How do you attach exterior siding without affecting the air barrier on a passive house?
I'm using the "Zip system" of exterior cladding. Over this I plan to install 6" of iso foam, for additional insulation, and siding over the foam.
I'm unsure how to attach anything to the "Zip system", without penetrating the airtight barrier.
Thanks, Scott
The Zip Sheathing System is an air barrier sheathing when the joints are taped as specified by the manufacturer. There should not be any notable air leakage from additional fasteners used to attach insulation that you need to worry about. A nail or screw driven into wooden sheathing will pretty much fill its own hole.
In our 2015 demo house build we did put small pieces of FlexxBand tape on the sheathing where future nail holes would go, if that is the source of your concern I would apologize and tell you not to worry, that was a pretty high level of overkill on our part that was a suggestion from the manufacturer if we ‘really wanted to be sure’ as we had lots of it around. They were perhaps just responding to our concern to make the house as airtight as humanly possible. In hindsight that was a step we would not repeat, but rather save that roll for another project.
I am also wondering about the fasteners into my air barrier for exterior insulation and the siding. Are you saying that it is not necessary to use the pieces Flexxband where penetrations go into the air barrier? That would certainly make life easier. I'm also wondering about using a trowel on air barrier. Don't see any information on your site about this: Is it a good option. The Delta Vent SA is too expensive for my project. Any suggestions are welcomed. Many thanks!
Hi Anwas,
Where you saw us putting pieces of Delta Flexxband where screws would go was a bit of overkill in our opinion. We had the product, and the manufacturer suggested trying it, but it is not something we think is really necessary.
About trowel-on air barriers, we haven't had any experience with that so we aren't in a position to answer either way, sorry. As for your budget, remember that the most important factor that will make or break an air barrier is attention to detail. Even in homes where something as basic as standard building tape and 6 mil poly are relied upon to act as the air barrier, they can have wildly different results depending on the care with which they were installed.
We prefer high quality tapes and air barriers that adhere to a substrate, but whatever membrane you apply and tape you choose, just be very careful during installation. Be careful not to puncture it, and when you do, be sure to tape it. Try to avoid areas where mebranes are folded over, and when you do have to fold it, take great care to tape it well as it is a very common spot for air leakage.