There are five questions that are key.
- % wet underfloor heating
- are radiators oversized
- levels of insulation in loft walls etc
- extent of double glazing
- do you have air conditioning
If you have mostly wet underfloor heating an Air Source Heat Pump should be fine.
If you are using radiators then they will need to be oversized for them to work with the reduced flow temperature of 80 -> 50C. Unless you fix it by insulation levels.
Levels of insulation need to be checked. It is well worth adding insulation to the loft and draught sealing loft hatches etc as the payback is very fast.
Good double glazing is absolutely essential for ASHP’s to work effectively.
If you have a modern inverter air conditioning system you already have an air source heat pump. So you have nothing to do. It also gives a good idea of running costs for heat pumping.
The insulation/double glazing/air tightness piece is well worth doing. We did it in lockdown #1 and our gas usage is 45% down in a Wandsworth Victorian house.
FYI our house was reasonably well insulated to start with and had 50% double glazing. We have a reasonable area of wet underfloor heating.
Let’s put it this was we had a 24kW boiler, which is tiny, which never worked very hard. Now it works even less hard.
If you have some hoofing 40kW boiler that looks like a steam locomotive when it gets cold then ASHP’s are not fit you: with present technology.
Insulating is not very exiting but it does reduce carbon footprint: a lot. It is also a vital first step to making an ASHP a viable proposition.
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