*
I have a house built in the early ’70s, and the wood panel siding is falling apart and needs to be replaced. I figured that while I had the siding off, I would replace the cheap insulation bats that are in the walls with new stuff. What I would like to ask is, do I need to put in a vapor barrier against the sheet rock, then use unfinished bats of fiberglass? The fiberglass strips with kraft paper normally have the paper facing the inside of the house as a vapor barrier.
dfwright
A new code-compliant, spill-safe outlet from Legrand offers a sleek solution for a kitchen island plug.
"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
Dig into cutting-edge approaches and decades of proven solutions with total access to our experts and tradespeople.
Start Free Trial NowGet instant access to the latest developments in green building, research, and reports from the field.
Start Free Trial Now
Replies
*
You may want to use a spray-in foam insulation instead of what you are contemplating.
The proper and useful installation of the vapour barrier after the fact like you describe would worry me. The foam is an easy out and would dramatically improve the R value of your walls.
*
Hi DFWright
Funny you should ask.
I'm seriously considering the purchase of a 1910 Queen Anne with all the beautiful stuff inside, but needs renovation/restoration badly. Its siding too is at the end of its useful life, but the interior horse-hair plaster is in great shape, needing only spot repairs. I won't want to do anything to damage this beautiful original plaster.
Well intentioned, but mistakenly blown into the 4" (and its is a true 4") wall cavity is cellulose insulation that is always wet by moisture from inside the house, as there is no vapor barrier in the wall. This moisture, over the years, as soaked into the siding, leading to dry rot, blistering paint, etc.
So, what I have been researching doing is what you are proposing.....take off the outside siding, line the studs and cavities with vapor barrier then apply insulation: batts or blow-in. Then reapply new siding. Because this will not protect the studs from inside moisture, I will have to repaint on the inside with a moisture retardant paint....but I have to do more researh on that. While I'm in there, I will also upgrade the electric wiring (it still has knob-n-tube)and run phone and cable wiring. It'll be a lot of work and take a lot of time, but worth it in the long run.
Bruce M
*
Bruce,
"Where is all the moisture coming from?" is your first priority. You have excessive
moisture. Un-vented "hour" showers by twelve people, lots of boiling of water with no
covers w/ no lower heat settings & no fan/vent running to the exterior, are you running a humidifier on max?...Lots of moisture coming from cellar?...Ask
yourself these questions and more.
The interior of your walls shouldn't be wet with water and you won't stop it with any
"barrier" you can dream up for the walls, you will just make things worse. How? All the moisture you have now if not stopped at it source will have to still get out of the house through even smaller leaks that are left behind any
"best method" you, me or anyone could dream up.
Get your moisture source figured out and under control and
your walls will dry out. Then "most"
anything you do to "fix up" your exterior will work. Back prime any new siding and
apply it on top of 15# felt or tyvek and fir
strips.
Watch this site "warm up" now!
Jack : )
*
I would tend to agree with Jack that the vapor barrier, at least on my house is not that big of a deal. On the few panels I've removed, the paper cover on the old 4ft bats has completely disintegrated, so I can't imagine that it is doing too much vapor resisting. Jack, would you say then that I could simply place unfaced bats of fiberglass into the walls, put 15# felt over the outside of the studs, and put the siding on over that? Somewhere I saw someone else suggesting using furring strips over the felt to provide drainage between the siding and felt.
Dfwright
*Fred Lugano must have done your job? I could see why you would have problems.
*Thanks for the input! I will check out the spray in foam. What is the difference between 4" of foam vs 4" of fiberglass? Is the R value difference that significant?
*
I have recently seen advertisment for a fiberglass batt that is completely contained in a platic covering like a batt-in-a-bag so to speak. Also I do not see any difference between you lining the cavity between studs and then using unfaced batts to achieve the same effect as pre-faced batts.
Feeling itchy now,
Pete Draganic
*dfwright,fur strips over housewraps, not as necessary over felt.Jack : )
*
Jack
Yes, in response to your suggestion to use Tyvek in this application seems to go against your strong advice in other postings. What gives? Why is this problem different than the application of a house covering in new construction. I think the best approach may been fiberglass insulation, no house wrap, let the moisture at least have a way to escape and forget the attempts to provide better wall insulating values through the use of celluose, rockwool, foam?. I used celluose and rockwool. I live in a very dry area, thank goodness!
Thanks,
Kevin
*dfwrightFoam in place polyurethane will obviate the need for the poly. etc. Itis in of itself an air tight barrier. But it is expensive. R factors vary with the Co. that produces it but the range is 6.2 to 6.9/inch. A good source of info. is the foam Assoc. 1 800 523-6154. An excellent source for "up to date construction methods" can be found at http://www.buildingscience.com . They also publish 3 books that discuss different building stratiges based on different climates- I got the one on cold climates and have found it to be excellent. At the very least the web site is well worth your time to look at.
*
I don't think Jack recommended using Tyvek.
-Rob
*I don't think the batt-in-a-bag is a good idea. I have no information to back this up, but the bag seems like it might cause a few problems.1 - snag on nails, splinters, etc. and not let the batt fill out to the back of the cavity.2 - Cause the batt to not fill into the corners of the cavity. This would leave a small area in each corner, perfect for convection.3 - Trap moisture?4 - Generally, make it even easier, or even more appealing to do a less than perfect job. Example - can't flufff the batts with a knife, or not fluff them before installation.-RobNo Facts, just opinions
*
I have a house built in the early '70s, and the wood panel siding is falling apart and needs to be replaced. I figured that while I had the siding off, I would replace the cheap insulation bats that are in the walls with new stuff. What I would like to ask is, do I need to put in a vapor barrier against the sheet rock, then use unfinished bats of fiberglass? The fiberglass strips with kraft paper normally have the paper facing the inside of the house as a vapor barrier.
dfwright