It may be time to take a lead from the Continent and look passive cooling technologies.

As air conditioning installers are harder to find than NHS dentists, passive cooling options such external shutters, blinds and awnings that are common across much of mainland Europe might provide a simpler and more sustainable route.

Not all existing houses can suddenly redesign around the stack effect, or increase insulation, there still remain ways to cool down.

Passive cooling works, according to the Social Market Foundation (SMF) studies have shown external shading alone can cut indoor temperatures by more than 6C, and it reduces energy bills where air-con is still needed.

Some measures are easier than other, and some meet the planning system head on. The most effective external measures (external shutters or blinds) risk triggering planning permission decided case-by-case and council-by-council and coin flip by coin flip.

The SMF recommends planning be eased for such measures, and regulations to ensure building stock can be retrofitted where possible.

Part O is a section of England’s new Building Regulations (which came into effect nationally in 2022, with a similar policy previously in place in London) which focuses on preventing overheating. The regulations stipulate that developers must make reasonable provision in residential buildings to limit solar gains (heat that makes its way into a home though the walls and windows) in summer, as well as to provide adequate means to remove heat from the indoor environment (primarily through ventilation, either passive or mechanical). Part O allows for the installation of different types of external shading, including shutters, blinds, awnings and overhangs – all of which can be used by the developer to ensure a comfortable indoor air temperature on hot days. For removal of excess heat, ventilation through opening windows, external wall louvres or mechanical ventilation are all permitted. The regulations also specify that passive cooling should be used as far as practically possible before making use of active cooling options like air con.

Naturally, the new ‘Building Regs’ contradict with other Building Regulations. For example, Part O requires windows to open fully at night in order to relieve excess heat from the property, but Part Q (which is concerned with security) restricts how much windows on the ground floor can open by, in order to help prevent break-ins. The requirement to open windows fully for cooling can also contradict the conditions of acceptable levels of noise as a result of ventilation, that is required under Part F of building regulations. The potential mismatch between requirements (and assumptions) for Part O and the requirements of other older more established building regulations can cause issues for developers. Acknowledging the common issues with the Regulation, the government have announced their intention to conduct a full technical review of Part O.

Arguably, though, the biggest issue is that Part O is not applied retrospectively.

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