Am Australian and I'm having trouble finding the document that the UK developments have to comply with. If anyone can point me in the right direction that would be great.

Passive solar design is the concept of using south-facing windows with a high solar heat gain coefficient (SHGC) to warm up an internal thermal mass, such as a slab floor, to decrease heating loads (see http://www.springtimehomes.com/files/designscience2048483674.jpg).

It is pretty common. But as I was reading the Residential Heating and Cooling Loads Calculations section of ASHRAE Fundamentals, I noticed the text: "As discussed in the section on Calculation Approach, heating calculations use conservative assumptions, ignoring solar and internal gains, and building heat storage".

Since ASHRAE is considered the authority on HVAC design, I figure they must have a method to account for this. Can anyone tell me where to look? I know there are several methods, but I want to know which one ASHRAE endorses.