While modern air conditioning is still rare in UK homes, many period properties have an overlooked feature that helps beat the heat. Sash windows in these historic houses provide natural ventilation, but only when opened in the right way.
- Sash windows create natural airflow via displacement ventilation.
- Open top and bottom sashes equally by 10-15 cm for best cooling.
- Open windows early and late in the day to avoid heat gain.
What happened
Two recent record-breaking heatwaves in the UK pushed temperatures to unprecedented levels, sparking fresh conversations about how homes in the country cope with extreme heat. The Met Office's measurement of 37.3 °C in Suffolk during late June highlighted a challenge for the UK’s predominantly older housing stock.
Despite the allure of period features in Georgian, Victorian, and Edwardian homes, these properties often struggle to maintain comfort during hot spells. However, a common characteristic—their sash windows—offers a natural way to ventilate and cool these homes effectively when used correctly.
Why it feels good
Sash windows comprise two vertical sliding panels that create a flow of air when both top and bottom sashes are opened simultaneously. This setup facilitates 'displacement ventilation,' where warm air exits through the upper sash while cooler air enters from below, naturally cooling the indoor environment.
Scientific research from the University of Cambridge confirms that this ventilation method significantly enhances indoor air quality and reduces heat build-up. The effectiveness depends on how the windows are opened; opening both sashes equally and modestly, around 10 to 15 cm, creates the optimal airflow for cooling.
What to enjoy or watch next
For those living in period properties with sash windows, the upcoming hot days present an opportunity to rediscover an original design feature that can help make the home more comfortable. By opening windows early in the morning and late in the evening when outdoor temperatures are lower, homeowners can maximize cooling while minimizing heat entry during peak sun hours.
Complementary measures such as using external shutters or reflective roof coatings can further improve comfort as climate change increases the frequency of heatwaves. Embracing and correctly using period design elements like sash windows provides a sustainable, historic, and elegant solution to keeping cool indoors.