While a passive solar gain is not required in a Passive House, it has substantial impact on the envelope of the house. Better sun exposure let’s us use a bit less insulation and more affordable windows. As this project is located in an urban area we trying right now to calculate how much help we can expect from the bright NYC winter sun. The photos above were taken from the lower residential floor of the building approximately in the middle of the large south facing rear glass wall. The light blue curve represents the sun’s path at winter solstice and the yellow line is the sun on March 21. What we can see on the graph is that at this floor we only have direct sun on 12/21 from about 10:45AM to 11:45. This is only an hour and the sun radiation is further reduced by the large trees in the neighbors rear yard. We expect to have a much better exposure in the floor above but to easily verify this on site we have to wait another couple of weeks until the next floor is built. (yes, i know that this can be done by calc’s too but it’s fun to see it in the real world) While the December solar gain data does not look to good it is important to note that the required heat demand in NYC is much higher later in the winter… mid January and Feb-March when the Solar Elevation is already higher.
time to give some credit:
thxs to David White to point out his concerns about the importance of verifying the shading data in the PHPP and also thank you to the guys at ozPDA for making such a cheap and easy to use iPhone application called “Sun Seeker”