march 11, 2010 11:23am

Actual space heating revisited

A few entries back I presented numbers for January and February that show the amount of space heating we actually used compared to the PHPP predictions. I think a bit more explanation is due.

After checking average temperatures of a third weather station in the region, and re-crunching the numbers, my calculations do seem correct.

The explanation for the seemingly low space heeat numbers is fairly simple (I think):
1) Our PHPP certification is based on "Standard" internal heat sources (as calculated by PHPP for our house and usage).
2) Our climate model has long term averages for temperature and insolation which do not include a 30-year cold period like 2009-2010.

For the adjusted percentages of 88% and 80% I switched to "PHPP-Calculation" which only includes our actual appliance usage. A few months ago our trusty 20+year-old Bosch washing machine stopped working. We are still using our fantastic cold larder for all fresh food storage, and we do not have a fridge or freezer. Our only mostly-on appliance is a laptop and speakers that use <50W. Consequently our PHPP calculated space heat requirements increase.

In addition I have only considered the actual mean temperatures and do not have actual insolation data to enter into PHPP. I believe that February in particular produced higher insolation levels than our PHPP climate model indicates.

Taking the above into consideration I think our actual space heating for January and February may be 5-10% less than general predictions. But whatever the future holds it does show how well the house is already performing... and what an excellent tool PHPP is for low-energy house design.

Posted By: MarkTiramani

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