Energy recovery systems have long been known in the UK, but their popularity is often hampered by insufficient information on the advantages and benefits of using energy recovery systems. It is the lack of reliable information that has so far largely hindered the faster development of the heat recovery system industry.
In order to improve the situation and fill in the white spots, in a series of articles in cooperation with Airy Forces specialists we will try to provide objective information on room ventilation, heat recovery units, their possibilities and advantages, the importance of providing a constant supply of fresh air, the choice of heat recovery units and many other issues that will help our readers develop a better understanding of this area.
What is a heat recovery unit?
A heat recovery ventilator is a ventilation unit that supplies and exhausts air, transferring heat from the outgoing air to the incoming cold air. It is the heat exchange process, during which the warm air flowing from outside the room warms the cold, fresh air coming in from the street in a special unit (heat exchanger), that is the main difference between a heat recovery unit and a conventional ventilation unit.
In the case of conventional ventilation, the exhaust air carries with it the heat stored in it, while the incoming air is cold and has to be re-warmed, which requires additional energy consumption. Heat recovery units can recover up to 90% of the exhaust heat (depending on the temperature difference between the incoming and outgoing air, as well as a few other, less important parameters). It is the possibility to significantly reduce heat consumption that is the main advantage of their use.
Combinations are possible
It is important to distinguish between heat recovery units and some other commonly used appliances, such as air conditioners or heat pumps. An air conditioner does not provide air exchange, it only cools the air in the room. An air conditioner can be installed in combination with a central ventilation unit, which is a very good solution. A heat pump can heat the air in winter and cool the air in summer, but it also does not provide air exchange.
But when it comes to decentralised ventilation, which also includes heat recovery units, it is possible to create a “duo” of heat recovery unit and air conditioner – it is possible to buy units that will help to keep the indoor air as cool as possible in summer (up to the same 90%), while providing the necessary fresh air supply in parallel. The hot air coming in will be cooled by the cooler air going out before entering the device, reducing the load on the air conditioner and the amount of electricity it consumes.
Advantages of using heat recovery ventilators
When it comes to ventilation systems, a distinction needs to be made between centralized and decentralized ventilation. Centralized ventilation consists of a single unit operating on a group of rooms and ducts connecting these rooms into a single system. The construction of such a system requires a large variety of repair and installation work, considerable effort and working time.
Decentralised ventilation equipment also known as heat recovery unit, is installed one per room. This requires much less work and at the same time allows a separate climate to be maintained in each room. They also have the advantage that they do not require extensive design work – a single hole drilled in the wall, into which the heat recovery unit is inserted, and the job is done. Other advantages include the fact that these units are easier, faster and more efficient to clean.
Need to choose equipment of sufficient capacity
There are practically no restrictions on the use of decentralised ventilation, only the capacity of the equipment, or the need to provide sufficient fresh air for a given period of time. This is determined by the size (cubic capacity) of the room and the number of residents. Most often, heat recovery units are installed in rooms with no more than 10 persons, but technical solutions are available that allow them to be installed in larger rooms with more people (e.g. classrooms, offices, etc.).
These can be 2-3 smaller units per room, or very powerful heat recovery units providing up to 800 m3/h air exchange and thus able to provide the required air supply even in such public spaces. Only in large public spaces (theatres, cinemas, supermarkets, etc.) with a large number of persons (over 30 – 40), a centralised ventilation system is necessary. In all other cases, it is possible to find suitable heat recovery units for the specific space. You can read more about how to make the right choice in our next article.
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