort of be a little too late, if you know what I mean.
The easiest, least expensive, and fastest thing might be to just spray an aftermarket fire retardant on the kraft paper.
Bad idea to take the paper off. It's a vapor barrier. Without it, moisture can diffuse through the insulation. Once it gets to the other side of the insulation, it can condense on the cold surface of the roof deck. Not good. It's neglect of details like this, coupled with the tighter building envelop, that leads to some of the issues with mold that's talked about so much.
Tyvek is an air infiltration barrier, intended to prevent wind from getting through the sheathing and circulating to the insulation. But it is not a vapor barrier; in fact is it specifically designed to let water vapor go through it and escape to the outside air. in this application, it would allow house moisture to diffuse into the insulation.
As another poster said, cover the kraft paper with Tyvek if you want to, but leave the kraft paper in place. Or replace it with another vapor barrier. If this is attic storage and not living space, if it were me I'd leave it as is.
Dear BarryOThanks for your input regarding my idea of putting Tyvek over insulation between rafters in my attic. I had not really been clear about the differences between an air infiltration barrier (tyvek) and a vapor barrier (paper on insulation, which I assume is basically kraft paper).I plan to leave the paper on, but cover it with tyvek which is probably overkill. Thanks to you and everyone for commenting on my question.Adrian in Santa Cruz, Ca.
The difference is very important. Moisture (in the form of water vapor) can pass fairly freely through Tyvek. This is important when it's used as a house wrap and place on the outside of a structure. It allows any moisture that gets into the walls to migrate through and out, but it prevents wind from blowing through.A vapor barrier is intended to prevent water vapor from passing through. The plasticized kraft paper on paper-faced insulation is a mediocre vapor barrier, but what is often used. Better is a sheet of plastic film stretched across the inside of the wall. It keeps moisture from getting into the wall from the inside.The basic issue here is that (at least in cooler climates) it's important to keep moisture from getting into the wall from the inside, and, if it does, it's important for it to be able to get out.
(at least in cooler climates)
Hmm, Santa Cruz is probably a "mixed" climate, neither cooling nor heating exclusively. Given its proximity to the coast, I wonder if the VB would best be o nthe outside, not the inside.Occupational hazard of my occupation not being around (sorry Bubba)
Wouldn't that amount to sandwiching the roof sheathing between two VBs?
You don't want a vapor barrier on the outside unless you're in a hot climate where the AC is run fairly constantly. (And where you more than occasionally see condensation on the OUTSIDE of windows, due to the coolness of the air inside.)In most homes a fair amount of moisture is generated by showers, cooking, humans breathing, etc, and that moisture must not get trapped in the walls.
It looks like it might be a new marine climit.http://www.buildingscience.com/housesthatwork/hygro-thermal.htmBut the don't have any design information on that (at least on in the Houses that Work).But for a mixed climate I think that the best is no vapor "barrier", but rather vapor retarder.
for a mixed climate I think that the best is no vapor "barrier", but rather vapor retarder
Yeah, makes sense, particularly if the actual location is more mountain/arroyo than true maritime/marine/coastal.
Should we just pester OP for photos, instad? <g>Occupational hazard of my occupation not being around (sorry Bubba)
The house that has the exposed paper facing is about a mile from the beach. Coastal - yes, Marine- ???yes? No air conditioning - summer highs in mid- 80smostly we are in the 70s in summerThe house was built in the 1930s so insulation was added much later.Adrian
Bill & I were talking of the Building Sciences recommendations, which name areas by their climates, and recommend construction techniques accordingly. They are very sensitve to moisture & how it affects construction (possibly too much, but that's a separate debate).
Their web site has a new designation for your climate, but no recommended construction method yet. This can make it easier to answer people who don't live next door. You have moist air outside, and you have moist air inside--except during the heating season, which is likely shorter than in, say, the northeast.
Which means, like as not, the paper side of the batts probably should have gone to the roof side, not the attic side. Except, when it was insulated, that would not have "looked" right to the installer.
summer highs in mid- 80s
LoL! That's what it's been here, the last two weeks. It was 5º over ambient (84º) inside last night at 2000, so I actually broke down and programmed the t-stat for cooling. The heat program hasn't run in three months, so it's been kind of dormant. The humidity will get me here soon, I'll need a/c just to dry things out for evaporative cooling (dew point was 64-68º yesterday).Occupational hazard of my occupation not being around (sorry Bubba)
Thanks for the detailed info on climate as it relates to the location of vapor barriers - fascinating. I visited the building sciences website and looked at the climate map and reading the description of climate characteristics of my zone. I am not sure I completely understand why the paper side should be facing the roof... Could you explain this part to me?Adrian
Someone will correct me if I am wrong, so here goes.
Thermodynamics tell you that energy (heat) will move from a higher state to a lower state (cooler).
In a cooling climates, that means the hotter outside environment will be trying to get into the home, and with it the the higher levels of moisture that is present outside.
Placing the vapor retarding membrain on the outside of the building envelope in those climates, reduces the infiltration of the highly humid air. The principle object is to keep the humid air out of the wall cavity as much as possibel because at some point as it approaches the inner surface of the wall it will reach the dew point temperature. At that temperature gradiant point the moisture in the air will condense on whatever surface is available. The insulation, studs and back side of the wall, etc. become wet.
This a bad situation. Think mold, loss of R value in the insulation, and rot starting in the framing.
Dave
The theory is correct.However, he is in a much different climate.On the Ocean just south of San Fransisco.Buliding science calls it a Maraine climate. Wet and cool (by our standard) in the winter. Dry and warm, but not hot in the summer.So a lot of the driving forces are reversed. However, I don't think that the differentals are that strong.
