As independent MVHR installers (Mechanical Ventilation with Heat Recovery), we are not contracted to any specific manufacturer or model. We are committed to sourcing the most up to date, energy efficient heat recovery ventilation system currently available on the market, one that is SAP Appendix Q listed and Energy Saving Trust best practice compliant.
We recommend installing MVHR units with in-built cross counter-flow heat exchangers. The heat exchange efficiencies are much higher (up to 90%) and the operating costs are much lower (0.4 W/l/s) compared to that of cross-flow or rotary wheel heat exchangers.
A cross counter-flow heat exchanger transfers heat from one air-stream to another. At its core is a stack of plastic plates, within which are a series of airflow channels. These channels are aligned precisely to ensure that heat from the extracted warm is transferred to the cooler incoming supply air. Unlike a rotary heat exchanger, a cross counter-flow heat exchanger does not exchange humidity and there is no risk of mixing the air-streams. It is typically used in buildings where hygienic standards require that both air streams are kept completely separate from one another.
This technology is designed to deal with large volumes of warm moist air, thus enabling us to position extract air valves directly over shower enclosures. By extracting steam at its most intense point we can dramatically reduce condensation levels whilst recover the highest possible temperature from the warm air before extraction to the outside.
It is important to remember that the heat exchanger is only one part of the entire ventilation system. Choosing the correct ducting and installing it properly will significantly improve the performance of any heat recovery ventilation unit, regardless of the type of heat exchanger selected.
The reason being; warm air extracted from a wet room (e.g. kitchen, bathroom etc.) must travel through the ductwork to reach the heat exchanger. Fresh incoming air passing through the heat exchanger must travel through the ductwork before terminating in a habitable room (e.g. living room, bedroom etc.) If this ductwork has been poorly insulated, little to no heat energy will be recovered.
Careful consideration should be given to the location and positioning of ductwork so as to limit airflow restriction. By limiting restriction, the fan motors can run slower, hence the power consumption will be reduced. We recommend installing rigid thermal ducting throughout non-conditioned areas and rigid PVC ducting within the heated envelope.