What happens if my MVHR is not on the PCDB?

The SAP calculation uses default performance values, which are deliberately cautious, so the unit counts for less than its real performance. This can make a home harder to pass under Part L.

Is the PCDB the same as the Passivhaus database?

No. The PCDB feeds UK SAP and EPC calculations, while the Passivhaus Institut database supports Passivhaus certification. A unit may appear on one, both or neither.

The Product Characteristics Database is at ncm-pcdb.org.uk. You can search it for a brand and model to see its listed performance data.

Do I need Appendix Q for a normal home?

Only if a SAP calculation or EPC is involved, such as a new build, a major renovation or a sale. For a typical homeowner with no assessment under way, it is background detail.

Approved Document F Explained: UK Home Ventilation Rules

SAP Appendix Q and the PCDB

SAP is the calculation the UK uses to rate how energy efficient a home is, and it feeds the EPC. Appendix Q is the route by which a specific product tested performance can be used in that calculation instead of a cautious default. For MVHR, that means the unit must be listed on the Product Characteristics Database, or PCDB.

By VentRight Editorial · Last updated 2026-07-08 · Impartial · Sourced

What is SAP Appendix Q?

SAP Appendix Q is the part of the UK home energy assessment method that lets validated, independently tested product performance be used in the calculation. Without it, the calculation uses default values, which are deliberately cautious. For an MVHR unit, Appendix Q is how its actual heat recovery efficiency and fan power count toward the home energy rating.

SAP, the Standard Assessment Procedure, is how new homes show compliance with the energy rules and how EPCs are produced. Appendix Q exists so that a genuinely good product is not penalised by a pessimistic default. The catch is that the product has to be listed with its tested data, which is where the PCDB comes in.

What is the PCDB?

The Product Characteristics Database, or PCDB, is the official database at ncm-pcdb.org.uk that holds tested performance data for products used in SAP calculations. MVHR units listed there have their heat recovery efficiency and specific fan power recorded, so an assessor can use the real figures rather than a default. It is maintained on behalf of the government.

The PCDB is the SAP counterpart to the Passivhaus component database. Both list tested ventilation performance, but they serve different systems: the PCDB feeds UK SAP and EPC calculations, while the Passivhaus database supports Passivhaus certification. A unit can appear on one, both or neither.

Sources: BRE / DESNZ

Why does my MVHR unit need to be listed on the PCDB?

If the unit is on the PCDB, the SAP assessor uses its tested efficiency, which usually helps the home energy rating. If it is not listed, the assessment falls back to default values that assume poorer performance, which can make the home harder to pass under Part L. So a listed unit can be the difference between a comfortable pass and a fail on paper.

For a new build or a major renovation being assessed under SAP, this is a practical design decision, not just paperwork. Specifying a listed unit means the effort and money spent on good ventilation actually shows up in the energy result, rather than being discounted by a cautious default value.

How do I check if an MVHR unit is on the PCDB?

You can search the PCDB directly at ncm-pcdb.org.uk for the brand and model. Most mainstream MVHR units are listed by their manufacturer. If you are specifying a unit for a new build or an EPC, check it is on the database before buying, so its real performance can be used in the calculation.

Manufacturers list their own products, so a gap in the database usually means a niche or older unit rather than a problem with a mainstream one. If a unit you want is not listed, ask the manufacturer whether it is being added, or choose an equivalent listed model so the assessment can use tested figures.

Sources: BRE / DESNZ

Who needs to worry about SAP Appendix Q?

Mainly self-builders, developers and their SAP assessors, and anyone getting an EPC where the ventilation system affects the result. For a typical homeowner it is background detail, but if you are specifying MVHR for a new build or a major renovation, choosing a PCDB-listed unit is worth doing.

If no SAP calculation or EPC is involved in your project, Appendix Q does not directly affect you. The moment a home is being assessed for compliance or rated for an EPC, though, whether the ventilation unit is listed can change the outcome, so it is worth checking early.

Questions

What happens if my MVHR is not on the PCDB?: The SAP calculation uses default performance values, which are deliberately cautious, so the unit counts for less than its real performance. This can make a home harder to pass under Part L.
Is the PCDB the same as the Passivhaus database?: No. The PCDB feeds UK SAP and EPC calculations, while the Passivhaus Institut database supports Passivhaus certification. A unit may appear on one, both or neither.
Where is the PCDB?: The Product Characteristics Database is at ncm-pcdb.org.uk. You can search it for a brand and model to see its listed performance data.
Do I need Appendix Q for a normal home?: Only if a SAP calculation or EPC is involved, such as a new build, a major renovation or a sale. For a typical homeowner with no assessment under way, it is background detail.