Building Airtightness Research Articles

Indoor Volatile Organic Compounds in Prefabricated Timber Buildings—Challenges and Opportunities for Sustainability

Prefabricated timber buildings offer a low-carbon approach that can help reduce the environmental impact of the building and construction sectors. However, construction materials such as manufactured timber products can emit a range volatile organic compounds (VOCs) that are potentially hazardous to human health. We evaluated 24 years (2000–2024) of peer-reviewed publications of VOCs within prefabricated timber buildings. Studies detected hazardous air pollutants such as formaldehyde, benzene, toluene, and acetaldehyde (indoor concentration ranges of 3.4–94.9 µg/m3, 1.2–19 µg/m3, 0.97–28 µg/m3, and 0.75–352 µg/m3, respectively), with benzene concentrations potentially exceeding World Health Organization indoor air quality guidelines for long/short term exposure. Most studies also detected terpenes (range of 1.8–232 µg/m3). The highest concentrations of formaldehyde and terpenes were in a prefabricated house, and the highest of benzene and toluene were in a prefabricated office building. Paradoxically, the features of prefabricated buildings that make them attractive for sustainability, such as incorporation of manufactured timber products, increased building air tightness, and rapid construction times, make them more prone to indoor air quality problems. Source reduction strategies, such as the use of low-VOC materials and emission barriers, were found to substantially reduce levels of certain indoor pollutants, including formaldehyde. Increasing building ventilation rate during occupancy is also an effective strategy for reducing indoor VOC concentrations, although with the repercussion of increased energy use. Overall, the review revealed a wide range of indoor VOC concentrations, with formaldehyde levels approaching and benzene concentrations potentially exceeding WHO indoor air quality guidelines. The paucity of evidence on indoor air quality in prefabricated timber buildings is notable given the growth in the sector, and points to the need for further evaluation to assess potential health impacts.

Guidelines for Predicting Airtightness in Residential Buildings under Climatic Pressure Conditions

This paper presents a generalized approach for predicting building airtightness based on pressure difference measurements. Furthermore, it provides practical guidelines for applying this method. Studies have proposed a method for predicting the airtightness of high-rise residential buildings in winter using the pressure difference caused by the stack effect. This method was validated using tests under various temperature differentials and building heights. However, practical guidelines for its implementation are lacking. To generalize the airtightness prediction method, a 95% confidence interval for the results was calculated using the blower door test. The applicable pressure difference was calculated based on the calculated results. For each building, the minimum differential pressure within a 95% confidence interval was at least 20 Pa. To provide guidelines for utilizing the proposed airtightness prediction method, acceptable conditions characterized by ΔH × ΔT ≥ 750 m∙°C were calculated. An acceptable condition, characterized by ΔH × ΔT ≥ 750 m∙°C, showed the highest agreement between predicted and measured values across all buildings. This study outlines practical guidelines for using the proposed methodology under these conditions. Overall, we present a straightforward method that relies solely on measuring pressure difference, thereby eliminating the need for a complex and challenging blower door test, typically used in real-world scenarios. By applying this method to predict airtightness in building conditions, the accuracy of predictions for energy use intensity and indoor air quality can be significantly improved.

Assessing the performance of infrared thermography and PIV methods to identify and characterize the air inlets and outlets in wall assemblies

Building airtightness is crucial for reducing energy demand in the building sector and preventing moisture damage and indoor environment quality issues. Mandatory airtightness tests are now commonly performed in many countries to quantify the total envelope leakage rate of real buildings. For a more precise diagnosis, air leakages are usually identified by infrared thermography or visualized by smoke. However, a finer analysis is also needed to characterize precisely the air flow through specific leaks. Numerical models have been developed for this purpose but experimental data are necessary to validate them. In this paper, two experimental approaches are tested on simple light-wall assembly configurations to address this need: infrared thermography (IRT) and the innovative use of particle image velocimetry (PIV) with a specific experimental set-up and protocol developed. The results are compared with each other as well as with numerical simulations. Results showed that both techniques can be applied for the experimental characterization of the air inlet/outlet of a wall assembly with different advantages and drawbacks. IRT is easy to implement, non-intrusive, possible for in-situ investigations, but the correlation between the thermographs and the air dispersion at the outlet is not straight forward due to thermal inertia and heat conduction issues. PIV gives direct results on the velocity field and enables quantitative analysis of air flow rates for various configurations, with some limitations: a difficult implementation; restrictions on the possible infiltration velocity range and difficulties to visualize the flow exactly at the interface with the wall assembly.

