Trade-offs between ventilation rates and formaldehyde concentrations in new-build dwellings in the UK

The current policies and regulatory frameworks in the construction sector aim to improve energy efficiency of new buildings whilst maintaining acceptable level of indoor environmental quality (IEQ) including indoor air quality (IAQ). In practice, however, there are often important trade-offs between these objectives. The aim of this paper is to investigate the concentrations of volatile organic compounds (VOCs) in a recently built residential block in the UK and the potential trade-offs between ventilation rates and VOCs. Concentration levels of VOCs that are likely to have concentrations higher than their respective exposure limit values (ELVs) in low energy dwellings were measured in five sample apartments in this block during typical weeks in winter and summer using diffusive sampling methods. Whilst most target VOCs had concentrations lower than ELVs, benzene and formaldehyde levels were regularly higher than the limits. Measurement of outdoor concentrations showed that benzene levels were predominantly driven by outdoor sources whilst formaldehyde concentrations were driven by internal sources including construction material and furniture. To investigate how formaldehyde levels can be reduced in a given context determined by typical material used in the industry, two models were developed to calculate the effect of enhanced ventilation on formaldehyde levels and energy efficiency of the apartment with highest formaldehyde. Lack of clear definition of VOC characteristics of building material and ever-increasing use of material with high formaldehyde emission factors such as medium-density fibreboard (MDF) in indoor furniture may contribute to high formaldehyde concentrations in indoor air.  The study found that to offset the effect of the existing internal sources in the case study apartment and comply with the best practice ELV for formaldehyde, the ventilation rate should be more than three times the existing rate required in the current Building Regulations, and this can significantly increase energy use. Formaldehyde is currently not regulated in the UK Building Regulations. Given the potential health impact of high formaldehyde concentrations and the empirical evidence, it is necessary to cover formaldehyde in the next edition of the Building Regulations.  This study points to the significance of improving the existing regulations and standards to clearly define maximum permissible emission factors for various VOCs in building material and indoor furniture. It is also important to improve source control measures to reduce the concentration of formaldehyde. These measures may be complemented by enhanced ventilation. It is, however, necessary to investigate the implications of enhanced ventilation for energy efficiency.