A maximum allowed temperature should be considered for hospital wards, an environmental watchdog said in a stark warning that England is ill-prepared for increasingly scorching-hot summers.
Heatwave-related deaths are predicted to triple to 7,000 a year by the 2050s if nothing is done to deal with the combination of rising temperatures blamed on climate change and an ageing population.
But 90% of wards are of a type prone to overheating even in present temperatures and staff have only limited control over conditions because window opening has been restricted over health and safety fears, according to soon-to-be-published Cambridge University research.
The findings are highlighted in the latest analysis of action to cope with increasingly sweltering summers by the adaptation sub-committee of the Committee on Climate Change which advises government on reducing greenhouse gas emissions.
" The Care Quality Commission should consider setting standards for maximum temperatures in hospitals and make sure staff can control internal temperatures," the sub-committee's report concluded.
The sub-committee also warned that too few individuals were aware of the risks or adapting their homes to deal with hotter conditions and urged the Government to encourage cost-effective changes such as insulation, ventilation and tinted glass.
A minimum standard should also be put in place "to ensure that new buildings can be kept cool without having to rely on air conditioning".
Around one in five homes would already overheat in a mild summer and the increasing number of flats and diminishing urban green spaces will worsen the threat, it said.
Simple changes could help protect against both extreme heat and cold - which would remain the biggest threat to life, it suggested.
The sub-committee renewed calls for the Government to increase spending on flood defences, warning that present policy " will increase the potential for avoidable flood damage".
New plans being published in the autumn should spell out the risks of failing to do so and of staff cuts in the flooding operations of the Environment Agency.
Hundreds of new projects are on hold and three quarters of existing schemes not being maintained, it said.
The Government came up with emergency cash to help deal with the impact of this winter's severe flooding in parts of the country but faces demands from MPs to significantly increase investment in protection.
Action was also needed to enforce recommendations made by an inquiry into devastating floods in 2007 such as saving front gardens being turned into car parking spaces, the panel said.
The sub-committee, which will give its first full assessment of the country's readiness to deal with climate change next year, said w ater firms, roads, ports and airports were falling behind the electricity industry and Network Rail in safeguarding themselves from extreme weather.
There was little evidence of smaller firms taking the necessary action either, it said.
Another concern was the failure of UK firms to compete with foreign rivals in the lucrative market for adaptation equipment.
Chair Lord John Krebs said: " There is more to be done to counter the increasing risks of severe weather that are likely to be associated with climate change.
"As well as making vital infrastructure services more resilient to flooding and storms, the country needs to adapt homes and other buildings so they are suitable for higher summer temperatures.
" The impacts of climate change on the UK in the decades ahead are likely to include rising sea levels, more flooding, summer heatwaves, and perhaps more frequent storms and droughts.
"We have found good evidence of positive action being taken in a number of areas to safeguard public health and the economy from the impacts of climate change.
"Despite the disruption experienced by many in the storms this winter, the impacts would have been much worse if it hadn't been for past investment in flood defences, and in flood forecasting and emergency planning.
"This is a clear demonstration of the benefits that result from investing in greater resilience, but there is no room for complacency.
The work on hospitals has been led by Professor of Architecture Alan Short whose research group has been looking at ways to cool wards without resorting to costly air conditioning which could exacerbate the climate problem,
It found that while the Department of Health advocates natural ventilation for wards and offices, the policy was often thwarted because window opening had been restricted over fears about safety, infection control and security.
The cost of installing the necessary improvements across 627 buildings was put at around £17.5 billion.
A Department of Health spokeswoman said: "The annual Heatwave Plan for England recognises the importance of long-term planning.
"We have also issued guidance this year on how to protect NHS buildings and ensure they are resilient to climate change."