We have a 110 year old farm house that I grew up in and we have gutted. The exterior walls are all masonry (exterior brick and interior hollow speed tile with plaster directly applied to the inside face). The old knob and tube wiring is being removed and new wiring will be installed, but the exterior walls must be furred out first to allow for the wiring and also to accommodate the insulation. We are using closed cell spray foam insulation and my question is what is the best means to furr out the walls? I would like to leave a 1/2 gap between the furring and the existing exterior walls to allow the spray foam to get behind the furring to create a complete air / vapor barrio as well as a thermal break. I naturally thought of conventional wood framing first, then thought of metal studs, but was concerned about the thermal conductivity of metal. I also have explored the idea of recycled plastic studs that can be fastened directly to the existing walls and have no thermal conductivity. Has anyone tackled this issue and if so what was your solution, and how has it performed?
Also, I am looking for advice on spray foaming the attic. Is it common practice to foam directly to the underside of the roof and eliminate the air flow? Will this create a conditioned attic space, and if so what other steps must I take in the attic?
I appreciate the advice and help.
Whitetail Springs Farm