Resources / Heat pumps
Heat Pumps in Older Homes: What Actually Works
Solid walls, mixed floors, limited insulation and real South West stock — what has to be right for an air source heat pump to perform, and what usually goes wrong.
Quick Answer
Yes — heat pumps can work well in older Devon and Cornwall homes. They work poorly when the building is treated as a simple boiler swap and fabric, emitters and heat loss are ignored.
Homes that succeed usually tackle the worst heat loss (or plan it in parallel), use suitable emitters at a realistic flow temperature, and get a proper room-by-room heat loss. Homes that disappoint usually skip those steps and then blame the outdoor unit.
View printable checklist Planning aid — not a quote
Why older South West homes are different
A lot of stock in Devon and Cornwall is solid-wall — stone, cob, pre-1930 terraces, and mixed-age houses that were never designed for low-temperature heating. Heat loss is often higher, air leakage is higher, and floor and wall build-ups are less predictable than a modern box.
That does not make a heat pump the wrong choice. It means order of work and design quality matter more than on a well-insulated new build.
A heat pump delivers heat at lower water temperatures than a typical gas or oil boiler. If the house loses heat quickly and the emitters cannot deliver enough at those temperatures, you get higher bills, rooms that never quite get there — or both.
What actually determines success
| Factor | Why it matters in older stock |
|---|---|
| Heat loss calculation | Guessing from floor area or the old boiler badge is how undersizing starts |
| Emitters at low flow temp | Small original radiators often cannot deliver design output at 35–45°C |
| Worst fabric wins first | Naked loft, major draughts, single glazing — cheap wins before oversized plant |
| Flow temperature honesty | Cranking flow to “feel like gas” destroys the efficiency case |
| Controls & expectations | Steady operation beats deep setbacks on high-mass solid walls |
| Siting & noise | Tight plots, neighbours and conservation still need a real MCS 020 path |
Deep dives: heat loss · radiators · flow temperature.
Solid walls, stone and cob
Solid walls are not an automatic no. They are a higher heat-loss envelope that must be in the calculation — not wished away.
- •External wall insulation can transform load where planning allows and detailing is moisture-aware
- •Internal insulation is possible but needs careful vapour and cold-bridge design
- •Many projects succeed with loft, draughts, glazing and correct emitters first — without full EWI
- •Conservation areas often constrain external appearance; floors and lofts are freer levers
If someone says “heat pumps don’t work in solid-wall houses” without a heat loss and emitter schedule, that is ideology, not design.
Radiators vs underfloor in older properties
Radiators still work when they are large enough for the design flow temperature. Expect upgrades in many rooms — not always every room, but often the cold ones and high-loss elevations.
Underfloor heating pairs well with heat pumps when the floor build-up allows. On solid ground floors, overlays are the usual renovation path. Upstairs joists need plates or structural boards — not a casual wet screed.
Guides: UFH for renovations · overlay vs screed · HP + UFH worth it?
Common mistakes in older homes
- •Sizing from the old boiler nameplate
- •Leaving a naked loft and blaming the heat pump
- •Keeping undersized radiators “to save money”
- •Running high flow temperatures all winter and wondering where the SCOP went
- •Deep setbacks on solid-wall rooms that take hours to recover
- •Ignoring damp and ventilation when tightening the house
- •Assuming solar will fix an undersized outdoor unit on a design day
Related: not heating properly · condensation & mould.
What tends to work well
- •Room-by-room heat loss with a local design outdoor temperature
- •Loft insulation and draught-proofing done before or with the install
- •Emitter schedule at the flow temperature you will actually run
- •Weather compensation commissioned properly
- •Steady setpoints in solid-wall rooms
- •A tariff that matches heat pump use
- •Honest handover — not “it’s the same as your old boiler”
Oil, LPG and rural switches
Off-gas homes on oil or LPG often have the strongest economic case for a heat pump when design is done properly. BUS support is typically £7,500, with £9,000 available for many oil/LPG replacements where there is no mains gas — confirm current GOV.UK rules.
Do not let the grant rush the design. A funded but undersized system is still an undersized system. Grants in Devon & Cornwall · running costs vs fossil heat.
Realistic expectations
In a prepared older house, a well-designed heat pump can deliver comfortable heat and running costs in a similar band to modern gas — sometimes better, sometimes a little higher depending on tariff, fabric and how the house is used.
It will not feel identical to a high-temperature boiler. Response is often slower, especially with underfloor heating or high-mass walls. That is normal. The gain is steadier comfort and better efficiency when the system is left to run properly.
If the fabric is left poor and the emitters are undersized, no brand of outdoor unit will rescue the result.
A sensible sequence for older properties
- Gather bills, note cold rooms, photo loft / boiler / radiators / outdoor space
- Commission room-by-room heat loss
- Do easy fabric wins (loft, draughts) you can afford now
- Design emitters at a realistic flow temperature
- Size and site the heat pump; check noise assessment
- Plan electrics for future solar if relevant
- Commission controls and learn the first winter
Whole-house framing: where to start.
Honest bottom line
Heat pumps work in older South West homes when the building is designed for, not ignored. Solid walls raise the stakes; they do not invent a different physics.
Heat loss, emitters, fabric priorities and steady controls decide the outcome. Skip those and the outdoor unit becomes the scapegoat.
Frequently asked questions
Can a heat pump heat a solid-wall cottage?
Yes, if heat loss is calculated properly and emitters can deliver at a sensible flow temperature. Many solid-wall homes run successfully once the worst fabric issues and radiator/UFH sizing are addressed.
Do I need external wall insulation first?
Not always. It helps a lot where practical and permitted. Loft, draughts, glazing and correct emitters often get you most of the way. Let the calculation drive the decision.
Will rooms still feel warm enough?
They should if the system is designed for the actual building. Cold rooms after install usually point to undersizing, weak emitters or fabric — not a mysterious older-house curse.
Is underfloor heating required?
No. Correctly sized radiators work. UFH is excellent with heat pumps when the floor allows, especially in renovations.
What about listed or conservation properties?
External changes may be limited. Focus on loft, floors, secondary glazing where allowed, emitters and plant siting. Get advice early on planning and appearance.
Next step
Get a realistic planning band for your home, then use the checklist when you speak to installers.