C.T.E. DB HS. Requirements of the Technical Code for air renewal

C.T.E. DB HS 3. Indoor air quality

The Technical Building Code in its basic document HS 3 - "Indoor Air Quality", defines a series of requirements for a ventilation system to be efficient and fulfill its purpose:

• In the habitable rooms of a home, the flow supplied from the outside will allow that in each of them the average annual concentration of CO2 is less than 900 ppm.
• Contaminants must be completely eliminated, regardless of their origin, whether they are related to human presence or the smoke produced in a kitchen.
• Ventilation flows will be provided through constant flow ventilation or variable ventilation regulated with presence detectors, contaminant detectors, or other similar systems.

Below are the volumes of outside air that must be brought inside each premises and in each type of building. These are the values included in the latest version of the Technical Building Code in its document HS 3. "Indoor Air Quality", which will come into force in September 2017.

• Principal bedroom: 8 l/s
• Other bedrooms: 4 l/s
• Living room and dining room: 8 l/s
• Storage rooms: 0.7 l/s per m2 of usable area
• Parking lots: 120 l/s per space
• Waste storage: 10 l/s per m2 of usable area

The movement of air. The Beaufort scale

Along with proper ventilation of inhabited premises, there are other factors that influence the comfort sensation of its occupants. Such is the case with air movement which, for example, reduces our sensation of heat when it comes into contact with the skin during the months of the year when the ambient temperature is high. The air can be in motion, which is when it is called wind, or at rest, then it is called calm. Although the scales that measure wind speed do not consider that there is speed in the air until it reaches 1.5 m/s, in reality, much lower speeds, such as 0.5 m/s, are indeed perceptible to the human body. The force of the wind is determined by its speed, as defined in the Beaufort scale:

LEVEL	WIND	SPEED
Level 0	Light air	0.5 m/s
Level 1	Light breeze	1.5 m/s
Level 2	Gentle breeze	3 m/s
Level 3	Moderate breeze	6 m/s
Level 4	Wind at rest	8 m/s
Level 5	Fresh breeze	11 m/s
Level 6	Strong breeze	14 m/s
Level 7	Moderate wind	17 m/s
Level 8	Fresh wind	21 m/s
Level 9	Strong wind	24 m/s
Level 10	Strong wind	28 m/s
Level 11	Storm	32 m/s
Level 12	Hurricane	36 m/s

Another factor that significantly influences our comfort sensation is the activity we are performing. If several people are in a room wearing normal clothing, at rest or engaging in light activity, with a temperature between 20 and 24 °C, air movement at a speed of 1 m/s will provide them with a sensation of coolness. But if they are engaged in an activity that requires significant physical effort, that sensation of relief will not occur until the speed of the air affecting them reaches at least 1.3 m/s. In this example, the temperature of the air must be lower than that of the body and the humidity level must be low enough to allow for the evaporation of bodily sweat.