Learn Stop Heat Coming Through Windows in the summer.
During hot weather many homeowners struggle to stop heat coming through windows, especially in properties with older sash windows.
If your rooms feel like a greenhouse during hot weather, your windows are likely allowing solar heat gain to enter the property.
In this guide, our specialists at Golden Ratio Sash Windows & Doors explain why heat comes through windows and the most effective ways to reduce it, particularly for period homes with sash windows.
In some cases older windows may need complete sash window replacement to achieve modern energy efficiency standards.
Why Does Heat Come Through Windows in Summer?
Windows allow heat to enter a home through three main processes.
Solar Radiation
Sunlight passes through glass and is converted into heat inside the room. This is known as solar heat gain and is one of the biggest causes of overheating in homes.
Heat Transfer Through Glass
Single glazed windows allow heat to pass through much more easily than insulated glazing systems.
Air Leaks Around Frames
Gaps around timber windows can allow warm outdoor air to enter the property.
Many Victorian and Edwardian homes in London still have traditional sash windows, which means overheating problems are often caused by a combination of single glazing and draughts.
How to Stop Heat Coming Through Windows
There are several proven solutions that can help keep your home cooler during warm weather.
1. Upgrade to Double Glazed Sash Windows
One of the most effective ways to stop heat coming through windows is upgrading to modern double glazed sash windows.
Double glazing uses two panes of glass with an insulating gap between them. This significantly reduces heat transfer compared with single glazing.
Benefits include:
- improved thermal insulation
- reduced solar heat gain
- improved comfort year-round
- lower energy bills
Modern double glazed sash windows can still maintain the traditional appearance of period properties, making them suitable for many heritage homes.
2. Install Solar Control or Low-E Glass
Modern glazing technology can help control indoor temperatures.
Solar control glass contains a microscopic coating that reflects infrared heat while still allowing natural light to enter the room.
This type of glass can:
- reduce overheating in sunny rooms
- block UV rays that damage furniture
- improve comfort during heatwaves
When combined with double glazing, solar control glass provides one of the best solutions for reducing heat through windows.
3. Use Natural Ventilation with Sash Windows
Traditional sash windows actually have a unique advantage when it comes to cooling homes.
Opening both sashes slightly creates natural airflow:
- cool air enters through the lower sash
- warm air escapes through the upper sash
Because warm air rises, opening the top section allows heat to escape from the room. This natural ventilation method has been used in sash window design for centuries.
4. Draught Proof Your Sash Windows
Small gaps around windows can allow warm air to enter the property.
Professional draught proofing systems seal these gaps while still allowing the window to operate normally.
Benefits include:
- preventing warm air entering the home
- improved insulation
- smoother sash operation
- reduced noise and dust
For many homeowners, draught proofing is one of the most cost-effective improvements for traditional sash windows.
5. Apply Solar Control Window Film
Window films are a simple solution that can help stop heat coming through windows by reflecting solar radiation.
These films work by reflecting infrared radiation and blocking UV rays before they enter the room.
High quality films can significantly reduce solar heat gain and are particularly useful for:
- south facing windows
- conservatories
- rooms that receive strong sunlight
6. Install Blinds, Curtains or Shutters
Window coverings can help block sunlight before it heats the room.
Popular options include:
- thermal curtains
- blackout blinds
- cellular shades
- plantation shutters
Closing blinds during the hottest part of the day can reduce the amount of solar heat entering your home. The Energy Saving Trust, recommends blocking direct sunlight and prioritising windows that receive the most sun exposure.
7. Install Secondary Glazing
If you want to keep your original sash windows, secondary glazing is another effective solution.
This involves installing a second pane of glass on the inside of the existing window.
Benefits include:
- improved insulation
- reduced heat gain
- improved noise reduction
- preservation of original windows
Secondary glazing is often used in listed buildings and conservation areas where replacing windows may not be permitted.
8. Shade the Outside of Your Windows
Stopping sunlight before it hits the glass is one of the most effective ways to reduce overheating.
External shading options include:
- awnings
- external shutters
- outdoor blinds
- shade screens
External shading prevents the glass from heating up in the first place.
Best Solutions for Sash Windows in Period Homes
Many homes across London still have Victorian, Georgian or Edwardian sash windows.
When improving these windows it is important to balance:
- energy efficiency
- heritage appearance
- ventilation
- planning restrictions
In many cases, the best results come from combining several improvements such as draught proofing, upgraded glazing and solar control glass.
Comparison of Window Cooling Solutions
| Solution | Cost | Effectiveness |
|---|---|---|
| Window film | Low | Moderate |
| Thermal curtains | Low | Moderate |
| Draught proofing | Medium | High |
| Secondary glazing | Medium | Very High |
| Double glazing | Higher | Best long-term solution |
Expert Advice from Golden Ratio Sash Windows & Doors
At Golden Ratio Sash Windows & Doors, we regularly restore and upgrade traditional timber sash windows across London.
Many overheating problems we see are caused by single glazing combined with poor draught proofing. Upgrading or restoring sash windows can dramatically improve comfort while preserving the original character of the property.
Frequently Asked Questions
Why do windows make rooms hotter?
Sunlight passes through glass and becomes trapped as heat inside the room, creating solar heat gain.
Are double glazed windows better for summer?
Yes. Double glazing reduces heat transfer and helps maintain more stable indoor temperatures.
Do blinds stop heat coming through windows?
Yes. Closing blinds or curtains during strong sunlight can significantly reduce solar heat entering the room.
Are sash windows good for ventilation?
Yes. Opening the top and bottom sash allows warm air to escape while cooler air enters the room.
Need Help Improving Your Sash Windows?
If you’re trying to stop heat coming through windows, upgrading or restoring your sash windows can dramatically improve comfort during summer.
Golden Ratio Sash Windows & Doors specialises in:
- sash window repairs
- draught proofing sash windows
- double glazed sash windows
- secondary glazing solutions
Contact our team to discuss the best way to improve the comfort and energy efficiency of your home.
