Testing and Inspection

MVHR Commissioning

MVHR commissioning sets up a mechanical ventilation with heat recovery system so each room receives its design airflow, then measures and records the result. It produces the commissioning certificate Building Control asks for. We arrange commissioning once the installer has finished.

It covers MVHR balancing and the ventilation commissioning certificate. It is booked by developers, self-builders and MVHR installers at the end of a new build or major refurbishment.

Commissioning is carried out once the installer has finished the system. We check that before booking, so the visit is not wasted.

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What the MVHR commissioning record contains

Identification of the dwelling, unit and commissioned installation.
Room references distinguishing supply terminals from extract terminals.
Design airflow values used to assess the room measurements.
Measured terminal flows with the relevant operating modes identified.
Recorded unit or control settings where included in the commissioning record.
Limitations or outstanding installation issues affecting the completed checks.

Avoiding problems with MVHR commissioning

Moved valves	Decoration or cleaning can disturb a balanced terminal if its final position is not protected.
Restricted unit access	Leave enough working space to reach controls and filters without dismantling finished cupboards.
Wrong room schedule	Resolve renamed bedrooms and altered room uses before assigning design flows to terminals.

Ventilation ductwork running along a ceiling

When MVHR commissioning is needed

Approved Document F says mechanical ventilation systems must be commissioned and a commissioning notice given to the building control body. In new dwellings, air flow rates must be measured and a notice of the measured rates given to the building control body. Regulation 42 sets the deadline for that notice as not later than five days after the final test.(Source: Approved Document F, Volume 1: Dwellings (GOV.UK))

For continuous systems such as MVHR, Approved Document F explains how the system should be balanced so the measured rates meet the design rates, and says a copy of the completed commissioning sheet should be given to the owner with operating and maintenance information.(Source: Approved Document F, Volume 1: Dwellings (GOV.UK))

How air moves through an MVHR system. Labels on the diagram: MVHR unit; with filters and; condensate drain; Fresh air intake; Stale air exhaust; Supply air; Living rooms; and bedrooms; Extract air; Kitchen, bathrooms; and utility. — Commissioning measures and balances the air flow at every supply and extract valve.

Records supplied after MVHR commissioning

You receive an MVHR commissioning certificate and completed commissioning sheet, listing each terminal's design and measured airflow and the final unit settings. It goes to Building Control as the commissioning and air flow notice, and a copy goes to the homeowner.(Source: Approved Document F, Volume 1: Dwellings (GOV.UK))

The certificate records final fan speeds and settings, so if the system is serviced or altered later the engineer has a baseline to work from. The measured results also feed into the as-built SAP calculation where the system is part of the energy assessment.

Projects that use MVHR commissioning

Individual new homes
Make the unit accessible after joinery is fitted, not just while surrounding cupboards are unfinished.
Repeated apartment layouts
Check handed duct arrangements rather than assuming identical fan settings will give identical room flows.
Altered installations
Provide the previous settings and describe changes to ducts or terminals before rebalancing is scoped.

Understanding the outcome of MVHR commissioning

Commissioning fails when ductwork is crushed or disconnected, filters are blocked by construction dust, terminals are the wrong type, or the unit is undersized for the design. Commissioning cannot fix a design or installation fault. Ask the installer to check ducts and filters before the visit.

If the measured rates cannot be reached, the engineer records the shortfall and the likely cause. The installer can then put it right and commissioning can be completed on a return visit.

Preparing information for MVHR commissioning

The room-by-room supply and extract airflow schedule for normal and boost operation.
As-installed duct layouts and the MVHR unit make, model and control instructions.
Confirmation that ducts, terminals, filters and external intake and exhaust connections are complete.
Access to the unit, controls, every room terminal and relevant transfer air paths.
Plot references and details of changes from the original ventilation design.