MVHR Heat Recovery Ventilation

MVHR ductwork is embedded into the fabric of the building and would be very disruptive to have to replace, so it is worth investing in a high quality system from the outset. We recommend galvanised steel spiral wound rigid ducting for our systems, designed to last the lifetime of the building.

We carefully calculate air flow rates of our systems to each room and look to select MVHR units that have constant volume flow fans. Ductwork airtightness is important to ensure that the designed air flow is delivered to the rooms. Air leakage is designed out through use of rigid steel round ducting systems with airtight joints. By minimising air leakage we reduce air speeds within the system, helping ensure lower energy consumption and noise levels.

By designing the ducting to minimise air resistance and to suit the air flow requirements in each part of the building, our designs deliver the appropriate amount of fresh air to each room in the house while minimising the energy required to move the air.

We offer a wide range of units from manufacturers including Zehnder and SALDA, to suit all projects and specifications. We help you choose a quality MVHR unit to suit the ventilation demands of the building and to achieve optimal heat recovery efficiency.

Condensation within an MVHR system could cause damage to ductwork, the unit or the building fabric. We design out potential problems by paying attention to the ductwork detailing and insulation requirements where temperature and humidity differences will cause condensation, either inside or outside the duct.

It is essential that MVHR systems run quietly, especially within already quieter well-insulated buildings. Unlike the majority of our competitors, we model the acoustics of our systems so that we choose the right size of sound silencer for each duct run. We specify primary attenuators (silencers) to reduce noise generated by the MVHR unit fans, and secondary ‘cross talk’ attenuators, to reduce voice transmission between rooms. The cross talk attenuators also offer further sound suppression for duct generated noise. Duct sizes in our designs are typically larger than those specified by other companies, helping to keep air speeds low, thus minimising duct generated noise. As a result, we design our MVHR systems to have noise levels of no more than 30 dB(A) at the extract valve and no more than 25 dB(A) at the supply valves.

We offer telephone support for installers and supply clearly labelled ducting drawings to facilitate step by step installation.

It is critical that the system is correctly commissioned in order to maximise comfort and energy efficiency. 21°s optional commissioning service also offers a valuable check on the installation process and functioning of the MVHR system.

21° has a national reputation for designing high quality MVHR systems for Passivhaus and low energy builds, from one-off houses to large social housing schemes and community centres.