Last update: Jan. 16, 2019.
I've got a rental house that oddly enough has no framing. It's a brick house, and the inside walls are the same brick you see on the outside. So there's no insulation and it's ugly. The typical solution is to put up foamboard insulation and some wall covering over that, but I have a few challenges:
So with all these
challenges in mind, and armed with advice from the super-helpful
community at Green
Building Advisor, I came up with twelve different
options that keep the intrusion into the living space at 1-1/8" or less:
| Options for insulating an exterior brick wall from the inside, minimizing added depth | ||||||||
| Depth | Insulation | Code-compliant thermal barrier |
Ease of Installation |
Ability to hang items on wall |
Evens out uneven brick |
Aesthetics | Materials cost (203sf wall insulated, 283sf wall finished) |
|
| Carpet (no thermal barrier needed...I think) | ||||||||
| (1) 1/2" furring + 1/2" pad between furring + 3/8" carpet | 7/8" | 5/8" non-cont. | (n/a) |
3 | 5 | √ |
2 | $404 |
| No thermal barrier — not code-compliant | ||||||||
| (2) 1/2" foamboard + 1/8" paneling | 5/8" | 1/2" continuous | x |
4 | 2 | x |
3 | $196 |
| (3) 3/4" furring + 3/4" foamboard between furring + 1/8" paneling | 7/8" | 3/4. non-cont. | x |
3 | 5 | √ | 3 | $268 |
| Thermax foamboard, fire-rated, doesn't require thermal barrier | ||||||||
| (4) 3/4" white (no printing) Thermax, with white finish tape | 3/4" | 3/4" continuous | √ | 5 | 1 | x |
1 | $258 |
| (5) 3/4" white Thermax + 1/8" paneling | 7/8" | 3/4" continuous | √ | 4 | 2 | x |
3 | $335 |
| (6) 3/4" furring + 3/4" Thermax between furring + 1/8" paneling | 7/8" | 3/4" non-cont. | √ | 3 | 5 | √ | 3 | $370 |
| Drywall as thermal barrier | ||||||||
| (7) 1/2" foamboard + 1/2" drywall | 1" | 1/2" continuous | √ | 1 | 3 | x |
2 | $245 |
| (8) 1/2" foamboard + 1/2" drywall + 1/8" paneling | 1-1/8" | 1/2" continuous | √ | 2 | 3 | x |
3 | $269 |
| Plywood planks as thermal barrier | ||||||||
| (9) 1/2" foamboard + 1/2" plywood ripped into 4" tall boards (hardwood effect) |
1" | 1/2" continuous | see note | 2 | 4 | x |
5 | $312 |
| (10) 1/2" furring + 1/2" foamboard b/n furring + 1/2" ripped plywood | 1" | 1/2" non-cont. | see note | 2 | 5 | √ |
5 | $347 |
| Bamboo as thermal barrier | ||||||||
| (11) 1/2" foamboard + 5/8" solid bamboo | 1-1/8" | 1/2" continuous | √ | 3 | 4 | x |
5 | $672 |
| (12) 1/2" furring + 1/2" foamboard b/n furring + 5/8" solid bamboo | 1-1/8" | 1/2" non-cont. | √ | 2 | 5 | √ |
5 | $722 |
I chose #6. (Or rather, my wife did.)
(1) Pad+carpet: R-Value of materials is R-2.9, not bad. But most tenants probably would probably prefer something other than carpet on the walls. At GBA, Martin doesn't think mold will be a problem in Climate Zone 2, but Dana does.
(2,3) Not code-compliant so can't do these, which is a shame, because they're a thin stackup and easy to install.
(4,5,6) DuPont/Dow makes Thermax, a brand of foamboard which is fire-rated and doesn't require a thermal barrier. It's more expensive, but that's balanced by the savings in labor + materials of not having to install a thermal barrier. One flavor of it is white (no printing on it), so it can be used as a finish wall, especially with the seam tape that's the same color. Downsides are:
(7,8) Drywall is labor-intensive, with the taping, floating, priming, and painting. But it's a standard wall finish. Installing paneling over it is a bit of work, but probably a little less than taping, floating, priming, and painting.
(9,10) Does ripped plywood satisfy thermal barrier requirement? My idea for #s 9+10 was to rip 1/2" plywood into 4" wide planks to place over the foam, making it look like hardwood, for great aesthetics with minimal cost. I presume that the extra joints between the board when the plywood is ripped (rather than being full sheets) doesn't compromise the thermal barrier, but I don't know that for sure, and I don't know how a local building inspector would feel about it. (Check with the inspector before building.)
(1,9,11) Furring not available off-the-shelf, because cheap framing lumber isn't made as small as 1/2". Options include:
Based on:
Materials reference
Prices are without tax, and based on Home Depot Jan. 2020 unless otherwise linked.
Plywood, 1/2" sheet, $15.65
3/4" Furring: 1x2x8, $1.18 ea.
Tapcon screws: $5.98 for 25. (5 screws per furring strip = 70 screws needed, or 3 boxes)
Polyiso, normal: 1/2" sheet for $10.44, 3/4" sheet for $15.77
Polyiso, Thermax, white finish: 3/4" sheet: $34 • from Lonestar Materials ($100 min. order)
Polyiso, Thermax, foil finish: 3/4" sheet $30.29 ($35.24 for 1") • from Lonestar Materials. Action Gypsum is same price for 1", they can't get 3/4".
Thermax white finish tape, $45.95 (150')
Foamboard adhesive: $3.98/tube, says will do 4 sheets, I assume actually only 2; for 7 sheets, assume 4 tubes
Construction adhesive: $1.77/tube. I assume this can be used for the foil side of the polyiso (need to verify).
Paneling: 1/8" x 4x8 MDF sheet for $9.97
Drywall: $9.48/sheet
Joint compound $8.85, and tape $1.98
Primer: $11.98 (eco-primers not available in Austin)
Paint: $29.98/gallon (eco-paints not available in Austin)
Bamboo planks: $47.99 for 24.12 sf; 12 cases = $575.88
Prices are rounded to nearest dollar.
Option 1
Option 2
Option 3
Option 4
Option 5
Option 6
Option 7
Option 8
Option 9
Option 10
Option 11
Option 12
Houston Foam Plastics > San Antonio office, Renee 210-646-8288
$100 minimum, 3/4". Action Gypsum, Lonestar Materials, LNW
1" $33.43, 3/4 $24.22.
Disclaimer: While I believe all the above is correct, I'm not responsible for any errors or omissions. I'm pretty irresponsible, actually. Don't rely on my novice understanding of building code for your own particular application.