What Does MVHR Commissioning Include? A Homeowner’s Checklist for Handover Day

Overview

MVHR commissioning is the process of checking, setting up and recording how a mechanical ventilation with heat recovery system performs once it has been installed. In simple terms, it is where the installer confirms that the system is safe to run, the airflow is balanced, controls work as intended, and the home is handed over with enough information for the occupier to use it properly.

For UK homes, this sits squarely in the area of compliance and best practice. A system can look neatly installed and still perform badly if commissioning is rushed or skipped. Poorly balanced airflow can leave bedrooms stuffy, bathrooms slow to clear, and running noise higher than expected. In a tighter, better-insulated home, those errors tend to show up quickly as condensation, comfort complaints or disappointing energy performance.

At minimum, a homeowner should expect commissioning to cover:

• Visual inspection of the completed installation
• Confirmation that supply and extract points are correctly located and labelled
• Checks on ductwork, condensate drain, insulation and access
• System start-up and functional testing
• Airflow measurement and adjustment at valves
• Balancing and commissioning of whole-system supply and extract rates
• Control checks, boost function checks and user settings
• Handover documents, operating guidance and maintenance advice

That last point matters more than many homeowners expect. Good commissioning is not only about measured airflow; it is also about clear handover. The source material available for this article highlights that skilled ventilation engineers are expected to install and service MVHR and PIV systems while ensuring compliance with regulations. In practice, that means commissioning should be treated as a professional compliance task, not an optional courtesy at the end of the job.

Before handover day, it helps to know what MVHR is supposed to do. The system should continuously extract stale, humid air from wet rooms such as kitchens, bathrooms and utility spaces, while supplying filtered fresh air to living rooms and bedrooms. Heat is transferred from outgoing air to incoming air within the unit, helping reduce heat loss compared with simple extract-only ventilation. If that airflow pattern is not checked and adjusted, the system may still run, but it may not ventilate the home correctly.

Think of commissioning as the difference between installation and performance. It is your opportunity to confirm the system is finished properly and to ask for any issues to be put right before the installer leaves.

Checklist by scenario

Use the relevant checklist below depending on whether you are attending a first handover, checking a recently occupied home, or auditing a system after problems have appeared.

Scenario 1: Handover day for a brand-new MVHR installation

This is the most important stage. Walk through the house with the engineer and check each item in person where possible.

• System identification: You have the make, model and serial number of the MVHR unit, plus confirmation of where replacement filters can be sourced.
• Unit access: The main unit can be safely accessed for filter changes and servicing without dismantling unrelated fixtures.
• Filters fitted correctly: Filters are installed, seated properly and appropriate for the system. Ask which side is supply and which is extract.
• Ductwork complete and secure: Duct connections appear sealed and supported, with no obvious loose sections, kinks or crushed flexible duct.
• Insulation in cold areas: Ducts running through lofts or other unheated spaces are insulated where required to reduce condensation risk and heat loss.
• Condensate drain installed: The condensate connection is present where the unit requires it, falls correctly and discharges appropriately.
• Outdoor terminals fitted: Intake and exhaust terminals are in place externally, clear of obstructions and not obviously positioned to short-cycle air between them.
• Correct room terminals: Supply valves are in habitable rooms and extract valves are in wet rooms, as per the design intent.
• Valves are labelled or documented: There is a record of which valve serves each room and what setting it was left on.
• Power and isolator: The electrical connection is complete and any local isolation arrangement is identified to you.
• System starts and runs: The engineer demonstrates normal operation and confirms there are no fault codes.
• Airflow measurement: Room airflows are measured rather than guessed. Ask to see the readings and the final balanced values.
• Boost tested: Boost controls are demonstrated at bathroom or kitchen switches, humidity sensor, cooker-linked input or app, depending on the setup.
• Normal speed explained: You are told what the normal background setting is and why it should not usually be turned off.
• Noise check: Listen in bedrooms and living spaces. A quiet low-level airflow is normal; whistling, rumbling or noticeable vibration needs investigation.
• Door undercuts or transfer paths: Internal air movement routes are present so air can move from supply rooms toward extract rooms.
• User controls explained: You know how to use boost, holiday mode, summer bypass if fitted, frost protection behaviour and any app or wall controller.
• Documentation handed over: You receive manuals, commissioning records, settings, warranty information and maintenance guidance.
• Maintenance intervals discussed: You are told when filters need checking and when the system should receive professional servicing. For ongoing care, see our MVHR maintenance checklist.

