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What is a Passive House?

A Passive House is the most comfortable, healthy and energy efficient home available today. Based on a German energy standard, Passive Houses  use about 90% less energy to heat, while increasing the overall comfort through super insulation, airtight construction and
mechanical ventilation.

Since a Passive House is primarily heated by passive solar gains and secondarily from the heat of its inhabitants and electronic and electrical appliances, a conventional heating system is not needed. The money saved can be used  to offset some of the increased cost of other components. The savings in energy costs make it possible to live in an extremely comfortable Passive House, without increasing your overall monthly expenses.

The Passive House is a newer development of the energy efficient homes built in Denmark and Sweden in the 1980s. The first Passive House was built in Germany in 1991. Today there are more than 10,000 Passive Houses worldwide. 

Per definition,  A Passive House can use no more than 1.4 kWh for heating 1 sq. ft. of living space annually (a 2000 sq.ft. house can use 2800 kWh for heating per year = $ 280, assuming 10 cents per kwh).


1) Super insulation. A Passive House is extremely well insulated around all exterior surfaces - including below ground.

2) Virtually airtight construction.. A traditional home loses up to 40% of its heat through ventilation (fans, leaks, draft). A Passive House needs to be virtually airtight. This is tested with a blower door test during and after construction.

3) Mechanical ventilation. A constant supply of fresh, filtered outside air is brought into the house through an efficient central ventilation system. At the same time the stale air is blown out.

4) Heat recovery. Separated by an ingenious membrane system, the outgoing warm air passes side by side with the incoming cold air. Because the cold air is warmed, 90% heat recovery results. This works in reverse in the summer by cooling the incoming hot air.

5) Highly insulated windows. A Passive House typically has triple pane windows with low e glazing and argon gas are contained in an insulated frame.

6) Passive solar gains. By placing more windows with southern exposure and fewer with northern exposure, passive solar gains are maximized. To avoid overheating in the summer, carefully planned shading and window glazing are crucial.

7) Avoiding thermal bridges. A thermal bridge is a break in the thermal insulation surrounding the house. In a traditional home this would include all framing members. As the insulation layer around the house is increased possible thermal bridges would lead to massive heat losses making the super insulation much less effective.

8) Computer modeling. A very powerful software program, the PHPP, has been developed in Germany to accurately predict the energy usage and performance of a house during the design phase.

Before a Passive House can be certified by the Passive House Institute US a  complete set of calculations must be submitted.

The actual performance characteristics for a passive house are:

Energy usages for heating must be below 1.4kWh pr. sq.ft. pr. year

A 2000 sf house =  2800kWh = $300 for heating per year (assuming 10 cents per kWh).

Maximum energy usage incl. heating below 3.8kWh pr sq.ft. pr. year

A 2000sf house = 7600 kWh = $ 800 for all utilities incl. heating (assuming 10 cents per kWh).

Air tightness. Less than 0.6 air change pr. hour at 50 pascal pressure, tested with a blower door test. (Much, much tighter than a conventional home).


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