Does anyone out there wrap the rim boards on TJI’s with tyvek under the bottom plate, also for continous envelope in basement vapour barrier. Ever heard of this??
a 2 foot piece of house wrap placed centered under the length of the plate, all the way around the foundation?
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Replies
I'm sorry but I'm not following you. When you say under the "bottom plate" I'm think the bottom plate of a wall. Are you referring to the sill?
a 2 foot piece of house wrap placed centered under the length of the plate, all the way around the foundation?
Maybe I'm dense, but I don't get it. I guess this probably means it's not something we do! LOL.
Seriously, can you break it down a little?
yes here it is from the ground up. - top of foundation- 2 foot piece of house wrap, centered along wall- sill compression gasket- then sill plate.
The idea I think is for a better outside wrap on a brick home(maybe) by overlapping wall tyvek
and for a continious spot to seal off vapour barrier on basement walls.
How do you seal off your rim joist spaces in the basement??
In gov't sponsored research of the Flair Homes R2000 project (Winnipeg-mid 80's), the "rim joist wrap" was determined to be about the most cost effective innovation for the air tightening of homes. You actually get a tighter home for less cost!!!! You must use a vapour permeable wrap for this procedure. I have seen untrained carpenters using polyethylene for this. It will lead to rot of the rim joist!!!
Edited 12/21/2005 6:43 am ET by experienced
That's interesting. We have started doing it this way, while other builders drive by and look bewildered, I was curious though what other carpenters used to create an effective vapour barrier seal around the rim, seen alot of 6 mil stapled inbetween joist spaces, can't be too effective as far as i can tell.
If they're just stapling the poly and not using caulking (acoustic sealant is best), then they've got no seal at all. Even before the house was turned over to the owners, I've seen some of the sealed and stapled poly already pulling away in what we called in R2000, "fish mouths" (little open folds) and the seal already failing.
I was an R2000 site advisor, inspector, troubleshooter and researcher from inception 'til 1992. If a builder chose to seal the rim joist from the interior, we always wanted a "solid, long lasting' seal here. Materials we allowed were sprayed, extruded and foil-faced foams, OSB and plywood pieces caulked/foamed to to appropriate surfaces........no caulked/stapled plastic which our local municipal inspextors still allow today.
The second of my client builders that was named as "Canada's R2000 Builder of the Year" had a problem on the first house I air tested for him. His insulator/vapour barrier installer (first R2000 house for him also) had used about 2-3 times the amount of acoustical caulking and sheathing tape really necessary to make the home tight enough to meet the requirement of 1.5 ACH @ 50 pascals......but it didn't pass. I left my blower door running in place for them and told them to call me when one of the gauges got down to a certain area. 6 hours later, I get the call and return to complete the test. They just barely got in under the line!!
I told the contractor about the "rim joist wrap" and that he should talk to his framer (GC was a total "desk builder"/manager who subbed everything out) about installing this for a price at each rim joist. I made a few other recomendations about air sealing techniques and some misconceptions his airsealer's men had about what had to be sealed (like the outer surface of a solid piece of poly to the studs when of the poly goes around an inside corner!!!!). The next 4 houses I tested for him all passed by about a 20% margin of safety. And the next year he won his award since all he would build was R2000 homes, nothing else!!!
Edited 12/21/2005 11:14 am ET by experienced
What is the brand name of the acoustic sealant you use. I wanted to use it down here in NY and couldn't find it at my local lumberyard. I used to use it in Ontario all the time. Interesting that you worked on the R2000 house's in Manitoba. I remember them, IIRC FHB did a story or two on them way back when.
Tremco and a PL product
Good morning.
There is an article, written by Steve Lentz, over at JLC. Building airtight homes: Start the polyethylene air barrier under the mudsill and seal every seam.
Thought that this article might help. You can find it over at JLConline. It is a free PDF article. It was in the February 2002 issue. It can be found under the "Thermal & Moisture Control" section. It might detail what it is that you are trying to describe.
http://www.jlconline.com/cgi-bin/jlconline.filereader?43aacfb500234d1e27177f000001059d+EN/catalogs/1097
- Hope the link works.
Thanks!!! very similar but this is done with the inset rim joist due to using poly to wrap. It's very good detail for a frost wall or if you'll never finish the basement but wanted a heated, insulated space for workhsop, storage, etc.
Searched another 45 minutes this AM an still no example came up.
Anyone still interested in this rim joist air-barrier topic? Here is an air/vapor barrier detail circa 1985 used here in Pugetropolis. It shows a two story and heated basement wall with rims wrapped in tyvek/typar and poly vaporbarrier inside.
Thanks, JB. Just about what I was looking for; it gives the pertinent details of what wraps and joins where. I will still try to get one scanned in with just the exploded details of a single rim joist rim joist with permeable joist wrap. This is poly wrap; the other replaces the poly at the rim with a permeable wrap such as Typar.....a more forgiving detail.
Edited 12/24/2005 9:09 am ET by experienced
thats some good diagraming
JB:
Just noticed that you said in your post that there was a permeable wrap. I guess I just "saw" poly due to the exterior insulation which I assumed was a replacement for the inset rim joist.
It's a great diagram since we now have replaced the low R value wood sheathing with insulation. There is the "1 by" inlet corner brace and when the drywall goes on the interior, we'll be "overbuilt" by most codes since they require either the corner bracing or certain thickness of interior drywall to meet structural requirements.
