New-build UK homes can still overheat, especially flats and glazed rear extensions on speculative houses. The best time to install air conditioning is at first fix, with outdoor siting in the drawings. Part O wants gains reduced first. Cooling remains a legitimate comfort and, sometimes, a compliance tool.
New does not mean cool
Tight fabric, big glass, and limited opening windows produce houses that are cheap to heat and uncomfortable in a heatwave. Buyers notice in year one. Specifying a surveyed split or a ducted system in the construction programme is cheaper than chasing plasterboard later.
Part L covers energy. Part O covers overheating in new dwellings. Neither bans cooling. Both want a design, not a portable unit in the hallway. Show homes with bi-folds and dark kitchens are the rooms that fail first. Size those, not the smallest bedroom. The overheating assessment guide and the building regulations guide sit next to this page.
- First-fix pipe routes beat a retrofit after plaster.
- Ask the developer where a condenser can legally sit before exchange.
- Glazed kitchen-diners fail before box bedrooms.
First fix versus retrofit
First fix: pipe routes, condensate, cables, outdoor pad or brackets, and penetrations sleeved properly. Retrofit: face-fixed trunking, more making good, and arguments with the developer's warranty. If you are still at slab or timber kit, put cooling on the drawing.
Multi-split or ducted can serve several rooms from one outdoor if the plot can take it. Estates with tiny rear gardens still need a neighbour-aware condenser position. Warranties: some new-build warranties fuss about penetrations. Get the developer's process in writing before you drill.
Heating as well as cooling
New builds with heat pumps or small radiators sometimes use air-to-air as the upstairs comfort layer. That can work. Hot water is still a separate system. Can air conditioning replace a boiler is the wrong question if you never had a boiler. Ask whether air-to-air is in the heating design.
Do not double-count: if the house already has a designed heat-pump heating system, extra splits are a comfort overlay. Size them for summer first unless the heating engineer says otherwise. Running costs in a tight new build can be modest if you do not overcool.
Buyers and snagging
If you are buying off-plan, ask where a condenser could go before exchange. A plot without a legal outdoor position is a future planning fight.
If you already live there and it overheats, you are in retrofit territory. Still survey. Do not accept the site manager's just open the windows if the flat is on a trunk road. Use the quote form with plot number, drawings if you have them, and photos of the rear elevation.
Frequently asked questions
Do new-build homes come with air conditioning?
Rarely as standard in the UK, except some high-end or build-to-rent blocks. Most houses still expect you to retrofit. Ask at reservation if it matters to you.
Will installing AC void my new-build warranty?
It can if you puncture the fabric without approval. Use the developer's process, competent installers, and recorded penetrations. Do not DIY a through-wall hole in week two.
Is a new build a 2.5 kW job?
Bedrooms might be. The glazed kitchen-diner often is not. Survey the hot rooms.
Core buying guides
Start with these high-intent guides, then dig into the rest of the library.
Related guides
Sources and further reading
How this guide was prepared
This guide was written by the Local AC Installers Editorial Team. We compare official guidance, legislation and established consumer information, separate general information from project-specific advice, and show publication dates and sources. We do not accept installer accreditation claims at face value.