Heat recovery ventilation has been widely used already for several years. Air exchange takes place without losing thermal energy, namely, outgoing warm air masses warm up (in winter – cool down) incoming ones, giving away their heat.

This technology makes it possible to recover up to 90% of the thermal energy that is conveyed through the ventilation shafts together with the used air.

The two most common types of recovery equipment: using a plate heat exchanger and a rotary heat exchanger.

A lesser-known solution is a reclamation from sewage. The principle is quite simple – wastewater heat is used to heat water. Before the wastewater gives off heat, it needs to pass through various types of filters that separate impurities.

For the system to work effectively, an accumulation tank is installed, because the flow of wastewater does not always coincide with the amount of water required. If water is not needed at a particular moment, for example during the night hours, it is stored.

Heat recovery from sewers is most useful for buildings with a lot of hot water use, pools and showers, laundries and dry cleaners, the textile industry, food factories, residential homes, etc.

Heat recovery can also be used in the opposite direction – to cool the building from the outside cold source. Since Latvia is located in the northern part of Europe, we have not had a great need for cooling solutions, but as the summers get hotter, the demand will only grow. The cold energy in the ground and water bodies is most often used as a source of cold because using it has low production costs and greater energy savings compared to other cooling methods. In groundwater is chosen as the resource source, it is necessary to consider the drilling to obtain water at a temperature of 6–12 °C, which in some cases can then be used as technical water.