To get a fuller picture of the performance of the house there are two extra things I'd like to take into account: the amount of sunshine and the amount of wind. Both are significant because we have a lot of south-facing glass (and a lot of draughts!)
Since the house is a complex shape and shaded by the adjecent property by a differing amount seasonally, I know there's no point going for anything more than a crude estimate of insolation. I've been wondering whether I could get a useful approximation from two small (5.5v) PV panels, mounted on the same plane as the windows on either side of the house.
Could I connect these across an analogue pin and read directly to give a sunlight proxy?
I'm less sure about wind infiltration. I've currently got a pair of D18B20 sensors midway through the loft insulation above the same room, but one is next to the eaves (which are vented) and one is further towards the middle of the house. They show a variable temperature difference and I'm hoping to see the readings diverge when there's a lot of wind (and if I perfect the airtightness detail, will no longer diverge when it's windy).
Should I just get something like this reed switch anemometer and stick it on the roof, counting pulses? The other thing I've considered is fitting a PC case fan somewhere so that it gets spun up by the wind entering the house at which point the motor might act as a dynamo and generate a voltage I could measure?
Any thoughts very welcome!
Re: Isolation and wind infiltration monitoring
Here's an example of passive solar in action: you can see the green line (bedroom 1) jumps up for some afternoon sun then drops off again before the heating kicks in at 16:30
I'd like to measure this directly (so I can differentiate the sun from other stuff (bedroom 2 faces north-east... who knows why the temperature suddenly spikes?)