Hi Chris, the overarching methodology for compliance is dictated by Part O which states the following:
It sounds like meeting this to the letter is going to be difficult with the simple openings, but as a minimum I would feel a lot more comfortable with a system which uses a gradual opening for both the day and night time condition as this would put us in a reasonable degree of accuracy in terms of what Part O is asking for, and from what you have described this sounds possible using the simple openings.
This would allow us to run parametric studies relatively quickly, and IF a full model is required at a later stage we can always fall back on the AFN method to ensure we are following TM59/Part O exactly, at the expense of significantly longer run times…
The constant flow rate seems like a viable alternative but I’m not sure how we would correlate a m3/s flow rate at night to what a window opening would provide, given that window sizes vary between rooms?