Air quality in the building regulations
We set out below the basic requirements that a ventilation system in a home must meet, expressed in terms of litres of fresh air per second per m2. For both new construction and renovations, this is the current standard as stated in the 2012 Building Decree (the most recent version):
In a living area, where you spend time sitting or sleeping, the required capacity is at least 0.9 litres per second per m2
Wherever a cooking appliance is installed in a kitchen or a living room with an open kitchen, the minimum capacity requirement is 21 litres per second per metre of floor space.
A minimum of 7 litres per second is required for a toilet.
To prevent mould and other moisture problems in the bathroom, the minimum capacity requirement in the wet room is 14 litres per second.
Central heating engineers also use this value to calculate how to compensate for heat loss through ventilation. Which in turn calculates how much heating is needed in the bathroom.
The Building Regulations calculations are based on a unit of litres per second. Fro realistic day-to-day work, this is converted to litres per hour and or m3 per hour. Technology is always advancing, and progress moves faster than the regulations can be updated. We like to set the bar a little higher than the minimum limits of the Building Regulations, while paying close attention to the routing of fresh air through the house. We work on the basis of a 50/50 balance between an air supply coming directly from outside and an overpressure of fresh air that moves through the house.
Airflow to achieve good air quality
We start with the supply in the bedroom where as much fresh air as possible is desirable. After all, we spend about 30% of our lives asleep. At night, CO2 levels in a bedroom increase rapidly. This is because when we exhale, we emit carbon dioxide, which remains in the room until and unless enough fresh air is supplied. Ideally, the routing of the heat exchange system starts in the bedroom and brings in as much 100% fresh outside air as possible to that location. Between 10 and 14 litres per hour is ideal for two people. The exhaled air from the bedroom disappears under the door via air extraction in the bathroom. The overpressure from the fresh air can flow to the landing and from the hall or entrance to the living room and (open) kitchen. The overpressure flow is supplemented in the living room/kitchen with fresh air from outside to at least meet the capacity requirement. Especially in the kitchen. According to TNO (the Dutch independent statutory Applied Research Organization), this room is a source of ultra-fine particles during cooking and frying.
Air quality in hospitality and commercial buildings
Whereas in homes, calculations are made based on the surface area, with a fixed value per type of room (usage), different requirements apply in, for example, offices, catering establishments and hotel rooms. There, the air volume is determined according to the level of occupancy of the rooms. Capacity is then calculated from the number of employees or guests per room.
In conclusion
The Building Regulations do not lay down regulations regarding the maximum concentrations of various substances (e.g. concentrations of CO2 or fine particles), or other factors that put good air quality at risk. These can be monitored using an air quality meter or with sensors that control the heat extraction system. In addition, in practice, the performance of a ventilation system varies significantly depending how it is used and maintained. The latter can be managed through a maintenance contract and timely filter replacement for maximum efficiency of the units.
