With such an aggressive energy target based on usable square footage, Passive House design is sensitive to window areas to maximize potential solar gain. It is also sensitive to the "compactness ratio" of the design. My house was a relatively long, narrow rectangle due to lot limitations. This means a fairly high exterior surface area to usable floor area. In general, you will find Passive House architects trend to more compact, cubic configurations with large, south-facing windows that have high solar heat gain coefficients.

I should point out that the normal Passive House airtightness standard is 0.6 Air changes per hour at a pressure of 50 Pascal (ACH @50 Pa). However, in order to achieve the heat load demand and heat loss, the consultant recommended lowering the airtightness level to 0.2 ACH@50 Pa. Although I did not proceed with trying to meet the Passive House standard, I did ensure the house tightness was under that 0.2 ACH@50 Pa limit, just for bragging rights.