C.T.E. DB-HS 3. The air quality. Thermodynamics and aerothermal energy

Demands of the C.T.E. DB HS 3 regarding air quality

To guarantee the air quality inside homes, the C.T.E. DB HS3 requires a series of requirements that must be applied in all types of housing: block housing, detached houses, row houses, and semi-detached houses. The Technical Code requires that the ventilation systems used be hybrid or mechanical ventilation systems. Through these systems, air must circulate from dry rooms to wet rooms, so in kitchens, toilets, and bathrooms, the extraction openings will be located, while bedrooms, dining rooms, and living rooms will have admission openings. It is also regulated the minimum flow of air that must be replenished in each of these rooms:

• Bedrooms: 5 l/s per occupant
• Living rooms and dining rooms: 3 l/s per occupant
• Toilets and bathrooms: 15 l/s in each room
• Kitchens: 2 l/s per m2 of usable area
• Storage rooms and common areas: 0.7 l/s per m2 of usable area
• Parking and garages: 120 l/s per parking space

Thermodynamics

The air is composed of a series of gases that are mainly oxygen and nitrogen plus a certain amount of water in the form of vapor, which is what we call humidity. Thermodynamics is a branch of science that studies the properties of dry air and the effects that variations in these properties have on it (such as pressure and volume).

Aerothermal energy

Another important property of air is temperature, which has allowed the development of very efficient air conditioning systems such as aerothermal energy. It takes advantage of the energy from the outside air, which is a practically inexhaustible source, making it a renewable energy like solar energy or wind energy.

The aerothermal energy uses a heat pump with an air-water system that extracts the heat present in the outside air in the form of energy to transfer it to the water. This water provides the heating system with the heat needed to condition the interior of the dwelling. It can also be used as sanitary hot water. This happens even in winter when the outside air is at low temperatures. Even under these conditions, the air contains energy in the form of heat, which is absorbed by a refrigerant circulating inside the system. Aerothermal energy systems are designed to operate even at temperatures as low as -20ºC.

Heat pumps have an outdoor unit and an indoor unit. Generally, the outdoor unit acts as an evaporator in winter while the indoor unit serves as the condenser that transfers heat to the water in the heating circuit. In summer, when cooling instead of heating, the process is carried out in reverse.

Aerothermal systems are designed for use in small places. Although they have high efficiency and performance, the heating power is not very high, so they cannot condition very large areas. Therefore, they can be installed in single-family homes and small premises.