*
My wife and I just bought a new house in Juneau, Alaska. The exterior consists of painted T-11 siding(ugly and high maintenance) over 2 x 4 studs. I would like to install a new exterior that is relatively ‘maintenance free’ and at the same time I would like to beef up the R-value of the walls by adding a layer of some type of insulation. This area gets a LOT of rain. Would there be any problems with moisture or rot by simply adding a layer of insulation(foam board?) then a new layer of siding(what would be the most practical?)?
Discussion Forum
Discussion Forum
Up Next
Video Shorts
Featured Story
The RealTruck AMP Research Bedsteps give you easy access to your truck-bed storage.
Featured Video
Highlights
"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.
Replies
*
Tensmoke: Kudos to you for trying to upgrade Alaskan architecture! I'm sure the other Alaskan posters here can confirm that T-111 gets used way to much and way too badly up here. (We went cedar shingles in the gable ends above cedar clapboards).
I'm thinking rigid insulation between furring strips on 24-inch centers. Or two layers of the same at 90° to each other. Vinyl siding if you want cheap and low maintenance. Check if anyone makes it with some anti-mildew/moss agent built in. I'll let others discuss placement of vapor barriers. They feel more passionate about it than I do.
For other posters unfamiliar with Juneau's weather: think about the amount of rain Seattle supposedly gets (but doesn't) and add some more. Also subtract about 20°F.
*I'm planning on doing much the same to my house (NW Oregon) this summer. So if anyone thinks this is a bad idea I'd like to know. The walls now are 5/8" T1-11 over felt paper over 1/2" CDX on 2"x4" studs, with blown-in insulation. I've already ordered wooden windows with 6 9/16" jambs to replace the orginal ugly aluminum units, so I'd like to trim the walls out to the same thickness as a 2"x6". I'm thinking of adding 2"x2" firring w. foam insulation inbetween, covered with 3/8" CDX, feltpaper, and then either cedar clapboards or shingles.
*
I'll better neither the Juneau house or the Oregon house have vapor barriers at the interior. This is more of a problem in Juneau, since it’s much colder there. You could check by taking off a receptacle.
Tensmoke didn't mention plywood sheathing behind the T-111. That might be a problem for installing additional layers on top, T-111's not much of a substrate. If your area gets a lot of moisture (or even if it doesn't) you have to start with a sound base to get a watertight exterior. Here in New England we have tens of thousands of houses rotting because they covered up problems with vinyl siding, without fixing the problem. So make sure you have plywood sheathing, or add it. The other consideration is your windows & doors, water has a habit of getting in at the joints to the siding or trim, so the added thickness of the wall needs to be handled perfectly there. Sorry for the lack of answers, just other things to consider...
BarryO's plan sounds good, especially since it involves new, deeper, windows, but you should definitely consider Tyvek (or equal) rather than felt.
*
Since you get a lot of "liquid sunshine" there moisture is a big thing to protect against. So, first I'd be sure whether there was or was not a vapor barrier in the house now. You don't want to put a second one on the exterior of the house. One thing I've seen is a deliberate puncturing of the interior vapor barrier but that is a lot of work and I've not followed up to see what the long term consequences were.
Since T1-11 is exterior rated and is also an acceptable substrate you may or may not have to fir out depending on what you pick as a new exterior. David's post is right on I think for one type siding. But you could just go through the T1-11 to the studs if you picked the proper insulation and siding. Maybe rigid board and vinyl. If you went for class and used cedar clapboards you definitely would need to fir out.
By the way are you really in Juneau, or in one of the suburbs?
*I'm assuming the existing felt in the wall is neither a vapor- nor an air-infiltration barrier, based on what I've read in FHB and elsewhere, and experience (on the rare, really cold winter days we get, I can easily feel the cold drafts coming through the switchplates on exterior walls). The felt vs. Tyvek debate has been debated extensively here. Felt is very water-proof, but provides little air infiltration or vapor barrier effect. Tyvek seems to disintigrate when in contact with the oils from woods such as cedar. Tyvek is a relatively new material; felt paper has stood the test of time.
*Tensmoke,Two layers of strapping with sheet insulation (per Davit Thomas's recommendation) and attention to detail (at windows and doors) will do a lot to tighten up your place. You may not need house wrap. I would strap horizontally first and then vertically. If you use nominal 1" strapping you will get 1 1/2" of additional high density insulation and thernmal breaks.
*
My wife and I just bought a new house in Juneau, Alaska. The exterior consists of painted T-11 siding(ugly and high maintenance) over 2 x 4 studs. I would like to install a new exterior that is relatively 'maintenance free' and at the same time I would like to beef up the R-value of the walls by adding a layer of some type of insulation. This area gets a LOT of rain. Would there be any problems with moisture or rot by simply adding a layer of insulation(foam board?) then a new layer of siding(what would be the most practical?)?