Our two key goals are super-insulation (high R-value) and air-tightness (elimination of leaks and drafts). Simple enough, isn’t it? To my surprise, this issue got me deep into rocket science. There was a very steep learning curve and my ideas and aspirations on insulation options had changed several times over the past year based on emerging facts and realities.
While we were house hunting, we were only considering buildings with a masonry shell for the structural and longevity aspects (see also “Dream home wish list” post). Another idea of mine was to use the masonry building shell as thermal mass by leaving it exposed to the interior and applying the insulation on the outside.
Fast forward. We now own our house with typical Chicago common-brick side elevations and an ornate front elevation. Our dream of exposed interior brick walls radiating warmth appears to materialize. To get there, we will need to super-insulate the building from the outside. I began to research our options, and ran into a brick wall (pun intended).
Do we really want to hide our ornate front elevation behind insulation? Of course not! We would insulate the front from the inside – and would be left with big thermal bridges to the left and right. Not good.
Then there is the dimensional issue. Portions of the west side of our building are almost on the property line. We would encroach into our neighbor’s property if we began to insulate on the outside of these wall sections.
How about insulating portions on the outside and others on the inside? Not only is this getting really complicated, but I end up with a whole bunch of thermal bridges that would defeat our insulation goal.
And, of course, there are code issues to contend with. Chicago common brick has an excellent fire rating. Whatever I would use to cover the outside insulation will have to meet the one-hour fire rating requirement.
Most innovative ideas start with an uphill struggle. If we really pushed it and worked long and hard, we possibly would find a way to make it work. The question is: Is it worth it?
I talked with a lot of friends, contractors and green building professionals and did not receive any encouragement for my idea – absolutely none. Nor did I find any supporting clues in my research. The consensus was that insulating our building from the outside was too resource intensive and expensive to justify any thermal mass benefit in the interior – thermal mass we may not even need with a super-insulated and airtight envelope.
Time to hit the reset button! How about insulating the shell from the interior? But what would be the best material choice? And how can we do this without compromising the integrity of the 100+ year old Chicago common-brick walls?