Heat pumps by UK property type: terrace, semi or detached

Start with the actual building, not its estate-agent label

Two homes described as three-bedroom semis can have very different heating requirements. One may have insulated cavity walls, modern glazing and an unheated garage; the other may combine a solid-wall original house, a lightweight rear extension and a loft conversion. MCS design requirements use room and fabric information rather than a single floor-area rule. Ask the designer to record the construction, dimensions, ventilation assumptions, target room temperatures and local external design temperature used for every room. The resulting heat loss should drive heat-pump output and emitter choices; the property label is only a prompt for where to investigate.

Keep the heating decision separate from the equipment brochure. The quotation should say what proportion of space heating and domestic hot water the proposed system is designed to supply, the design flow temperature, any supplementary heat source and whether existing radiators can deliver each room's required output at that temperature. Also record cylinder or alternative hot-water storage, electrical work, controls, outdoor siting, drainage, access and commissioning. This evidence makes competing quotations comparable and exposes a proposal that merely replaces a boiler by nominal kilowatts.

Terraced homes: compact fabric, constrained outside space

A mid-terrace often has fewer exposed external walls than an end-terrace, but that does not automatically mean a small heat pump. Heat can still leave through the roof, suspended floor, windows, doors, ventilation and rear or front elevations. Loft rooms, open-plan knock-throughs and rear extensions frequently have different construction from the original house and need separate room assumptions. A room-by-room schedule should therefore distinguish the original fabric from later work and show whether each radiator, fan convector or underfloor zone can meet its own design load.

Siting is often the harder terrace question. A short rear garden or yard can place the outdoor unit close to a neighbour's habitable-room window, reflective walls or a narrow passage. Compare candidate positions for airflow, declared sound power, the applicable MCS planning calculation, condensate management, pipe length, service access and the effect on doors or escape routes. Check ownership and boundaries before relying on a wall or alley. Limited indoor storage can also change the system route: an air-to-water proposal normally needs a credible domestic-hot-water solution, while air-to-air room units generally do not replace that hot-water service.

Semi-detached homes: use the extra elevation carefully

A semi may offer a side passage or gable wall that shortens pipework and keeps equipment away from the main garden. That position is not automatically best. A narrow passage can restrict airflow or maintenance, amplify sound between hard surfaces, sit beside either household's windows or interrupt bins and access. Ask the installer to compare at least the realistic positions on a marked plan, including assessment points, mounting method, clearances, route length, visual effect and how the unit will be reached for servicing without entering a neighbour's land.

The exposed side wall also changes heat loss compared with the adjoining party wall. Bay windows, attached garages, two-storey extensions and different upstairs layouts make a generic semi-detached allowance unreliable. Request the room losses and emitter schedule together, then identify where fabric work or a larger emitter would reduce the required flow temperature. If several rooms need independent cooling as well as heat, compare an air-to-water system with a properly designed air-to-air or multi-split route rather than assuming that one technology supplies identical comfort or hot water.

Detached homes: more siting freedom, more exposed fabric

Detached homes may have more possible outdoor locations, yet all external walls are exposed and larger properties often contain mixed ages, floor constructions and heating zones. A whole-house headline load can hide one cold room or an extension with different emitters. Ask how the designer has treated intermittent rooms, conservatories, vaulted ceilings, multiple heating circuits and planned renovations. Oversizing for reassurance is not a substitute for the documented heat-loss method: it can affect cycling, controls and cost just as undersizing can affect comfort.

More land does not remove planning, noise or electrical constraints. England's current permitted-development guidance treats detached houses differently from other houses in the number of qualifying air-source units, but every applicable limit and condition still needs to be checked and other UK nations have their own rules. A larger home may need zoning, hydraulic separation, a larger or faster-recovery hot-water store, supply upgrades or more than one heat pump. Require the quotation to explain those choices, the output available at design conditions and how simultaneous space-heating and hot-water demand is controlled.

Choose air-to-water or air-to-air for the service you need

Air-to-water systems connect to a wet distribution system and can be designed for space heating and domestic hot water. They may retain some radiators, but only where calculated output is adequate at the proposed temperatures; other rooms may need larger emitters or building improvements. Air-to-air systems transfer heat directly through indoor fan units and can provide useful room cooling, but they normally leave domestic hot water to a separate appliance or system. That difference matters more than the house label when comparing capital scope and annual energy.

Map the required service room by room. A household wanting whole-home heat and stored hot water has a different brief from one wanting heating and summer cooling in three bedrooms while retaining an existing hot-water route. Use the Multi-Room Split Designer for a first comparison, then ask qualified designers to price the same written brief. Grant eligibility, planning treatment and installer certification depend on technology, location and current scheme rules; never treat a reversible product description as proof that a particular project qualifies.

A quotation checklist that works for every house type

Before comparing totals, obtain the room-by-room heat-loss report, design temperatures, exact outdoor and indoor equipment, output at the stated conditions, emitter schedule, hot-water calculation, controls strategy and estimated seasonal performance assumptions. Add electrical scope, foundations or brackets, pipe and cable routes, condensate disposal, penetrations, making good, planning evidence, noise calculation, access equipment, commissioning, handover documents, warranties and maintenance. Mark every excluded item so a lower price cannot hide work that will arrive later as a variation.

Treat calculated energy use as a scenario, not a promised bill. Keep useful heat demand, seasonal performance, electricity tariff, standing charges, backup heat and hot-water assumptions visible. Compare the same inputs across proposals and retain the source and date. If an installer changes a radiator schedule, flow temperature or unit after the survey, ask for the performance and cost model to be reissued rather than assuming the original result still applies.

Decision checklist

Frequently asked questions