Airtightness Is the Critical Factor

Airtightness determines whether MVHR is a viable or necessary specification. At test pressures above 5 m³/h/m² at 50Pa, natural infiltration still provides meaningful background ventilation and a full MVHR system may not be justified. 

Below that threshold, and especially below 3 m³/h/m² for Passivhaus-level builds, mechanical balanced ventilation becomes essential. If you are specifying a heat pump retrofit and the contractor is also upgrading insulation and draught-proofing, ventilation strategy must be addressed at the same time. 

Our guide on MVHR pros and cons is a useful reference when presenting the case to clients or design teams.

Building Type and Occupancy Pattern

Building type also shapes the decision. Residential new builds in England and Wales must comply with Part F and Part L simultaneously, which in practice means MVHR is the most efficient route to compliance in airtight dwellings. Commercial buildings assessed under SBEM follow different ventilation and energy standards, and the business case for each system changes accordingly. 

Schools and healthcare facilities, for example, have IAQ requirements that often make MVHR the primary driver regardless of the heating strategy.

What Are the Key Differences in Cost Between MVHR and a Heat Pump?

Cost is one of the most common questions contractors and specifiers ask when comparing these two systems. The two technologies sit at very different price points, and the total project cost depends heavily on building type, size, and airtightness.

A whole-house MVHR system for a typical new build will generally cost between £2,000 and £5,000 in equipment, with installation adding another £1,500 to £3,000 depending on ductwork complexity. 

Our dedicated guide on MVHR system costs breaks this down by property size and system type. Air source heat pumps typically range from £8,000 to £15,000 installed, with ground source systems costing considerably more.

Running Costs and Energy Efficiency

MVHR units consume very little electricity, typically between 30W and 200W depending on airflow rate and system size. Their primary energy benefit is reducing heating demand by pre-warming supply air, which offsets boiler or heat pump load. 

Heat pumps consume more electricity but replace direct gas or oil consumption, lowering carbon emissions significantly when paired with a low-carbon electricity tariff.

For projects targeting EPC A ratings or Passivhaus certification, combining both systems is common practice. MVHR reduces the heating load to the point where a smaller, lower-output heat pump can be specified, lowering both capital cost and running costs over the building's lifetime.

When Should You Specify MVHR Instead of a Heat Pump?

MVHR is the right specification when ventilation compliance and indoor air quality are the primary drivers. Under Building Regulations Part F, new dwellings and major renovations must meet specific whole-dwelling ventilation rates. In airtight buildings, MVHR is frequently the only practical way to achieve this without energy penalty.

Specify MVHR when:

• The building is being constructed or retrofitted to high airtightness standards (below 5 m³/h/m² at 50Pa)

• Passivhaus, BREEAM, or Part L compliance is required

• The client wants continuous balanced ventilation without draughts or noise from trickle vents

• The project is a school, office, or residential development where indoor air quality is a specification requirement

When Is MVHR Not Enough on Its Own?

MVHR recovers heat from exhaust air but does not generate heat. In a poorly insulated building with high heat loss, MVHR alone will not keep occupants comfortable during a UK winter. You still need a primary heating source, whether that is a gas boiler, heat pump, or district heating connection. 

For projects comparing centralised versus room-by-room approaches, our comparison of MEV vs MVHR is a useful starting point for scoping the ventilation strategy first.

Can MVHR and Heat Pumps Be Used Together?

Yes, and in high-performance buildings this combination is increasingly standard. The logic is straightforward: MVHR reduces heating demand by recovering exhaust heat, and a heat pump supplies the residual space heating and hot water load at high efficiency. Together, they form a low-carbon, low-energy mechanical services package that supports net zero targets.

Many Passivhaus designers specify a compact MVHR unit with a small integrated heating coil connected to a heat pump, distributing warmth through the supply air ductwork rather than a separate wet radiator circuit. This approach simplifies the mechanical services installation and reduces material costs on large residential schemes.

Practical Considerations for Combined Systems

Ductwork coordination is the biggest practical challenge when running both systems in the same building. MVHR supply and extract ducts need to be designed alongside any fan coil units, underfloor manifolds, or radiator pipework to avoid clashes. 

Our guide on MVHR system design covers duct sizing, unit placement, and commissioning requirements in detail, which is essential reading before combining both systems on a single project.

Which System Is Better for Retrofits?

Retrofitting a heat pump is relatively straightforward in structural terms, provided the building fabric is upgraded to reduce heat loss. An MVHR retrofit is more complex because it requires a full balanced duct network, which means running supply and extract ducts to every room. 

In practice, many retrofit contractors install single room heat recovery units as an alternative, particularly in properties where full MVHR ductwork is not feasible.

Single room heat recovery units mount through an external wall, recover heat from individual rooms, and require no central ductwork. They are a practical intermediate solution for bathroom and kitchen retrofits where a whole-house system is not viable. They also support Part F compliance in refurbishments where wet room ventilation is the primary requirement. 

eFans MVHR Units for Trade and Commercial Projects

eFans stocks a full range of heat recovery and MVHR units from Vent-Axia, Zehnder, Elta, and S&P. The range covers everything from single room heat recovery units through to whole house MVHR systems, with heat recovery efficiency up to 93% and airflow rates from 32 m³/h to 900 m³/h.

If you work primarily with one manufacturer, you can browse dedicated ranges including Vent-Axia MVHR units and Zehnder heat recovery systems. Whether you are fitting a single bathroom unit or specifying a centralised system for a multi-unit residential development, the range is built around trade supply with competitive pricing and technical support.

Our guide on the best MVHR systems is useful for narrowing down unit selection for a specific application.

Frequently Asked Questions

Can MVHR replace a heat pump?

No. MVHR recovers heat from exhaust air but cannot generate heat to warm a building. It reduces heating demand by pre-warming incoming fresh air, but a primary heat source such as a heat pump, boiler, or electric heating system is still required to maintain comfortable indoor temperatures during cold weather.

Does MVHR work with underfloor heating?

Yes. MVHR and underfloor heating are commonly paired together, particularly in new builds. MVHR reduces the overall heat load, which means the underfloor system can operate at lower flow temperatures. This improves efficiency when the heat source is a heat pump, as lower flow temperatures produce a higher COP.

Is a heat pump required for Passivhaus certification?

No, a heat pump is not a Passivhaus requirement, though it is commonly used. Passivhaus certification requires that the building's specific space heating demand does not exceed 15 kWh/m² per year. MVHR is effectively mandatory under Passivhaus because the airtightness standard makes mechanical balanced ventilation essential, but the heating source can be any low-energy system.

How do you size an MVHR system relative to a heat pump?

Size the MVHR system first based on whole-dwelling ventilation rates required under Part F or the Passivhaus Planning Package (PHPP). Once the MVHR heat recovery contribution is factored in, the residual heat load can be calculated and used to size the heat pump. Oversizing either system reduces efficiency and increases capital cost unnecessarily.

Do MVHR systems affect heat pump efficiency?

MVHR systems improve heat pump efficiency indirectly. By recovering heat from exhaust air and pre-warming supply air, MVHR lowers the building's heat loss and reduces the demand placed on the heat pump. A lower heat demand allows the heat pump to operate closer to its design COP, particularly during mild weather, resulting in lower running costs over the heating season.

Is MVHR classed as a ventilation system or a heating system for building regulations purposes?

MVHR is classified as a ventilation system under Building Regulations Part F. It is assessed for compliance with whole-dwelling ventilation rates, not as a heating appliance. However, its contribution to reducing heat loss is recognised under Part L energy compliance calculations through the specific fan power (SFP) and heat recovery efficiency inputs used in SAP or SBEM assessments.