Friday, October 23, 2015

Building Science

At Geometra Design we strive on building science research of new technologies.
New products available out there may not be used at their best, or sold to the proper applications.
We decided not to use spray foam insulation in our retrofit projects in Toronto's buildings.
The existing exterior double brick walls with interior plaster were meant to perform in a way that in the tested conditions the build up of moisture would occur in the created drainage layer between the bricks.
Once the interior walls are stripped from the lath and plaster, and a new layer of insulation is added, the dew point moves on the internal layer of the double brick. That is where a non ventilated air space (conduction) should be left for the condensation/moisture to dry, and also create a separation with the new insulated stud wall.
Insulation always need more attention in the planning because of condensation on the cold inside of the masonry can hardly be avoided. A vapor barrier / brake seems to solve this problem, has in practice but often not the hoped effect.
One more example is the adoption of an exterior EPS (Expanded Polystyrene Insulation) layer on the exterior surface of the brick wall, where in the tested conditions allows not buildup of condensation.

Typical Toronto wall composition

Typical Toronto double brick wall insulated with Batt Insulation
Typical Toronto double brick wall insulated with Batt Insulation+exterior EPS

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