The importance of alternate flow heat recovery | Vent-Axia

The importance of alternate flow heat recovery | Vent-Axia

Although Mechanical Ventilation with Heat Recovery (MVHR) is ideal for new build properties, it is Alternate Flow Heat Recovery ventilation that is set to be vital to the retrofit market and existing homes. Tom Wodcke, Product Manager at Vent-Axia, explains more.

Later this month the UK is set to host the 26th UN Climate Change Conference of the Parties (COP26) where it is likely there will be a call on all countries to set 2030 emissions reductions targets to put us on a path to net-zero by 2050. This is important since the UK has enshrined in law the need to achieve carbon neutrality by 2050, but there is a long way to go.

To reach this target, however, improving the energy efficiency of existing homes is essential since almost 40% of carbon emissions are currently generated by buildings. To achieve these reductions, it will mean improving insulation, making homes more airtight, and adding heat recovery ventilation to ensure good indoor air quality.

It can be difficult to retrofit a whole house mechanical ventilation with heat recovery (MVHR) system in an existing home since it requires an electrical rework and the addition of ductwork, which then becomes a major project and is almost impossible to accommodate in small homes where ducting can steal valuable space.

With whole house MVHR far from ideal for retrofitting, traditional decentralised mechanical ventilation with heat recovery (dMVHR) might be seen as an alternative option since it is simple to install through a wall. That said, although dMVHR is very effective for single room use – such as in the bathroom or kitchen – it isn’t scalable to provide a whole house system.

Alternate Flow Heat Recovery

Fortunately, there is now a new type of decentralised heat recovery ventilation available that is ideal for retrofitting in existing homes and can be combined into a system of up to eight units to provide a whole-house retrofit system – Alternate Flow Heat Recovery.

Alternate Flow Heat Recovery is new to the UK and offers a balanced modular customizable ventilation system that can be easily retrofitted, supplying both supply and extra while recovering heat from the air. This new type of technology, such as Vent-Axia’s Lo-Carbon Heat Save, provides extract and supply ventilation to improve indoor air quality (IAQ) and supply fresh air to rooms as part of a modular system.

Using two or more fans in habitable rooms, the units use a reversible fan that alternates between supply and extract fan modes every 70 seconds to extract dirty air from the room and replace it with outside air that has been passed through a filter to ensure that clean air enters the room. It’s ideal for use in pairs – as one unit is extracting, the other is supplying fresh air to provide a single room or whole house balanced ventilation system with heat recovery.

It’s also easy to expand as required, adding more units for a whole house solution which can all be controlled from one controller that can operate up to eight units in synchronization. Fully customisable via a control panel, this type of technology achieves up to 84% heat recovery, via an innovative ceramic thermal accumulator. This new type of dMVHR uses the warmth from outgoing air to heat incoming air to avoid heat loss, reducing a home’s carbon footprint and energy bills.

The heat recovery is achieved by a thermal accumulator, which features a highly efficient design (inspired by beehives) that maximises the surface area of the contact between the thermal accumulator and the air passing through it.

Benefits for households and electricians

For electricians, Alternate Flow Heat Recovery increases ventilation to prevent condensation while providing multiple avenues for up-sell. It’s also easy to install since there is no need for ducting, a wall sleeve is included and the unit simply goes through an external wall.

For households, Alternate Flow Heat Recovery offers ‘Fresh air without the breeze’ – no need to open windows and let out heat in winter. As a retrofittable heat recovery ventilation unit with a G4 air-cleaning filter, households will see drastic energy consumption savings and improved IAQ.

The units are also easy to maintain and clean, with filters simple to change since the units are not in the loft. Offering sophisticated controls, the Heat Save has a SENWZP Sentinel wired-zone controller, which is fully modular and controllable with customised ventilation profiles available so every room in the house can have perfect ventilation.


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