It is well known that compactness is an important aspect of a well designed and cost effective Passivhaus as it has a considerable impact on the overall heat demand. Having now modeled a number of projects in PHPP (Passive House Planning Package), I decided to do a quick comparison of the ratio of envelope to floor area (known as the form factor) as well as the average R-value of the entire envelope. Here are a few examples:
Emerson
envelope to treated floor area: 3.8
average R-value: 39.4
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Skidmore
envelope to treated floor area: 3.7
average R-value: 29.7
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18th Ave Residence
envelope to treated floor area: 3.2
average R-value: 24.1
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Haig Haus
envelope to treated floor area: 2.7
average R-value: 25.9
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Ankeny Apts
envelope to treated floor area: 1.5
average R-value: 19.7
While there are many variables at play that make each project distinct, it is clear that form factor has a huge impact. Remember boxy can be beautiful!