Insulating against old brick
Hello All,
I’m renovating my 1930 brick townhome. I’m wary of closing the air/moisture envelope on old exterior walls and need advice.
Goals: Improve insulation and control air flow, minimize wall thickness. Its a small home, so material cost isn’t a big constraint.
Current wall:
-Brick (seems to be double layer — at least 6″ thick)
-Layer of what appears to be a thick tar-like coating painted on the inside of the brick
-Approximately 1×3 furring strips nailed to brick (will be removed)
-Perforated Gypsum Lath Board (will be removed)
Some ideas for reaction:
OPTION 1:
– 1/4″ gap
-3/4″ Foamular or Foil Board
-2×3 wall w/insulation (its not structural)
OPTION 2:
-Closed Cell Spray Foam (the “no airflow” approach)
-2×3 wall (with 1″ gap behind for foam to fill)
OPTION 3:
-Use 1.5″ Roxul mineral wool board against the wall (so it could breathe)
(-Vapor barrier??)
-2×3 wall
Comments:
-I’ve read many conflicting articles about what to do. None mention the tar layer, and most assume weep holes — so I’m not sure if my home was designed differently?
-There is no drainage that I can see, making me think that this wall was not intended to weep. I would strongly prefer not to attempt to create this. There has been no evidence of water issues during my 5 years here.
(Should I add a newer air/moisture sealing layer over the tar? Like an elastrometric or plasticized coating?)
Other details:
-Home was originally heated with a very powerful hot water boiler. It is now heated and cooled by a less powerful high-velocity air/heat-pump system (Unico) –but it is very good at mitigating indoor humidity.
-Located in Virginia — cooling/humidity is typically a bigger concern than heating.
-I have an active tiny ant population … I would like to be careful not to create a habitat for them.
Thanks so much everyone. Appreciate your help.
Replies
When we renovated our small 1960 3-course-thick brick house that had 3/4" nailers for drywall with 3/4" batt insulation in between, we opted against thicker insulation inside because the rooms were already pretty small. Instead, we installed polyiso on the exterior, plus furring strips, plus cedar siding. Our old brick rambler looks like a cedar cottage in the woods now.
If I were faced with your situation, I would opt for option #2. The closed cell foam will simply add to whatever vapor barrier the tar may be, but the way you describe it, there would be no void between the brick and the foam. I'm no expert, but I would think that this would give you a cozier home, and whatever moisture may be in the brick will not reach the 2x3s to cause any damage.
I agree. Closed cell sprayfoam is the way to go. It will act as an air barrier too. Something else to think about is that Ants actually enjoy eating the pink rigid foam. I left some salvaged foam outdoors and I had an ant farm in some of the boards,
I agree with the previous statements. Option 2 will suit you perfectly from what you have proposed, it will last longer and be more comfortable for you.
Thanks all. Appreciate the advice and motivation to consider spending a little more on one of the spray kits.
Yes. I think you should go with option 2.