What is MVHR?
Essentially, MVHR does exactly what it says on the tin. An MVHR system will Mechanically Ventilate a space and Recover the Heat that would otherwise be lost to the atmosphere.
In short, MVHR systems replace outdated means of ventilation within a building, be that air bricks, trickle vents and bathroom extract fans. All of which will suck stale air out of a building, but also take the heat out with it.
Typically the air change rate within a building will sit at 1.5 to 2 air changes per hour. This comes with heat loss via air changing in the space, accounting for up to 35% of a buildings heat losses in some cases.
This means that every 1.5-2 hours your property could be loosing up to 35% of the energy you have put into it, to keep it warm.
An MVHR system would recover up to 90% of that energy. Providing full ventilation with tempered fresh air entering the building, replacing stale, humid foul air.
The Process
An MVHR system starts with ductwork being run through a building. Traditionally this would be a branched rectangular ducted system, with offshoots from a central duct entering each room. At Baystar however, we opt for a circular radial ductwork approach.
Radial duct is quieter, more flexible, requires less space and presents less pressure loss, so keeps fan running speeds low, there by increasing efficiency.
In each habitable room of building you will have a vent. Extract vents in foul air rooms such as; bathrooms, kitchens utilities and W/C’s. These such air from high points in the room, removing heat and excess humidity.
To balance this extract air flow, in the living areas, such as; bedrooms, living rooms, offices etc. You would inject fresh supply air.
Once the ductwork is in, it is connected from each room to a central set of manifolds. One for supply and one for extract, these are in turn connected to the MVHR machine itself.
The MVHR machine itself is a set of filters and fans with a heat exchanger in the middle. The foul air runs across the heat exchanger, transferring heat to the fresh supply air, whilst remaining separate.
Foul air is then ejected to atmosphere along with excess moisture and smells. Warm fresh air then enters the building in its place.
This is how up to 90% of energy is recovered from extract air and able to be recycled into a building.
Additional Services
As bolt on to basic MVHR systems, there are many variants of MVHR units that could be considered depending on the applicaiton.
Heat pump assisted MVHR units provide all the same services as passive MVHR. With the added ability to actively add heat or cooling into the inject air. In some Passive House instances, this could be all that is required to heat and cool a building, given the low energy nature of Passive House construction methods.
In addition to the heat pump assisted MVHR units, there are also systems that recover the waste heat from extract air and use it to create hot water. The unit below shows how this is done with the Nilan Compact P.
The Net Effect
All of this then results in a property that is fully ventilated and in some cases fully heated, simply from smart ventilation and careful design and installation.
Contact Baystar today to find out how an MVHR system might work within your building.