As temperatures in England and Wales soar this week, many office buildings will become unusable says real estate sustainability expert Chris Bennett of consultancy Evora Global - it should act as a powerful warning for real estate investors he says.

Bennett, who is co-founder and managing director of the sustainability services company says: "The climate emergency has huge, long-term implications for the real estate market."

There is much evidence of an increased incidence of overheating in buildings without air-conditioning, particularly in offices, blocks of flats and individual homes during heatwaves. This is especially true of a temperate climate like the UK where the retention of winter heat has always been the main focus of thermal design.

Overheating has been particularly notable in new-build homes and in office and housing existing stock. And as we have been constantly reminded this week, excess heat affects the health and wellbeing of occupants, especially if sleep is degraded.

In extreme cases, the heat stress caused can lead to premature death especially amongst the elderly. In the pan-European heatwave of 2003, there were 15,000 premature deaths

Those high-rise blocks

No less affected are those high-rise blocks of flats whose residents are being forced to seek-out shelter in buildings with air conditioning to work and sleep in, and some even sleep out in the corridors.

'We are obsessed with building with glass. Our city centres are dominated by glazed steel skyscrapers '� giant airtight greenhouses that trap the sun's heat and don't let it go,'� says Henrik Schoenefeldt, professor of sustainable architecture at the University of Kent.

Air-Con the saviour?

It is only by providing air conditioning that enables people to live and work in many of these 'glass palaces'� '� typically high-rise blocks facing south - that are becoming wholly unsustainable environmentally.

It is only by artificially cooling these office blocks and residences that we can even step foot inside them. 'You can't actually inhabit a glass tower without it being mechanically' air conditioned - it is actually not possible,'� Schoenefeldt says.

Relying on air conditioning to offset the extreme temperatures generated inside glass fronted buildings is creating what the International Energy Agency (IEA) has called a 'cold crunch'�. Air conditioning now accounts for around 10 per cent of the world's electricity demand.

But with two in every three global households expected to have air conditioning by 2050, according to one new report, with China, India and Indonesia accounting for half the total number, it means the stock of air conditioners will grow to 5.6 billion by then, from 1.6 billion today. The impact will be around 10 new ACs sold every second for the next 30 years says the IEA. This will consume more new electricity by 2050 than is currently used by the US, EU and Japan combined.

Clearly this is not sustainable long-term and flies in the face of energy efficiency targets. It's not good news, unless you're in the air-conditioning business, so something has to be done. Bob Ward, policy director of the Grantham Research Institute on Climate Change at the London School of Economics told The Sunday Times:

'We're baking in - literally baking in - a massive cost in terms of future retrofitting, as well as increasingly uncomfortable working and living circumstances.'�

Schoenefeldt warns that we face a new kind of fuel poverty crisis:

'We have to stop building homes and offices that can't cope with the heat and then have to rely very heavily on air-conditioning,'� he says 'which isn't to do with the inability to heat a home but actually to cool it down'�.

Chris Bennett of Evora Global, whose clients include Legal and General, Hines and M&G says the current heatwave is final warning for real estate:

"The climate emergency has huge, long-term implications for the real estate market. The UK's buildings and offices aren't designed for temperatures in the high 30Cs, let alone the 40Cs.

"A stiflingly hot office is not a pleasant or productive place to be. Extreme heat will render some workplaces unusable, or barely usable. Some will be practically deserted as working from home re-emerges. When there is such competition to get employees back into the workplace, uncomfortable offices will become devalued.

'All of this will bring into question their overall value. Workplaces that can cost effectively cope with a heatwave will be valued more highly than those which are effectively forced to shut down. Investors could be looking to invest in real estate assets that are easy and cheap to keep cool; for people, for perishable goods and for IT. Properties that have the capacity to cope with high temperatures.

"Does the office have the capacity to keep cool without costing the Earth? Can the building manager see how the building is working and how much energy this is using? And still hit their emissions targets?

Domestic homes too have their temperature problems: floor-to-ceiling bifold doors, glass roof kitchen extensions and conservatories are all increasingly popular, but for small homes with south facing gardens and little by way of building mass and airflow become oven-like in summer.

Meeting the highest standards

Passivhaus standard homes might well cope because with soaring temperatures as ventilation is built into the buildings, are carefully orientated according to the the direction of the sun's path. But few new homes going up on modern UK housing estates have this advantage and meet these standards today.

The new Part O Building Regulation that deals with overheating in domestic dwellings and residential type commercial buildings such as care homes and student accommodation, limits glazing areas to no more than 26% of floor area.

The new regulations take effect from 15 June 2022, but progress is likely to be slow - any development that is subject to a building notice, has made a full plans application, or submitted an initial notice before this date will not have to comply, provided that the work is started on site before the 15 June 2023.

Guidance given to builders states that, 'it would still be good practice to reduce overheating as much as possible within a development even if not bound by the Building Regulations. There may also be other deciding factors such as Planning Conditions that need to be satisfied regarding overheating.'�

London mayor, Sadiq Khan, has issued guidance that major developments in London should reduce the amount of heat entering buildings in the summer by: careful orientation of a property, providing shading, fenestration (window openings design), insulation, green roofs and walls, all heat reduction techniques often suggested.

Relearning old lessons

As has often been the case in building architecture and design, the lessons learned in the past, the old methods, need to be brought back. Schoenefeldt says this: 'look back in time and get back to architectural basics when early glass structures'� '� Crystal Palace being a case in point, was shaded on the outside with canvas screens, as were older greenhouses.

Wooden shutters and shades were standard fixtures in on fittings on older properties, along with recessed balconies and smaller windows. Ward has suggested that UK architects look to French and Tuscan farmhouses as examples:

'We're going to have to fit shutters and get used to shutting them in the day.'� That's because external shutters are much more effective at reflecting the heat than are internal blinds.

Stefan Thor Smith, associate professor at the University of Reading's school of construction management and engineering, told The Sunday Times, that these old lessons, 'go beyond how we keep out the sun and extend to the very fabric of our buildings. Over the past 20 years or so we've been building with lightweight construction and lots of insulation. The more thermal mass you have, it alleviates some of the problems.'�

Heavy building materials including stone, brick and concrete will absorb the heat by day and release it at night. Buildings like this will smooth out the heat curves inside and outside, cool in summer and acting like radiators to provide warmth in winter, once they have reached their optimum temperature.

Contrast this with the modern tower block and the relatively thin skin and glazed exterior. Many even have limited inside ventilation. Smith has suggested that insulation or cladding be installed on the outside rather than the inside of these buildings, providing it has the correct fire rating after the lessons of Grenfell, to offset the effects of poor building materials mass.