Zero Carbon? Before too many people get hot under the collar about this, let’s be clear what I mean by this.
The plan—and we won’t know for at least a year whether we’ve succeeded—is to build a house which is neutral in terms of the CO2 it emits. The solar thermal panels contribute to the heating of the domestic hot water (DHW) and of the house without emitting any carbon. Of course CO2 was generated in their manufacture—and I’m not counting that.
The solar photovoltaic (PV) panels should generate at least as much electricity , measured in kilowatt– hours (kWhr) as the house uses over the course of a year. Some will be used immediately, but the rest will be fed back into the mains supply—particularly during the summer—and if the calculations are correct, the amount of power drawn from the mains supply at night and during the winter will be equal to this or, better, less. Essentially, the mains supply is being used as though it were a battery. And yes, the PV panels needed quite a lot of energy in their manufacture.
The log burner burns logs (!) and emits the carbon that was stored in the wood while it was growing. This is neutral as the wood cannot emit more carbon than is in it.
Some will point out that there’s a lot of concrete in the ground slab and that concrete is a very energy demanding product—cement requires much energy in its manufacture. True. Limecrete would have been better—but less satisfactory as a thermal mass, and more expensive. I have to cut my coat according to my cloth. The solid wall between dining room and bathroom is there for thermal mass reasons. It’s partly made of second hand bricks and it also incorporates some other old heavy blocks in the part that’s rendered.