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MVHR provides a golden opportunity

May 2013 Energy Efficiency | Comments Off on MVHR provides a golden opportunity
MVHR provides a golden opportunity

With housebuilders facing tough efficiency goals in new build properties there is a great opportunity for electrical contractors to install Mechanical Ventilation with Heat Recovery (MVHR). Ian Mitchell explains how ventilation is central to improving a home’s Dwelling Carbon Dioxide Emission Rate, as well as household comfort and cutting energy bills.

With the Government keen to cut UK carbon emissions, housebuilders have been striving to improve the efficiency of homes in tricky trading conditions. As the efficiency of new homes improves, it becomes more difficult to shave off extra points to improve a property’s Dwelling Emission Rate (DER).

At the same time, as buildings become more air tight and thermally efficient it becomes increasingly important to ventilate effectively and efficiently to ensure good indoor air quality. This is a tough juggling act, but it is set to further drive the adoption of continuous centralised Mechanical Extract Ventilation and Mechanical Ventilation with Heat Recovery (MVHR), so creating an opportunity for electrical contractors.


The latest revisions to Part L and Part F of the Building Regulations have already resulted in a shift away from the use of intermittent fans in favour of more energy efficient continuous ventilation.

These factors are driving the adoption of MVHR which now boasts a significant foothold in new UK housing. According to the Zero Carbon Hub VIAQ (Ventilation and Indoor Air Quality) Task Group Interim report, over 18,000 MVHR units were sold in 2010-11. The report forecasts that MVHR is set to dominate new sustainable homes post-2016. This is because MVHR is beneficial in terms of the SAP assessment and ventilation heat loss is minimised. The sales quantity for 2012 for MVHR has already risen to over 24,000.

Recent advances in energy efficient MVHR technology, in particular those with high thermal efficiency and low specific fan power, mean that these systems can demonstrate a net cost saving over their lifetime. A unit ventilating a three bedroom house may consume 20W, which equates to an annual running cost of £22.77 at 13p kW/hr. Energy recovered may be ten or twenty times this figure.

In addition, new homeowners will also appreciate the ‘fresh air’ benefits of MVHR which cannot be underestimated. MVHR can reduce excessive moisture in the air, combating condensation and subsequent mould growth, thus saving households money on maintenance and decoration in both the long and short-term.

The improved indoor air quality also offers the duel health benefits of reducing microscopic fungal growth and eliminating the conditions in which house dust mites thrive, both of which are linked to allergic reactions and asthma.


Another benefit of MVHR is thermal comfort. Low energy, highly insulated modern homes are now causing a new comfort challenge as the homes are at risk of overheating in summer. This is a more serious problem than keeping homes warm in winter.

Not only is overheating a potential health risk, but the discomfort of living in an overheated house could lead to households offsetting the energy efficiency of their home by using portable air conditioning units. One strategy to deal with overheating is to fit MVHR.

The term ‘Mechanical Ventilation with Heat Recovery’ does the technology a disservice; instead it should be known as ‘energy recovery’. An MVHR system seeks to maintain the target temperature of the internal environment, therefore in summer the unit recovers ‘coolness’. This can prevent dwellings overheating by pushing the internal peak temperature later in the day. If overheat point is reached, more sophisticated MVHR units can use a summer-bypass to accelerate cooling by taking advantage of lower external air temperatures.

Dwelling Carbon Dioxide Emission Rate (DER)

As well as thermal comfort, quiet operation is essential to household comfort. Using a Competent Person to install MVHR will help a system achieve optimum performance, providing good indoor air quality, high efficiency and silent operation.

Selecting a Competent Person to install an MVHR system not only helps to ensure a system is performing to its optimum efficiency it also offers housebuilders a valuable SAP benefit that reduces a home’s DER. This offers electrical contractors a potential raft of work if they train to become a Competent Person.

Currently, conservative ratings are applied in SAP calculations to the performance figures of centralised Mechanical Extract Ventilation (MEV) and MVHR because specific fan power (SPF) can increase if a system is not installed correctly, affecting efficiency. The Government therefore applied ‘in use’ performance penalties to the technology’s laboratory data results in initial SAP calculations to compensate, adding a 40% specific fan power penalty to MVHR and 30% to MEV systems.

Competent Persons

Following changes to SAP, since January 2012 a housebuilder can choose to have ventilation installed by a competent person resulting in a reduction of these penalties.

Under the scheme, a trained electrical contractor, who must be a member of a Competent Person Scheme, ensures that an installation is in line with competency requirements and complies with or at least meets the performance laid out in the original system design. The installation details are then captured on a commissioning sheet which is submitted to Building Control and the SAP assessor. This information can reduce MVHR penalties from 40% to 30% and MEV from 30% to 25%, enabling housebuilders to achieve a better value for their spend in SAP.

Meanwhile, for electrical contractors becoming a Competent Person offers an opportunity to add value and differentiate themselves from their competitors while winning work from developers and housebuilders.

To help deliver this, manufacturers and trade associations have been active in establishing a training package through BPEC and helping to train contractors. Installers interested in this training course are able to take it at a number of training providers around the country.

BPEC course

For instance, there is the BPEC course. Designed to meet the requirements in the Domestic Ventilation Compliance Guide 2010 for the installation, inspection, testing, commissioning and provision of information for Fixed Domestic Systems for both new and existing residential buildings, the course runs over two days and gives candidates both theoretical and practical training including the commissioning of a working MVHR system.

Once candidates have completed the course and enrolled with a Competent Person Scheme, they will be able to add value and differentiate themselves from their competitors helping them to win work from developers.

As we move towards the zero carbon homes target and the Government continues to try to lower the carbon emissions generated from the built environment, the drive for greater energy efficiency will continue. As a result MVHR systems will accelerate in growth and installers that are able to fit them competently will be in high demand since it will be increasingly important to prove homes are built as designed to ensure high performance.

To be eligible for the course, installers must hold or be taking a formal qualification such as N/SVQ level 3, or have a number of years’ experience in heating, electrical or ventilation installation. To find out more, or to apply for,Vent-Axia’s course, visit the Training section at