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Part L update deadline fast approaching

The HVAC industry faces significant changes in October as the latest revisions of the Approved Documents Part F (Means of Ventilation) and Part L (Conservation of Fuel and Power) come into force.

Part L’s new target emission rate represents a 25 per cent improvement over the previous 2006 Building Regulations, in line with achieving Code for Sustainable Homes Level 3. For the HVAC industry, this means trends in product specification are set to change as the government looks to cut carbon emissions.

Part L and Part F feature a number of major revisions that include minimum energy efficiency levels for all ventilation systems. The launch of Part L’s new Domestic Building Services Compliance Guide highlights ventilation performance levels.

Here for the first time a specific fan power requirement of less than 0.5 watt/sec is included for intermittent fans used in new build developments. This is an important change and will drive ventilation manufacturers towards developing intermittent fans featuring energy-efficient DC motors. As a result, some AC motor-driven intermittent fans will disappear from product ranges, as they fail to meet the 0.5 watt/sec specific fan requirement.

Quality is key

As the drive for energy efficiency increases, the ventilation industry needs to ensure air quality does not suffer as a consequence of increasingly airtight homes.

To ensure this doesn’t happen, Part F includes guidelines for airtight properties with infiltration rates tighter than 5m3h/m2 at 50pa. For Intermittent System 1 and Passive Stack System 2 approaches, in airtight dwellings the guidance increases background ventilation rates by up to 50 per cent.

This looks set to cause some developers to re-evaluate their designs and move any new planning applications away from intermittent fans, since the previous provisions in Approved Document F 2006 have already been difficult to achieve when using trickle ventilators in windows.

As intermittent fans fall out of favour, changes to Part F and Part L are poised to increase the uptake of continuous ventilation, since it performs better in SAP, is easier to specify and easier to standardise, as trickle vents are not required.

For Continuous Mechanical Extract System 3 approaches, the guidance removes the need for background ventilation in dwellings designed with infiltration rates above 5m3h/m2.

It is likely these factors, along with the Dwelling Emission Rate benefits of SAP Appendix Q, will combine to boost the adoption of whole-house Mechanical Extract Ventilation systems (MEV and dMEV) and Mechanical Extract Ventilation systems with Heat Recovery.

Testing and compliance

Meanwhile, for the first time Part F will require post-completion testing of ventilation equipment. Part F’s new Domestic Ventilation Installation and Commissioning Compliance Guide has been introduced to ensure ventilation not only delivers the required airflow, but does it efficiently and quietly. The guide includes sign-off procedures and paperwork completion to ensure performance and efficiency are met.

Post-installation performance policing is critical to ensure air quality in increasingly airtight homes. This is especially important with the increased adoption of highly efficient ventilation systems, like MVHR, which require trained competent installers.

Heat recovery systems are more complex to install than single fan solutions and need to be fitted correctly to ensure performance - key when it comes to lowering carbon emissions.

Currently there is a shortage of skilled installers trained to fit MVHR, and without contractors undergoing training now we look set for a skills gap.

The new building regulations will also require sign off by a competent person, and BEAMA along with other trade associations are working on the delivery of the competence framework.

Lee Nurse is TEHVA Ventilation Committee chairman and Vent-Axia marketing director