In a recent post, we talked about some of the tools we use in designing the passive house. THERM is great for evaluating thermal bridges across assemblies of materials and visually comparing good and bad assemblies.
For example, below are two assemblies of the concrete footing, slab, and above grade wall. One is “bad” in that it does not adequately protect the interior from heat loss.
A BAD wall, footing, and slab assembly: It does not insulate the concrete footing
BAD: Though the slab is insulated, the concrete footing is not, which can have several undesirable results:
Visualization of heat loss of the BAD wall, footing, and slab assembly. Notice the level of heat loss through the footing.
- Building science and health complications in the form of interior condensation and subsequent mold growth
- Comfort issues in unnecessarily cold floors.
- Unnecessary energy expenditure towards compensating for the excessive heat loss.
GOOD: The second assembly is “good”—the concrete footing is insulated and has a insulation skirt that does an exceptional job at slowing heat loss through the ground and mitigate against the issues faced by the bad assembly. Notice how the gradients result in much more comfortable interior environments.
GOOD wall, footing, slab assembly. Note the additional insulation around the footing.
Notice how the inuslated footing and insulation skirt dramatically reduce the heat loss through the footing.
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I’m learning to use THERM in order to evaluate influence of thermal bridging. I think it’s very useful ’cause in high-insulated envelope, these details become very critical.
Maybe in the future we can share some of our experiences
kind regards
M. Fossati – Milan, Italy