The choice of the most suitable ducting is important in order to optimize the efficiency of a system, to make it as silent as possible, to keep it hygienic, and in order to get it installed easily. The efficiency of a system mainly depends on the smoothness of the inner surface, the dimension, the number of bends, the radius of the bends and the length of a ducting system.
Please note that the choice of ducting will in almost all cases be a permanent one for the lifetime of the building.
Flexible ducting for MVRH systems is really a thing of the past – and rightly so.
It is very inefficient and hardly ever cleanable. It is recommended to avoid fragile materials as foil or plastic ducting and rather use canvas material with wire. Flexible aluminium ducting tends to be rather noisy. Strict guidelines on installation have to be adhered to and all connections have to be secured with jubilee clips as tapes can come off through fatigue of the adhesive or movements.
The maximum length for MVHR and MEV systems is 300mm at a time and no more than 1.5m in total. However, we do recommend to avoid such ducting.
PVC ducting is very popular in the UK – but not in other European countries. There is a reason for this: Such ducting has a much higher resistance, as their bends have a very sharp radius (1/2 d). This will result likely in higher operating costs, more noise, as the fans have to work harder and it will be difficult or even impossible to clean the ducting in dour course due to the sharp 1/2 d radius bends.
Rectangular ducts have the advantage of a low profile, but they have even worse air flow properties and are uncleanable.
Therefore we generally do not supply this ductwork.
Highly efficient and hygienic ducting, often also referred to as ‘spiral ducting’. We recommend the safe system with double seals at all connection points. Standard dimensions of 100, 125 and sometimes 160 or 200mm are used for domestic applications. It is a top class domestic ducting system, which we often use it for either long stretched buildings, large dwellings or very small applications. The disadvantage is the number of different components (T-pieces, reducers, bends) and it has become quite expensive. Also cross-talk silencers need to be installed between the bedrooms.
The system is based on manifolds with multiple semi-rigid PE pipes that run into the various supply and extract rooms.
We offer ducting, which are smooth on the inner surface and therefore almost as efficient as spiral ducting. Semi-rigid ducting has become much more popular in Europe. It is more cost-effective, easier to install, especially when threaded through joists and it can be easily cleaned. They typically come in 50m rolls.
The ducting and components come in two different diameters:
We prefer the 90mm ducting as it has got more capacity and therefore allows reduced air velocities (max 2m/s), which makes the system more efficient and quieter.
Please note that we have noticed a huge different in quality between the different manufacturers.
Some ducts are fairly corrugated on the inside, some crease up when bent and some can be too rigid and break.
We have therefore decided to use only the best available ducting with anti-bacterial lining.
Associated components are:
We use the Lindab SAFE range of galvanised metal duct fittings, which are of superior quality and are inherently air tight through the long-life double seals at all connectors.
Lindab duct & fittings are manufactured from Z275 galvanised steel with a C2 corrosion rating, making them suitable for external use with a life expectancy of over 30 years in low pollution environments. On the market today, we are seeing spiral ducting and flange systems manufactured from Z200 or even Z140 which has half the life expectancy of Z275 in ideal conditions.
Like Safe metal components, semi-rigid ducting comes with proprietary sealing rings, so that you don’t need mastic to create an airtight connection.
We have tried different ducting systems and learned our lessons: That’s why we don’t use PVC ducting, as it has much more resistance than good ducting, which results in more energy use and noise. It is also not really cleanable – especially rectangular ductint – and therefore not a sustainable solution.
Think about this: How often do you expect to have the ducting system exchanged? You can more easily change the MVHR unit, but the ducting, once embedded into the ceilings and structure, will probably never be exchanged in the life-time of the building. We have therefore adopted a non-compromise approach in regards to ducting. We can talk about different qualities of MVHR units, but not about low quality ducting.
Stefan Huber
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MVHR systems will need some insulation of some sorts, to prevent condensation and minimise heat losses.
Noise attenuators, or commonly called silencers are a vital part of MVHR systems.
What is most visible should not just be pleasing to the eye, but also functional and easy to clean.
Fire protection measures are part of houses of multiple occupancy and in some other cases.
MVHR controls come in different forms and functions, from simple switches, app control to full automation.
MVHR filters can make a huge difference for the health and wellbeing of the occupants, but not all filters are the same.
01383 221 255
info@paulheatrecovery.co.uk
© 2024
Sustainable Homes Scotland Ltd
t/a PAUL Heat Recovery
Unit D, Pitreavie Business Park
Pitreavie Crescent, Dunfermline
KY11 8PU Scotland
Registered in Scotland – CRN: SC331209
Directors: Stefan Huber, Allan McEwan, Garrie Glasgow
