Bad indoor air quality due to:
o Insufficient ventilation, especially in bedrooms. In the Dutch legislation the mandatory ventilation rate is based on a required amount of ventilation per m2. This means that rooms with high occupancy (for instance the bedrooms) are often relatively poorly ventilated. Furthermore the ventilation systems are designed to meet the mandatory ventilation rates on the highest setting in order to save costs. Since the ventilation system produces the most noise in the highest setting, this leads to the use of lower settings which in turn contributes to low ventilation rates.
o Internal pollution of the ventilation system. Often the air ducts in newly build dwellings are polluted with dust and other contaminants generated during construction. Also, most of the time the ventilation units are not properly maintained.
o Overheating. The risk on overheating increases due to the (mandatory) increase in insulation of a house. This leads to a reduced heat loss during the whole year which translates to a lower energy use for heating in the winter (aim of the legislation) but also to higher indoor temperatures during the rest of the year.
Within the context of ‘health effects of modern airtight construction’ there are arguably two main variables: ventilation and source control. My own feeling is that while ventilation is a crucial aspect, it is fundamentally a regulated area (in the sense of building standards) and is measurable. For this reason, I am hopeful that things will improve in this area with concerted effort. Where I see the challenge is in convincing the industry, the regulators and society at large to take the issue of source control seriously. It is very difficult to establish any sort of ‘evidence-based’ cause and effect in this area, and any movement against the responsible manufacturers will meet with considerable resistance and obfuscation, as we have already experienced. The use of chemicals in construction and household maintenance / cleaning / fixtures will be extremely difficult to control and so I suspect we will need other tactics to move things forward. Best practice guidance, exemplars, making monitoring more widespread and a more ‘populist’ approach strike me at this stage as having potential.
o Post occupancy evaluation
o Integration of IAQ standards into building regulations
o Development of an effective natural ventilation solution
o Prototyping solutions through live build projects using inhabited dwellings
Sani Dimitroulopoulou, Public Health England
Current legislation recognises the significance of lethal indoor pollutants, such as carbon monoxide, and mandates specific actions. Thermal comfort is also well recognised in guidance and has led to actions such as programmes of home insulation, particularly in social housing. However, more needs to be done, in terms of indoor air quality that affects occupant health and it is currently poorly considered and not subject to the same actions.
In the UK, large-scale installation of MVHR systems, coupled with the very high degree of dwelling air-tightness may cause concern if the systems are not properly installed, maintained or used.
Unintended consequences of energy saving measures (within the wider context of climate change mitigation) and the potential impact on human health include:
o Indoor Air Quality (IAQ) problems associated with reduced ventilation, e.g. particulate matter, radon, VOCs, moisture (resulting in mites and mould) and environmental tobacco smoke in domestic buildings;
o Changes to the hygrothermal properties of building fabric resulting from improvements in thermal properties, causing cold bridges, condensation, mould growth and decay.
o Increased penetration of outdoor particle pollutants with higher ventilation rates in dwellings fitted with mechanical ventilation systems, unless there is control of outdoor air pollution levels or effective filtering of incoming air.
There is limited evidence on IAQ and its impact on health and wellbeing, as a result of reduced of inadequate ventilation in new/modern airtight dwellings. There are currently very few/close to none studies addressing simultaneously ventilation, IAQ and personal exposure in such dwellings.
Tom Woolley, Rachel Bevan Architects
My suggestion is the need for empirical data on the performance of hygroscopic and moisture buffering materials and whether these can reduce demands on ventilation systems.