Perfect Wall
2024-02-25
There are different techniques to insulate the house. The classical method is having 2x4 or 2x6 wall framing. The interior between the studs is filled with batt insulation. There are a number of options such as ROCKWOOL Comfortbatt or fiberglass insulation.
However this method always seemed a bit strange to me as it means we have insulation on the inside, that is broken up by wooden studs. Typically a layer of exterior insulation is applied.
In discusses issues with the assembly and explains it based on a heat distribution image.
In the assembly shown below it can be seen how the cold/warm freezing layer (where the dew point is located) lies within the interior stud cavier.
And alternative way to approach wall insulation is what has been called "Perfect Wall" by Joseph Lstiburek
In this assembly all the insulation is on the exterior and none is on the inside.
The Heat Distribution with continues insulation shown in the video shows that this way the studs always stay on the warm side and the dew point is located outside.
This kind of wall assembly is also described in Illustrated Guide - R22+ Effective Walls in Residential Construction in British Columbia here it's just called "Exterior Insulation" assembly.
Another source is FoamShield Perfect Wall Assemblies Perfect Wall Assemblies
Effective Insulation Values at different Thickness of insulation levels
| Thickness | With R-4 per inch | With R-5 per inch |
|---|---|---|
| 3 1/2" | 18 | 21.5 |
| 4" | 20 | 24.0 |
| 4 1/2" | 22 | 26.5 |
| 5" | 24 | 29 |
| 5 1/2" | 26.0 | 31.5 |
| 6" | 28.0 | 34 |
| 6 1/2" | 30.0 | 36.5 |
| 7" | 32.0 | 39.0 |
Some materials that exist:
| Type | R-Value per inch |
|---|---|
| White Korolite® EPS | 4.2 to 4.8 |
| Gray Korolite® GPS | 4.9 |
| ROCKWOOL Comfortboard® 80 | 4.2 |
