MVHR systems have been adapted to fit almost all different types of buildings. However in smaller dwellings and properties that are being upgraded, e.g. to the EnerPhit standard, whole house MVHR is often quite difficult to fit in, due to the size of the equipment and due to the amount of ductwork.
In recent years a few companies have dedicated themselves in developing de-central MVHR systems, which work continuously and on higher ventilation levels (up to 100-120 m3/h), compared to smaller oscillating de-central units.
The concept is simple, but stunning:
– A de-central MVHR unit is placed, e.g. in an external wall of a living room.
– Wet rooms and the kitchen are connected to the unit via an extract duct system, thus creating an air flow path through the dwelling.
– Bedrooms and other habitable rooms tap into the airflow through active transfer units within the internal bedroom wall. As stale air is expelled out of these rooms, fresh air is drawn in through door undercuts or other internal transfer openings.
– The ventilation rate is fully demand controlled according to CO2, humidity and temperature. The active transfer units in the bedrooms are independent, but also fully demand controlled.
Such setup comes with a number of advantages compared to the traditional whole house approach:
A) Demand controlled: The ventilation adjusts automatically to the use of the dwelling, ensuring that CO2 and humidity levels do not exceed the recommended levels. It minimises user-interference, but also counteracts over-dehumidification, which can sometimes be an issue with conventional MVHR systems.
B) It follows the usage cycle between living spaces and bedrooms. Therefore and due to their demand controlled operation, they use a fraction of energy compared to a standard MVHR.
C) The need for ducting is minimal, as only extract ductwork is needed.
D) Monitoring: Advanced control technology allows monitoring of all air quality parameters, if so desired.
One of these systems can serve about 70 m2 space and one story at a time. For two storey buildings, at least two of these MVHR units have to be implemented.
Usually such cascade MVHR can be treated as whole house MVHR system. The Fresh-r system has been tested for Appedix Q.