Expert reveals the coolest ways to beat the heat in your garden buildings

As forecasts point towards another “hotter-than-average” summer, particularly after the heatwave the UK experienced in May and June, many homeowners could find their garden offices, summerhouses and outdoor hobby spaces becoming uncomfortably warm.

While garden buildings provide valuable extra living and working space, they can quickly turn into heat traps during periods of hot weather, especially if they’re poorly ventilated or positioned in direct sunlight.

Christopher Murphy MBE, founder of Dunster House, garden building specialists, has revealed some of the most effective ways to keep garden buildings cooler during the summer months.

1. Create airflow with cross-ventilation

One of the simplest and most effective ways to reduce temperatures is to create a through-breeze. Opening windows or doors on opposite sides of the building allows hot air to escape while drawing cooler air through the space. Even a small amount of airflow can make a noticeable difference on warmer days.

However, the time of opening needs to be right to ensure it is effective. If the outdoor temperature is higher than the indoor temperature, you will only be letting the heat in. Ventilate early morning and late evening instead, then close windows during peak temperature times.

2. Keep blinds and curtains closed during peak sunshine

Just like with windows and doors, many people instinctively open everything up when it’s hot, but allowing direct sunlight into a garden building through open curtains, blinds, or shutters can dramatically increase indoor temperatures.

Keeping window coverings closed during the hottest parts of the day helps prevent solar heat gain and keeps interiors cooler for longer.

For extreme heat, a temporary reflective windscreen shade (like those used in cars) or aluminium foil, if windows are not glass, can be placed against south-facing windows to bounce sunlight away. For a more permanent solution, consider reflective window films as well as thermal blackout curtains.

3. Add external shade

External shading is often more effective than internal blinds because it stops the sun’s rays before they reach the glass.

Pergolas, awnings, shade sails and strategically placed plants can all help reduce the amount of direct sunlight hitting a garden building throughout the day.

For example, fast-growing climbers such as jasmine, clematis or grapevines on a pergola can create natural shade and, unlike solid structures, they also help cool the surrounding air through evaporation.

However, it is not advised that you grow these plants directly on the garden buildings as this can trap moisture and potentially damage the structure. Plants should be positioned on a nearby pergola, trellis, archway or shade sail structure instead to block direct sunlight while still allowing air to circulate through the garden building.

4. Use light-coloured exterior finishes

A simple but effective change is to brighten up the outside of your garden building; dark surfaces absorb significantly more heat than lighter ones. Choosing lighter paint colours, such as sage green or cream, can help reduce heat absorption and lower internal temperatures.

If you are looking to apply a new colour or have a new structure you are looking to paint, it is important to avoid doing so in direct sunlight or during the hottest parts of the day. When timber and paint become too hot, the paint can dry too quickly, leading to visible brush marks, patchy coverage and reduced adhesion.

For the best finish, paint early in the morning or later in the afternoon when temperatures are cooler, and the surface isn’t being hit by direct sun. Also, be sure to choose a UV-resistant paint appropriate for exterior use.

6. Install a roof vent

Heat rises, which means that with nowhere to escape, hot air temperatures can build up beneath the roof. Installing a roof vent gives this trapped heat somewhere to go, which can help to regulate temperatures and improve overall comfort, particularly in buildings with pitched roofs.

A roof vent works by encouraging natural airflow in a similar way to cross ventilation. As hot air exits through the vent, cooler air is drawn in through open windows, doors, or even lower-level vents; this continuous air circulation helps prevent the space from becoming stuffy and overheated.

Roof vents can be especially beneficial in garden buildings with large windows, dark roofing materials or south-facing positions, all of which can contribute to excessive heat gain during summer.

7. Switch off unused heat-generating equipment

It’s not just the weather that can make garden buildings feel too warm. Computers, monitors, printers and chargers in garden offices, powered fitness equipment in home gyms, and fridges, games consoles, TVs and speakers in garden bars and entertainment spaces all generate heat while in use, and these heat sources can quickly add up.

During hotter weather, switch off unused equipment completely rather than leaving it on standby and avoid running unnecessary electronics during the warmest part of the day.

Garden office users may also find that working from a laptop instead of a desktop computer, where practical, can help reduce the temperature during extremes such as heatwaves.

While each device may only produce a small amount of heat, together they can have a noticeable impact on the temperature and comfort of the space.

8. Introduce indoor plants

Houseplants aren’t just good at improving the aesthetics of a room; they can also help create a cooler-feeling environment through a process known as transpiration, where moisture is released into the air.

Species such as peace lilies, ferns and areca palms are particularly popular for creating a fresher indoor atmosphere. Although adding plants won’t dramatically lower the temperature of a garden building, they can help improve comfort levels and create a more pleasant environment during warmer weather.

Positioning plants near windows can also help filter some sunlight and create a cooler, more inviting atmosphere during periods of hot weather.

9. Add cooling devices where needed

For garden buildings that are used regularly throughout the summer, dedicated cooling devices can provide additional relief during periods of hot weather.

Freestanding fans are the easiest and cheapest option to help improve airflow and create a cooling breeze. However, in frequently used spaces such as garden offices or studios, homeowners may benefit from investing in a portable air conditioning unit. While these units require a fair amount of power to operate and can be costly, they can help maintain a more comfortable temperature when natural ventilation alone isn’t enough.