Individual research recommendation details

Recommendation ID

NG149/3

Question

What is the minimum air exchange rate to minimise the health effects of poor indoor air quality in the home?

Any explanatory notes
(if applicable)

Why the committee made the recommendations

Avoiding sources of pollutants
Evidence showed that some building materials can emit high levels of pollutants. There was no evidence on building materials and products that emit a low level of VOCs and formaldehyde. The committee agreed that specifying low-emission materials could help protect people's health. But because of the lack of evidence, they could only suggest professionals consider their use on a case-by-case basis when drawing up specifications.
The committee also noted that there are no national labelling schemes for building materials or consumer products in England (apart from a scheme for paints). They also noted government plans to set up a voluntary labelling scheme in England, as outlined in the government's clean air strategy 2019.
The committee noted the Department for Education's Building bulletin BB101: ventilation, thermal comfort and indoor air quality 2018 and considered that its recommended performance levels could also be applied to homes.
Evidence showed that open solid-fuel fires emit particulate matter and are a major cause of poor indoor air quality. This evidence was limited, but the committee agreed that designing heating options that avoid them will help protect people's health.

Heating and ventilation
Ventilation affects indoor air quality, and its role in removing potential pollutants is critical.
Evidence showed a clear link between cooking with gas and pollutant levels – these are higher in the kitchen when cooking using gas than outdoor pollutant levels unless there is an air quality alert.
Evidence also showed that some causes of poor indoor air quality, such as condensation, are the result of poor thermal performance, high moisture levels combined with poor ventilation. The current focus on draught proofing and energy efficiency can add to the problem.
Because buildings vary so much, the committee were unable to recommend specific types of ventilation or heating strategies. But they agreed it is important that design strategies achieve the correct balance between ventilation, energy efficiency and heating.
Outdoor pollutants entering through windows can contribute substantially to poor indoor air quality. This is particularly the case in deprived areas where housing is likely to be close to busy roads (see the government's clean air strategy 2019). The committee agreed that if opening windows is not safe or lets in more outdoor pollutants (for example, if the window faces a busy road) then other methods of ventilation or methods of preventing pollutant ingress without resorting to opening windows are needed. This includes mechanical systems with filtration to protect against outdoor pollutants including intelligent ventilation systems.
Building or refurbishing homes to improve heating without taking ventilation into consideration can affect the health of people who live in them. So the committee stressed the importance of balancing the need for heating and ventilation, and taking into account all factors affecting indoor air quality.
They noted that the British Standards Institute standards for domestic retrofits and energy efficiency could be a useful source of information for architects and designers.
The committee agreed that more research is needed about the benefits and harms of different air exchange rates, and the health risks associated with pollutants released from building materials over time in lived‑in home environments. This would improve understanding of the minimum ventilation thresholds and appropriate building materials that designers and builders should use. (See research recommendations 3 and 4.)

How the recommendations might affect practice
The recommendations will reinforce current best practice. Architects and building designers should already be aware of the potential risks of the products and materials that they specify.
Balancing ventilation, insulation and heating is already best practice to maintain good air quality so there should be no additional resource impact.

Full details of the evidence and the committee's discussion are in:
evidence review 1: associations between individual or building characteristics and exposure levels
evidence review 2: exposure to pollutants and health outcomes
evidence review 3.1: material and structural interventions
evidence review 3.3: ventilation design and use.

Source guidance details

Comes from guidance

Indoor air quality at home

Number

NG149

Date issued

January 2020

Other details