PAUL MVHR units are Passivhaus certified and exceptionally efficient – recovering up to 97% of the heat leaving the building and are also extremely quiet – one of the best on the market. For ducts we use Lindab rigid steel duct work, installed as we build the frame into pre-cut duct routes. These have a smooth internal surface to minimise restriction to the air flow.
Rigid duct work is a robust long term solution – the alternative being flexible weak duct work that easily tears during installation, and often has a rough internal surface restricting air flow.Saving money by installing a cheaper less efficient unit with weak duct work is a false economy – if for example a 75% efficient unit is installed, it would mean for every air change, 25% of the heat in the building would be lost. In an air tight house an MVHR unit is a vital component to achieve healthy indoor air quality, and the ducts are something which cannot be altered later on since they are embedded in the structure so it is important to get it right first time.
Weak, tearable ducts also mean there is potential for follow on trades (such as electricians / plumbers) to easily damage the duct work without realising that they have done so, meaning when it comes to commissioning the system failures will occur – poorly functioning MVHR units is an issue NHBC are looking into since the failure rate of installations is large.