Analysis of the regulatory and legislative base of Ukraine and the European experience in conducting energy audits of buildings

The article analyzes the regulatory and legislative base for the energy efficiency of buildings. It identifies the main areas for improving energy efficiency by improving the process of energy audit, as well as improving the system of indicators that determine the airtightness of the building and preservation of comfortable conditions for human stay in the room. The relevance of the work is determined by the problem of low energy efficiency of the housing stock of Ukraine, which affects the rational consumption of energy, necessitates the introduction of various measures aimed at rationalizing energy use in general and buildings in particular, setting maximum permissible energy consumption rates for buildings and strengthening relevant control. The imperfection of the regulatory and legislative base in the field of energy efficiency, the need to develop a state standard for the design of buildings with increased air permeability, the development of a methodology for determining the air permeability of a building, the legislative establishment of minimum requirements for building airtightness, the development of a methodology for testing buildings for airtightness, and the imperfection of the methodology for conducting an energy audit of a building form the basis for further research. To improve the energy management of buildings, it is proposed to introduce mandatory testing of the building for airtightness, which will standardize approaches to energy management and compliance with the relevant requirements for building airtightness will lead to an increase in the energy efficiency class of buildings. Keywords: energy efficiency, energy audit, air permeability, airtightness.

A Case Study of Air Infiltration for Highly Airtight Buildings under the Typical Meteorological Conditions of China

A Case Study of Air Infiltration for Highly Airtight Buildings under the Typical Meteorological Conditions of China

Study on air tightness and thermal comfort of high-rise Glulam structure buildings

ABSTRACT Building air tightness, indoor temperature, and humidity moment affect the building indoor personnel’s subjective comfort. Therefore, this article takes a six-story Glulam post and beam with shear wall construction as the main test object, with a light wood frame construction house and a log house in the same area as comparison objects. The research conclusion shows that the air change frequency of the tested building is 4.64 h−1, which is consistent with the normal situation; the air tightness is good. There are thermal bridges at the building nodes of each structure type. The joints of the enclosure structure members have a certain influence on the generation of thermal bridges. Compared with the comparison objects, the building has the best thermal insulation performance, the most stable indoor temperature and humidity, and the best way to keep the indoor environment at a more comfortable stage for the human body.

Model-Scale Reproduction of Fan Pressurization Measurements in a Wind Tunnel: Design and Characterization of a New Experimental Facility

In many countries, building airtightness is mandated by national regulations or energy efficiency programs, necessitating accurate measurements using the fan pressurization method. Given the significant influence of wind on measurement uncertainty and the need for reliable regulatory tests, experimental studies in a controlled environment are needed. This paper presents a novel experimental facility designed to replicate fan pressurization measurements on a model scale under controlled laboratory conditions. The key features of the facility include the ability to (1) conduct fan pressurization measurements, (2) generate steady wind conditions across varying wind speeds, and (3) accurately measure parameters like the pressure difference, wind speed, and airflow rate. The experimental facility includes a pressurization device, a wind tunnel, and a model representing a two-story house with nine distinct leakage distributions. A total of 96 fan pressurization measurements were executed using this setup, adhering to the similarity conditions specifically defined for assessing airflow errors due to wind. These tests followed the ISO 9972 standard, with the pressure differences ranging from 10 Pa to 100 Pa and steady wind speeds from 1 m·s−1 to 7.5 m·s−1. This experimental facility marks a significant advancement in understanding the effect of wind on building airtightness measurements.

