Millions of people living in private rented and social housing say they are trapped in homes they can’t cool, with little to no control over soaring indoor temperatures, according to Citizens Advice.

New research by the charity reveals that half of all tenants (51%) feel they lack the basic control needed to stop their homes overheating, compared with 40% of homeowners.

Issues range from renters who cannot open fixed or locked windows, to people on heat networks who cannot switch off central heating or control their thermostat.

People who live in a building with an old, gas-run heat network are among the most at risk of overheating due to hot pipework intensifying indoor temperatures. The charity’s research found 90,000 heat network consumers are unable to turn off their central heating even in summer.

The research also shows that people are taking drastic action to cope with this year’s extreme heat, including: sleeping in unconventional places like the kitchen, garden, or on a balcony; taking sick days, unpaid leave or annual leave; or paying for hotels with air conditioning. Others said they had to use makeshift solutions like taping tin foil, cardboard, or damp sheets to windows.

The charity’s research found poorly designed homes, which act like “heat traps”, and the high cost of cooling equipment like air conditioning are making people feel helpless against the hot weather.

Commenting on the research, Dame Clare Moriarty, Chief Executive of Citizens Advice, said: “For far too many people, a summer heatwave doesn’t mean enjoying the sun, it means being trapped in a sweltering home with no control over the temperature.

“We’re now facing a year-round crisis, where poorly designed housing stock is acting as a giant heat trap in summer and as an ice box in winter.

“The government has a vital opportunity to help fix this through the Warm Homes Plan. By investing in better insulation, ventilation, and heat network upgrades, we can ensure people’s homes are warmer in the winter and safer and cooler in the summer.”

Commenting on the problems faced by problems faced by people living in homes powered by heat networks, Gareth Jones, managing director of FairHeat, said: “The results of this Citizens Advice study shine a light on the number of people connected to heat networks who are unable to turn off their central heating.

“In terms of context this is equivalent to the entire population of a town the size of Stevenage, Halifax or Wigan, who are unable to turn off their central heating at a time when temperatures have regularly exceeded 30 degrees this summer.

“Since it was announced that the Heat Network Efficiency Scheme (HNES) will be extended to 2030, we have made the case that while £15m a year to upgrade heat networks is very welcome, it is not enough money to meet the scale of the challenge in terms of the number of people affected by overheating heat networks and also those affected by heat networks experiencing outages in winter.

“Ofgem estimates that 66% of the UK’s estimated 15,000 existing heat networks are owned and managed by social landlords and we know many of these not-for-profit organisations are struggling after a decade of rent cuts and below-inflation rent increases.

“In the forthcoming budget it is vital that the government commits more funding to HNES to improve underperforming heat networks.

“This new data also underlines the importance of minimum standards for heat network performance to ensure that thousands more people are not similarly affected by overheating and underheating networks in the years to come.”