“Failure to meet indoor air quality indicators, in all cases, corresponded with failure to meet the ADF ventilation recommendations.”
— Ventilation and Indoor Air Quality in New Homes, a research project conducted by the Building Research Establishment (BRE) for the UK Ministry of Housing, Communities & Local Government (MHCLG) and published by GOV.UK in October 2019.
The certified alternative to FENSA’s default trickle vent approach is the installation of a high-performance decentralised (Single-Room) Heat Recovery Ventilation (MVHR) system. Under Building Regulations Approved Document F (Part F), this mechanical solution is fully compliant and often superior for modern, airtight homes. The key benefit is that it achieves the mandated background ventilation rate—eliminating the need for bulky, aesthetically compromising trickle vents—while simultaneously recovering heat, preventing condensation, and improving indoor air quality. This approach bypasses the “ugly tax” compromise, securing your compliance with a silent, precision-engineered upgrade.
The increase of issues involving damp, mould and condensation in recent years is largely due to the fact that modern homes are built with a focus on airtightness and insulation, with ventilation being treated as a low priority and more of a tick box exercise.
As we live our daily lives, we produce a lot of moisture and mould spores through breathing, cooking, cleaning, washing etc. If this moisture is not effectively removed this will settle on the coldest places (externals walls, windows etc) and will form condensation. Also, if the air in the room is not kept moving and refreshed, the mould spores will settle where the moisture is and will propagate, causing black mould.
An average room in a UK house is 62 cubic metres, which is 62,000 litres of air – this is no small amount of air so an efficient ventilation system is surely important?
Continuous mechanical ventilation!
Ventilation can’t play a part time role; it is a continuous requirement for both human and building health. Mechanical ventilation is important to ensure the air is pulled and pushed using a motorised fan.
This is why the FLUXO unit was developed, which extracts stale air and supplies fresh air in a continuous cycle, and retains the heat in the room through its unique heat recovery function. Not only that, but it is also super quiet and costs only £5 a year to run!
The specific Part F (Ventilation) airflow requirements for a single habitable room, a kitchen, and a bathroom in a retrofit project in England depend on the overall dwelling ventilation strategy (e.g., natural, intermittent mechanical, or continuous mechanical).
Here are the key requirements, generally broken down by room function:
These rooms primarily require background ventilation (continuous low-rate supply) and purge ventilation (high-rate opening).
Kitchens require a higher rate of intermittent mechanical extract (to remove cooking fumes) and a lower rate of continuous mechanical extract (if a continuous system is installed).
These rooms require mechanical extract ventilation to control moisture and humidity.
The sum of all background ventilation and extract rates must satisfy the minimum whole dwelling ventilation rate based on the size of the house, which is generally calculated as the greater of:
