Air Source Heat Pump (ASHP)

This page contains our notes about our proposed air source heat pump (ASHP) installation.

Project status: dormant (March 2023): Not currently planning on doing this. (1) It seems clear that both solar PV and extra insulation should come before ASHP. (2) We have too many concerns about the system’s effectiveness and suitability in this particular house.

Not everything in here will be correct or make sense. I am no expert on these matters, just technically savvy and curious to learn and understand it all. That’s why we’re approaching installers for their expertise in design and installation.

I am learning as I go along, starting in November 2022.

Air Source Heat Pump (ASHP) System


  • Considering east-facing chimney breast above garage, at north-east corner of house. Discussed with surveyor. Ideal siting for connection to existing heating pipes in garage below, and access is good. It’s a potential bedroom, so vibration is a concern, but it’s old solid walls.

Control system (Central Heating, Radiators, TRVs, Time Switch)

Aim: upgrade to better control than simple whole-house thermostat and time switch.

  • controlled from smart TRVs? (related to “zoned” control?)


  • general introduction:
  • standards: OpenTherm?
  • compatibility: ???


  • Replace existing simple time switch with new controller (TBD).

ASHP Monitoring and Control

Outstanding Concerns, Requests, Questions (ASHP)

  • How suitable is ASHP with zoned heating in an old house? Podcast to listen to: The Multi-Zone Heat Pump Issue (
  • What control system? Research & add a smart/zoned heat demand control system?
  • What monitoring? How much is built in; what to add?
  • Remove gas flue
  • Minimise pipe runs in garage (ASHP to existing plumbing)

Other Installation Requests

  • Remove gas boiler flue completely and make good the roof. (Check: do we have spare tiles?) Aim: weatherproof.
  • Remove excess pipe runs from old boiler location in garage: route directly to new ASHP location. Aim: tidiness.
  • Site the hot tank for shortest possible outlet pipe run to domestic hot water supply. That would be south-west corner of garage. Aim: minimise time delay and waste in using domestic hot water.