The changes to Part F and Part L of the Building regulations came into effect this October. Stephen Neild looks at the impact they are likely to have on the ventilation industry.
The UK Government has acted decisively to enforce stringent legislation to achieve an 80 per cent reduction in greenhouse emissions by 2050. As 25 per cent of carbon emissions come from homes and a further 17 per cent from non-domestic buildings, every household and business, both public and private must increase their energy efficiency levels.
From October, the new amendments to Approved Documents Part F (Means of Ventilation) and Part L (Conservation of Fuel & Power) have played a crucial role in achieving this ambitious target resulting in the following three-fold effect on ventilation:


• Energy efficiency
• Installation
• Owner responsibility

Homes are being designed, built and improved to increase air tightness in order to improve energy efficiency in line with The Code for Sustainable Homes target emission rate - a 25 per cent increase on the previous 2006 target.

Ventilation is a necessary requirement of building a new property. As we continue to 'seal up' new dwellings with triple glazing, thicker loft and cavity wall insulation along with energy efficient heating; we increase the need for good ventilation. Coinciding with this is the launch of Part L's Domestic Building Services Compliance Guide.

Intermittent fans

For the first time, legislation sees the specific fan power of less than 0.5 Watt/l/s as a requirement for intermittent fans installed in new build developments. The guide states that the specific requirements for continuous extract ventilation systems should not be worse than 0.7 W/l/s, 0.5 W/l/s for continuous supply ventilation systems and 1.5W/l/s for continuous supply and extract with heat recovery systems.

This is a significant step forward for energy efficient DC motors as some of the traditional intermittent AC motor-driven fans will fail to meet the 0.5 W/l/s specific fan requirement and will consequently disappear from the market.


It was fundamental that the changes to Part F coincided with the changes to Part L to ensure that, while improving energy efficiency in the ventilation solution installed there was no compromise made on the air quality as a direct result of the new level of air tightness.
In 2007, the BRE document MEV & MVHR system monitoring for SAP Appendix Q, highlighted the bad practice surrounding the installation and commission of MEV and MVHR systems. It has been instrumental in bringing into force major revisions to Part F.

The conclusion to the BRE document was simple - poor installation of MEV and MVHR units resulted in inefficient systems which were under performing and not doing the job they were intended for; to provide good indoor air quality.

Poorly installed flexi ducting

In some cases, flexi ducting had been installed so poorly that the air flow (already constrained by the use of flexi-ducting) was restricted so much that the air had to negotiate a 'spaghetti junction' of ductwork in order to either extract or input any air into the property. Heat recovery units were fitted in line with Code Level requirements, however, they were failing miserably to perform and the need to enforce good practice had become apparent.

Part F's Domestic Ventilation Installation and Commissioning Compliance Guide will ensure that both mechanical and passive ventilation systems are commissioned correctly by competent installers. Furthermore, the airflow rates for mechanical ventilation must also be measured at commissioning stage.

'For mechanical ventilation systems installed in new dwellings, air flow rates shall be measured on-site as part of the commissioning process. This shall apply to intermittently-used extract fans and cooker hoods, as well as continuously running systems.'

In order to maintain an efficient system, the owner/occupier will be informed about the servicing of the unit installed. They will then be responsible for ensuring that sufficient airflow rates are constantly achieved. As evidence that the appliance has been commissioned and measured to standard a check list will have to be completed for each new dwelling and passed to the building control body.

It is no secret that the hvac industry is now looking at a skills gap especially when it comes to the correct installation of heat recovery systems which are much more complicated to fit than single fan solutions.