Choosing between PIV and MVHR comes down to three things: the airtightness of the building, the project budget, and what the ventilation system needs to achieve. PIV suits retrofit projects in older, leaky properties where a cost-effective mould prevention measure is needed.
MVHR is the right call for new builds and deep retrofits where airtightness is high, energy recovery is a priority, and Building Regulations Part F System 4 compliance is the target.
How Do PIV and MVHR Compare Across Key Project Criteria?
Rather than treating this as a binary choice, most specifiers benefit from working through the key criteria methodically. The table below provides a structured comparison to support that process.
| Criterion | PIV | MVHR |
|---|---|---|
| Suitable building airtightness | Low to medium leaky fabric | High airtightness required (under 5 m³/h.m² at 50 Pa) |
| Part F compliance (System) | Does not satisfy Part F alone | System 4 compliant |
| Heat recovery capability | None | 70 to 93% thermal efficiency |
| Installation disruption | Low | High in retrofit; low in new build |
| Typical installed cost per unit | Low | Moderate to high |
| Running costs | Low | Low to moderate |
| Wet room extract provided | No | Yes (supply and extract) |
| Best suited to | Retrofit, social housing, rental stock | New build, deep retrofit, high-performance spec |
| Maintenance requirement | Filter check annually | Filter and heat exchanger servicing required |
MVHR vs PIV: Which System Is Better for Your Project?
The honest answer is that neither system is universally better. They solve different problems, suit different building types, and perform well under different site conditions.
Picking the wrong one for the project context means you either end up with an expensive MVHR installation that haemorrhages heat through an uncontrolled fabric, or a PIV system that cannot adequately address moisture at source in a tightly specified new build. The decision framework below helps you work through the key variables.
Airtightness Is the Starting Point
MVHR only performs as intended when the building envelope is sufficiently airtight. The system works by controlling every cubic metre of air entering and leaving the property, recovering heat from the extract air before it leaves the building. If the fabric leaks uncontrolled air at a high rate, that heat recovery is bypassed and the efficiency figures quoted on the unit datasheet become meaningless in practice.
The generally accepted target for effective MVHR performance is an air permeability of 5 m³/(h.m²) at 50 Pa or below, with most MVHR designers recommending 3 m³/(h.m²) or lower for optimal efficiency.
New build properties constructed to current Part L standards will typically meet this threshold. Older social housing, pre-2000 commercial conversions, and most solid wall properties will not, without substantial fabric improvement works carried out in tandem.
PIV, by contrast, performs better in buildings with some background infiltration. The system introduces a small positive pressure from a central supply point, and that pressure drives stale, moist air out through background ventilators and natural leakage paths. In a highly airtight building, PIV cannot distribute air effectively and the positive pressure it creates can cause issues rather than solve them.
For a practical explanation of how airtightness interacts with ventilation system selection and Part F compliance, our guide to Building Regulations Part F ventilation requirements sets out the framework clearly.
Project Type and Scale
For new build residential properties, MVHR is the dominant choice at the top of the market and increasingly the standard specification in schemes targeting EPC Band B and above. It satisfies Part F System 4 requirements, contributes to Part L compliance through its specific fan power (SFP) rating and heat recovery efficiency, and supports SAP calculation targets where heat loss through ventilation is a limiting factor.
For developers and main contractors, understanding the full cost picture for MVHR at the outset of a project prevents budget surprises at the M&E procurement stage.
PIV is predominantly a retrofit tool. It has been widely deployed across social housing stock and privately rented properties where condensation and mould are recurring complaints. It does not provide extract ventilation at moisture sources, and it does not satisfy Part F requirements for wet room extract on its own.
However, as a complementary measure deployed alongside adequate kitchen and bathroom extract fans, it is a cost-effective way to improve whole-dwelling air quality in properties where full MVHR installation is not viable.
For mixed-use schemes or multi-unit residential developments, the choice between centralised and decentralised strategies adds another layer. A single centralised MVHR unit serving one apartment is straightforward. Specifying MVHR across a multi-storey block with no dedicated plant room space is considerably more complex and may make individual PIV units a more practical proposition for the common areas.
Energy Performance and Heat Recovery
This is where MVHR wins clearly. A well-designed MVHR system recovers 70 to 93% of the heat from extracted air and transfers it to the incoming fresh supply. Over a full heating season in a UK climate, this represents a material reduction in space heating demand. For projects where the client is targeting low energy bills, net zero carbon compliance, or Passivhaus-adjacent performance, MVHR is not optional.
