Proof of the pudding...

It's December, and time I blogged again. The last seven months of occupancy have been intense at ECF, not only with moving in but also just catching up with 'normal' family and work life. Despite the festive season being just round the corner, we at least feel we're getting there!

On the energy front, seven months of occupancy means we've got some data on energy consumption to compare with what we specified and predicted...and the results are quite a relief!

The bottom line is that we're using 25% less energy than we expected; and that's in a house already designed to use less than a quarter of the energy of the average new housing stock. In general hot water and space heating energy use are on target, although these account for less than half of our predicted energy use. The big savings have thus been made in other energy use, namely lighting and appliances. In particular the use of LED and CFL light fittings, coupled with A and A+ energy rated kitchen appliances has paid dividends.

Whilst in most houses heating and hot water use accounts for up 80% of domestic energy demand, our experience just shows that real savings can be made with little effort by replacing lighting and appliances (when worn out of course!) with more energy efficient equivalents.

Update...

Now we're in and the snag list getting shorter, it's nice to take stock and get back to 'normal' family and work life. The good weather of late is helping (why did we build a house in winter?!)
One of our outstanding issues is connection of phone and broadband to the house (ironically the caravan is still better connected than the house!) such that once this is done and we have more time, normal blog service should resume....

I've found the dinner plate.....!

Our aitightness test a week ago had me crawling around in the loft at the wekend with a big torch which revealed the achilles heel of our aitightness strategy - penetrations and unsupported joints!
For the most part the vapour/air membrane is continuous within the building with joints made with tape and silicone which were then mechanically trapped beneath battens or plasterboard.
The exception to this is the loft space where the membrane was simply stapled to the underside of the rafters, between which insulation was previously fitted. This clearly makes the membrane vulnerable to gravity (!) and any air pressure difference between outside and inside the house with the ultimate risk of the membrane pulling away from the rafters - which has started to happen in one place. I have also spotted two un-taped long joints with resulting gaping holes exposing the insulation, and an unsealed soil pipe penetration. These gaps must easily account for at least half of our dinner plate size hole given that the soil vent pipe ducts were open in the bathrooms during the airtightness testing.
The ultimate solution is probably to bring down the membrane from the rafters to the loft floor and place the insulation from between the rafters on top of it, thus creating a 'cold' loft. It goes wihout saying that the penetrations need sorting out also!

Passive house weekend...

After our airtightness test was done last Friday I switched off the heating, having 'cooked' the house for a couple of days to aid the thermal imaging tests. On Friday evening it was 20.5 deg. in the ground floor and 19 deg in our unheated 1st floor bedroom.
After a chilly and breezy Friday night, both these readings had dropped by just 1 deg overnight and still no heating. During the day the readings dropped a further 1 deg (tilers in - patio door fully open!) then raised a little towards the late aftenoon/evening as the sun peeped out.
Saturday night was again cold (as snow moved into northern Britain) but temperatures only dropped a couple of degrees in the house overnight, only to rise again during today to as much as 23 deg. in the ground floor and 20 deg. in our bedroom due to solar gain, despite the continuing biting cold wind outside (and leaky patio doors!).
In essence the house was behaving passively, with perhaps the circulation pump (set to continuous within the heat pump unit) helping to spread the heat from solar heated rooms to the rest of the house, an effect which will be helped further by the MVHR unit when switched on.