Do you know the modifications that the CTE has undergone in ventilation?

In order to adapt the content of the Technical Code to the European Directive 2010/31/EU on energy efficiency, it has been revised and modified. The sections that have been modified are Section HE 1 Energy Demand Limitation and Section HS 3 Indoor Air Quality. This modification was published in BOE no. 149, of June 23, 2017, on pages 51621-51626. In this article, we summarize the most significant modifications regarding ventilation and air quality.

Modification of CTE DB HE 1 Energy Demand Limitation

The most significant modification is that, for the first time, the CTE introduces the concept of Nearly Zero Energy Building. In this way, it reflects the goal set by the European Union to achieve that by 2018 all new public buildings be NZEB (Nearly Zero-Energy Buildings) and by 2020 this is the case for all, regardless of their use.

Modification of CTE DB HS 3 Indoor Air Quality

The CTE DB HS 3, as originally drafted, offered solutions to meet the indoor air quality requirement, but did not provide all possible solutions as it did not take into account variable flow or adjustable ventilation systems. Thus, the Basic Document stipulated minimum ventilation flow rates for the mandatory general ventilation of the dwelling, based on occupancy and area.

For the first time, the CTE establishes a maximum CO2 concentration in the air that must not be exceeded, considering this chemical pollutant as an indicator of indoor air quality. Thus, it establishes that the maximum annual level cannot exceed 900 ppm (parts per million) and an accumulated maximum annual value of over 1600 ppm of 500,000 ppm per hour. Depending on the CO2 concentration and based on the RITE, it establishes four categories of indoor air (IDA 1, IDA 2, IDA 3, IDA 4).

New ventilation flow rates

When the habitable spaces are unoccupied, the CTE establishes a minimum flow rate of 1.5 l/s, as it is considered that the ventilation system must dilute contaminants that do not originate from the metabolic processes of living beings.

The new minimum flows are detailed below:

• Main room: 8 l/s, regardless of the number of rooms in the dwelling.

• Other rooms: no minimum flow is specified for housing with one or no rooms; for housing with 2 or more, 4 l/s per dwelling.

• Living rooms and dining rooms: if the dwelling has one or no bedroom, 6 l/s; if it has 2, the minimum flow is 8 l/s; if it has 3 or more, 10 l/s.

• In wet rooms, two types of flows are set (minimum in total and minimum per room). For dwellings with one or no bedroom, the first is 12 l/s and the second is 6 l/s. In dwellings with 2 bedrooms, the first is 24 l/s and the second is 7 l/s. For dwellings with 3 or more, the first is 33 l/s and the second is 8 l/s. If two uses share the same space, the higher flow will be provided. If there is a dry area and a wet area in the same space, two different flows must be provided (extraction and supply).

Regarding the specific additional system for kitchens (extractor hood), the modification specifies that a minimum extraction flow of 50 l/s must be guaranteed.

For non-habitable spaces, the ventilation flows remain the same.

New design criteria

The modification presents a new appendix, which establishes the design conditions to establish the ventilation flow. As previously mentioned, the modification aims to take into account variable flow ventilation systems and not just constant flow systems.

To estimate whether the requirements related to CO2 concentration are met, a generation rate of 12 l/h per person while sleeping and 19 l/h per person while awake is established.

Regarding occupancy, more realistic data drawn from the INE have been taken into account. On the other hand, to optimize processes, different occupancy scenarios have been established according to sleep schedules, a series of absences, simultaneous occupation of rooms, and specific uses of washbasins and bathrooms.