Air to air versus air to water heat pumps

ispookie666

There are fundamental differences in the way both systems heat - directly moving the air using blowers over evaporators/condensers vs convective heating. Quicker heating with Air-Air vs Air-Water and cooling with Air-Air, you would need to work out a way to remove condensate if trying to build a Air-Water HP.  The energy output will not be much different, except water having larger heat capacity will take longer to warm up and longer to cool down.  

I have two air cons installed this year.  You need planning permission if installing Air-Air heat pumps and larger Air-Water HP and definitely if more than two units.  These are usually not classed as permitted development.  It is highly unlikely anyone would fall foul to these rules, but always the potential and possibility.  

JKenH

Switching to a heat pump can lower your home's green rating

Heat pumps may be better for the environment but they can lower EPC ratings

Elmhurst Energy, an energy assessment training firm, found that installing a heat pump in a 10-year-old detached property in the Midlands reduced the EPC rating from 63 to 60, though the building remained in band D.

Martyn Reed, of Elmhurst Energy, said this was due to high cost of electricity used by heat pumps, compared to gas. 

The headline EPC rating is based predominantly on a property's energy costs rather than its impact on the environment.

https://www.telegraph.co.uk/bills-and-utilities/gas-electric/switching-heat-pump-can-lower-homes-green-rating/

Verdigris

Further proof, if proof were needed, that EPCs aren't worth the paper they're written on.

Don't get me wrong, the idea is sound but the implementation leaves a lot to be desired.

2nd_time_buyer

I have encountered this on a flat we let. The flat is heated by electric oil-filled radiators. However, as it is first floor with flats above and below, the tenant says she very, very rarely puts the heating on. The flat is also well insulated. I was looking at getting a air-to-air heat pump fitted to reduce the running costs a bit further for the tenant and try and achieve a "C" rating. But the accessor said it would not be enough to change the EPC rating. Instead, I would need to install a gas boiler or night storage heaters both of which seem a backward step. So, I guess I am going to leave it and wait till the legislation catches up with the technology.