Reassessing ISO 9972 constraints: A mathematical analysis of errors in building airtightness tests due to steady wind and stack effect

Building airtightness significantly impacts its energy use estimation. The fan pressurization test, outlined in ISO 9972, is the most commonly used assessment method. A crucial component is the zero-flow pressure difference, influenced only by wind and stack effects. The ISO 9972 mandates that the absolute value of this pressure difference be less than 5 Pa and the minimum pressure station be either 10 Pa or five times the zero-flow pressure difference. The rationale behind these constraints is not evident, often excluding high-rise and buildings in wind-prone areas from standardized testing.This research examines these ISO 9972 requirements, aiming to clarify their basis and propose alternatives. Equations were developed to connect airflow estimation error with the ratio of the measured pressure station to zero-flow pressure difference. The external pressure measurement location during the test was found pivotal in determining airflow errors due to ISO constraints. While existing constraints limit airflow errors in many scenarios, enhancements are possible. If ISO 9972 conditions are unfeasible, always maintaining a 10 Pa buffer across façades can contain maximum airflow errors. This study suggests an alternative constraint with a similar error range (about 15 %) to current ones, enabling standardized testing in environments where existing ISO conditions are unattainable.

Exploring the Role of Airtightness for Achieving Carbon Neutrality in Canadian Residential Buildings: A Streamlined Life Cycle Assessment

This study delves into the relationship between airtightness levels and the entire life cycle carbon emissions of buildings across diverse Canadian climates. With the 2020 update of the National Energy Code of Canada for Buildings, whole-building airtightness testing was introduced as an option, prompting discussions on its mandatory nature. Using a net zero target, our assessment unfolds in two phases. Initially, we employ three-dimension (3D) modeling in Revit to replicate a typical Canadian detached house’s architectural features and material compositions. Subsequently, the model was imported into One Click life cycle assessment (LCA) to set parameters such as lifetime, gross interior area, and annual electricity consumption. Our analysis is bifurcated into assessing climatic conditions in Edmonton, Toronto, and Vancouver, alongside examining code-specified airtightness levels. We compared annual energy loss per unit area at varying airtightness levels accounting for the general deterioration of airtightness in new buildings during the pre-service phase to pinpoint the optimal airtightness value (ACH50) during the design stage. The subsequent phase evaluated increased carbon emissions from material replacement to meet this optimal airtightness condition and passive energy savings. Findings underscore that designing airtightness to an ACH50 value of 1.0 is the most energy-efficient. Comparative analysis reveals that achieving carbon neutrality solely through increased envelope airtightness and passive energy savings, is viable in Edmonton (18.4 years) owing to regional energy source disparities. In contrast, Toronto and Vancouver necessitate active energy-saving devices to attain carbon neutrality over the design lifetime.

Applying infrared thermography to a latest residential building in France: case study, verifying dwellings national thermal regulations RT 2012 mainly thermal bridges assessment

High-performance insulation and airtight building envelopes are the two most important factors to optimize the building energy efficiency and thermal performance. However, thermal performance of building envelopes can be significantly affected by thermal bridging. Thermal bridges can take place at different locations of the building envelope, causing added transmission losses, increasing heat flow, lower inner surface temperatures. Thermal bridges are regarded in all national regulations for new buildings of all states of European Union (EU) but there are no specifications assessing balconies to wall junctions and the impact on the building thermal performance is not well regulated. In this paper, balcony to wall thermal bridge assessment using infrared thermography is highlighted. The originality is that, infrared thermography, has been applied to a real living latest building in the north east of France showing that there is noncompliance in the national regulations as some exigencies are not met. Thermography of thermal break windows and window doors has also revealed air leakage. The goal, is to illustrate that thermal imaging is a means of quality assurance to new building specifications and should include a clause specifying quality assurance procedure for balconies junction in national building regulations for all states of the EU.

A Microalgae Photobioreactor System for Indoor Air Remediation: Empirical Examination of the CO2 Absorption Performance of Spirulina maxima in a NaHCO3-Reduced Medium

Microalgae-based photobioreactors (PBRs) have gained attention as a sustainable solution for indoor air quality (IAQ) control. This study investigates indoor CO2 absorption performance of Spirulina maxima (S. maxima) in NaHCO3-limited cultivation (standard: NaHCO3-free medium = 1:1 v/v%) of a lab-scale PBR system. Cultivation performance of three medium amendments (standard, 50% NaHCO3, and NaHCO3-free) was compared by observing cell growth for 30 days in a controlled environment. Empirical examinations were conducted to evaluate the algal CO2 uptake, and overall system performance in the culture volumes of 2, 4, and 7 L and natural indoor CO2 concentration of ~1100 ppm. We found CO2 was reduced by ~55%, in an air chamber of 0.064 m3, showing the greatest mitigation rate (~20%) on Day 4. Under a high concentration of CO2 (10,000 ppm), the CO2 levels were decreased up to ~90% before saturation. This research provides valuable insights into the development of S. maxima-activated IAQ control systems for airtight buildings.

