Insulating an Old House from the Outside
A popular way to retrofit insulation
Gregg Skoraczewski’s house in northern Wisconsin is framed with 2x4s and insulated with batt insulation–nothing unusual about that. What he’d like to do is strip the hardboard siding and fiberboard sheathing off the house, add new insulation from the outside and re-sheath and side the house, leaving interior walls intact.
In his post at GreenBuildingAdvisor’s Q&A forum, Gregg adds that he’s been advised to add rigid foam insulation on the outside of the house to reduce thermal bridging through the framing. He wonders, however, whether this insulation strategy will leave an air space inside the wall that contributes to moisture accumulation.
In addition to reviewing his plans, this week’s Q&A Spotlight also touches on a perennial question: when adding rigid foam to a building’s exterior, how thick should be material be to prevent condensation inside the walls?
(click here to enlarge image) Foam sheathing has long been billed as an ideal way to upgrade poorly-insulated homes, but some builders and designers are still worried that it might trap moisture in the walls.