Why is one room in my new build always cold?

In our inspections across Cambridgeshire developments, a cold room almost always traces back to one of a small set of causes. None of them are exotic, and all of them are the builder's to fix if they stem from how the house was constructed.

• Missing or displaced insulation — a section of loft or cavity insulation that was never fitted, has slumped, or was disturbed by later trades and never reinstated.
• Thermal bridging — a continuous path for heat through the structure, typically at lintels, junctions between walls and floors, or around window reveals.
• Draught paths — gaps around window and door frames, behind skirtings, at loft hatches, or where services pass through the external envelope.
• Heating imbalance — the radiator or underfloor loop serving that room is undersized, air-locked, or the system was never balanced after commissioning.
• Ventilation left open — a trickle vent, extract fan or purge vent stuck open, or ducting that was never connected properly.

A few simple checks before you call anyone. Feel the walls and ceiling of the cold room on a cold day: a single cold patch or cold line suggests a local insulation gap or bridge; a uniformly cold surface suggests missing insulation across the whole element. Check whether the radiator actually gets hot top to bottom — if it does, the problem is the fabric of the room, not the heating. On a windy day, dampen the back of your hand and move it slowly around window reveals, sockets on external walls and skirting lines to feel for moving air.

Note the pattern too. A room that is cold only in wind points to draughts. A room that is cold in still weather points to insulation or bridging. A room that never warms even with the radiator hot points to heat loss faster than heat input.

New homes are signed off against energy calculations that assume the insulation and airtightness were installed as designed. If a room cannot hold heat, the building as built may not match the building as certified — which is a defect, not a quirk. The developer's warranty covers exactly this kind of failure in the first two years, and the insulation itself for longer.

The mistake buyers make is normalising it: putting up with the cold room, buying an electric heater, closing the door. That converts a documented construction defect into your ongoing heating bill.

A thermal imaging survey is the decisive tool here. A FLIR camera shows surface temperature across walls, ceilings and floors, so missing insulation appears as a cold footprint, bridging as cold lines at junctions, and draught paths as cold streaks — all without opening anything up. Combined with a visual inspection of the loft, frames and heating system, it turns 'the bedroom is always cold' into a specific, photographed, located defect the developer can be sent to fix.

The report sets out the evidence image by image, referenced to the relevant standard, so the conversation with the site team starts from proof rather than suspicion.