I'm building my own 3 bedroom (204 m2 floor space total / volume 518m3) house with very high insulation levels (SIPs + 100mm K3 insulation, mechanical heat recovery ventilation, airtightness and so on). There's no mains gas, and for reasons too involved to go into, Air Source Heat Pumps are not a suitable answer for us, so it's an LPG system we want. We will have underfloor heating, so I know it will need to be a modulating boiler, but I'm getting conflicting advice on whether to fit a combi or system boiler. There will be 2 showers in the house, but it is very unlikely that the 2 will ever be in use at the very same time (and I can make the less used one an electric one if necessary if it saves fitting a much bigger boiler than is needed for 99% of the time). Our SAP thing (all 26 pages of it - good God it's gobbledygook!) says that with all our insulation etc our space heating requirement is 5650 kWh/year, or 27.42 kWh/m2/year which I gather is good. For DHW, the family is 2 adults and 1 child in late teens about to go to university. So there will mostly be just the two of us, but occasionally 3 or 4 occupants.
I've had such wildly different answers from 2 plumbers as to what size & type I should have installed that I'm looking for advice from someone who is not trying to sell me something! Any ideas?
I've had such wildly different answers from 2 plumbers as to what size & type I should have installed that I'm looking for advice from someone who is not trying to sell me something! Any ideas?