A very EnerPHit Christmas?

Now into our second heating season since the refurb, we are definitely reaping the benefits in terms of comfort. We have a house that is quick to heat up and slow to cool down (Hooray!)

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!

It's cold outside...

... but fortunately seems to be ok on the inside even when the temperature drops to -5 on the outside.

Strange but true - at 19 degrees C, the house feels warm (whereas it felt much less comfortable at the same temperature before the insulation and draught-proofing).

The plaster is still drying out and the brickwork is still warming up after a year of exposure to the elements, so the gas boiler is working harder than it will need to next year, all other things being equal.

The 3 tiny radiators are not really enough to keep every room at 19 or 20 degrees C under these circumstances, but we are happy with bedrooms dropping to 17 or 18 degrees C at the coldest point in the night. (It beats the 8-12 degrees C that was the midwinter norm in 2010 and 2011).

The other striking difference for me is the complete absence of joint pain, which was a permanent feature for at least 4 months through previous winters. I had a hunch it was down to cold and damp in the house and I'm really delighted to experience such a spectacular difference this year. (Of course, for those who haven't got an extensive collection of injured joints, it won't make much difference).

The energy bills will also have a story to tell, but I don't have enough measurements yet (and there are further efficiency improvements to make anyway before the house reaches its "as designed" state).

One thing you do have to get used to is condensation or ice on the outside of the windows (because heat loss through the triple glazing is so low that the ice can still be found on the outside of the windows for hours - until the sun melts it off). I'm not complaining - so much nicer than having the ice on the inside as was the case for days on end in winter 2010 and 2011.

Workshops and SuperHomes events

If you live in the Nottingham area and would like the chance to visit this house and find out more about it, March 2012 would be a good time!

On 3rd and 10th March there will be a set of 4 workshops for people looking to make modest or major home improvements of an energy-saving nature. This house is one of the case studies. For all the information, look out for the Homes Behaving Badly workshops on Transition West Bridgford's Eco House Group blog.

Then, on the weekend of 24th March, as part of SuperHomes open homes week, we'll be opening our doors to visitors. To book on a tour, just go to the SuperHomes website and look for Nottingham's Aspiring Superhome, or follow the link to the Homes Behaving Badly workshops and book your place that way instead.