Yeah, it's kind of an undecidable situation, but thankfully not extreme, so the issues discussed here aren't as critical as in Minnesota or Florida. It's probably just as well to forgo the vapor barrier entirely and just use infiltration barriers.
why the paper side should be facing the roof
Sure, you have--if I'm remembering rightly--two basic seasons; a heating season with mechanical heat, and a cooling season without mechanical cooling.
So, in the winter, there's moist air outside, and dry (by heating) air inside. In the summer, theres moist air outside, and moist air inside. So, in summer, there's a relative balance of moisture levels. But in winter there is not. We 'want' to keep moisture out of the building structure as much as possible, so, that means keep the VB to the outside.
Now, that's a gross oversimplification, and there are other considerations, of course, I'm just using rule-of-thumb rather broadly.Occupational hazard of my occupation not being around (sorry Bubba)
I think the main point is that you put one vapor barrier, on either the inside or outside, wherever it does the most good, most of the time. I would think in most climates, this is the inside, since people and their activities put alot of moisture into the air, and it has no place to go in a tight house.
The key thing to avoid is two vapor barriers. Water that between them has no place to go.
There was another one of those "toxic mold drives family from their new home" story on the local TV news a while back. They showed a portion of the house interior, with the moldy drywall and fiberglass insulation ripped away. Sure enough, their was also a 2nd vapor barrier on the outside of the wall!
But in this case an even more important rule is that fiberglass must have an infiltration barrier -- open face fiberglass is just about useless.
From the information you posted I get the idea you have central HVAC installed in this 1930s house, and that previous owners have installed insulation in places the builder didn't. That being the case, you need to find out how much air-exchanging is done by your system when it is operating in both heating and cooling modes.
The point of mechanical air-exchangers is to remove moisture-laden air from the building envelope to prevent it condensing inside the walls and roof structure. In older buildings, this process happened naturally through air leakage via the 'imperfect' vapour barriers that were then standard. But where modification of the insulating system has occurred in a haphzard manner over the course of years, this natural air exchange mechanism is often compromised.
Modern code requirements here call for dedicated air exchangers in all new construction. This is to address the problem caused by the super-insulating and sealing of buildings with vapour barriers such as polyethylene or mylar films instead of foil or tar-backed kraft. Older houses such as yours which were left in their original state never suffered from what is now called 'Sick Building Syndrome' which is a manifestation of the numerous moulds, microbes and generalized nasty bugs that live in over-damp, closed environments. However, they did cost more to heat and cool because the insulation was less efficient. Thus you have a trade off between priorities to organize.
As to the insulation in your attic, you need to find out: (a) whether or not the rafter bays are vented (pull down a bat of insulation to find out); and (b) if there is any roof-deck or structural framing rot that has developed as a result of either condensation or ice-damming (again, you will have to remove some insulation to do an inspection).
If (a) is true and (b) is none, you would be just as well advised to leave things as they are. The paper facing on the insulation will not be a major fire hazard compared to the attic framing itself, as others here have stated.
On the other hand, if (a) is false then (b) is likely 'some' or 'a lot'. In that case you need to pull down the isulation completely--not just the paper backing--repair the rot, and install vent chutes in each rafter bay before re-insulating the roof. This can be done using either commercially-manufactured polystyrene vent inserts such as Raft-R-Mate or by nailing Ten-Test over 2x2 blocking underneath the roof deck in each rafter bay and venting both the ridge and the soffits so there is free air flow all along underneath the roof deck to keep it dry and cold.
Dinosaur
A day may come when the courage of men fails,when we forsake our friends and break all bonds of fellowship...
But it is not this day.
Just leave it alone. The paper does not burn well. Try it.
I agree with csnow--it won't burn well and isn't worth replacing. The rafters will burn well, and if there's fire in the attic, flame impingement on the framing will be the overriding concern.
There is fiberglass insulation available with a foil face, for use in situations where it will be left exposed. Sometimes you see this in warehouses where there's no sheetrock on the lid. It's hard to find foil-faced but check with commercial insulation dealers or insulators.
I have the same question now in May 2025, 20 years after Adrian posted this question in May 2005. Wonder how Adrian solved his problem?
Today, if you search online (Google) this question:
"Can you install Tyvek Drainwrap to cover fiberglass batt insulation in attic rafters?"
The AI response is...
"Yes, you can install Tyvek DrainWrap to cover fiberglass batt insulation in attic rafters, but it's not a vapor barrier. Tyvek acts as an air barrier, preventing air leakage and drafts, but it allows water vapor to pass through, which is important in an attic space to prevent moisture buildup..."
There is more but you can go read it yourself. The key problem this solves for me is to help stop the air leakage inside our old home. The air leaks create the "stack effect" which sucks in cold air in the winter and lets heated warm air gush out! This raises your heating bills $$$ enough to really raise eyebrows. My 50-year old home has a large stand up attic that is 27 feet long by 12 feet wide and very tall pitch roof (over 8 feet in center of attic). There is 50-year old flat at R-19 fiberglass batt insulation between the 2x6 rafters. It's Kraft paper is facing out to the attic and brown and dried (baked for 50 years). I'm replacing it with "ROCKWOOL Comfortbatt R- 23.0 Attic Wall Unfaced Stone wool Batt Insulation" from Lowes. Since it's unfaced, the Tyvek vapor retarding layer will work perfectly, stopping the air leaks, but not allowing condensation. You do NOT want a vapor barrier inside most attics. A ventilated attic must breath, very slowly, and never pant or gasp every time the wind outside gusts, or allow warm air to rush out during the cold winter months because or that darn "stack effect" that pulls in cold frigid air to replace it.