Mouldy on internal window frame

Indoor air quality, overheating, and the future of English houses

People are generally driven to surround themselves with the latest in technology. We all want the latest smart phone, a new car with all the specs, and a faster computer. But, when it comes to our homes – the place where we spend around 65% or our time in England, and for owner-occupiers, likely the greatest investment in their lives – we seem to be happy in buildings constructed using technology from hundreds of years ago.

This might be dismissed as a consequence of living in a country with an aging housing stock, but the same concepts are employed in new constructions and when retrofitting old properties. And living in poorly designed housing has real implications for health. Cooking or smoking produce combustion pollutants similar to car engines; opening windows may help remove pollutants from indoor sources, but may increase exposure to outdoor pollutants. Damp and mould may occur if moisture from showering, cooking, and drying laundry is not removed, or if condensation occurs on windows, in attics, or within the building fabric. Insufficient ventilation can increase the rate of dust mite infestation. Poorly insulated, draughty homes may be too cold or expensive to heat, while new insulated and airtight houses may be liable to overheat, increasing health risks during heatwaves. Radon exposure is another significant health concern that may increase without sufficient ventilation.

There are a number of health consequences that can be observed due to housing, for example:

  • The UK has a higher cold-weather mortality than the Nordic countries, due in part to fuel poverty and energy inefficient housing;
  • The prevalence of asthma increases in more airtight dwellings;
  • Heatwave deaths have been observed to be higher in those living in poorly-insulated, top-floor flats;
  • In the UK, radon exposure is thought to cause over 1,100 deaths from lung cancer a year.

What this does this mean for the future?

There are a number of initiatives to encourage people to retrofit their old houses to become more energy-efficient, while new-build houses are required to meet tougher building requirements. Increasing energy-efficiency in the English housing stock can be achieved by increasing insulation levels and airtightness (e.g. reducing the uncontrolled loss of heated air through cracks, vents, and flues). Achieving adequate indoor air quality in new or retrofit dwellings is therefore dependent on having a minimal air change rate based on air infiltration, supplemented by occupant window-opening, additional purpose-provided ventilation such as trickle vents, and intermittent mechanical ventilation using extract fans to remove moisture and pollutants.

There are limitations to this approach. Air change rates will depend on wind speed and exposure, while window-opening will depend on occupant preference, and extractor fans may not be installed or maintained properly (the EHS found that in around 46% of English houses, they are either missing or do not work). There is increasing evidence that retrofit and newly-constructed dwellings are failing to meet minimum ventilation requirements. As a consequence, changes in the housing stock are predicted to lead to an increase in diseases associated with indoor air quality and radon, and may act to increase indoor temperatures during the heatwave events which are predicted to become more common due to climate change.

Recent research on indoor environmental quality in houses has enabled us to quantify the impacts of housing on health, and to project how this may change in the future with a modified housing stock and a warmer climate. But, the concepts behind the research aren’t new or ground breaking – the concept of ‘build tight ventilate right’ has been around for decades.

Learning from others

We can learn a great deal from countries that have gone through similar changes to the building stock over the past 40 years in response to energy requirements. Finland is a very good example of a country whose experience could teach England a great deal. Old Finnish houses were traditionally heated using a fireplace, like in the UK. The use of fossil fuels to heat houses increased rapidly from the early 1900’s until the energy crisis of early 1970’s, which resulted in significant changes to building regulations in order to make housing more energy-efficient. This did not come without consequences: Finnish houses built during the 1970’s are known for poor indoor air quality, often have damp problems, and many have been torn down because of this. Regulation changes in response to this saw mechanical ventilation systems become common, with air often drawn in through trickle vents and extracted through a centralised system, with inlets typically in kitchens and bathrooms. In 2003, regulations changed again to require at least 30% heat recovery from exhaust air, meaning Mechanical Ventilation and Heat Recovery (MVHR) systems are found in practically all post-2003 dwellings. The systems are user-independent, meaning occupants are not required to remember to turn on extract fans when cooking or showering, can be supplemented by natural ventilation through windows, and can filter pollutants from incoming air. In the most modern houses, systems adapt ventilation in response to indoor temperature and CO2 levels.

The nature of construction has changed as well. Around 70% of all new houses in Finland are now either wholly or partly prefabricated. Prefabrication allows for faster on-site construction, independence from weather conditions, better quality-control systems, and reduction of construction waste. Prefabricated houses have also been found to be more airtight than those built on-site. Infrastructure investments, such as district heating and the increased availability of district cooling also contribute to healthier indoor environments.

In England, there is the risk of repeating mistakes made in Finland 40 years ago. Older properties are being retrofit without compensatory ventilation, while the high cost of land means that developers are constructing new houses cheaply and without appropriate consideration for indoor air quality and performance under future climates in order to meet their margins. Dwellings are still largely constructed on-site, and in all weather conditions, which can lead to poor quality and construction damp.


So, how do we change housing and housing development in England? Well, it’s complex, and there are likely issues with land prices, building regulations, and building conservation that need to be addressed. But a lot of it comes back to the opening paragraph: we need to start demanding from housing what we demand from the other investments. We need to raise our expectations and start realising that there is more to housing than bricks and mortar. There also needs to be a culture shift; we should be more impressed when we see someone on “Grand Designs” install an MVHR – something that will improve energy efficiency and comfort – rather than a superficial Italian marble kitchen. The technology exists to design and construct an energy-efficient home that will help keep you and your family comfortable and healthy in the place where you spend the majority of your time. We need to start using it.

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