Fabric First in Cambridge — Which Upgrades Are Worth Doing Before a Heat Pump?
Last reviewed: 2 October 2026
Cambridge's frosty winters reward a tighter house, but not every upgrade earns its cost before a heat pump. This guide weighs each common upgrade by what it costs and what it saves in a typical Cambridge home.
Why fabric matters a little more in Cambridge
Cambridge records around 52 air-frost days a year at the NIAB weather station, considerably more than western cities such as Bristol. A heat pump is sized for the coldest days, so every bit of heat loss you remove can mean a smaller unit, fewer radiator upgrades and lower bills.
You don’t have to insulate before you can have a heat pump. The Boiler Upgrade Scheme dropped its EPC requirement in April 2026. But a few upgrades are so good value that it would be a shame not to do them first.
Upgrades weighed up
Costs are typical for a Cambridge Victorian terrace or 1930s semi. “Heat loss reduction” is a rough share of the whole house’s heat loss.
| Upgrade | Typical cost | Heat loss reduction | Verdict |
|---|---|---|---|
| Draught-proofing (sashes, doors, floorboards, chimneys) | £150–£600 | 5–15% | Do it first |
| Loft insulation topped up to 270 mm | £400–£1,000 | 5–15% if currently thin | Do it first |
| Suspended timber floor insulation | £1,000–£2,500 | 5–10% | Usually worth it |
| Cavity wall insulation (1930s+ homes only) | £600–£1,500 | 15–30% | Worth it if walls are unfilled |
| Secondary glazing on sashes | £400–£900 per window | Small–moderate | Worthwhile in conservation areas |
| Internal solid-wall insulation | £8,000–£20,000+ | 15–30% | Not needed for a heat pump |
| External solid-wall insulation | £12,000–£25,000+ | 20–35% | Rarely allowed on period streets |
The details that matter in Cambridge homes
Sash windows
Original sashes are a defining feature of Cambridge’s Victorian streets and, in conservation areas, usually have to stay. Draught-proofing them with discreet brush strips is cheap and effective. Secondary glazing, installed inside, cuts heat loss further without altering the view from the street.
Suspended timber floors
Victorian terraces in Romsey, Mill Road and Newnham Croft almost all have ventilated voids under the ground floor. Cold air rises through gaps between boards. Insulating between the joists — from below if accessible, otherwise by lifting boards — transforms ground-floor comfort. Keep the void ventilated underneath to protect the joists.
Gault-brick solid walls
The pale gault brick of Cambridge’s terraces is solid, typically about 225 mm thick, with no cavity. Insulating it internally means losing room space and disturbing period features, and the cost is high compared with the saving. A heat pump with correctly sized radiators will heat these houses without wall insulation. If you do insulate later, use breathable materials so the brick can dry out.
Cavity walls in north Cambridge and the villages
Many 1930s and post-war homes in Chesterton, Arbury, Cherry Hinton and the inner villages have cavity walls. If they haven’t been filled, it’s one of the best-value upgrades available. An installer can check with a borescope through a small drilled hole.
Free upgrades through CERP
Cambridge City Council leads the Cambridgeshire Energy Retrofit Partnership (CERP), which secured £8.5 million of Warm Homes: Local Grant funding for insulation, solar panels and heat pumps in low-income households. To qualify, your household needs to be on a low income and your privately owned home rated EPC D to G. Information is available through Action on Energy Cambridgeshire.
The Boiler Upgrade Scheme doesn’t pay for insulation, and ECO4 closed to new applications on 31 March 2026, so CERP is the main source of free fabric upgrades locally.
A sensible sequence
- This month: draught-proof and top up the loft.
- Survey: have an installer calculate heat loss with those improvements in place.
- Before installation: insulate the suspended floor or fill cavities if the survey shows a meaningful benefit.
- Install the heat pump.
- Later, optionally: internal wall insulation, room by room, when redecorating.
Don’t wait for solid-wall insulation before getting a heat pump. Few Cambridge period homes ever have it, and the heat pump works without it.
Related: Victorian homes and heat pumps in Cambridge and the heat loss survey explained.
See what a heat pump would look like in your Cambridge home
The mechanism is the same in every UK home; the design is specific to yours. Our team carries out a free in-home survey including a full room-by-room heat-loss calculation, identifies the system size and configuration that fits your property, and provides a written quote with the £7,500 BUS grant already deducted.
You'll see the actual figure you'd pay — not an estimate — and the projected efficiency for your specific install.