Insulation and furring, part 2

With that in mind and venting aside, lets talk about what works. Lets say you have a brick home that is over 60 years old. Then lets say that the walls you have on the inside are plaster-on-brick (with exception to most interior walls). You have an insulation value in that wall of less than 1 (remember, neither plaster or drywall, not even brick, are good insulators and you should always rate them at an R-value of less than 1). I know what you are thinking. You are thinking “this guy is full of it, my house has 15″ thick brick walls – that has gotta be insulating”, and/or  “less than 1 R-value, but my house is ;ike 3 feet from my neighbors and I couldn’t hear them running a jackhammer through my brick walls”, which is insulation – but not the heat/cold (thermal) kind – that is sound (acoustical) insulation.

You might think to say that 3-wythes of brick (in masonry, courses are vertical stacks and wythes are the measure of horizontal rows) thick, how much air can get through? Well, a lot is the answer. Imagine that brick is like a very hard cotton ball. Air still gets through it (called air infiltration) whether you realize it or not. Now, with good tuckpointing, and with a good interior plaster coat with a painted surface, that air leakage can be reduced but still exists.

Brick or masonry walls  do not insulate for temperature much better than – say – siding. Or even better…stone. Brick is of course man-made, but it shares several properties similar to that of stone. And when it comes to stone, have you ever been to Cold-Stone Creamery? They take a large slab of stone and set it on top of cooling tubes (refrigeration lines) because it transmits the cold so well and is great for slowing the melting of ice-cream as it is violently forced to coexist with various toppings. (It really is a beautiful process if you like ice cream). So stone is great for creamerying (??? what do they actually call that- toppinging?), but not so great as an insulator.

So you want insulation on those masonry walls? There are two common ways to achieve it. 1 is to use furring strips (1/2″ to 1″ thick strips of lumber that are on average 1.5″ wide) and try to use pieces of rigid (board insulation) to insulate. The insulation board is expensive but also it is on average R6 per inch. That is 2x better R-per-inch than fiberglass or cellulose can offer (see building insulation types post).

This method has its place but is not my preference if the situation allows me to do full-furring. Full furring is basically framing a 2×4 wall on the interior side and up against the brick wall. You can get at least R13 insulation in the cavities, there is plenty of room for electrical and plumbing lines to be installed, and you can even buy yourself some structural earthquake safety. See part 3 for that revelation….