Stop Unwanted Draughts
Worn seals and gaps around opening windows can allow cold air in and warm air out. Suitable draught-proofing can help where the existing window is otherwise in good condition.
Energy Efficiency Guide
How to Stop Heat Escaping Through Windows
Heat can be lost through the glass, frame and unwanted gaps around a window, making rooms feel colder and increasing the amount of heating needed to keep your home comfortable.
The best solution depends on whether the problem is caused by draughts, ageing glazing, a failed sealed unit or an inefficient older window.
Quick Answer
How Can I Reduce Heat Loss Through My Windows?
Improve the Glazing
Double or triple glazing provides better insulation than single glazing by using multiple panes separated by sealed cavities.
Check the Condition
Failed sealed units, damaged frames or windows that no longer close correctly may need repair or replacement rather than another temporary fix.
Understanding Heat Loss
How Does Heat Escape Through a Window?
Through the Glass and Frame
Heat naturally moves from the warmer inside of your home towards the colder outside. The thermal performance of the glazing and frame affects how quickly this happens.
Through Unwanted Gaps
Draughts around opening sections, worn seals or gaps around the installation can allow warm indoor air to escape while colder air enters.
Low-Cost Improvements
Start by Checking for Draughts
On a cold or windy day, check around opening sections of the window for noticeable moving air, rattling or whistling.
Suitable draught-proofing strips can be fitted around opening windows where there are unwanted gaps. Fixed gaps around non-opening sections may require an appropriate sealant or professional attention depending on their cause.
Do not block trickle vents or purpose-made ventilation openings. These provide controlled ventilation and are different from unwanted draughts.
Simple Improvements
Can Curtains Help Reduce Window Heat Loss?
Thermally Lined Curtains
Thick or thermally lined curtains can add another barrier at the window. Close them during colder evenings and open them when useful sunlight is available during the day.
Secondary Glazing
Where full window replacement is not suitable, secondary glazing can provide another layer on the room side of an existing window and help reduce heat loss.
Glazing Performance
How Does Energy-Efficient Glazing Keep More Heat Inside?
Multiple Glass Panes
Double and triple glazing use two or three panes rather than a single sheet of glass, helping reduce heat transfer through the window.
Insulating Cavities
Sealed spaces between the panes contain air or an insulating gas such as argon, helping improve the performance of the glazing unit.
Low-E Glass
Low-emissivity glass has a thin coating designed to reflect heat back towards the room while still allowing daylight through.
Check Your Existing Glazing
What if the Double Glazing Has Failed?
Condensation or misting trapped between the panes can indicate failure of the sealed glass unit.
This does not automatically mean the entire window needs replacing. If the frame is still in good condition, the failed sealed glass unit can often be replaced separately.
Read our guide to how to tell if double glazing has blown or find out more about replacing broken down sealed units .
Repair or Replace?
When Are Replacement Windows Worth Considering?
Existing Windows Are Still Sound
If the frame, glazing and hardware remain serviceable, draught-proofing, repair or another efficiency improvement may be more appropriate than replacing the entire window.
Existing Windows Are Inefficient or Deteriorated
Replacement may be worth considering where older windows have inefficient glazing, damaged frames, recurring draughts or several problems that cannot be addressed economically through individual repairs.
Whole-Home Heat Loss
Are Windows the Only Place a Home Loses Heat?
No. Heat can also be lost through the roof, walls, floors, doors and uncontrolled air leakage elsewhere around the property.
If your whole home feels difficult to keep warm rather than the problem being concentrated around the windows, read our guide to keeping warm in a cold house .
Common Questions
Window Heat Loss FAQs
Do windows cause heat loss?
Yes. Heat can pass through the glazing and frame, while unwanted gaps around a window can also allow warm air to escape and cold air to enter.
Can I stop heat escaping without replacing my windows?
Sometimes. Draught-proofing, thermally lined curtains, secondary glazing or repairing faults may help depending on the condition and construction of the existing windows.
Does double glazing reduce heat loss?
Yes. Double glazing uses two panes separated by a sealed cavity, providing better insulation than single glazing.
Is triple glazing always necessary?
No. Triple glazing can provide greater insulation than double glazing, but whether it is worthwhile depends on the property, existing windows, budget and desired performance.
Do misted windows need completely replacing?
Not necessarily. If only the sealed glazing unit has failed and the surrounding frame remains sound, the glass unit can often be replaced independently.
Are Your Windows Letting Too Much Heat Escape?
If your windows are draughty, ageing or no longer performing as they should, St Helens Windows can help you explore suitable replacement options for your home.