Subscribe or Renew Membership Subscribe Renew

Insulating brick and block walls loosing minimal sq. ft.

bigwindman's picture

I'm renovating a small cape cod home in Richmond, VA.  The house is a 1950's brick and block structure.  (4 x 8 x 16 block with brick venire)  The home is stripped to studs and sub floors and we area adding 650 sq. ft. to the home.  It origionally had furring strips attached to the block with no insulation.

My plan is to use Dow Corning's INSULPINK foam board 2' x 8'  1.5" foam panels.  They are slotted to be held in place by 1" x 3" 's.  (24" o.c.). Installed correctly, they add R-7.5 1" x 3" 's are on the long sides of the 2' x 8' foam panels so the 1" x 3" wood strip holds the two adjacent panels to the wall.  It's separated from the block by ~1" of foam so thermal bridging is elimated.  These strips then become the nailers for the Sheetrock screws.

Has anyone had experience with this product?  Any other approaches to insulating a brick/block wall?

R-7.5 and R-5 over the (post #207281, reply #1 of 11)

R-7.5 and R-5 over the nailers is a far cry from the recommended minimum of R-19 for walls. It's is a homogenous surface and a good thermal break and the Formular won't degrade over time. It would meet your criteria for not taking up much room. The foam sheets will quiet down the house. You'll have to use longer finish nails for the trim work and provide wood nailers around the perimeter of windows and doors, wide enough for your chosen casings.

It can take a bit more care using 3/4" nailers. If the walls are uneven or out of plumb, it's more difficult to shim the nailers while still getting a good attachment to the brick or block. An alternative is to use 2x3 nailers that are more robust, 1 1/2" foam board between the nailers and an additional layer of 1" foam board over everything. You'll lose an extra 1" of interior footage but bring the R-value up to 12.5. This will also give you enough room for outlet and switch boxes. It would be a big improvement over no insulation, more so than just the 1 1/2" sheets on nailers.

The next step is insulating and ventilating the attic where you may be able to get closer to the recommended R-values. Also deal with improving older doors and windows. A small pin hole can let a lot of cold air in, or out when air conditioning. Paying attention to sealing any air leaks is important.

In my own house, I used 1" Formular under the drywall over 6" studs with R-19 fiberglass, also on the ceilings. The house is much more energy efficient than a house with just fiberglass in the stud bays, very quiet. I heat with a wood stove in Maine and have to be careful about getting too hot. I usually only start a fire in the evenings until temps get to 0 or below.  I lose so little heat, I sometimes have to open windows to cool things off, like last night when it was 25 outside.

Beat it to fit / Paint it to match

Solid wall insulation (post #207281, reply #2 of 11)

You may like to consider fitting your insulation on the inside.

A solid wall will soak up a lot of heat, before the walls reach your indoor air temperature.

Placing the insulation on the room side of a wall, means the rooms heat more quickly and are comfortable sooner.

If you are at home 24/7 then having the insulation on the outside, means the walls will warm up once and then will act as a smoothing heat store. If on the other hand, you are out a lot and you turn the heating down or off, then each time the heating comes on, you have to heat the walls before the rooms are comfortable. In winter this may lead to cold miserable evenings while you figure out how long before you get home, you need to have the heating on to reach comfort level.

Perry (post #207281, reply #3 of 11)

That seems to be his plan.

These strips then become the nailers for the Sheetrock screws

A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.


Rhetorical Question? (post #207281, reply #5 of 11)

Why do people respond to a question with out reading the question?  

big (post #207281, reply #11 of 11)

bigwindman wrote:

Why do people respond to a question with out reading the question?  


I've done it many times............well, I read it but don't get it all.  

Half asleep, watching the game, attempting to do billing..........figuring a bid, playing ball with the dog, and the ever popular, conversing with the wife about something really more important............

[JOBSITE WORD] happens.

A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.


You might find the following (post #207281, reply #4 of 11)

You might find the following article useful: "The Perfect Wall" Insight-001 July 2010 at

"The Perfect Wall" Insight-001 July 2010 at (post #207281, reply #6 of 11)

Nice resource.  Thanks.

Thanks, this is a remodel in a moderate climate (post #207281, reply #7 of 11)

The origional exterior walls on a remodel are not required to meet current code.  We are just trying to maximize the energy savings within a 1.5 inch space.  My feeling is that this is the best option give our pramiters.  We will be tightening up the structure significantly, and will conduct a blower door test when we are done.  All the additions are 2 x 6 framing using advanced framing and sealing  methods.  All the crawls have been extensively cleaned, dryed and finished as conditioned spaces.

I'd really like to hear from someone who's used the product I described I'm my origional post.

big (post #207281, reply #8 of 11)

I've used the Dow and Formular products several times. 

I'd spot glue the foam in addition to the nailers.  I'd probably rip plywood strips if you don't want to cuss and moan when the furring splits (I usually use a Powder Actuated Device).  Tapcons seem to be a pain in the rear in this application.

Box installs and wire runs will take some time and ingenuity.  Some wire sheaths might not care for spray foam (read that somewhere but have no proof).  We've fastened the wire to the block, layed out the run on the backside of the foam, used a torch (carefully) to melt a channel.

My recommendation would be to run the wire up from below if possible, use wiremold run the finished surface if the look isn't a consideration-incorporate the wiremold in the baseboard if it is.

Also good if you can use spreaders / springboards to brace off the foam while the glue sets.

You'll get to the end and need to rip a panel-for the furring to work, you'd have to hog out the foam to fit the last furring.  I'd cut the panel short the width of the furring, use another pc of 3/4 foam as a backer.  With enough corners, it's quicker, nicer and easier.  Perhaps the same around windows openings, or go solid blocking if your windows need a place to fasten.  No thermal break, but you might opt for that over poor window install.

A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.


and...... (post #207281, reply #9 of 11)

Here's what I've done when I could afford another 5/8ths inch of space.

Lined the wall with 1/2" foam (use thicker if you can afford the space) glued.

Lay up an inch and 5/8ths metal stud wall-infill that with insulation of your choice (with a little putzing around, you can infill with 1-1/2" foam).  This affords you plenty of room for electrical boxes and wire runs.

A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.