Openings in ventilated Attics

How big should ventilation openings be in ventilated attics? In Denmark, guidelines describe what is sufficient to remove excess moisture penetrating through the ceiling. These guidelines are based on many years of experience. An important parameter is the tightness of the ceiling. With current regulations for the airtightness of buildings, convection through the ceiling is reduced compared to older buildings. Therefore, it is relevant to review these old rules of thumb and maybe revise them. In this two-year study, tests with different sizes of ventilation openings were conducted in a test house with 18 separate ventilated attics and airtight ceilings. One third of the attics were ventilated according to the guidelines, one third’s ventilation was reduced by one third and the last third had 50 % ventilation of the recommendations. Hourly measurements of temperature and relative humidity in the attics were conducted. Rafters in the attics were tested for mould growth. Six different types of insulation systems were used in the attics (with and without a vapour barrier, different insulation materials, and insulation thickness), therefore, the study also includes these differences. Earlier investigations, with full ventilation in all attics, showed no significant hygrothermal differences between them; consequently, it was assumed that the amount of ventilation would be decisive for the hygrothermal performance. This study follows up on this assumption. Results show little differences between the attics, mainly that having a vapour barrier becomes more important with reduced ventilation, and the insulation thickness and thereby U-value is of less importance. Reducing the requirements for ventilation of attics could be relevant, provided that the ceiling is airtight.

Policies and Energy Efficiency of Heat Recovery Ventilators in South Korea

To reduce national greenhouse gas emissions, the South Korean government has encouraged new energy businesses and implemented policies to reduce energy consumption in buildings, and aims to construct all new buildings as zero-energy buildings by 2025. According to the promotion of policies on passive houses and zero-energy buildings, the thermal insulation and airtight performance of new buildings have been further enhanced. However, to enhance indoor comfort and air quality in new airtight buildings, it is critical to secure an adequate amount of ventilation. Heat recovery ventilators (HRVs) in South Korea have been used for more than 20 years as high-efficiency energy equipment; however, the high-efficiency standard 20 years ago (cooling efficiency 45%, heating efficiency 70%) is still being employed without any change. Most HRVs in the Korean market either meet or exceed this standard. This study examined HRV performance changes from 2010 to 2020 based on the data of 847 HRV performance certifications given by a certification agency. It also analyzed how institutional strategies and related laws contributed to the enhancement of such performance. As HRVs in South Korea are only required to satisfy the pre-defined efficiency criteria, the development and use of HRVs focus more on cost reduction rather than efficiency enhancement. Under such market conditions, it is challenging to research and design highly efficient HRVs along with customer satisfaction. If better market conditions are offered that would welcome HRVs with higher efficiency, the development of better HRVs, as compared to those analyzed in this research study, would be possible.

Cold Climate Challenges: Analysis of Heat Recovery Efficiency in Ventilation Systems

As building energy consumption gains ever-increasing attention worldwide, the focus on addressing it through the examination and optimization of efficient heat recovery solutions continues to intensify. With well-insulated and airtight buildings, the proportion of heating needs attributed to ventilation is growing, leading to the widespread integration and optimization of heat recovery solutions in mechanical ventilation systems. Heat recovery in ventilation is a highly efficient strategy for reducing heat losses and conserving energy. This study involves the investigation of a ventilation unit installed in an apartment situated in Riga, Latvia, as a practical examination of heat recovery system efficiency within the Latvian climate conditions, representing a cold climate region. The objective of this study was to examine the heat recovery efficiency of the ventilation system in the Latvian climate with variable outdoor and exhaust air parameters, given that the dry heat recovery efficiency is different from the actual heat recovery efficiency. The ventilation unit was equipped with a plate heat exchanger at an airflow rate of 105 m3/h. To evaluate heat recovery efficiency, extensive measurements of air temperature and relative humidity were conducted. The collected data was analyzed, employing statistical regression analysis to ensure measurement reliability and assess correlations. The findings indicated a strong correlation between variables such as heat content, moisture content, and sensible air parameters. It was observed that the actual heat recovery efficiency was 6% higher than the calculated dry efficiency, emphasizing the importance of considering real-world conditions in heat recovery assessments. Additionally, regression analysis demonstrated a positive linear correlation with a coefficient of 0.77, highlighting the dependency between actual measurements and the theoretical model. These quantitative outcomes provide essential insights for optimizing heat recovery systems and enhancing energy-efficient ventilation practices, especially in cold climate environments. Moreover, this study highlights the strong correlation between variables such as heat content, moisture content, and sensible air parameters. Findings offer essential insights for optimizing heat recovery systems and enhancing energy-efficient ventilation practices, especially in cold climate environments.