Scenario 2: You have moved into a home with a “new” MVHR system

This is common in new-build purchases and renovated properties. Sometimes the system was commissioned before the home was occupied, and small issues went unnoticed until people started living with it.

• Find the paperwork: Ask the seller, developer or managing agent for manuals, commissioning sheet and warranty details.
• Check filter condition: Even a recent system may have construction dust in the filters if they were not changed after works finished.
• Confirm room airflow pattern: Bedrooms and living rooms should receive supply air; bathrooms, en-suites and utility rooms should extract.
• Test boost in wet rooms: Steam from showers should clear in a reasonable time, and boost should activate as designed.
• Check for blocked terminals: External grilles can be obstructed by debris, covers, insect mesh loading or poor finishing works.
• Listen for imbalance: Excessive hiss at one valve and weak airflow elsewhere can indicate the system was never balanced properly.
• Review occupant settings: Previous owners sometimes turned speeds down to reduce noise, which can increase humidity problems.

If you suspect the setup is not right, it is often worth arranging an independent ventilation maintenance service or commissioning check rather than assuming the problem is “just how MVHR works”.

Scenario 3: You are troubleshooting complaints after installation

Use this list if the home has condensation, poor air quality, high noise or comfort problems soon after the system went live.

• Condensation on windows: Check whether the issue affects wet rooms only, mornings only, or the whole house. Compare this with boost operation and occupancy patterns. If your main concern is moisture, our guide on how to stop condensation on windows in winter can help separate ventilation issues from wider moisture sources.
• Stuffiness in bedrooms: Confirm supply valves are open to the commissioned setting and not closed by occupants.
• Persistent odours: Verify extract airflow from kitchens and bathrooms, and check that recirculation or short-circuiting at outside terminals is not occurring.
• High noise: Look for over-tight valve settings, fan speeds set too high, poor attenuator arrangement, or vibration transmission at the unit.
• Cold draught complaints: Ask whether the supply air temperature expectation is realistic. MVHR tempers incoming air; it does not normally heat it to room temperature on its own.
• High energy use concerns: Confirm filters are clean, controls are not left permanently on boost, and summer or bypass settings are understood.
• Uneven performance room to room: Request a balancing and commissioning review with measured room-by-room airflow results.

Scenario 4: Retrofit or complex-property handover

Retrofit projects often need extra care because space constraints can affect duct routes, access and noise control.

• Check serviceability: Loft-mounted units, boxed-in ducts and ceiling valves must still be accessible for cleaning and future maintenance.
• Review compromises openly: If room layouts forced non-ideal duct runs, ask what effect this may have on airflow or sound.
• Confirm insulation and condensation control: This is especially important where ductwork passes through colder zones.
• Ask about legacy fans: Existing bathroom or kitchen fans may need to be disconnected, retained or coordinated with the MVHR design.
• Document any deviations: If the installed system differs from the original proposal, the handover pack should show what changed and why.

If you are still deciding between systems rather than signing off an MVHR installation, it can help to compare broader options such as PIV and extract-only approaches. Related reading: MVHR installation cost in the UK and PIV system cost in the UK.

What to double-check

The most useful homeowner checks are often the simplest ones. These are the points worth slowing down for before you sign anything off as complete.

1. Measured airflow, not visual reassurance

A valve in the ceiling does not prove the room is being ventilated correctly. Commissioning should involve actual airflow measurement at terminals and adjustment to reach the intended rates. Ask for the room-by-room figures and keep them with your house documents. If an installer cannot show what was measured, treat that as unfinished business.

2. Balanced supply and extract

MVHR balancing and commissioning should leave the system with sensible overall supply and extract rates for the dwelling and appropriate distribution to each room. Exact design values vary, but the principle is constant: the home should neither be starved of fresh air nor pushed into avoidable imbalance because one side was set up carelessly.

