An air source heat pump is big, about twice the size of an air conditioner, and is mounted externally, which might mean that it will require planning permission in our conservation area. Heated water is distributed through radiators or underfloor. It doesn’t provide cooling, ventilation or domestic hot water.
If you live in a house or a ground floor flat you can probably position one on the rear wall or in the garden. If you live in an upper floor flat it is unlikely that you will be able to fit one.
You might find an air source heat pump combi of interest.They are more expensive, and at the moment don’t qualify for a government grant (but hopefully that will change). They are quite large and heavy to install. However, they do have the advantage that they are fitted internally, so don’t require planning permission. Heated air is distributed through duct work and grilles in the floor or ceiling.
Pichler and Viessmann combis both provide heating, cooling, ventilation and hot water all in one unit.Insulation is the top priority in retrofit. Ideally 10 cms of wood fibre should be fitted to the external walls, probably internally, with as much as possible in the ceiling and floor. Any draughts should be stopped. The next priority is double glazing. Both of these should be carried out before a heat pump is installed. One or two electric heaters can be added if needed.
There is some support offered to residents. Camden lists the energy efficiency grants available at https://www.camden.gov.uk/energy-efficiency-grants.
Stay in touch on retrofit@belsize.org.uk.