Insulation Basics – Double Brick Walls
I have previously carried out a worked example of the insulation of a Brick Veneer Wall, so as a comparison here is double brick wall.
I have also shown (in brackets) the effect of using a hebel block in place of one of the brick ‘leaves’:
| Element |
R value |
| Outside surface air layer |
0.03 |
| 110mm brick |
0.08 |
| 25mm cavity |
0.12 |
| 110mm brick (*or 125mm Hebel Block) |
0.08 (*0.81) |
| Plasterboard 10mm |
0.08 |
| Inside surface air layer |
0.12 |
| Total R value |
0.51(*1.24) |
| U value = 1/R |
1.96 (*0.81) |
The heat losses or gains for 150 sq m (fairly typical external wall area) of this type of double brick wall at 15 degrees above, or below, outside temperature will be:
Area x ‘U’ x temperature difference = watts per hour
150m2 x 1.96 x 15degrees = 4410watts per hour
Heating/Cooling Requirement = 4.41kw/hour
Using Hebel for one of the leaves will improve the heat loss as follows:
150m2 x 0.81 x15degrees = 1822watts per hour
Heating/Cooling Requirement = 1.82kw/hour
Still not as good as the 1.17 kw/hour of the typical brick veneer construction
Don’t forget heat is also lost through windows, ceilings floors and ventilation.
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