What did your grandma tell you about good practice for the home?
Open the windows in the morning and let the room breathe!Well, that’s almost right! Today that old and wise advice is superseded.
The layout of buildings does not help natural ventilation because the spaces are too deep to be ventilated from the perimeter, or the air paths are being mitigated by the internal partitions. Natural ventilation absorbs any poor local air quality and pollution. Highly dense areas will not have enough wind velocity to pump enough airflow into a building.
This is why – without fitting expensive air conditioning systems – a controlled mechanical ventilation system is an efficient method to control indoor air quality using external air.
Although there are various systems of mechanical ventilation, the base principle is that the exhausted internal air (warm and humid) gets pushed out of the building, while external air gets pumped in, after passing through purification filters.
The Mechanical Ventilation Heat Recovery system (MVHR) is an energy recovery ventilation system that adds an air-to-air heat exchanger, recovering the heat that is usually wasted. Heat recovery units can recover up to 90% of normally lost heat depending on the unit and the application. An MVHR system works independently from a heating system, and due to the heat recovery feature, it can have significant savings on your energy bills.
Mechanical ventilation systems can be centralised (C-MEV) when a single unit in the technical room (or loft/roof space) supply air to all rooms via ducts. Or they can be decentralised (D-MEV) when only specific areas (i.e. bathrooms, kitchens, utility rooms) need to be served.
When full supply+extraction systems are not feasible, like for example in old listed properties, smaller solutions can be a good alternative; Positive Input Ventilation (PIV) can be achieved merely fitting a wall or loft mounted unit that pushes filtered, fresh air through a property. A PIV system is a perfect method to combat condensation in the home.
So, MVHR, C-MEV, D-MEV, PIV... which one are you?