Spain

As a consequence of the sustainable politics demanding regulations that allow the use of more efficient ventilation systems, the IAQ Spanish regulations were modified and enforced in 2017. The new regulations became performance-based in order to accommodate the use of systems which are capable of adapting required ventilation rates to real needs. The new requirement is based on both CO2 concentration and a minimum ventilation rate. 

The new IAQ requirement is able to keep acceptable IAQ values and to reduce energy demand in relation to the previous IAQ requirement. 

Radon gas is a well-known building´s pollutant which can affect negatively people´s health (WHO, 2009). Radon´s source is the soil underneath buildings. Radon moves from the soil to the buildings by advection through cracks and joints, and diffusion through porous materials. Once radon enters buildings it can accumulate in lower areas due to lack of ventilation. Ventilation is one of the main ways to prevent radon from accumulating in enclosed spaces in the case of moderate radon concentrations up to 600 Bq/m3 (Collignan, 2008). 

Addressing the airtightness of the building envelope is key to achieve thermal comfort, good performance of ventilation systems and to avoid excessive energy consumption. Previous studies have estimated an energy impact on infiltration on the heating demand between 2 and 20 kWh/(m2·y) in regions with temperate climates. In Spain, this issue has not yet been addressed in depth. This study aims to assess the energy impact of uncontrolled air flows through the building envelope in residential buildings in Spain.

Outdoor air change qualifies the air that enters into the buildings. The outdoor air moves freely along the urban mesh favoured by the wind forces and stresses. Buildings, trees and other constructions alter the natural air flow pattern inside the cities, creating stagnated air masses in those wind-protected regions. Some outdoor spaces such as light shafts and confined light shafts inhibit the correct exchange of the stagnated air with fresh air coming from the outskirts and suburban areas. 

The Spanish Technical Building Code establishes the criteria for indoor air quality fixing minimum and constant ventilation rates per local. Currently, there is a proposal to modify the regulations so that the IAQ criteria becomes more useful by setting it based on average concentrations of CO2 and accumulated CO2 in the habitable rooms. However, the indoor average concentration is not the average concentration at which the occupants are exposed.

In high density occupation rooms, it is necessary to control indoor air quality (IAQ) combined with other comfort parameters. An adequate IAQ in classrooms enhances children learning and academic results are improved.

It is estimated that HVAC systems represent the highest energy consumption (approximately half of the total energy consumed) and one of the highest cost, especially in non-residential buildings. Therefore, that energy consumption in related to the cost of the building, the energy consumption and the thermal comfort.
Although the comfort of the users should be a factor to be aware of, it may not be the only one. It is advisable to have a balance between this variable and energy consumption, because of its impact on the environment and climate change.

It has already been proved that air leakage causes a great impact in the energy performance of buildings in cold climates. In recent years, many studies have been carried out in northern Europe, US and Canada. Regulations in these countries establish maximum air leakage rates for the construction of new dwellings and the refurbishment of the existing ones. However, there is a lack of knowledge relating to the housing stock in Spain.