Are we anywhere near our aspirational design target - EnerPHit?
The five little radiators (2 more than last winter) are easily enough to heat the house up quickly after a week away and the washing dries in no time. Dealing with children in the middle of the night is less of a rude awakening now the night-time temperature is over 18 degrees C rather than below 12 degrees C.
And it has been even more comfortable than November and December 2012, when we had just moved back in. Back then, the house had stood empty for a year and had just been replastered throughout - so a fair bit of of drying out and heating up was required. This year, the summer warmth held in the walls meant that no heating was needed in October, and we put the heating on in November more to keep the walls up to temperature rather than because anyone felt less than warm.
What about the energy use?
November 2010 gas use (heating plus hot water and cooking) was over 2600kWh for the month. November 2012 dropped to ~1000 kWh for the month (heating and hot water only - cooking now electric), and November 2013 came in at 475 kWh.
So in terms of space heating, we used 3 times more gas in the first November after the refurb compared with the second. Perhaps not surprising, but more significant than I had imagined.
And what about EnerPHit?
Taking total gas use for 2013 (well, 21st December 2012-13) and subtracting the hot water component gives us about 3400 kWh space heating for the year - or 27 kWh / m2 / yr for our 125m2 house.
(Using the typical method of measuring floor area, the house is 140m2, but for Passive House calculations a different method is used, hence the lower figure of 125m2).
So we are somewhere close to the EnerPHit target of 25 kWh / m2 / yr.
However, it must be said - we don't run at 21 degrees C day and night (we like the bedrooms at 18-19 degrees at night, and the downstairs at 20 degrees in the day). That said, the first few months of 2013 were colder than the average winter, and it was still our first heating season post-refurb.
And the building fabric? While the insulation and cold bridge detailing were built very much as per the spec, the air tightness is not below 1 ACH at 50 Pa at the moment. At the end of the build it stood at 1.08 ACH in spite of a very leaky door seal, subsequently resolved. However, 12 months of DIY have taken their toll and we now have some work to do fixing the leaks created by "him indoors"!
Even so, it's high on comfort and low on energy use. And it is very cozy at Christmas - having family and friends round is not only fun and sociable, but also keeps the house very toasty without any heating thanks to the increased occupancy!