This wall is really where you get seriously improved energy efficiency for lower costs!!!
That's very interesting - especially based on what Experienced said... I don't quite get the picture though. Is the idea that the strip of wrap is pulled up on the outside of the rim joist after all sheathing is installed and then the regular sheathing wrap installed directly on top of that? And, then in the basement, the strip of wrap is pulled down over the vapor barrier?
Edited 12/21/2005 7:42 am ET by Matt
We were using 9' Tyvek cut into 3' sections of roll with a chainsaw (ah! always good to have chainsaw on site. LOL). The piece is laid over the sill plate with about 1.5' inside the inner edge of the plate. After the floor system including subfloor is done, the outer hanging piece is wrapped up the rim joist, inward over the subfloor and stapled down.
Both the flanges above and below the floor are then sealed to the polyethylene interior air/vapour barrier with acoustical or sheathing tape at the doubled top plates and bottom plate. Make sure the joint occurs over wood so that when the DW goes on, there is a mechanical pressure seal on the joint.
Thus, you get the tighter rim joist for less cost than cutting/fitting/caulking foam/plastic pieces or spray foaming the inner joist!
It sounds like you don't end up with a VB covering the rim joist itself -- is this true?(Not saying this is a fatal flaw or anything, just trying to understand the concept.)Also, I assume that exterior housewrap on the wall is taped to the exposed outer wrap surface??
If ignorance is bliss why aren't more people
happy?
the wrap is pulled up the rim joist and fastened, then the wall wrap laps over it and taped. I will work on a diagram....
I think we need a diagram to make this clear.You get out of life what you put into it......minus taxes.
Marv
I'm not getting you. In the referenced post you said the flanges are sealed to the poly vapor barrier, whille in the post immediately above you seem to indicate not.
If ignorance is bliss why aren't more people
happy?
I'm confused too DanH.
I like the concept for reasons that might be differnent than the intended goal. I don't understand why the wrap should be stapled to the bottom of the joists.
I also would prefer to seal the wall where it meets the deck with glue.
blue
Later on, at the insulation airsealing stages, the inner flanges of the Tyvek/Typar are sealed the the interior poly air/vapour barrier at the top plates of the lower wall and the bottom plate of the upper wall.
At framing, when you have the flange/wrap installed and stapled to the subflooring, you then build the wall, stand it up, and then cover the exposed wrap at the rim joist with what ever the sheathing was- ply, OSB, foam sheathing. Then you install the exterior tyvek/typar. At the rim joist, you now have, from in to out: the rim, the interior extension of the air barrier (the rim joist wrap), sheathing, the outer building paper/sheathing membrane
I'm just hopin' you guys left this mess in the 80's where you found it.
What's the problem with this wall?
It is highly energy efficient, meets codes in most locations except maybe in earthquake zones (I really don't know what code is there!!) and is cost efficient for the level of energy efficiency it gives.
First saw this in houses in 1984 in Moncton, New Brunswick (annual DD-about 8500) and these homes still stand with normal maintenance requirements 21 years later........and with lower energy costs!! That says something as they were built on a shoestring budget as co-op housing.
Heres my attempt at some visuals. Pretty colors though!!
Does this method apply to crawl space houses too? I know you guys up north don't build many of those... You probably would if your footers only had to be 12" below finish grade like ours...
My take
If ignorance is bliss why aren't more people
happy?
Pretty good rendition just going from text. The overlay at the foundation can be on top of the foam seal or over the sill plate/mud sill and between the rim joist. The sheathing, be it foam or wood, is put on next and the exterior air barrier/sheathing membrane is not attached to the inner air barrier. For a VB between the joists (as the BI will want, just cut the top unused portion of the inner poly and staple to the joists,etc after the rim joist insulation is installed.
Looked for a proper diagram on the web for about 15 min. and couldn't find even one. Found reference an old list of 12 things to do to airseal a house that I co-authored with my old gov't supervisor!!!
Also, what do you mean by "rim joist insulation". Around here I see something like 1-1/2" foam inset on the outside of the rim joist. (The rim joist is kicked in from the edge of the sill by the thickness of the foam.) On the inside FG is generally stuffed into the joist cavity above the plate. Not clear how you'd then cover this with VB.
If ignorance is bliss why aren't more people
happy?
Not many people here are using the inset rim joist + rigid insulation anymore (was an early R2000 technique). This was used when people used poly vapour barrier as wrim joist wrap and it had to be kept warm to prevent condensation that might get trapped. It could be used with a permeable rim joist wrap if desired.
With the airtight but permeable (Tyvek/Typar) rim joist wrap, you do not have a vapour barrier at the joist area. And it still is required in codes in northen climates.
When making the seal at the lower wall top plate with the inner poly + joist wrap, make sure the poly is on the inner side of the seal. After installing inside joist insulation, take the upper waste extension of the interior wall poly air/vapour barrier (its usually 10' wide) and cut it to fit between the joists. Just staple the poly to the joist sides and bottom of subfloor- this gives you the vapour barrier at the warm inside. This extension is the poly that does not have to be sealed.
The diagram you show is how we used to do it in Ontario in the 80's. We used acoustic sealant instead of tape though.