demand-controlled ventilation

The buildings ‘sector is facing multiple challenges due to the need to generalize a sober approach and to reduce its energy consumption, its CO2 emissions and its impact on climate change, to reduce its environmental impact and its carbon footprint, to reduce the burden of disease due to exposure to unhealthy indoor environments and to adapt and be resilient in the face of climate change and environmental changes such as the increase in pandemics, the urban heat island and outdoor pollution.

The purpose of this paper is to summarize the status of promising low carbon building services solutions fitted for a low emission building stock in urban areas.  

Buildings account for approximately 40 % of energy use in the European Union, as well as in the United States. In light of the European Energy performance of buildings directive, efforts are underway to reduce this energy use by targeting zero or nearly zero energy buildings. In such low energy buildings in cold climates, ventilation to ensure suitable indoor air quality is responsible for half or more of their energy use. The use of heat recovery and demand-controlled ventilation are potential solutions to reduce ventilation-related energy consumption.

With 35 years of existence and more than 10 million equipped dwellings, mechanical humidity-based demand-controlled ventilation (RH-DCV) can provide a comprehensive feedback on installation, aging, and maintenance of its components. Their working principle is based on the extensions and retractions of a hygroscopic fabric, which pulls on a shutter to modify the device’s cross-section – hence the airflow – upon humidity changes in their environment. 

In order to better address energy and indoor air quality issues, ventilation needs to become smarter. A key smart ventilation concept is to use controls to ventilate more at times it provides either an energy or IAQ advantage (or both) and less when it provides a disadvantage. This would be done in a manner that provides improved home energy and IAQ performance, relative to a “dumb” base case. A favorable context exists in many countries to develop smart ventilation strategies.

In 2017, the Air Infiltration and Ventilation Centre (AIVC) identified smart ventilation for buildings as a new and important topic to be addressed. One of the tasks was to agree on a definition of smart ventilation, which was published in March 2018. The purpose of this presentation is to explain and illustrate the smart ventilation definition by AIVC.

For zero and low energy buildings, high-energy efficiency ventilation is very often confused with a complex mechanical ventilation system with heat recovery. In school gymnasiums, where large volumes have to be ventilated, and where intermittent occupation is very usual, demand controlled natural ventilation has several advantages, making this technique very attractive. High stack height makes natural ventilation very efficient, limiting the necessary number and dimensions of windows.

Numerous studies have investigated the application of multi-zone demand-controlled ventilation for office buildings. However, although Swedish regulations allow ventilation rates in residential buildings to be decreased by 70 % during non-occupancy, this system is not very common in the sector. The main focus of the present study was to experimentally investigate the indoor air quality and energy consumption when using multi-zone demand-controlled ventilation in a residential building. The building studied was located in Borlänge, Sweden.

The Marienlyst School is the first educational building in Norway built according to the passive house standard. This building benefits from a super-insulated and airtight envelope. While this reduces the heating demand largely, it also enhances the risk for poor indoor air quality and overheating compared to conventional buildings. It is therefore particularly important to implement an efficient ventilation strategy in order to avoid adverse effects on the health, well-being and productivity of the pupils.

Is Demand-controlled ventilation a relevant answer to face the new challenges of the Building sector, which requires everyday higher energy efficiency and better indoor air quality? Can Demand-controlled ventilation be considered as an alternative to heat recovery ventilation, through an affordable and low maintenance solution? Since the take off of the DCV in the early 80’s, these questions have been considered many times.