Slam the Door Shut: Improving Building Energy by Evaluating Building Airflow

Scientists highlight the significance of addressing interzonal airflow across household entrance doors in reducing heat loads

The building sector is a major contributor to the increasing demand for energy and corresponding carbon emissions. As focus shifts to low-energy buildings, it is vital to comprehend the precise factors contributing to increased energy use. Now, scientists from Korea have studied the impact of external air infiltration and interzonal airflow on heating loads in multifamily high-rise buildings (MFHRBs), establishing a framework for evaluating airtightness in similar structures across different climate zones.

Buildings can play an essential role in the transition to a sustainable society as their construction, operation, and disposal require energy in different ways. For low-energy multi-family high-rise buildings (MFHRBs), the Korean government has consistently strengthened external thermal insulation. In winters, however, the height and compartmentalized nature of MFHRBs make the airflow between building spaces bring cold air into the house through air leaks in building elements (such as doors), inflating heating demands. Despite accounting for a sizeable portion of energy consumption, weather-driven airflow has garnered little attention.

Fortunately, a duo of scientists from Incheon National University, Korea, Mr. Juhyun Bak and Prof. Sungmin Yoon, recognized the importance of addressing weather-driven airflow to achieve low-energy building standards. In their recent study published in Renewable and Sustainable Energy Reviews, the scientists identified the prevalence of interzonal airflow in MFHRBs in Korea. “Several studies have focused solely on outdoor air infiltration across the building envelope as a cause of rising energy consumption,” says Prof. Yoon, explaining the motivation behind the study. “However, in MFHRBs, the interzonal airflow across the entrance door is the dominant factor in calculating household heating loads. We wanted to highlight this phenomenon and the role of entrance doors in air leakages.”

The scientists investigated the weather-driven airflow and the corresponding heating energy demand in MFHRBs using coupled thermal and airflow network simulation with measured and calibrated leakage datasets, and chose eight representative locations in Korea to exemplify different regional weather conditions. They compared the simulation outcomes to the approved heating energy demand of 15 kWh/m2⋅year and airtightness of 0.6 ACH50 (air changes per hour at a pressure difference of 50 Pascals — a standard metric used to assess airtightness).

They found that interzonal airflow rates were larger than external infiltration rates. This was due to strong stack effect (air movement due to temperature difference) during winters. Even with improved thermal insulation, the majority of Korea’s heating energy demand could not meet the standards. The airtightness limit (0.6 ACH50), while acceptable for southern regions, needed to be reduced for central regions. Furthermore, the weather-driven airflow dynamics made the conventional airtightness measures (ACH50) unreliable, calling for the use of other standard metrics (e.g., leakage area metrics for each airflow path) in such conditions.

“When recommending optimal airtightness levels for low-energy buildings, it is essential to consider the entrance door airtightness. Likewise, door manufacturers can market their products in compliance with the new regulations to achieve energy savings. We believe our study will redefine the approach to measuring airtightness,” comments an optimistic Prof. Yoon.

Let’s hope that this study will be a big step towards building sustainable vertical cities!

Reference

Authors: Juhyun Bak (1), Sungmin Yoon (1,2)

Title of original paper: Dwelling infiltration and heating energy demand in multifamily high-rise and low-energy buildings in Korea

Journal: Renewable and Sustainable Energy Reviews

DOI: https://doi.org/10.1016/j.rser.2021.111284

Affiliations:

(1) Division of Architecture and Urban Design, Incheon National University, Republic of Korea

(2) Institute of Urban Science, Incheon National University, Republic of Korea

About Incheon National University

Incheon National University (INU) is a comprehensive, student-focused university. It was founded in 1979 and given university status in 1988. One of the largest universities in South Korea, it houses nearly 14,000 students and 500 faculty members. In 2010, INU merged with Incheon City College to expand capacity and open more curricula. With its commitment to academic excellence and an unrelenting devotion to innovative research, INU offers its students real-world internship experiences. INU not only focuses on studying and learning but also strives to provide a supportive environment for students to follow their passion, grow, and, as their slogan says, be INspired.

Website: http://www.inu.ac.kr/mbshome/mbs/inuengl/index.html

About the author

Dr. Sungmin Yoon is an Assistant Professor at the Incheon National University, Korea. He earned his Ph.D. from the Department of Architectural Engineering at the University of Nebraska-Lincoln, USA in 2018. Building airflow and intelligent buildings are two of his primary research interests. He is currently focused on researching virtual sensing-driven intelligent applications in a smart city. In 2019, the Building and Environment journal honored him with the Best Paper Award. He has published 48 papers with over 300 citations to his credit.

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Incheon National University

Academic excellence is paired with an unrelenting devotion to innovative research & global education. Link: http://www.inu.ac.kr/mbshome/mbs/inuengl/index.html