Designing Healthy Buildings
Why do we need ventilation?
Most people have benefitted from improvements in housing with double glazing, draught proofing, improved insulation – all strategies designed to reduce heating bills. But modern lives in the UK mean that we currently do not have adequate ventilation strategies to cope with how we live and how our houses cope with the moisture generated from living, leading to mould and poor internal air quality.
New build houses and Passivhaus designs are very airtight to reduce heat losses and automatic ventilation is essential to ensure healthy air quality. Vital to new and retrofit houses alike is the need to extract water vapour to reduce the risk of mould. Where warm moist air meets a cold surface such as single glazing or an uninsulated wall then condensation will occur leading to mould risk.
Sometimes mould is caused by specific water damage from leaks and can be identified as a localised event. Often humidity levels are too high which allows mould growth to flourish. Some modern building materials such as plasterboard and woodchip substrates all retain moisture after exposure to leaks and are likely culprits in growing mould. Choosing the right materials in areas of potential moisture exposure can help to avoid mould.
What is the best strategy?
Reduce moisture
Firstly take self-help measures to reduce moisture in the home through using extract fans and dehumidifiers.
Retrofit
Evaluate retrofit options to reduce the risk of condensation and improve the energy efficiency of your home. Check insulation designs are not likely to cases interstitial condensation i.e. condensation in the layers of the wall itself.
Ensure attention to detailing of insulation to avoid thermal bridging where the moisture is driven to the corners in bad retrofits.
Ventilation
Seek advice on ventilation options to continuously extract air from moist or wet rooms and input fresh air into other living spaces, exchanging the energy on the way. This is called Mechanical Ventilation with Heat Recovery or MVHR.
This can be done on a whole or part of your house or even on a room basis. Having extract on humidity controls is essential so it doesn’t just switch off after 5 minutes.
