Winter is well and truly upon us and Britons across the country are cranking up their central heating. But just how much of this heat is actually keeping us warm, and how much is escaping from our poorly insulated homes?

This gallery of images shows heat escaping from homes of every shape and size across the UK during the cold snap that’s enveloped us this week.

The images were captured by users of the rugged Cat S61 rugged smartphone using its built-in thermal imaging camera.

They clearly show how poorly insulated many of our homes actually are with heat leaking through gaps in windows, doors, roofs and walls.

Homes captured using the thermal camera on the Cat S61 include:

• Georgian, Edwardian and Victorian terraced houses in London
• Modern 21^st blocks of flats in Reading, Berks
• Victorian flats in London
• 18^th century houses in the Cotswolds
• A converted silk mill in Wiltshire
• A 60s tower-block in East London

Generally, the newer houses hold their heat more efficiently – thanks to modern insulation and double-glazing – however, one image taken in Shoreditch, east London, shows how much heat is lost through the large feature windows of a modern flat.

Another image, taken in the north of the capital shows the stark contrast between a Victorian block of flats and a recently completed modern block built right next to it.

The thermal image shows heat being lost through the windows and walls on the old building, whilst the external walls of the modern block are cold showing the heat being kept inside.

Another image taken in Malmesbury, Wiltshire shows a converted silk mill. The new flats within the building do not appear to be well insulated. The top left windows are dark and cold indicating the heating is off and the tenants are unlikely to be home. Whereas the rest of the building is very yellow – suggesting a lot of heat is being lost through both the windows and the brick walls.

Paul Holmes, Technical Product Manager at Bullitt Group, makers of the Cat S61, said:

“When looking at a building using thermal imaging, it’s the contrasting colours that are important to focus on. Yellow and white/yellow spots show heat, and dark plum colours show cold spots. Both of these can be a bad sign because it usually means that either heat is escaping or cold is coming in.

“The lighter or brighter a patch is, the hotter it is, and the bigger the colour difference the bigger the difference in temperature.

“Equally, from the outside of the house it’s important to take note of particularly warm spots as this could be a sign of heat escaping. In general, the goal is for the exterior of your house to be cold – including windows, external walls and the roof – as this means that the heat is staying inside rather than leaking out.”

In a typical British home, around one-third of the heat produced by its heating system is rapidly lost through the roof, ceiling and walls, according to the National Energy Foundation. But simple insulation measures will greatly reduce heat loss.

Anthony Crossman from A-J-C Plumbing said:

“A properly insulated home will keep you warmer for longer and help to save money on the heating bills. The key is to work out where you’re losing heat and a tool like the Cat S61 is obviously very good at doing that.

“It’s worth checking doors, window frames, ceilings and walls inside and outside your property to see if you are losing heat. Loft insulation can also be an issue so it’s worth seeing what heat you’re losing through the roof if you have easy access.”

“The most important tip I have is to have your boiler serviced every year. If you want your heating to work efficiently throughout the winter, you must look after the boiler. A lot of winter break downs can be avoided by correctly servicing the boiler.”

A spokesman for Cat phones said:

“Even the best insulated homes will leak heat particularly at this time of the year when many of us have our central heating on day and night.

“Working out where in your home you have a problem is not always easy and can be a costly exercise if you have to call in the experts.

“Lots of our customers are turning to the Cat S61 to spot where they’re losing heat and then fixing the issue themselves.”

In a typical building, problem areas highlighted by thermal imaging might include:

• Gaps around doors and windows (especially in older properties)
• Ceilings, external walls and internal walls (often behind radiators or around damp and cold spots)
• Chimneys and roofs
• Poorly insulated pipes or under-performing radiators
• Old extractor fans or gaps in lighting fixtures/pipework
• Gaps in floors (especially wooden floorboards).

WAYS TO IMPROVE ENERGY EFFICIENCY:

• Increasing insulation (e.g. loft insulation, cavity wall insulation and solid wall insulation)
• Internal and external draught-proofing (e.g. fitting door seals, letterbox brushes and filling gaps in wooden flooring)
• Servicing or upgrading radiators (thermal imaging technology can help you compare thermal performance before and after)
• Treating windows and window frames to stop heat escaping (or fitting double/triple glazing for the best results)
• Insulating pipework and fitting radiator reflectors
• Filling cracks and gaps in flooring and around fittings/fixtures

On average, a poorly insulated UK house will cost the homeowner between £168-£250 a year due to heat loss through lofts, roofs, and walls.

According to Which?, without loft insulation of 0-270mm the average sized detached, semi-detached, mid-terrace, and bungalow homes are losing between £120 and £225 a year and adding to unnecessary CO₂ wastage:

According to Britain’s Energy Saving Trust, 45% of heat loss from an uninsulated home is through solid walls, 33% through other walls, 25% through the loft or roof space, and 20% through windows and doors. This means that insulating your walls and roofs is an easy way to reduce heat loss.

In an uninsulated home, a quarter of heat is lost through the roof and a third of escapes through the walls.

Houses built after the 1920s are likely to have cavity walls: made up of two walls with a gap in between, known as the cavity; the outer leaf is usually made of brick, and the inner layer of brick or concrete block. This will reduce the heat loss through the walls.

Houses built pre-1920 are more likely to have solid walls. A solid wall has no cavity; each wall is a single solid wall, usually made of brick or stone. This type of building is more likely to lose heat through the walls and will cost homeowners more in heat loss.