Hej,

Can anyone tell me how Primary Energy if factored by Passiv Haus please? For example, lets say I have a building which is using the following fuels quantities per year - how does Passiv Haus work these back to Primary Energy?

Mains electricity - 50kWh/m2/year
Mains gas - 50kWh/m2/year
Wood pellets - 20kWh/m2/year

Clearly this totals 120 kWh/m2/year which is at the threshold of the Passiv Haus requirement for total energy demand but the Primary Energy demand will of course be more due to the reletive inefficiencies of the different fuel types?

Thanks for any pointers.

Thanks Ed, that helps.

Does anyone have a good source of figures for primary energy usage in the domestic UK housing stock to compare against?

Robur, the 120 kWh/m²/year is for primary energy, not total energy. That is, you have to multiply the electricity by the fudge factor before adding it all up. IIRC there are fudge factors for the other fuels too although they are much closer to 1. The factors are in PHPP and may well be online somewhere but I don't know where, sorry. The numbers for your building show it to be so far outside passivhaus specs that I'm not even sure that PHPP would give sensible answers for it.

Based on PHPP version 2007, the relevant fudge factors seem to be (Primary/Delivered):

Natural Gas: 1.1
Wood: 0.2
Electricity (mains): 2.7
(Electricity (PV): 0.7)

So, in your example, it would be:

Mains electricity - 50kWh/m2/year = 50*2.7 = 135kWh/m2.a
Mains gas - 50kWh/m2/year = 50*1.1 = 55kWh/m2.a
Wood pellets - 20kWh/m2/year = 20*0.2 = 4kWh/m2.a
Total 120kWh/m2/year = 194kWh/m2.a

The PE ratio for wood is very low, presumably because they are not taking into account the energy from the sun to make the tree grow in the first place.

The numbers may have changed in the newer version of PHPP but I doubt that they are very different.

Hope this helps.

Thanks folks - appreciated,

Mark, your figures look correct to me, thanks for digging them out.

I have been hunting high and low looking for Total Primary Energy figures per property in relation to existing UK housing stock and there seems to be little out there - very surprising - the best I can get to at the mo is a figure of about 450kWh/m2/year for a typical UK home - more hunting required I think :-)

Not sure if this helps, seems to be a report about what we use, not had time to read it yet:
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/48195/3224-great-britains-housing-energy-fact-file-2011.pdf