Influence of building envelope on indoor air quality: Field measurements, analysis, and method development related to indoor odors
Doctoral thesis, 2023
The ventilation system should provide occupants with fresh air while removing excess pollutants from the building. However, increasing ventilation may inadvertently draw more pollutants into the occupant area or prove ineffective in altering emission rates from building materials and furnishings. If not addressed properly, this can make raising the ventilation rate inefficient, resulting in unnecessary heat losses or, in the worst case, reduced indoor air quality. This thesis addresses two previously insufficiently understood situations of contaminant transport within buildings, both manifested as unpleasant indoor smells: contaminant transport from adjacent compartments and early-stage emissions of air pollutants in new buildings.
The former, inspired by school buildings in Sweden demolished due to 'moldy' smells, was thoroughly explored in my Licentiate thesis, Contaminant Transport by Air Infiltration from Crawl Space to Occupant Area-Numerical Simulations and Field Measurements in Swedish schools, and is presented here as a summary.
The latter focuses on indoor air quality in new buildings, which often have initial high volatile organic compound (VOC) levels, typically perceived as a 'new smell.' In Sweden, it is common to run the ventilation system at full rate for several months as a remedy due to the negative effects of high VOC levels on occupants. However, the drawback of this strategy is the risk for over-ventilation with unnecessary energy losses. Two methods, ‘VOC-passport’ and ‘Ventilation threshold’, are developed to assess how ventilation can improve indoor air quality in more energy-efficient ways.
Results show that with VOC-passport, it is possible to simulate dynamic variations in VOC concentrations in new buildings based on passive VOC measurements and building physics modeling. With this method, it is possible to find an optimal ventilation strategy for low VOC concentrations and minimal energy losses. In addition, an analytical analysis of the diffusion of VOCs in materials shows that if ventilation rates exceed a certain threshold, further increases will not affect the emission rate. A quantified ventilation threshold is useful for setting the ventilation rate regarding optimal off-gassing and an important complement to the VOC-passport.
The former, inspired by school buildings in Sweden demolished due to 'moldy' smells, was thoroughly explored in my Licentiate thesis, Contaminant Transport by Air Infiltration from Crawl Space to Occupant Area-Numerical Simulations and Field Measurements in Swedish schools, and is presented here as a summary.
The latter focuses on indoor air quality in new buildings, which often have initial high volatile organic compound (VOC) levels, typically perceived as a 'new smell.' In Sweden, it is common to run the ventilation system at full rate for several months as a remedy due to the negative effects of high VOC levels on occupants. However, the drawback of this strategy is the risk for over-ventilation with unnecessary energy losses. Two methods, ‘VOC-passport’ and ‘Ventilation threshold’, are developed to assess how ventilation can improve indoor air quality in more energy-efficient ways.
Results show that with VOC-passport, it is possible to simulate dynamic variations in VOC concentrations in new buildings based on passive VOC measurements and building physics modeling. With this method, it is possible to find an optimal ventilation strategy for low VOC concentrations and minimal energy losses. In addition, an analytical analysis of the diffusion of VOCs in materials shows that if ventilation rates exceed a certain threshold, further increases will not affect the emission rate. A quantified ventilation threshold is useful for setting the ventilation rate regarding optimal off-gassing and an important complement to the VOC-passport.
material emissions
VOC
odor
ventilation
indoor air quality
Author
Fredrik Domhagen
Chalmers, Architecture and Civil Engineering, Building Technology
Method for Detecting Contaminant Transport through Leakages in a Condemned School
Proceedings of the 7th International Building Physics Conference, IBPC2018, Syracuse, NY, USA, 23-26 September 2018,;(2018)
Paper in proceeding
Impact of weather conditions and building design on contaminant infiltration from crawl spaces in Swedish schools—Numerical modeling using Monte Carlo method
Building Simulation,;Vol. 15(2022)p. 845-858
Journal article
Modelling VOC levels in a new office building using passive sampling, humidity, temperature, and ventilation measurements
Building and Environment,;Vol. 238(2023)
Journal article
Domhagen, F., Langer, S., Kalagasidis, A. S. Theoretical threshold for estimating the impact of ventilation on materials' emissions
Domhagen, F., Langer, S., Kalagasidis, A. S. Dynamics of VOC emissions from a new material
Two well-known yet previously insufficiently understood situations of contaminant transport within buildings, both manifested as unpleasant indoor smells, are addressed in this thesis: contaminant transport from adjacent compartments and early-stage emissions of volatile organic compounds (VOC) in new buildings.
When addressing potential pollutant sources in nearby spaces, such as crawl spaces, it's essential to consider natural ventilation and the distribution of air leakage when adjusting intentional ventilation. Otherwise, increasing ventilation may worsen indoor air quality by allowing contaminants to infiltrate through internal leaks. This observation is supported by both measurements and simulations.
Contrary to common practices in Sweden, increasing ventilation, often causing more energy losses, doesn't effectively address high VOC levels in new buildings. Two new methods, the ‘VOC-passport’ and ‘Ventilation threshold, help to evaluate ventilation's role in improving indoor air quality more efficiently. The VOC-passport helps find the best ventilation strategy for low VOC levels and minimal energy losses. Practical measurements and simulations validate the efficacy of this method.
Analyzing VOC diffusion in materials shows that beyond a certain ventilation threshold, further increases don't increase emission rates. This threshold helps determine an optimal ventilation rate for effective off-gassing, complementing the VOC-passport. Most importantly, the threshold can be calculated with minimum input data
When addressing potential pollutant sources in nearby spaces, such as crawl spaces, it's essential to consider natural ventilation and the distribution of air leakage when adjusting intentional ventilation. Otherwise, increasing ventilation may worsen indoor air quality by allowing contaminants to infiltrate through internal leaks. This observation is supported by both measurements and simulations.
Contrary to common practices in Sweden, increasing ventilation, often causing more energy losses, doesn't effectively address high VOC levels in new buildings. Two new methods, the ‘VOC-passport’ and ‘Ventilation threshold, help to evaluate ventilation's role in improving indoor air quality more efficiently. The VOC-passport helps find the best ventilation strategy for low VOC levels and minimal energy losses. Practical measurements and simulations validate the efficacy of this method.
Analyzing VOC diffusion in materials shows that beyond a certain ventilation threshold, further increases don't increase emission rates. This threshold helps determine an optimal ventilation rate for effective off-gassing, complementing the VOC-passport. Most importantly, the threshold can be calculated with minimum input data
VOC-pass. En metodik för proaktiv och energieffektiv ventialation av tidiga VOC i byggnader
Swedish Energy Agency (P2021-00173), 2021-12-01 -- 2023-12-29.
How to improve the indoor air quality in schools with a focus on contaminant transport from the building envelope accounting for the interaction with the ventilation system
Formas (2015-1589), 2016-01-01 -- 2019-12-31.
Subject Categories
Building Technologies
ISBN
978-91-7905-963-7
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5429
Publisher
Chalmers