Heat pump in a Victorian terrace; the honest retrofit

Solid brick walls release and absorb heat slowly, suspended timber ground floors leak air at the perimeter, microbore pipework constrains flow rate, and a tight rear yard complicates outdoor unit placement. None of these are deal-breakers on their own, but together they explain why the Victorian quote tends to land 20 to 30 per cent higher than the equivalent semi.

The arrival of credible R290 high-temperature units; Vaillant aroTHERM plus, Daikin Altherma 3 R290; has quietly retired the old advice to 'rip out every radiator before installing'. Most modern Victorian retrofits upsize two or three emitters, not twenty.

Loft insulation to 300mm. Draught-proofing around floorboards, skirting, sash boxes. Heavy curtains or secondary glazing on north-facing rooms. None of it is glamorous, none of it is expensive, and all of it shrinks the heat pump you eventually install.

Internal wall insulation is the big-ticket fabric decision. It's intrusive and reduces room sizes, but a heat pump in a fully insulated solid-wall Victorian behaves like a heat pump in a 1990s semi. Do it during a kitchen or bathroom rip-out, not as a standalone job.

Most Victorian rear yards are tight, walled and acoustically reflective. The outdoor unit needs to be on anti-vibration mounts, ideally on a side wall rather than directly under a bedroom window; yours or a neighbour's.

Permitted-development rules eased in 2024 in many councils, but always check before installing. A pre-emptive note to the immediate neighbour about a quiet R290 unit is cheaper than a planning dispute six months in.

An MCS heat-loss survey will usually return 7–9 kW for a typical 3-bed Victorian terrace before fabric improvements, and 5–7 kW after. Pick the lower number and run it longer. Heat pumps fail in Victorians when they're run like boilers; short, hot bursts. They thrive when allowed to maintain a steady flow temperature all day.