![]() We don’t pay special attention to these “add-ons” for nothing. Much Ado About Porches, Decks, and Overhangs Thermal bridges lead to massive heat loss, negating the benefit of “over insulating” the structure.Įxample of a possible combination of insulation layers for a Passive House Design. In a traditional home, this would include all framing members of the structure, and things like porches and overhangs. Special attention is also given to eliminating thermal bridges.Ī thermal bridge is a break in the insulation surrounding the house. A wide range of thermal insulation materials can be combined to provide the required high R-values. This configuration significantly reduces the heat transfer through the walls, roof and floor compared to conventional buildings. This necessitates installing siding to cover and protect the membrane. ![]() The outermost layer of the insulation-sandwich is a water/wind membrane, which tends to be UV sensitive. To be continuous, the insulation goes on the outside of the framing, opposed to between studs in a conventional building. This insulation covers the entire envelope of the structure, including under the footing,with the only exception being the windows and doors. The insulation itself is generally comprised of multiple layers, all with high R-values. To achieve this efficiency, we’ve discussed how the structure’s envelop must be air-tight, but we also need to insulate the heck out of it. For example, a 2,000 ft² house would only use 2,800 kWh per year, which comes out to $280/yr 10 cents/kWh). Per the definition of Passive House-it can use no more than 1.4 kWh per 1 ft² of living space annually. A big part of how Passive House Design minimizes thermal gains and losses is through super insulation.Ĭomparison of heat gains and losses for different house types. On the other hand, a passive house will be 20x more efficient compared to the leaky house, and 10x more than a typical modern house. A “leaky house” will have double those losses - think older windows, no wall insulation, and degraded door seals. Today we explore the importance of insulation, and avoidance of thermal bridging.Ī typical modern house loses and gains approximately 150 kWh/m²a of heat, where the units refer to energy per floor area. You can have all of the best windows, doors, and insulation, but their effectiveness is diminished if the orientation of the structure isn’t correct. Site analysis is the first step, because it informs all the other steps. If you missed either of the previous, click on the links below to get up to speed! LEAP’s intelligent design process consists of four main steps, each building on the previous. This is the third post in our series on Passive House Design.
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