How do Heat Recovery Ventilation Systems work?
The warm, stale, moisture-laden air from all wet areas in your home e.g. bathrooms, wc's, kitchens and utility areas etc. is continuously extracted and filtered back through the heat recovery unit. This exhaust air passes through a heat exchanger where the heat energy is transferred to the incoming supply air but the two air streams can never mix. As a result you will have a continuous supply of fresh, filtered, tempered air to all habitable rooms in the home e.g. bedrooms, living rooms and dining areas etc.
What are the benefits of a Heat Recovery Ventilation System?
Continuous supply of fresh, filtered, tempered air into the home
Reduces heating costs by recovering up to 95% of the heat extracted from the wet rooms
Balanced heat distribution throughout the dwelling
Creates a healthier living environment
Clinically proven to help allergy and asthma suffers
Prevents condensation and eliminates mould growth
Removes unwanted odours e.g. cooking smells
Extremely low power consumption
No longer require trickle vents in windows and intermittent extract fans in wet rooms
How can we help?
Atlantic Air can provide expert advice on all fundamental design factors to ensure the envelope of the building is made as airtight as possible. We can carry out visual site inspections or if necessary undertake preliminary air tightness testing, to ensure the 'airtight' design is built correctly on site.
IMPORTANT: Air tightness needs to be addressed at the earliest possible stage. The design of a building and the quality of its construction will have a major effect on air leakage and consequently the efficiency of your heat recovery ventilation system.
At low levels of air leakage (typically 3 m³/ (hr*m²) @ 50 pa or less) heat recovery systems can offer significant reductions in overall energy use, offsetting heating demands by pre-warming incoming replacement air for the occupants of the dwelling. However this can only be optimised if the best systems are to be installed, and only then if they are installed correctly.
What effect does air tightness have on the Heat Recovery Ventilation System?
Air tightness refers to the infiltration of cold air into the building and the loss of heated air from inside through gaps, holes, cracks etc. in the building fabric. In order to create the most comfortable living conditions it is necessary to design air tightness and ventilation strategies to work in harmony.
Constructing an airtight dwelling without a system of controlled ventilation is neither comfortable nor healthy for the occupants. It is as equally impractical to install a mechanical ventilation system in a property with inadequate air tightness. You will effectively create an environment that is over ventilated and much more difficult and expensive to heat.
IMPORTANT: To ensure client satisfaction and guarantee optimum energy efficiency Atlantic Air insist on implementing all practical measures to minimise air leakage. If you are not interested in achieving the desired level of air tightness we would advise you not install a heat recovery ventilation system
Choosing the best Heat Recovery Ventilation System
Atlantic Air are independent mechanical ventilation with heat recovery (MVHR) installers. 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.
When selecting a heat recovery ventilation system it is important to take the following factors in to careful consideration;
- The Type of MVHR Unit – Cross Counter-flow Heat Exchanger
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.
- The MVHR Ducting – Rigid PVC/ Rigid Thermal Ducting
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 must also 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.
Design and Installation