PIV does not recover heat. It introduces outdoor air that must be heated to room temperature by the existing heating system. In a loft-mounted PIV installation, the unit draws on the relatively warmer loft air temperature during winter, which reduces the heating penalty compared to drawing directly from outside, but this is not comparable to active heat recovery.
For clients sensitive to running costs or retrofit projects under the Social Housing Decarbonisation Fund, understanding the efficiency gains that MVHR heat recovery delivers over the system lifetime is an important part of the business case conversation.
Installation Complexity and Disruption
MVHR requires a full duct distribution network, a plant unit with adequate access for filter maintenance, and careful commissioning to balance airflow across all supply and extract terminals.
In new builds, the ductwork is coordinated at first fix and the system is designed into the building from the outset. In retrofit, routing ducts through existing floor structures, ceilings, and walls to reach every wet room and habitable space involves significant disruption and cost.
PIV installation is comparatively simple. A loft-mounted unit requires one supply outlet into the landing or hallway. A wall-mounted flat unit requires an external wall penetration and a power supply. Installation is typically completed within a few hours, and the disruption to occupants is minimal. For housing providers or landlords managing occupied stock, this distinction is practically significant.
Getting MVHR ductwork design right from the start is critical to system performance. Poor layout decisions made at design stage are expensive to correct post-installation. Our MVHR system design guide covers the key design principles contractors and M&E engineers need to get right.
What Are the Costs of PIV vs MVHR?
Cost is frequently the deciding factor in PIV versus MVHR conversations, particularly across social housing and private rented sector projects where capital budgets are tightly controlled.
PIV System Costs
A standard residential PIV unit costs between £150 and £400 for the unit itself, with installation typically adding £100 to £250 for a straightforward loft-mounted installation. Wall-mounted flat units sit at a similar price point. Total installed costs per dwelling are generally in the range of £300 to £650. Running costs are low, with most units drawing between 5 and 25 watts in normal operation.
MVHR System Costs
Whole house MVHR installation costs vary considerably depending on property size, ductwork complexity, and unit specification. For a three-bedroom new build, a typical MVHR installation including unit, ductwork, terminals, commissioning, and labour sits in the range of £2,500 to £5,000.
In retrofit contexts, costs rise significantly due to the labour involved in routing ductwork through an existing structure. Single room heat recovery units, which provide local heat recovery ventilation for a single space, offer a more accessible entry point at £200 to £600 installed.
How Does Part F Compliance Differ Between PIV and MVHR?
PIV alone does not satisfy Building Regulations Part F. Approved Document F defines four ventilation systems for dwellings, and PIV does not correspond to any of them as a standalone solution. It has no defined system category under Part F, no minimum airflow rate requirement, and no commissioning protocol within the document.
This does not mean PIV is prohibited, but it does mean that properties fitted only with PIV require additional extract ventilation in kitchens and bathrooms to meet the minimum requirements of Part F System 1 or System 3.
MVHR, when designed and installed to meet the supply and extract airflow rates in Part F Table 1.1 and commissioned in accordance with the Domestic Ventilation Compliance Guide, satisfies Part F System 4 fully.
The commissioning notice required under the 2021 Part F revision must be submitted to the relevant building control body, and tenants must receive a ventilation user guide. This documentation trail is particularly important for housing providers subject to HHSRS inspections and Awaab's Law compliance assessments.
Is MVHR Suitable for Retrofit Projects?
MVHR can be installed in retrofit, but the conditions that make it viable are not present in most existing UK housing stock without additional investment. The building needs to achieve or be improved to achieve adequate airtightness, there needs to be a practical route for duct distribution, and there needs to be a location for the central unit with adequate clearance for filter access and maintenance.
In high-specification retrofit projects, whole house MVHR is achievable and increasingly specified. Passivhaus retrofit, EnerPHit-standard projects, and deep fabric improvement programmes under the Great British Retrofit scheme are all contexts where MVHR is being delivered into existing properties. The key is integrating the MVHR design with the fabric improvement works from the outset, not retrofitting the ventilation as an afterthought once the building work is complete.
For projects where full MVHR is not viable but some degree of heat recovery is still desirable, single room heat recovery units provide a practical intermediate option. These through-the-wall units serve individual rooms and require no duct distribution network. If you are also considering how MVHR compares to heat pump systems in a retrofit context, our MVHR vs heat pump guide explores the relationship between the two technologies clearly.
