Can you have a heat pump in a semi-detached house?

Semi-detached homes tend to have more outdoor space than a terrace and less exposed wall than a detached house. Here is what matters, what the rules actually say, and what to look for in a survey.

Why semi-detached houses are often workable

A heat pump is sized to replace the heat your home loses on a cold day, so anything that cuts that loss helps. A semi has one advantage over a detached house of the same size: one side is attached to a neighbour’s home.

That shared wall typically loses less heat than an exposed wall, because the other side is usually a heated home rather than the outdoors. It is a tendency rather than a fixed rule. In research for the government on 54 English homes with uninsulated cavity party walls, most walls performed at least as well as insulated cavity walls, but a small proportion lost more. The same report says nearly all party walls built before 1945 are solid, so that particular problem is less likely in a 1930s semi.

The Energy Saving Trust’s installer toolkit says to record party wall construction along with the internal and external walls. Our guide to what size heat pump you need explains how heat loss turns into a kilowatt rating.

Where does the outdoor unit go on a semi?

There are three usual places:

The unit moves a lot of air, and manufacturers set out how much space it needs for airflow and servicing. Clearances differ between models, so go by the installation manual for the unit being quoted. MIS 3005-D, the MCS heat pump design standard, says equipment specified should be able to be installed in accordance with its manufacturer’s instructions. In a tight side passage, the walls around the unit can also affect the noise result.

Do you need planning permission on a semi?

Usually not, if every permitted development condition is met. These are the main ones in England, under Class G of Part 14 of the General Permitted Development Order 2015, as changed by S.I. 2025/560 from 29 May 2025:

• One unit. A house that is not detached can have one air source heat pump. The two-unit allowance is for detached houses only, and the Order defines those as not sharing a party wall.
• Size. The outdoor unit, including any housing, must be no more than 1.5 cubic metres.
• Noise. The heat pump must comply with the MCS Planning Standards, which means MCS 020(a).
• Roofs. It cannot go on a pitched roof, and on a flat roof it must be at least 1 metre from the edge.
• Listed buildings. Class G does not apply to a listed building or land within its curtilage (the grounds around it).
• Conservation areas and World Heritage Sites. It cannot go on a wall or roof fronting a highway, or nearer to a highway bounding the plot than the nearest part of the house.
• Road-facing walls elsewhere. It cannot go above ground-floor level on a wall fronting a highway.
• Siting. So far as practicable, it must be placed to minimise its effect on the look of the building and the amenity of the area.

The road-facing limits matter if your semi is on a corner, because your side wall may also front a road.

Wales has its own rules. They sit in Part 40 of the 1995 Order, and the Welsh Government says they were updated on 1 June 2026 by W.S.I. 2026/79. The old rule keeping a heat pump three metres from the boundary has gone. A home that is not detached can have one unit of up to 1.5 cubic metres, and the unit must comply with MCS 020(a). The roof, listed building, conservation area and road-facing wall limits are similar to England’s. Our guide to heat pump planning permission covers both nations in full, including what to do if you need to apply.

Noise, the party wall and your neighbour’s windows

This check is likely to shape the design, because a neighbour is close. MCS 020(a) is a calculation that confirms whether the permitted development limit would be met:

• Where it is measured. A point 1 metre outside the centre of any door or window to a habitable room of a neighbouring property. Bathrooms, hallways and utility rooms are excluded, and so are rooms used solely for cooking.
• The limit. The calculated level must be 37.0 dB(A) or lower at every assessment position. If it is higher, the unit does not comply with permitted development.
• Which windows count. Neighbouring properties on all sides, at ground floor, first floor and so on. The closest position is not always the worst, as a further window with a clearer line of sight can come out higher.
• Reflections. The ground and nearby walls within 1 metre of the unit bounce sound and raise the level. A position with more than three reflective surfaces will not meet the standard. A tight side passage can add up quickly: the ground, your wall and a long wall or fence opposite.
• Barriers. A solid wall or fence with no gaps can reduce the result, depending on its construction and the line of sight. Open fences, vegetation and walls in poor repair do not count.

Keep this in proportion. The party wall itself is not what is being tested: the assessment is at doors and windows, outside. A pass is not a promise that a unit will never be heard, only that the calculated level meets the permitted development limit. If no position passes, you would need to look at another position or a different unit, or apply for planning permission.

The standard says the installer must keep one copy of the completed calculation and give you another. It is good manners to tell your attached neighbour your plans. Our guide to heat pump noise and neighbours goes through this in detail, and are heat pumps noisy? covers the basics.

Separately, the Party Wall etc Act 1996 can apply to a shared wall, which can include a garden wall but not a wooden fence. GOV.UK says you must tell your neighbour about work on an existing party wall, such as cutting into it, but not about minor changes such as drilling to put up shelves or cabinets. The government’s booklet says the key point is whether the work could affect the wall’s strength and support, or damage your neighbour’s side. Neither mentions heat pumps, so if fixings or pipes would involve a shared wall, ask your installer and check the party wall guidance first.

Typical things to check in a 1930s semi

Many semis date from between the wars and raise the same questions. None of these rules out a heat pump, but each should be dealt with in the design.

