What it is and how it works

Mechanical ventilation with heat recovery runs two air paths through one unit. Stale air is pulled out of the parts of the building that produce it, such as kitchens, toilets, changing rooms and meeting rooms. Fresh air is drawn in, filtered and delivered to the places people sit and work. Inside the unit the two streams pass through a heat exchanger without mixing, so the outgoing air gives most of its heat to the incoming air on the way past.

The result is a building you can ventilate properly in February without paying to heat outdoor air from scratch.

In a commercial building the unit is rarely the interesting part. The ductwork, the void it has to fit in, the acoustic treatment and the commissioning are what separate a system people never notice from one they complain about.

What the regulations ask for

Ventilation. Approved Document F Volume 2 covers buildings other than dwellings, and the current edition came into force on 15 June 2022. It is the document your airflow rates are measured against, and it is unchanged by the 2026 round of amendments.

Energy. That 2026 round does change Approved Document L. The Future Homes and Buildings Standards amendment regulations come into force on 24 March 2027, with higher-risk building work following on 24 September 2027. The 2026 editions update Approved Document L Volumes 1 and 2 and Approved Document F Volume 1, which is dwellings. For non higher-risk work there is transitional protection where a building notice, initial notice or full plans application was given before 24 March 2027 and the work begins before 24 March 2028.

The equipment itself. Non-residential ventilation units placed on the market in Great Britain have had to meet ecodesign requirements since 1 January 2018. A bidirectional unit must include heat recovery, and the minimum thermal efficiency is 73%, or 68% for a run-around system.

Figures reviewed 20 September 2026.

Where commercial MVHR goes wrong

It is worth being blunt about this, because the failures are predictable and all of them are decided before installation starts.

The void. Ceiling void depth is fixed by the building. Ducts sized to fit a void that is too shallow run too fast, and air moving too fast is noise. We measure the voids at survey and size from what is actually there.

The commissioning. A system is not finished when it is installed. It is finished when each grille has been measured, adjusted and recorded against the design figure. Systems handed over without that are the ones that feel stuffy in one room and draughty in the next.

The filters. A commercial system draws a great deal of air, and its filters load up. Whoever maintains the building needs to know what the filters are, where they are and how often they change. That goes in the handover pack rather than being left to be discovered.

The demand. A building ventilated at full rate all day when it is a third occupied wastes both fan power and heat. Carbon dioxide sensing lets the system follow the occupancy instead, and on a building with meeting rooms and variable attendance it repays itself.

Ventilation with the rest of the building

Ventilation and cooling are separate jobs and get confused constantly. MVHR brings fresh air in and keeps the heat. Commercial air conditioning changes the temperature of air already in the room. A building with a heat problem needs the second one, and fitting the first instead will disappoint. Most buildings that need either end up needing both, sized against each other rather than separately. Where fan power is a concern, the standing electrical load is a good candidate for solar PV, because it runs through exactly the hours the roof is generating. Our design and consultancy work sets the two against each other before anything is specified.

Pros and cons

Pros

Meets the ventilation requirement of the building regulations without opening windows on a cold day
Keeps most of the heat from the outgoing air, so ventilating the building stops fighting the heating
Non-residential heat recovery units sold in Great Britain must hit at least 73% thermal efficiency, or 68% for run-around systems
Filters the incoming air, which matters on a main road or near a car park
Demand control from carbon dioxide sensors runs the fans hard only when the building is full
Removes moisture and cooking smells at source in kitchens, changing rooms and wet areas

Cons

It needs ductwork to everywhere, which is straightforward in a new build or a strip-out and difficult in an occupied building
The fans run continuously, so there is a standing electrical cost the old system may not have had
Filters need changing on a schedule, and a system whose filters are ignored stops working properly
Ceiling void depth is often the real constraint, and it is fixed before you start
A system that is not commissioned and balanced properly will be noisy, uneven or both
The standard rate of VAT applies to commercial premises

Who it suits

Offices being refurbished or fitted out, where the ceilings are coming down anyway
New build commercial units and light industrial buildings
Buildings being made airtight as part of an energy retrofit
Schools, nurseries and surgeries, where air quality is part of the brief
Any building where opening the windows for air means heating the street

What is included in a Bespoke installation

A survey of the building, the ceiling voids, the plant space and the intake and discharge positions
A ventilation design with airflow rates room by room, set against Approved Document F Volume 2
Duct routes, sizing and acoustic treatment worked out before anything is ordered
Supply and installation of the unit, ductwork, attenuators, grilles and controls
Electrical connection, and integration with carbon dioxide or occupancy sensing where it is wanted
Commissioning and balancing with measured airflow readings recorded and handed over

Frequently asked questions

Which building regulations apply to ventilation in a commercial building?

Approved Document F Volume 2 covers buildings other than dwellings. The current edition came into force on 15 June 2022. The 2026 edition published under the Future Homes and Buildings Standards updates Approved Document F Volume 1, which is dwellings, and Approved Documents L Volumes 1 and 2. So the ventilation guidance for your commercial building is unchanged, while the energy guidance in Approved Document L Volume 2 changes from 24 March 2027.

Does that 2027 date affect a project we are planning now?

It can. The amendment regulations come into force on 24 March 2027, and higher-risk building work follows on 24 September 2027. For non higher-risk work there is transitional protection where a building notice, initial notice or full plans application was given before 24 March 2027 and the work starts before 24 March 2028. A scheme designed now may therefore be built under either set, which is worth settling early rather than late.

How efficient does the heat recovery have to be?

Non-residential ventilation units placed on the market in Great Britain have had to meet ecodesign requirements since 1 January 2018. A bidirectional unit must have a heat recovery system, and the minimum thermal efficiency is 73%, or 68% for run-around systems. Those are floors, not targets, and good units are well above them.

Can we retrofit MVHR into an occupied office?

Sometimes, but the ductwork is the problem rather than the unit. It needs a route to every space and enough ceiling void to run it without crushing the duct into something noisy. Where the ceilings are coming down for a refurbishment it is straightforward. Where they are not, we look at the voids at survey and tell you honestly whether it can be done well.

Will it be noisy?

Not if it is designed for. Noise comes from undersized ducts, too few bends allowed for, no attenuation and a unit placed somewhere with nothing between it and the occupied space. Those are all design decisions, which is why we size ducts and specify attenuators before ordering rather than after a complaint.