What Are the Noise Considerations for MVHR Compared to PIV?
Noise is a common concern raised by clients and occupants when MVHR is specified. A well-designed and properly commissioned MVHR system should be inaudible in habitable rooms. The noise risk with MVHR comes from two main sources: mechanical noise from the unit itself, and air velocity noise from incorrectly sized ductwork or poorly positioned terminals. Both are avoidable with correct design and commissioning practice.
PIV units are generally quieter in practice because they operate at lower static pressures and serve a single supply point. For occupied social housing or rental properties where tenant complaints about noise are a risk, PIV's simpler operation profile carries a practical advantage. That said, specifying a quality MVHR unit from a reputable manufacturer and designing the ductwork correctly eliminates noise as a concern in new build and planned major works contexts.
Where to Source MVHR Units for Your Project
eFans stocks a full range of heat recovery and MVHR units from Vent-Axia, Zehnder, Elta, and S&P, covering applications from single room installations through to whole house systems. Units in the range achieve heat recovery efficiency up to 93% and airflow rates from 32 m³/h to 900 m³/h, giving specifiers the flexibility to match the unit to the project demand precisely.
You can browse the full range by category below:
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Heat recovery and MVHR units (full range)
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Single room heat recovery units for individual room applications
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Whole house MVHR systems for full property ventilation
All orders include free UK delivery, and the eFans team is available to support product selection across projects of any size. For a wider look at how MVHR compares against other continuous ventilation strategies, our MEV vs MVHR guide and the MVHR vent positioning guide are both worth reviewing before finalising your specification.
Frequently Asked Questions
Can PIV and MVHR be used together in the same property?
In practice, PIV and MVHR serve the same function of managing whole dwelling ventilation and should not be installed together in the same property. Running both systems simultaneously creates conflicting pressure regimes that will undermine the performance of both. If MVHR is installed and commissioned correctly, there is no role for PIV. Where PIV is already in place and an upgrade to MVHR is planned, the PIV unit should be decommissioned and removed as part of the MVHR installation project.
Does PIV help with damp and mould in social housing?
PIV can help reduce condensation and mould in social housing properties when the underlying cause is insufficient whole dwelling ventilation and background infiltration. By introducing a small, continuous flow of drier external air and creating a slight positive pressure, PIV encourages the movement of moist internal air out of the dwelling.
However, PIV is not a remedy for structural damp, rising damp, or penetrating damp, and it does not substitute for adequate extract ventilation in kitchens and bathrooms. Housing providers should treat PIV as one component of a broader damp and mould prevention strategy rather than a standalone fix.
Does MVHR work with an air source heat pump?
Yes, and the combination of MVHR and an air source heat pump (ASHP) is increasingly standard in new build properties targeting low energy performance. MVHR reduces the ventilation heat loss that the heat pump must compensate for, improving the overall thermal efficiency of the dwelling. The heat pump handles space heating and hot water, while MVHR manages air quality and reduces the heating load on the building.
Both systems require careful coordination at the design stage to ensure they complement rather than conflict with each other in the energy model. Our MVHR benefits guide explores how MVHR contributes to the wider low carbon building strategy in more detail.
What maintenance does a PIV system require compared to MVHR?
PIV systems require minimal maintenance. The main task is an annual check and replacement of the inlet filter, which prevents dust and debris from being distributed into the dwelling. Some units include a filter change indicator. MVHR systems require more regular attention: filters on both the supply and extract sides typically need checking every three to six months and replacing every six to twelve months depending on local air quality and occupancy.
The heat exchanger core should be inspected annually and cleaned if necessary. Duct terminals should be kept clear of obstructions. Both manufacturers and CIBSE Commissioning Code A recommend maintaining a service record for MVHR installations, particularly in social housing and commercial contexts where compliance evidence may be required.
Is MVHR a requirement under Building Regulations for new build homes?
MVHR is not a mandatory requirement under Building Regulations, but it is the highest-performing of the four ventilation systems defined under Approved Document F and the one that most consistently satisfies Part L energy efficiency requirements in highly airtight new build dwellings.
In practice, the combination of high airtightness standards required under Part L and the ventilation adequacy requirements of Part F means that MVHR is the logical solution for most new build residential properties. Developers and contractors who try to meet high airtightness targets with passive or intermittent ventilation frequently encounter difficulties satisfying both Part F airflow requirements and Part L energy targets simultaneously.