In Situ Airtightness Measurement Using Compressed Air Flow Characteristics

The airtightness of a building has a significant impact on energy savings, structural longevity, and indoor air quality for occupants. Therefore, it is essential to accurately measure the airtightness of buildings, though the widely used fan pressurization method suffers from several shortcomings. For this reason, transient methods have recently emerged to assess airtightness by monitoring pressure changes over time, but studies using transient methods in this field are rare. In this study, we selected three representative buildings to conduct field tests to verify the practical applicability of the improved transient method. To verify the results of the transient method, we conducted a comparison experiment with the blower door test: a widely used measurement method. When measuring the effective leakage area, the average standard deviation of the transient method was 0.903 cm2, which was much smaller than the blower door test result of 1.488 cm2. In addition, the recorded standard errors ranged from 0.197 cm2 to 0.816 cm2 for the transient method and from 0.269 cm2 to 1.801 cm2 for the blower door test. Notably, the transitional method was more reproducible than the blower door test while showing similar accuracy. Given these results, it is expected that the improved transitional method can be used to evaluate airtightness performance in the field.

Airtightness Assessment under Several Low-Pressure Differences in Non-Residential Buildings

The thermal performance of building envelopes is significantly affected by building insulation and airtightness. However, most studies have focused on improving thermal performance in building envelopes, while few studies on improving airtightness in buildings have been conducted. The present study measured airtightness and infiltration in non-residential buildings using fan pressurization and tracer gas methods. By analyzing the results obtained from both methods, the distribution of the correlation factors was identified, which can be used for the air leakage rates obtained from the blower door test to estimate the infiltration rates under natural airflow conditions. Since it is difficult to get the values of ACH50 through the blower door test in buildings of large volume or where large air leakages occur, the study proposed a method to convert the values of airtightness under several low-pressure differences of 20 Pa, 25 Pa, 30 Pa and 35 Pa into ACH50 using conversion coefficient. By dividing the air leakage rate under 20 Pa pressure difference by the conversion coefficient of 0.60, the values of ACH50 can be estimated. Results converted to ACH50 using conversion coefficient for various pressure differences of 20 Pa, 25 Pa, 30 Pa, and 35 Pa showed an error of 0.1–4.4%, respectively, compared to actual ACH50 measurement results.

Quantitative correlation between buildings air permeability indicators: Statistical analyses of over 400,000 measurements

Several building airtightness databases were created in many European countries thanks to the development of commissioning tests. However, comparing building performance across countries can be challenging, as various indicators are used to measure the air permeability of buildings depending on the specific application and the nation’s regulation. This paper examines the comparison of air permeability indicators used in various countries and seeks to establish default conversion equations between these indicators. To do so, a statistical analysis was conducted on the French database. The most frequently used indicators are the specific air leakage rate per envelope area and the air change rate at a reference pressure of 50 Pa in most countries and 4 or 10 Pa in a few other countries. The compactness appears to be a relevant geometric parameter for characterising the relationship between the air permeability indicators, as it encapsulates both the shape of the building and its contact with adjacent buildings. Correlations between the different indicators have been calculated according to the building type and compactness. Thus, this study concludes that indicators can be reliably estimated by knowing the building type and geometry. A general correlation is provided with a higher estimation error if the geometry data is missing.

