The average Briton spends 22 hours of their day indoors, equating to 90% of their day. With all of us spending so much time enclosed within four walls, a comfortable indoor atmosphere is critical to wellbeing. The best way to facilitate this is through Mechanical Ventilation with Heat Recovery (MVHR).
What is it?
MVHR, HRV or Comfort Ventilation are all names commonly used to describe a heat recovery ventilation system that, when properly fitted into a house, provides an uninterrupted supply of fresh filtered air. This means the quality of the air is maintained, whilst remaining virtually undetectable.
MVHR extracts air from polluted sources – typically, areas where food is prepared, as well as toilets, bathrooms and utility rooms. At the same time, it supplies fresh, filtered air to living spaces and bedrooms. The extracted air is taken through a central heat exchanger and the heat recovered into the supply air. This works both ways: if the air temperature inside the building is colder than the outside air temperature, then the cool air is maintained within the building, resulting in a ‘cold air recovery’ technique.
Why does it matter?
The difference between a highly efficient unit working unnoticed in the background and a noisy, noticeable (and often annoying) unit that wastes both heat and electrical energy, is down to system design. Ducting also plays a role: MVHR systems require ducts to be run through a building, and these must be of the highest possible quality to ensure effectiveness.
When the appropriate ducting is selected and installed correctly it can greatly improve and prolong the efficiency of the whole system, leading to long-term low maintenance. However, the wrong choice could result in an underperforming ventilation system, leading to longstanding and potentially costly issues. Poorly-installed duct work can potentially damage the ventilation unit and fabric of the building, as well as leading to discomfort and inconvenience for occupants.
Why choose semi-rigid ducting?
Choosing quality semi-rigid ducting brings several advantages:
- It delivers zero leakage and therefore enables a ventilation system to operate at its optimal performance.
- Installation is a simple, repeatable process that requires the minimum of skills, yet ensures peak standards.
- Top semi-rigid ducting systems have high crushability levels, with some able to withstand up to 13 kN/m2 of force.
Some semi-rigid ducting systems offer the installer the kind of versatility that most other systems can’t match by allowing them to switch between oval and round ducting, causing minimal pressure loss.
Semi-rigid: the key benefits
- Semi-rigid ducting is flexible enough to work around joists, but still resilient enough to avoid creating sharp bends or kinks. Airtight locking systems mean no glues or sealants are required on-site.
- Low velocity can be put through the ductwork, resulting in lower system pressure drop and lower noise levels.
- It is cleanable, making it ideal for Housing Association properties and social housing developments.
- Some semi-rigid ducting can be set into concrete.
- Unlike metal ductwork, semi-rigid products are corrosion-resistant, lightweight and food grade “virgin” polyethylene, meaning they are fully recyclable.
Standing up for standards
Behind any ducting system of real worth must be the standard it lives up to – and the Passive House standard is recognised as the leading international low-energy design standard, with more than 65,000 buildings designed, built and tested to this benchmark worldwide.
A ‘Passive House’ doesn’t need to be actively heated, because it uses passive heat gains to heat itself. Consequently, only a minimal amount of additional heating needs to be supplied. The concept is based on excellent thermal insulation and a highly efficient heat recovery system. The heat stays indoors and, therefore, doesn’t need to be provided by an active system. Passive House also applies to retrofit projects, achieving similar savings in space heating requirements.
Passive House buildings are calculated to achieve a 75% reduction in space heating requirements, compared to standard practice for UK new-build. The Passive House standard offers a powerful way forward in helping the industry achieve the 80% carbon reductions that are set as a legislative target for the UK Government.
By Rupert Kazlauciunas, Technical Product Manager, MVHR, Zehnder UK