Page 80 - Build 151

Departments/Research By Ian Cox-Smith, BRANZ Building Physicist
Edge insulation of concrete slabs
Heating costs could be cut if we do as Americans and Europeans do and add perimeter edge insulation to heated concrete oor slabs.
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perimeter edge insulation to concrete oor slabs. This is common
practice in North America, Canada and Europe but less so here.
Reasons include that it can be di cult to install and make durable 1.8 and that it can be visually intrusive.
R 1.2 insulation under slab
only external perimeter insulation
Particularly useful for rebuild in Christchurch 1.4
The BRANZ project aimed to counter negative perceptions by demon- strating how it can be done and the performance that can be achieved. The option to add exterior perimeter edge insulation to oor slabs is particularly pertinent for the rebuild of Christchurch. These oor slabs may contain more concrete and steel and the ground underneath the slabs is compacted to a higher density, which increases potential
heat loss from the slab.
Perimeter insulation is most e ective with heated oor slabs,
A BRANZ BUILDING RESEARCH LEVY-funded project has been investigating the practicalities and e ectiveness of adding exterior 2.2
2.0 1.6
1.2 1.0
Figure 1: 100 m2 oor slab with 0.6 m high perimeter insulation.
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2.2 2.0 1.8
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0.0 0.4 0.8
R-value of external perimeter insulation
1.2 1.6 2.0
R 1.2 insulation under slab
only external perimeter insulation
including ones that capture solar energy.
Research involved modelling and monitoring oor slabs
As well as using computer models to predict performance, the
project monitored heat loss over the winter months from three 1.6
oor slabs at BRANZ and a residential oor slab in Christchurch. Exterior perimeter insulation consists of rigid foam insulation
applied to the vertical face of the exterior edge of a oor slab. The 1.2
foam insulation normally extends from just below the bottom edge of the exterior wall cladding to the bottom edge of the wall footing. It is protected from impact damage and moisture accumulation.
1.0
78 — December 2015/January 2016 — Build 151
0.0
0.2 0.4 0.6 Heightofperimeterinsulation(m)
1.0 1.2
Figure 2: 100 m2 oor slab with R1.0 perimeter insulation.
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R-value of oor slab R-value of oor slab