What Does MVHR Actually Do?

 

An MVHR system continuously removes stale, humid air from areas such as:

• kitchens

• bathrooms

• utility rooms

• WCs

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At the same time, it supplies fresh filtered air to spaces such as:

• bedrooms

• living rooms

• studies

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Before the outgoing air leaves the property, much of its heat is transferred to the incoming fresh air through a heat exchanger.

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The two air streams remain separate, but some of the heat is recovered rather than simply being lost outside.

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Why Do Homes Need Better Ventilation?

 

Everyday living produces moisture.

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Cooking, showering, drying clothes and simply occupying a home all add water vapour to the air.

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If ventilation is inadequate, that moisture can contribute to:

• condensation

• mould

• stale air

• excessive humidity

• poor indoor air quality

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Older homes often relied heavily on natural ventilation and uncontrolled draughts.

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Once insulation is improved and windows are replaced, the home can become considerably more airtight.

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That is good for energy efficiency, but it can make controlled ventilation much more important.

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When Does MVHR Make Most Sense?

 

MVHR tends to become particularly interesting where a property is undergoing substantial energy-efficiency work.

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For example:

• major refurbishment

• whole-house insulation

• new high-performance windows

• improved airtightness

• loft conversion

• extension

• low-energy renovation

• major heating upgrade

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In these situations, ductwork may be easier to accommodate and the overall building can be designed to work with the ventilation system.

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MVHR can therefore make much more sense as part of a planned refurbishment than as an isolated retrofit after everything else has been completed.

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Is MVHR Suitable for an Existing House?

 

It can be, but retrofitting MVHR into an existing property can be challenging.

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The main issue is usually ductwork.

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Supply and extract ducts need to travel between rooms and the central MVHR unit.

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In an existing house, this may require routes through:

• ceilings

• loft spaces

• cupboards

• floor voids

• boxing

• service risers

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A system that is simple to install during a major renovation may become considerably more disruptive after the home has been decorated and finished.

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That is why timing matters.

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Does the House Need to Be Airtight?

 

MVHR works best when the building is reasonably airtight.

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If the property has large amounts of uncontrolled air leakage through gaps, chimneys, floors, windows and other parts of the building fabric, the benefits of a carefully controlled ventilation system can be reduced.

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This does not necessarily mean the home needs to achieve Passivhaus levels of airtightness.

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But it does mean that MVHR should be considered alongside:

• draught reduction

• insulation

• window upgrades

• sealing around services

• unused chimneys

• other areas of uncontrolled air movement

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Improving one without considering the other can reduce the benefit of the overall investment.

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Can MVHR Help With Condensation and Mould?

 

Effective ventilation can play an important role in controlling indoor humidity.

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By continuously extracting humid air from bathrooms, kitchens and other moisture-producing areas, MVHR can help reduce the conditions that contribute to condensation and mould.

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However, it is important to understand the cause of the problem.

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Mould may also be associated with:

• cold surfaces

• thermal bridges

• inadequate insulation

• water penetration

• leaks

• heating patterns

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Installing ventilation without understanding the wider problem may therefore not provide the complete solution.

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Can MVHR Save Energy?

 

The heat-recovery element of MVHR is designed to reduce the amount of heat lost through ventilation.

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Rather than throwing warm indoor air directly outside, much of its heat is transferred to the incoming fresh air.

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This can reduce ventilation-related heat loss.

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However, the financial benefit depends on the building, system efficiency, airtightness and running costs.

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MVHR should therefore be considered primarily as part of a strategy for ventilation, indoor air quality and energy efficiency, rather than simply as a device for reducing bills.

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What About Running Costs and Maintenance?

 

MVHR systems use electricity to operate their fans.

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They also require ongoing maintenance.

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This normally includes:

• cleaning or replacing filters

• keeping external terminals clear

• checking air valves

• occasional servicing

• maintaining accessible ductwork where required

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Filters are particularly important because they protect the system and help maintain good indoor air quality.

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A poorly maintained MVHR system will not perform as intended.

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MVHR or Extractor Fans?

 

For some homes, a full MVHR system may be unnecessary.

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Other ventilation strategies may include:

• upgraded bathroom extract fans

• kitchen extraction

• continuous mechanical extract ventilation

• demand-controlled ventilation

• decentralised heat-recovery units

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The right solution depends on how extensive the energy improvements are and what the property actually needs.

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Installing the most sophisticated system is not automatically the best answer.

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MVHR and Insulation Should Be Planned Together

 

This is one of the most important considerations.

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If you are planning to substantially improve:

• wall insulation

• roof insulation

• floor insulation

• windows

• airtightness

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you should also think about how the property will be ventilated afterwards.

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As uncontrolled draughts are reduced, deliberate ventilation becomes increasingly important.

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This is why MVHR belongs within a whole-home energy strategy, rather than being treated as a standalone gadget.

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Should MVHR Be Installed Before or After Other Improvements?

 

Ideally, the ventilation strategy should be decided before major refurbishment work begins.

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That allows duct routes, ceiling voids and equipment locations to be incorporated into the project.

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It may also influence other decisions about:

• insulation

• ceilings

• lighting

• heating

• air conditioning

• room layouts

• loft use

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Planning MVHR late can lead to compromises, unnecessary boxing or additional disruption.

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What If You Are Also Considering a Heat Pump?

 

MVHR and heat pumps are often considered as part of the same low-energy renovation.

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They perform different jobs.

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The heat pump provides heating.

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MVHR provides controlled ventilation while recovering heat from outgoing air.

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The benefit of both systems can be greater when the home itself has been properly insulated and heat loss has been reduced.

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This is another reason to consider the building as a complete system rather than buying individual technologies independently.

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Grants and Financial Support

 

Financial support for home energy improvements changes over time, and eligibility varies between different schemes.

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Some grants may focus primarily on insulation, heating or renewable technologies rather than standalone ventilation systems.

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However, MVHR may form part of a wider package of improvement where other recommended measures qualify for assistance.

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As part of your Green Home Assessment, APN Green Homes considers the current grants, incentives and financial support relevant to the overall improvements recommended for your property.

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This can help you decide what work should be undertaken and in what order.

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Do Not Start With the Equipment

 

An MVHR supplier naturally looks at your home from the perspective of installing an MVHR system.

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APN Green Homes takes a different approach.

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We do not start with the ventilation unit. We start with the property.

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The question is not simply:

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Can MVHR be installed?

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It is:

Does MVHR make sense for this home, at this stage of its improvement, and is it the best ventilation strategy for the money being spent?

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Find Out Before You Spend

 

Before committing to an MVHR installation, it is worth understanding:

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• Is my home airtight enough for MVHR to work effectively?

• Can the ductwork be installed practically?

• Should insulation or airtightness be improved first?

• Would another ventilation system be more appropriate?

• Could MVHR help with condensation and humidity?

• How will it work with a heat pump or other heating system?

• Should it be installed as part of my refurbishment rather than afterwards?

• What financial support may apply to the wider energy improvements?

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Get Independent Whole-Home Advice

 

APN Green Homes provides independent Green Home Assessments for homeowners planning significant energy improvements.

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Your personalised report can consider:

• ventilation

• MVHR

• airtightness

• condensation risk

• insulation

• windows and glazing

• heating

• heat pumps

• cooling

• solar and battery storage

• grants and incentives

• priorities for future improvements

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The aim is simple:

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to help you understand whether MVHR is appropriate for your home, when it should be installed, and how it fits into the wider energy strategy before you commit.

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Green Home Assessment — £495 + VAT

 

Get the plan before you start spending.