Designing Homes for Heat Pumps: Key Design Principles

As heat pumps become the standard heating system for UK homes, architecture is evolving to accommodate them. This guide sets out the design principles that matter when a home is built or renovated around a heat pump, from new builds designed around heat pumps from day one to sensitive retrofits of Victorian terraces. Good design can make the difference between a heat pump that merely works and one that works brilliantly.

The relationship between architecture and heating is changing fundamentally. For over a century, British homes were designed around a simple premise: a gas boiler in a kitchen cupboard, connected to radiators on every wall. The boiler was small, the hot water was instant, and the house design barely needed to acknowledge the heating system at all.

Heat pumps change this calculation. They require an outdoor unit, a hot water cylinder, potentially larger radiators or underfloor heating, and — most importantly — they perform best in well-insulated buildings. Architects who understand these requirements produce homes where the heat pump is not an afterthought but an integral part of the design. For the technical details of installation, see our comprehensive installation guide.

The Fabric-First Approach

If you want the best possible heat pump performance, start with the building envelope. A well-insulated, airtight home needs a smaller heat pump and is cheaper to heat; a poorly insulated home needs a bigger one and costs more to run. The building fabric matters most.

The fabric-first philosophy means investing in the building's thermal performance before specifying mechanical systems. For new builds, this means exceeding minimum Building Regulations standards for insulation. For retrofits, it means addressing the biggest heat loss areas before installing the heat pump.

A home built to the "heat pump optimised" column in the table above typically needs a heat pump of just 4-6 kW for a 3-bedroom house — compared to 8-12 kW for a home built to minimum standards. The smaller unit costs less to buy, less to install, and less to run.

Designing New Builds for Heat Pumps

In a new build, there is every reason to design around the heat pump from day one. The outdoor unit position, the plant room and the heating distribution should all be resolved at the design stage, not retrofitted as an afterthought.

Under the Future Homes Standard (expected to be fully implemented by 2025-2026), all new homes in England must be built with low-carbon heating. This effectively mandates heat pumps for most new developments. Architects designing new builds are now routinely incorporating:

• Dedicated plant rooms — space for the indoor unit, hot water cylinder, and buffer vessel
• Outdoor unit zones — planned locations with proper foundations, drainage, and acoustic screening
• Underfloor heating — particularly on ground floors, for maximum efficiency at low flow temperatures
• Solar-ready roofs — south-facing roof areas pre-wired for solar panel installation
• Mechanical ventilation with heat recovery (MVHR) — to maintain air quality in airtight homes while recovering waste heat

Retrofitting Existing Homes

Retrofit is where the real challenge lies. Every home is different: Victorian terraces with solid walls, 1930s semis with cavity walls and 1960s system-built homes each need a different approach, and a good designer looks for the best solution for each specific building.

Retrofitting a heat pump into an existing home requires architects to work within constraints that new builds do not face. The most common challenges include:

• Finding space for a cylinder — homes with combi boilers typically have no hot water cylinder, and finding 0.5 m² of floor space can be challenging in smaller properties
• Outdoor unit positioning — tight plots, small gardens, and close neighbours can limit options
• Insulation limitations — listed buildings and conservation areas may restrict external insulation options
• Existing radiator systems — most existing radiators can work, but some may need upgrading. See our radiator compatibility guide

The good news is that retrofit is almost always possible. Our cost guide covers the economics, and the BUS grant helps with the financial barrier.

Plant Room and Cylinder Space

Plan the plant room early. Homeowners switching from a combi boiler often don't realise they will need a hot water cylinder, which can be around 2 m tall and 600 mm across and needs to go somewhere: an airing cupboard, a utility room or even a corner of the garage.

A heat pump plant room or area typically needs to accommodate:

• Hot water cylinder (typically 200-250 litres, approximately 600mm diameter × 1.5m tall)
• Indoor controller/hydraulic unit (approximately 400mm × 400mm × 700mm)
• Buffer vessel (if specified — adds another 400mm × 1m)
• Expansion vessel, valves, and pipework
• Access space for maintenance

Outdoor Unit Positioning

Position the outdoor unit where it gets good airflow, the least visual impact and the lowest noise transmission to bedrooms. In a new build you can design the landscape around it; in a retrofit you are usually looking for the best compromise.

Key positioning principles:

• Avoid corners and recesses that restrict airflow
• Position away from bedroom windows (yours and neighbours')
• Ensure a solid base (concrete pad or wall brackets) with anti-vibration mounts
• Allow for condensate drainage
• Consider screening with planting or fencing (maintaining airflow clearance)

Heating Distribution: Underfloor Heating vs Radiators

For new builds, underfloor heating on the ground floor is a common choice because it runs at low flow temperatures (around 30-35°C) that suit heat pumps; on upper floors, larger radiators work well. In retrofits it is usually about upgrading a few key radiators rather than ripping up floors.

Aesthetic Integration

Heat pumps don't have to be ugly. Screening such as timber enclosures, green walls and planting can hide the outdoor unit while keeping airflow clear, and the cylinder can be built into bespoke joinery.

Aesthetic integration is increasingly important as heat pumps become standard. Architects are developing solutions that include timber-slatted screening around outdoor units, planted borders that soften the visual impact, bespoke cupboards and utility spaces for indoor components, and colour-matched units that complement the building facade.

Future-Proofing Your Home

Even if you are not ready for a heat pump now, a renovation is a good time to make the home heat pump ready: good insulation, space for a cylinder and a suitable outdoor unit location. Future-proofing during a renovation usually costs far less than retrofitting later.

Future-proofing measures include specifying larger radiators during any renovation work, pre-wiring for a heat pump electrical supply, designating cylinder space in the layout, preparing a suitable outdoor unit foundation, and installing insulation to higher standards than the minimum. These measures cost very little during construction or renovation but save thousands if you install a heat pump later.

Architects also recommend combining heat pump readiness with solar panel readiness — ensuring south-facing roof areas are unobstructed and pre-wired for future solar installation.

Frequently Asked Questions

How do architects design homes for heat pumps?

Architects use a fabric-first approach (superior insulation), specify underfloor heating where possible, include dedicated plant rooms, plan outdoor unit locations, and design with larger radiator capacity.

What is the fabric-first approach?

It means investing in the building envelope before specifying mechanical systems. A well-insulated home needs a smaller, cheaper heat pump and costs less to heat.

Can existing homes be redesigned for heat pumps?

Yes. Key considerations include finding cylinder space, identifying outdoor unit locations, upgrading insulation, and potentially upsizing some radiators.

Do architects recommend underfloor heating with heat pumps?

Most prefer it for new builds because it operates at 30-35°C, maximising efficiency. For retrofits, upgraded radiators are usually more practical. Our ASHP guide covers both options.

Where should the outdoor unit be positioned?

Where it has clear airflow, is away from bedroom windows, is accessible for maintenance, sits on a solid base with anti-vibration mounts, and has condensate drainage.