 |
| I should have bought shares in sticky tape. |
 |
| Seal all the gaps. Tedious, tedious work. |
It seems like I've experienced an eternity of installing the poly vapour barrier and taping the seams/joints and all the holes. Shortly after we started, I really began to wonder- is this the best we can do for a residential-grade vapour barrier? It seems ridiculous in the low-tech use of plastic and sticky tape to prevent water vapour from getting into the cold side of the outside wall. In commercial construction, we use an exterior applied peel & stick membrane, and then put the insulation on top [also on the outside] of that.
Oh well. I really hope we have covered all the small holes, gaps and taped well enough around the electrical outlets, switches and duct penetrations. We're going to do a blower door test before drywall to check. Cross your fingers!
Shafraaz, Have you read about the REMOTE method used in Alaska? It is similar to your explanation. The Poly or Ice and Water sticky membrane is applied over the sheathing, then rigid foam insulation is added to the exterior.
ReplyDeleteRecently, there have been a couple of articles about Thorsten Chlupp's house in Alaska. He built an internal frame, sheathed it, vapour barrier, added a modified Larsen Truss to the exterior and filled the cavities with dense packed cellulose. His walls are R75 with ceiling values of more than R100.
If you Goggle his name, the articles are reprinted repeatedly.
Recently, I read about the "Chainsaw Retrofit" of Orr and Dumont. This would be an embryonic version of the REMOTE method.
Jim
Hello Jim,
ReplyDeleteYes, at my day job, we always put a peel & stick membrane on the exterior sheathing and insulation over it. It's just not "economical" for standard residential construction- and the trades that focus on residential don't have a clue how [or why] to do this.
I know what you mean. I deal with people every day who wonder why anyone would want to build better than "code".
ReplyDeleteOJ Clark (Phoenix Renovations) built a house on 84th Avenue/98 Street for Rob McDonald and Lydia Newfeld using commercial practices: 2x4 framing with peel & stick membrane on the sheathing, covered with foamboard and stucco. It is a complicated geometry and they had a hard time finding people to do the job. What I wonder about this method is why you would leave the stud spaces empty. If you have enough foam on the outside of your memberane you can safely put batts in the joist spaces without risking moisture buildup, and at little extra cost.
ReplyDeleteHello Philip, I don't have any experience with stucco, but, in the past few months the greenbuildingadvisor.com website has had several blogs and discussions about types of stucco, the concerns, and the EIFS method of application. They discussed problems with stucco when applied over OSB sheathing. Some stuccos will breathe the moisture while others trap it, making the OSB fail. This would be in cases where the vapour barrier is next to the drywall and the stucco is the exterior finish. Applying the peel and stick membrane outside of the sheathing may prevent this failure. However (this is only a guess) the builder may have left the interior cavities empty to allow the sheathing to breath and dry to the inside unimpeded.
ReplyDeleteJim