3. Transfer air paths inside the home

Even a well-balanced unit will struggle if air cannot move through the property. Closed doors, thick carpets and missing undercuts can all affect performance. During handover, ask how air is intended to move from supply rooms to extract rooms when doors are shut.

4. Filter access and routine maintenance

Homeowners often discover too late that the unit is awkward to reach or the filter orientation is unclear. Have the engineer physically show you how to open the unit, remove filters and identify replacement types. If you also run a PIV system elsewhere in your property portfolio, compare maintenance expectations with our PIV maintenance guide.

5. Noise at normal speed, not only with doors open and people talking

Ask for a quiet moment while the system is running normally. Stand in a bedroom and then beneath the main unit location. Noise issues are easier to resolve before handover than after the home is fully occupied.

6. Controls that make sense to a non-specialist

Some systems are technically capable but poorly handed over. You should leave knowing which setting is everyday operation, what boost is for, and which controls should not be changed casually. If the interface is app-based or connected, ask what happens if the internet fails and whether the unit still runs normally.

7. Evidence of compliance-minded workmanship

The source material behind this brief emphasises that ventilation engineers working with MVHR and PIV systems are expected to install, service and repair systems while ensuring compliance with regulations. For a homeowner, the practical takeaway is to look for disciplined workmanship: labelled settings, recorded results, clear explanations and no guesswork around the final setup.

Common mistakes

Many post-installation complaints come from a short list of avoidable errors. Knowing them helps you spot a weak handover early.

• Treating commissioning as a five-minute finish: Proper setup takes time. A quick power-on and a verbal “all working” is not the same as commissioning.
• No documented readings: Without a commissioning record, later disputes about performance become much harder to resolve.
• Valves altered after balancing: Homeowners, decorators or cleaners sometimes twist valves without realising they are calibrated positions.
• Dirty filters from construction dust: In new-builds and refurbishments, early filter loading can affect airflow before the occupier even moves in.
• Ignoring noise because airflow seems acceptable: A system can hit target airflow and still be uncomfortable if attenuation, mounting or valve setup is poor.
• Poor handover of controls: Occupiers then turn the system down too far or switch it off, which defeats the point of a whole-house ventilation system.
• Confusing MVHR with a cure-all: MVHR helps manage indoor air quality and humidity, but it cannot compensate for leaks, plumbing faults or extreme moisture generation on its own.
• Skipping early follow-up: Small adjustments after occupation are sometimes needed once normal living patterns begin.

If your concern is broader indoor air quality rather than commissioning alone, it is worth thinking about the home as a system: airflow paths, moisture generation, filter condition, heating patterns and user behaviour all interact.

When to revisit

Commissioning is not a one-time topic you forget forever. The best time to revisit your MVHR handover checklist is whenever the inputs change.

Come back to this checklist:

• At first seasonal change: The first autumn or winter often reveals condensation, comfort or control issues that were less obvious in mild weather.
• After the first few months of occupancy: Real-life routines can show whether boost settings and room airflows feel right.
• When filters are first changed: This is a good time to confirm you still understand access, orientation and normal operating sounds.
• After building work or decorating: Dust, moved valves, boxed-in access panels or altered door clearances can affect performance.
• If occupancy changes: More people, more showering, home working or new drying habits can all increase humidity loads.
• When faults, noise or odours appear: Recheck the commissioning record before assuming major equipment failure.
• Before annual servicing: Use the handover information to compare how the system is currently running with how it was originally set.

Your practical next step is simple: create a small handover file for the property. Keep the commissioning sheet, model details, filter sizes, installer contact, control notes and any photos of valve labels together. Then do a fifteen-minute review at the start of each colder season. Test boost, inspect filters, listen for new noises and check whether wet rooms are clearing moisture as expected.

If anything does not match the original handover, arrange a professional review rather than making repeated trial-and-error changes yourself. MVHR works best when the installation, balancing and maintenance are treated as one continuous process. A careful commissioning day sets that process up properly.