The effect of airtightness required in building energy conservation regulations on indoor and outdoor originated pollutants

Fatemeh Zahed; Alireza Pardakhti; Majid Shafiepour Motlagh; Behrouz Mohammad Kari; Azadeh Tavakoli

doi:10.1016/j.heliyon.2023.e20378

The effect of airtightness required in building energy conservation regulations on indoor and outdoor originated pollutants

Heliyon. 2023 Sep 21;9(10):e20378. doi: 10.1016/j.heliyon.2023.e20378. eCollection 2023 Oct.

Authors

Fatemeh Zahed^{1

2}, Alireza Pardakhti¹, Majid Shafiepour Motlagh¹, Behrouz Mohammad Kari², Azadeh Tavakoli³

Affiliations

¹ School of Environment, College of Engineering, University of Tehran, Tehran, Iran.
² Energy Department, Road Housing and Urban Development Research Center (BHRC), Tehran, Iran.
³ Department of Civil Engineering, Faculty of Engineering, University of Zanjan, Zanjan, Iran.

Abstract

The contradiction of indoor air quality (IAQ) and energy conservation by isolating the indoor environment from the outdoor through airtightness is one of the challenges of the building sector. The key issue is, what are the optimum airtightness limits that can ensure IAQ in naturally ventilated buildings, taking into account the paradoxical effect of house leakages on the infiltration of outdoor pollutants and accumulation of indoor-generated pollutants? For this purpose, the effect of different levels of airtightness required in energy-compliant, low-energy, and very low-energy buildings on the concentration of two pollutants with outdoor and indoor origin, PM2.5 and formaldehyde, respectively, were studied. This study used a multizone model, CONTAM(W), which was validated using measured data to study the distribution of selected pollutants in a typical relatively old dwelling, to investigate the situation in Iran. Subsequently, we conducted simulations based on different combinations of scenarios for airtightness, user behavior, source strength, and meteorological parameters. The results showed that increasing the airtightness from the baseline scenario (ACH50 = 11.11/h) to 3, 1.5, and 0.75 in closed window conditions reduced the PM2.5 by 15%, 38%, and 58%, respectively, and elevated formaldehyde by 23%, 77%, and 169%, correspondingly. Under normal outdoor PM2.5 pollution, indoor formaldehyde levels exceeded the permissible limit only in closed window conditions, and IAQ remained acceptable in other scenarios. However, there is no indication that IAQ can be ensured by any degree of airtightness under severe outdoor air pollution, demanding specific solutions, such as those proposed in this work.

Keywords: CONTAM; Envelope airtightness; Formaldehyde; PM2.5; Simulation; User behavior.