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Part L (Energy) England & Wales, SAP & Appendix Q

HRV 2 Q PlusBuilding Regulations Approved Document L requires all new homes to undergo a Standard Assessment Procedure (SAP) that calculates the energy consumption and carbon emissions of each dwelling.

Revisions to Part L and SAP have raised performance standards to a level that provides a strong incentive to consider lower carbon systems. Through the implementation of Appendix Q of SAP, the energy performance of new technologies and advanced versions of existing technologies can be used in SAP calculations in place of automatic default performances, previously only reflecting the performance of older technologies.

To be entered into a SAP calculation using Appendix Q, continuous mechanical ventilation products with or without heat recovery have to be independently tested by the BRE or an approved independent test house. Qualifying products are featured on the sap-appendixq.org.uk website, which provides a searchable database of performance data.

The SAP test calculates the energy consumed by a ventilation system, known as “specific fan power” (SFP). This is expressed in Watts per litre of air moved per second (W/l/s). For heat recovery systems, the efficiency of the heat exchange is tested and this is expressed as a percentage of the heat returned to the incoming air. The are minimum SFP and heat exchanger efficiency performance requirements for a listing on the sap-appendixq website.

In addition, the SAP Q website also provides information about Energy Saving Trust (EST) good practice compliance. This is based on GPG 268: “Energy efficient ventilation in dwellings”. To qualify for EST compliance, products must meet more demanding performance criteria than those for SAP Q listing.

In conclusion, a few words of caution. To achieve an appropriate SAP rating and comply with Building Regulations and the Code for Sustainable Homes requirements, it may not be necessary to use a SAP Q ventilation product. The less expensive alternative of using “traditional” local extract fans with window trickle ventilators may still be used in many circumstances. Much depends on the balance of energy saving features within any one build, so always ask your SAP assessor to provide result comparisons before making your choice.

It must also be highlighted that in order to qualify for SAP Appendix Q and capitalise on ventilation system performance they must be installed appropriately, following the recommendations of the manufacturer and in accordance with good practice.

Regulations undergo a constant review process, with the aim to improve building standards considerably in the coming years.