MECHANICAL VENTILATION & HEAT RECOVERY
While it’s not strictly a heat source (MVHR recycles warmth from other sources), this type of setup provides an efficient solution for channelling stale air out of your house and introducing a fresh supply. It also extracts and recycles warmth from the outgoing stream, transferring the heat to the incoming flow. The result is a dualpurpose arrangement that can supplement the heating setup in a well-insulated, airtight home, creating a pleasant, predictable environment.
Conventional solutions, such as trickle vents, air bricks and windows offer an uncontrolled form of ventilation. However, the heat exchanger in an MVHR system can recover energy that would otherwise be lost – in general, approximately 90% can be recaptured. To achieve the maximum benefits, this setup should be installed in well-insulated, airtight homes that do not leak energy through weak points in the building fabric.
A fan-powered air-handling unit in the loft or plant room forms the beating heart of the setup. It is hooked up to a network of ducts and extract/supply points throughout the property. Stale air is drawn out of each room – particularly bathrooms and kitchens – and is transferred through a heat exchanger before being channelled outdoors. The warmth is then conveyed into the fresh supply of air, which is introduced to each zone via the ducting.
It’s important to engage a reputable engineer to design and fit your system, as it must be properly matched to your dwelling. They’ll calculate the correct output for appliance, as well as planning the ducting runs and terminal locations. Pipes should be configured in the shortest, straightest runs possible to ensure good airflow and minimise heat loss.
If possible, try to factor MVHR into your house design from the initial stages of the project. Trying to implement the setup as an afterthought can lead to an installation that is more complex than necessary, and sometimes less efficient as a result.