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Demand controlled heat recovery ventilation systems, which combines heat recovery (HRV) and demand controlled (DCV) is growing fast among ventilation manufacturers.
Several categories can be identified, from global dwelling regulation, to fine room-by-room regulation of the airflow rate. Simulations show that room-by-room demand controlled heat recovery ventilation is the best compromise to optimize at the same time indoor air quality, comfort, and energy savings.
To reinforce this assessment, four room-by-room demand controlled HRV have been monitored since May 2013. The system is an innovative ventilation for individual treatment, which modulates automatically the supply airflow according to CO2 concentration in the main rooms, and exhaust airflow according to humidity concentration in the wet rooms. The balance of the airflow is made using two specific compensation valves at the exhaust and at supply.
Three projects are located in Germany: Nuremberg, Dortmund and Frankfurt, and one takes place in France, near Paris. The dwellings have from three to five main rooms, and a real occupancy of two to five people. They are all existing dwellings. The comparison was made between three different types of installation: two in the heated space, one in the attic (slightly insulated), and one with the heat recovery unit in the heated space and the ductwork in the attic (non insulated).
The results have shown the good functioning of the system in terms of balancing, adaptation of the airflow rates to the needs, and filtration. The relevance of using CO2 concentration to modulate the airflow rate at supply has been verified by presence sensors in the main rooms. Temperature sensors revealed the necessity to carry on the installation in the heated space to optimize energy savings. Besides, the collected data gave the opportunity to validate a simulation model of the system using CONTAM (multizone indoor air quality and ventilation analysis program developed by NIST).
The monitoring also demonstrated the good performance of this type of heat recovery, in terms of indoor air quality, comfort and energy savings. The CO2 and the humidity level stayed in the comfortable range thanks to demand controlled ventilation. The supply temperature, when the HRV is located in the heated space, is mostly between 18 and 20°C, thanks to heat recovery (the outdoor temperature being in the range of 0 to 14°C). In-situ measures and surveys occupants supplied complementary information regarding the acoustic and thermal comfort.