HEATING, VENTILATION & SERVICES 61


AN AIRTIGHT CASE FOR MVHR IN NEW HOMES


Ruth MacEachern of EnviroVent explains why mechanical ventilation with heat recovery systems are the key to improving energy effi ciency in modern homes.


H


ousebuilders are building to ever more stringent Building Regulations requirements for


airtightness, however to ensure an energy effi cient home with a good level of indoor air quality, mechanical ventilation with heat recovery is essential. Mechanical Heat Recovery entilation (MHR) is effective in extracting excess moisture in the air to prevent humidity build-up and condensation in wet rooms like bathrooms and kitchens, yet by also recovering the heat from the outgoing stale air, it reduces the energy demands of the home.


HEAT RECOVERY & ENERGY SAVING MHR systems can be the answer to making an airtight home energy effi cient, whilst achieving high levels of indoor air quality.


These systems are designed to recover the heat from the outgoing air and transfer it to the incoming fresh air. This heat exchange process means MHR systems can signifi cantly reduce the energy required to heat or cool the incoming air, resulting in lower energy consumption and reduced carbon emissions. Heat recovery systems can typically recover about -9 of the heat in exhaust air – they can also signifi cantly improve the energy effi ciency of buildings.


Overheating can be mitigated with the summer bypass function measuring indoor and outdoor temperatures and adjusts the ventilation speed accordingly. However, it is important to fi rstly consider the main fabric of the building, orientation and shading to avert any potential overheating issues. While mechanical ventilation systems offer numerous benefi ts, their integration in airtight homes comes with its own set of challenges. Maintaining the integrity of the building envelope is crucial as any unintended air leakage can compromise the performance of the mechanical ventilation system. Typically in newly constructed buildings, duct leakage can range


from 2-40 (Source Department of Energy Report), which is unacceptable for high-performance buildings such as Passivhaus designs. To address this challenge, it is essential to ensure correct sealing of ductwork, which should minimise leakage to less than  of the system’s air volume. This requires a combination of effective design, quality installation and rigorous testing to achieve optimal airtightness.


Insulation and seals should be inspected to ensure they are intact and there are no gaps or leaks that could compromise the airtightness inherent to the Passivhaus concept. Carrying out regular checks and maintenance is particularly important with Passivhaus ventilation systems.


BUILDING THE HOMES OF THE FUTURE For housebuilders, the integration of MHR supports the requirement to build


homes that are not only compliant with current standards but are future-proofed to address the evolving requirements, such as the Future Homes and Building Standard (FHBS). The latest Building Regulations require that all new build homes need to be future-proofed with low carbon heating and world-leading levels of energy effi ciency. They set out the ambitious target of a 0 reduction in carbon emissions for new dwellings as an interim target, up to the introduction of the Future Homes and Building Standard in 202.


Achieving this requires a comprehensive approach that extends beyond traditional insulation methods. As this standard sets a higher benchmark for energy effi ciency, incorporating highly effi cient MHR systems has become essential. As technology advances, it further strengthens the position of MHR systems


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