PHPP – treated floor area

[Mark Siddall]

I've been working throught some PHPP calcs and the example that I'm looking at really seems to be struggling to achieve the PassivHaus performance target. In a despirate bid to avoid making the fabric even more high performance (already averaging < 0.85 W/m2) I've sought to review the floor areas. In effect I'm in search of treated floor area to get more favourable results. With this in mind the PHPP Manual makes the following statements:1) Stairs with more than three steps and their landings are not considered to be part of the floor area.
2) the floor area of rooms and parts of rooms with a clear height of over 2m is added completely.
3) The floor area of rooms and parts of rooms with a clear height beteen 1 – 2m is added with half the area.
4) Rooms with heights lower than 1m do not form part of the area.

What about the English/UK habit for putting rooms beneath stairs? (Which I have in my example.) Surely this approach confuses the above. I am begining to think that I should add area in. Items 2-4 seem to be quite clear but it does begin to throw into question item 1. Does anyone have an interpretation?

Cheers,
Mark

[Alan Clarke]

Seems fairly clear, I think, that if you don't use the space beneath the stairs, it doens't count, but if it is used, then it should be counted as per 2-4. So the area of the treads themselves isn't counted, but useful floor area below is counted.

[Mark Siddall]

Yeah, as logic goes, that's how I was seeing it. Just wasn't to sure about letter of the law and whether I was stretching things.

M

[Nick Grant]

Hi Mark

If area under stairs will almost tip the balance then probably a very small dwelling and a possible candidate for special case treatment as discussed in 1998 conference?

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