We chose to create an expensive air barrier inside the house with Siga Majpell, a breathable membrane that forms an air barrier while allowing for the drying of the interior of the wall or ceiling should they get moisture inside. To protect the membrane from most penetrations and also to allow for a nailer for the drywall that is firmly screwed through the 1 1/2 inch polyiso insulation layer on the ceiling, we installed 1×4 battens similar to these pictured on a Green Building Advisor posting. These battens also create a service chase for wiring in the ceiling.
Sample Ceiling Service Chase
I think because I allowed the garage wall to be wired internally the principle of no penetrations did not set well with the workers. The electrician commented several times that he wished all the insulation and membrane were not “in the way”.
Garage wall used for wiring before membrane is installed.
For a narrow outside wall near the master bedroom outside door we had to install an outlet to meet code. That was also the most convenient spot for the outside light switch. I chose to fur out the wall to a 1 x 2 depth to avoid penetrating the membrane. The project manager was OK with that plan to install the outlet and switch in front of the membrane.
Imagine my surprise when the electricians cut the membrane and pulled out insulation to install the boxes in that wall!
Cut Membrane
When I told the electrician that the membrane could not be cut, he argued that the size of the box was a certain cubic inches and had to be used. I said no, the membrane could not be cut. It was a difficult thing to have the argument and it made both of us upset. But I said we could ask the project manager. He was called and he came over to investigate and told them they could use a different kind of box in that wall. So they took out their boxes and I repaired the membrane overnight.
Insulation replaced and membrane repaired
I also sealed the outside light wire through the membrane again, this time from the edge.
Outside Light Penetration
The electricians were then able to use a different kind of box to stay within the service chase. It was not pleasant but isn’t the customer always right?
New Boxes
I found that in the article about the service chase another builder was frustrated by the trade workers. His answer was to forget using a service chase in the future.
I disagree that as occupants we will continually be annoyed by the service chase though. Instead we will enjoy the benefits of a well sealed home with very few service penetrations.