Cavity walls

Government guidance says a home built after 1920 probably has cavity walls: two layers of masonry with a gap between. That gap may or may not have been filled. Some older cavities are narrow, and a government-commissioned study treats those under 50 mm as non-standard because they hold less insulation and need more care about moisture, especially in exposed locations. If you do not know what you have, the surveyor should assess it.

Bay windows

The front bay is a feature of many semis of this period. It adds window area and outside wall to a room, sometimes with a thinner build around the glass than the main walls. A bay room can therefore need more heat than its floor size suggests, and it may be the room that sets the design water temperature for the whole system.

Loft and insulation

The surveyor will note how thick your loft insulation is and the type of roof, and the room-by-room heat loss reflects what they find. A converted loft or later extension may be built differently from the rest of the house, so mention it.

Radiators

Heat pumps are most efficient at lower water temperatures, so some radiators may need to be larger to give out the same heat. A room-by-room design shows which ones. See do I need new radiators for a heat pump?

Hot water space

Your current arrangement matters, particularly if an airing cupboard was cleared for a combi boiler. Ask your installer to spell out how hot water will be provided and what space that needs. Our guide to heat pumps and hot water covers the options.

The pipe run

Pipework has to get from the outdoor unit into the house and join your heating system. In a semi, the boiler may be on the far side of the house from the outdoor unit, so ask how the pipes will be routed and what you will see of them.

The grant and what affects the cost

You may be eligible for the Boiler Upgrade Scheme, which offers £7,500 towards an air source heat pump in England and Wales. Being a semi makes no difference. Generally you must own the property and be replacing fossil fuel heating, such as gas, oil, LPG or electric. Most new builds, social housing and hybrid systems are not covered. Your installer applies for you, and the grant comes off the amount you pay. There is more on our grants and rebates page.

The cost depends on the property: the size of system it needs, whether radiators or pipework need upgrading, where the outdoor unit goes and how far the pipe run is, hot water and any electrical work. See heat pump costs in Manchester, or get in touch for a survey and an itemised quote.

What a survey checks on a semi

A good survey covers the whole house, including:

• Wall construction on every side, including the party wall, plus windows, floors, loft insulation, bays and extensions.
• Every radiator, and whether there is space for a larger one.
• Possible outdoor unit positions, with clearances from the manufacturer’s manual.
• Neighbours’ doors and windows on all sides, and a noise calculation for each one that could be affected.
• The pipe route, your hot water arrangement and your electrical supply.

For the full picture, read what happens in a heat pump survey. If your home is joined on both sides, see can a terraced house have a heat pump?

What to ask, and where ByEco stands

Whoever you speak to, ask:

• Where would the unit go, and which neighbouring windows did you assess?
• Can I have a copy of the MCS 020(a) calculation?
• Did you treat the party wall as its own wall type in the heat loss calculation?
• Which radiators would change, and at what design flow temperature?
• How will my hot water be provided, and how will the pipes be routed?

We are MCS certified for air source heat pump installation (certificate IAA10330), and we apply for the £7,500 Boiler Upgrade Scheme grant on your behalf. Get in touch for a free survey: we will look at your semi room by room, explain what it needs and give you an itemised quote. If you are happy with it, we go ahead. Find out more about our air source heat pump service or book a free survey.

Sources

Every figure on this page was checked against primary sources on 30 October 2026. Grant rules, planning rules and prices change — if you are reading this much later, verify before acting.

• legislation.gov.uk — General Permitted Development (England) Order 2015, Schedule 2 Part 14 (revised text)
• legislation.gov.uk — S.I. 2025/560, General Permitted Development (England) (Amendment) Order 2025
• legislation.gov.uk — W.S.I. 2026/79, General Permitted Development (Amendment) (Wales) Order 2026
• legislation.gov.uk — W.S.I. 2012/1346, the 2012 Welsh order with the former three metre rule
• Welsh Government — Planning permission: domestic heat pumps
• MCS — MCS 020(a) Air source heat pump sound calculation, Issue 1.1
• MCS — MIS 3005-D:2025 Heat Pump Design Standard, Issue 2.0 (5 December 2025)
• Energy Saving Trust — Heat pump installer toolkit: heat loss calculations, detailed guidance
• Leeds Beckett University and Bridgewater Surveyors for BEIS — Cavity Party Walls: Measuring U-values (2018)
• DECC — Keeping the heat in: a simple guide to wall insulation
• BEIS — Quantification of non-standard cavity walls and lofts in Great Britain
• Welsh Government — Explanatory Memorandum to W.S.I. 2026/79
• GOV.UK — Party walls and building work
• GOV.UK — Party walls and building work: work you must tell your neighbour about
• GOV.UK — The Party Wall etc Act 1996: explanatory booklet
• GOV.UK — Apply for the Boiler Upgrade Scheme
• GOV.UK — Apply for the Boiler Upgrade Scheme: what you can get
• GOV.UK — Apply for the Boiler Upgrade Scheme: check if you’re eligible
• GOV.UK — Apply for the Boiler Upgrade Scheme: how to apply