Production deficit during power peaks in the electric grid is expecting to increase in the future during the most critical cold periods of the winter in Sweden. Several studies are pointing towards single-family houses as a potential actor to contribute to demand flexibility in the grid in the user side by applying load shifting of electric heating systems. At the same time, the interest in Variable Air Volume (VAV) ventilation in residential buildings is increasing (lowering ventilation airflow when the building is unoccupied). This study aims to investigate if VAV ventilation can impact the power use and improve the thermal comfort if load control of the heating system is performed in the building. The study has been carried though a simulating case study of a single-family house (Dalarnas villa), using a digital model of the building in IDA ICE 4.8. Exhaust Air Ventilation (EAV) system and Mechanical Heat Recovery Ventilation system have been simulated and investigated separately, both in combination with a ground source heat pump and waterborne underfloor heating. A scenario with VAV ventilation and load control of the heating system has been compared to Constant Air Volume (CAV) ventilation with load control.
By simulating a scenario during the coldest winter week of 2021, the results showed that VAV reduced the space heating power demand by 30 % during airflow reduction. There covery time after a load control was lowered by 30 % for a EAV system with VAV compared to CAV, when the airflow is reduced during recovery and load control. The power demand and recovery time for the corresponding scenario with a MHRV system was not affected noticeable. All load control strategies simulated showed a similar magnitude of power demand after the heat was turned back on, which was significantly larger than without load control.
The results also indicates that the thermal comfort is improved when combining VAV with a EAV system. The operative temperature drop during load control was lowered by 30 % and the average operative temperature was increased by 0.4 °C for the whole study period (5 days during the coldest week of 2021). When applying VAV with Mechanical Heat Recovery Ventilation (MHRV), no significant impact was observed for the thermal comfort, recovery time, or the load curve of the building