Air infiltration and related building energy consumption: A case study of office buildings in Changsha, China

Past studies reveal that air infiltration through the building envelope and its impact on the indoor environment and energy consumption are significantly influenced by climate characteristics. However, little relevant information is available for buildings in southern China, where the building design traditionally follows a philosophy of being open and shaded. The present study employs both experimental measurements and numerical simulations to investigate the airtightness of buildings in Hot Summer and Cold Winter (HSCW) climate region of southern China and the associated energy consumption. The measurements and simulations are based on a typical office building in Changsha. Measurement results show that the air change rate of six tested spaces at the natural pressure difference ranges from 0.10 to 0.30 h−1 with an average of 0.17 h−1 in summer, and from 0.09 to 0.32 h−1 with an average of 0.16 h−1 in winter. The operation of the air-conditioning system affects largely air infiltration, and each unit change in setpoint air temperature can result in an average of one-third or more change in air infiltration rate. Simulation results show that a decrease in air infiltration rate from 0.17 h−1 to 0.01 h−1 reduces the infiltration-related cooling energy consumption from 14.29 to 0.75 kWh/m2·year and heating energy consumption from 8.20 to 0.39 kWh/m2·year. The same change in the setpoint air temperature of air-conditioning system in summer and winter results in different infiltration-related energy consumption. The findings would contribute to an improved energy simulation and assessment of buildings in southern China.

Applicability and evaluation of airtightness prediction method using pressure differences under actual climate conditions

The blower door test and tracer gas test methods are commonly used to measure airtightness and infiltration in buildings. Nonetheless, these methods can be costly and time-consuming. To address these issues, the air pressure measurement and prediction system (APMPS) was proposed. This method predicts the airtightness of a building by measuring the differential pressure across its components. However, the effectiveness of this method has yet to be verified under various conditions. The aim of this study is to analyze the effectiveness of the APMPS under different building and weather conditions. Three residential buildings of varying heights were analyzed, and measurement of differential pressure and temperature differences were taken. The actual airtightness was determined using blower door tests, and the results were compared to the predicted airtightness calculated by the APMPS. The results indicate that APMPS is effective in predicting building airtightness, with the majority of predicted values falling within the range of 2-3 h−1 at 50 Pa. The accuracy of the predictions improved as the building height, differences in indoor and outdoor temperatures, and differential pressure increased. Furthermore, a significant correlation was observed between the error rate, height difference, and differential pressure at a significance level of 1%. The APMPS has demonstrated its value as reliable tool for accurately predicting the airtightness of multi-story buildings under various conditions. This method simplifies the measurement of airtightness in building components, which is crucial for evaluating building energy demand and air quality.

Quantifying suite-level airtightness in newly constructed multi-unit residential buildings using guarded suite-level air leakage testing

Improving inter-zonal airtightness in multi-unit residential buildings (MURBs) has wide-ranging benefits including reduced odour/pollutant transfer, reduced sound transmission, and improved energy efficiency. The current metric used to assess inter-zonal airtightness in MURBs is the unguarded air leakage rate, which measures the air leakage through all interior and exterior suite boundaries. While this metric provides a general indication of overall suite airtightness, it provides no information on the location or distribution of leakage pathways across the individual suite partitions. Depending on the construction type(s) of suite partitions there may be variability in air leakage rates at the partition level, which is masked by the whole-suite metric. This makes it difficult to identify potential areas for improvement in design and construction practices.Guarded blower door testing was completed in 14 suites in six newly constructed/renovated MURBs, in Southern Ontario, Canada. Whole-suite air leakage rates for the sample were generally low, consistent with previous studies. Broken down by partition type, floor/ceiling and suite-to-suite walls exhibited similar levels of airtightness, with sample means of 0.36L/s/m2 and 0.32L/s/m2, respectively, at 50Pa (0.07cfm50/ft2 vs. 0.06cfm50/ft2). In contrast, the average suite-to-corridor wall air leakage rate was nearly eight times higher (2.46L/s/m2 (0.49cfm50/ft2)). The results highlight the need to develop targeted air sealing strategies to improve suite-to-corridor wall air leakage rates. Recommendations for improving inter-zonal air sealing practices in new construction are discussed. The measurements reported in this work will also help to improve building airflow simulations, which rely on partition-level air leakage metrics for model inputs.