Thermal images reveal how heat loss spots in YOUR home could be adding £750 a year to energy bills
A DRAUGHTY home means you are burning energy and wasting money.
Ignoring these problems could be adding around £750 a year to your energy bill.
This week, Rosie Taylor borrowed a thermal imaging camera from Octopus Energy to uncover the hidden heat loss hotspots in her home.
When the camera is used inside it shows heat loss as blue patches, helping to pinpoint where it’s disappearing outside.
Outside your home the heat loss shows as yellow and orange and it indicates where warm air is escaping from inside.
Octopus Energy offers free loans of a thermal imaging camera to customers struggling to pay their bills.
Read more on energy bills
Local councils and charities in some areas, such as St Albans, Oxford and Walmer in Kent, also offer loans of the cameras to anyone interested in reducing heat loss from their home.
Or if no scheme is available in your area, you can rent one privately from around £70 per day.
Here Rosie reveals what the camera found – and asks Phil Steele, future technologies specialist at Octopus Energy, for tips about what you can do if your home has similar problems.
Window pains
WHEN I use the thermal imaging camera outside, it doesn’t pick up any real difference between the heat being emitted from the wall and my double-glazed window, showing they are doing an equally good job of keeping heat inside.
But when I turn it to look at a single glazed window, the screen shows a huge square of yellow where is coming through the panes much faster than through the wall.
“Single glazed windows have just one sheet of glass which heat can travel through easily,” explains Phil Steele.
“But double-glazed windows have a gap between the two panes. Inside this gap is a vacuum or an inert gas which heat really struggles to get through – it’s this gap which is key to stopping heat transfer.”
Installing PVC double glazing in the average semi-detached home would have saved you £95 per year (or £115 if you install A++ rated windows) based on 2021 prices - and is likely to save considerably more now, according to the Energy Saving Trust. But typically costs around £4,250 to put in.
So what can you do if you have single glazing but can’t replace your windows?
Phil recommends trying secondary glazing to get an extra layer of protection and create that air gap which is so important at preventing heat loss.
“It’s also worth checking around the edges and replacing any putty or sealant that is broken or old,” he adds. “The key is to seal up anywhere air is leaking.”
You can buy DIY kits which involve covering windows using a cellophane type film or get plastic windows professionally fitted.
Secondary glazing film produced by firms like Stormguard, Tesa Moll and Wickes costs around £1 to £6 per square metre, meaning it costs roughly £4 to £24 per window on average.
Getting professionally-fitted secondary glazing costs around £1,250 to £1,800 for four windows - and could bring nearly the same annual saving as fitting double glazing.
Clever curtains
ANOTHER easy fix for cold windows or doors is to draw a curtain over them. I am astonished by the difference it makes when I use the camera to look at my window with and without a curtain drawn.
Research has shown drawing curtains at dusk could reduce heat loss by around 15 per cent.
“Just like with clothing, adding extra layers helps keep out the cold,” explains Phil. “If you have thin curtains, you can also use safety pins to attach blackout liners to the back for extra protection.”
He recommends shortening curtains or tucking them in so they don’t hang over radiators – as this just sends the heat behind the curtain out through the window.
Draughty doors
A DARK blue patch on the camera’s footage reveals a gap at the bottom of my front door is letting out lots of heat. But putting a draught excluder in front of it visibly reduces the heat loss.
Phil recommends using the back of your hand to test your letterbox, keyhole and around the edges of your external doors on a cold day. If you feel a breeze coming in, then heat will also be going out.
“You can buy letterbox brushes and keyhole covers which help reduce heat loss from these points,” he says. “It’s also definitely worth buying draft excluder tape and sticking that around your door if you are getting a breeze around the edges.”
Stopping draughts around windows, doors and through gaps in floorboards could save you £95 per year off your heating bills based on the new April 1 price cap, the Energy Saving Trust says.
While most modern doors are insulated, older doors may be formed of just one layer of wood which heat easily passes through. If you don’t want to replace the door, hanging a curtain over the inside may help. Phil says it’s even possible to nail decorative pieces of carpet to the inside to add extra warmth.
Leaky lofts
MY loft hatch shows up as a major source of heat loss when I use the camera to look upstairs.
Phil explains that as lofts typically aren’t heated and can be colder and damper than the rest of the house, any weaknesses in the hatch will let cold air in from the roof space. Warm air also rises up and will disappear out of your home into the roof if there are any gaps around the loft hatch.
“Heat will escape through even slight gaps around the edges,” he says. He recommends using draught excluder foam strips - costing from around £5 per 5m roll - to seal the edges. You can also insulate the hatch itself by glueing on a sheet of insulation foam, which costs around £9 for a 1.2m-long sheet.
Dodgy insulation
MY roof space is boarded out so I can’t see how well insulated it is but the thermal imaging camera reveals areas of heat loss along the edges of the roof and walls, suggesting that insulation hasn’t been properly fitted right up to the edges. That helps explain why it always feels so cold up there.
Having insulation in your loft isn’t enough in itself – you need to make sure it’s good quality and covers the whole area.
Phil says classic problems include insulation being squashed down too much, not being put back properly after building works or gaps being left for old equipment – like water tanks – which are no longer used.
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“Insulation should be at least 10 to 20cm thick all over,” he adds. “If it isn’t, replace old worn or tatty insulation or ask your landlord to – they have a responsibility to ensure the property meets minimum energy efficiency requirements.”
The Energy Saving Trust predicts the average semi-detached home could now save up to £255 per year on heating bills by installing loft insulation which is at least 270mm thick. And even upgrading your existing insulation from a thickness of 120mm to 270mm will save you £25. Insulation typically costs around £465 to install.
You might be able to get insulation installed for free via your energy supplier through the Government’s Affordable Warmth Obligation Scheme. You need to be receiving certain benefits and own your home, have permission from your private landlord or live in a council property with an energy rating of E or below.
You can check if you’re eligible via the to apply.
Cold walls and damp spots
THE thermal imaging camera picks up a lot of heat escaping through the wall of my bay window, which is made of a wall just one layer of brick thick.
Like single-glazed windows, single layer walls like these easily transfer heat straight outside. Modern buildings are usually built with two layers of brick or concrete blocks, known as cavity walls, which can be insulated. But older buildings may have single layer construction in parts.
A thermal imaging camera can also help identify any damp areas caused by cracks in your brickwork or gaps in your cavity wall insulation.
Even without a camera, you can spot theses patches if you see areas of mould or peeling paint, or feel the walls for areas of cold or damp.
“Anywhere damp is getting in, heat is getting out,” explains Phil. “These areas as thermal bridges, sucking heat away from the house and taking it outside.”
Once you have identified where damp spots are, it’s best to try to get them fixed by filling any cracks, replacing damaged bricks or filling in missing insulation – you may need to get an expert to do this.
Affordable Warmth
Extractor fans and vents
MY bathroom extractor fan showed up as a major source of heat loss – perhaps unsurprisingly because it is essentially a tunnel through the wall to outside.
If you no longer use an extractor fan or chimney, blocking these up could have saved you £20 per year on your heating bill based on last year’s prices and is likely to save you more now, according to the Energy Saving Trust.
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Air bricks and other types of vents can also let heat escape, but you should leave those well alone.
“Vents are important to let air flow around the property – they are there to help prevent damp and to ensure adequate airflow as a safety precaution if you have a gas boiler,” explains Phil. “It’s important not to block these - but you can replace them with modern ones which are designed to let less air in.”
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