Green Homes Grant scheme - ventilation requirements


The Green Homes Grant scheme provides vouchers to part-fund energy efficiency measures including insulation, double glazing and draught-proofing. While adding these measures to a home reduces the amount of heat escaping, they will also limit the amount of air that naturally passes through gaps in the building structure, referred to as ‘natural infiltration’. Many existing homes rely on this natual infiltration to provide fresh air for the occupants and to remove pollutants and moisture in the indoor air, which can be harmful to our home and our health.

Accredited installers working under the Green Homes Grant scheme will follow the legal requirement to ensure that the indoor air quality of a home is not made worse by adding insulation, double glazing or draught-proofing measures. For any building work on existing homes the Building Regulations require that “the rest of the building should not be made less satisfactory in relation to the requirements (including ventilation) than before the work was carried out.”

In most cases the safest approach is to install mechanical ventilation at the same time as the energy efficiency measures, providing confidence that the home will have good indoor air quality after work is complete. Alternatively, tests can be carried out before and after the building work to check the effect on the airtightness of the building and to assess the level of risk. The latter approach may also result in mechanical ventilation being installed at the end of the work. 

Government guidance on the scheme makes it clear that subsidy received by consumers in the form of the Green Homes Grant voucher can be used to cover “reasonable enabling work to support the retrofit.” A specific item listed in this guidance is repairing and improving controlled ventilation. This means that the provision of ventilation alongside insulation can form part of the grant.

Ventilation manufacturers have created the Green Home Compliance Scheme to help installers identify products that will meet the Building Regulations requirements and deliver effective ventilation. It is important that an extract fan will remove air at a defined rate when installed–overcoming any resistance to air-flow from ducts or grilles etc. A list of compliant products can be found on the Product Lists page. Selecting and installing products listed here will ensure that installers overcome any potential problems that could occur as a result of increasing the airtightness of the dwelling.