The role of complex airflow simulation tools for overheatingassessment of passive houses

Passive Houses are characterized mainly by construction concepts that greatly reduce energy usage during the winter, but that can lead to significant overheating during the hotter summer days. Since in the Passive House concept thermal comfort during the summer mainly relies on natural ventilation to provide indoor cooling, the importance of airflow modeling tools for overheating prediction needs to be investigated. This research analyzes the effect of simplifications commonly made in airflow modeling techniques on the overheating assessment of Passive Houses by collecting measured data and calibrating a thermal model with a Passive House case study. Utilizing the calibrated model, a standalone Building Energy Model (BEM), BEM coupled with an Airflow Network Model (AFN), and BEM coupled with an AFN supported by the wind pressure coefficient values obtained from Computational Fluid Dynamics (CFD) simulation were created. The outcome of each modeling approach was then compared against each other. Results showed that the default infiltration and natural ventilation input values commonly utilized in literature, when compared to those obtained from either the AFN or AFN+CFD, are significantly overestimating the natural ventilation potential of Passive House buildings, resulting in a lower number of overheating hours (39.9% decrease) and inaccurate overheating evaluation outcomes. Therefore, the paper concludes that the use of at least an AFN is necessary when estimating the overheating hours of Passive Houses.

ENERGY EFFICIENT CONSTRUCTION IN UKRAINE AND FRANCE

Problem statement. The building materials choice is usually based on non-environmental criteria, such asfunctionality, technical characteristics, aesthetics, cost, etc., and the environmental and human health impact is rarely takeninto account. Greenhouse effects, climate change, and energy issues remain a key issue at both European and internationallevels. Today, energy-efficient and eco-friendly areas are gaining more and more popularity in the construction industry, sothe design and construction of energy-efficient and environmentally friendly buildings in Ukraine, considering the worldexperience, including European, remains a live issue today. The purpose of this article is to explore the concepts ofenergy-efficient buildings and so-called "green" construction, as well as to analyze and explore the experience of usingenergy-saving resources in Ukraine and France. Results. Ecological and passive houses in Ukraine, energy-efficient andecological buildings in France, Hitachi technologies have been analyzed. Scientific novelty and practical significance. Theanalysis of the problem of improving the energy efficiency of buildings and ways to solve it allowed to identify ofpromising areas of green construction in Ukraine, which will form the basis for further improvement of methods offormation, evaluation, justification, and selection of rational organizational and technological solutions for energy-efficientconstruction and reconstruction.

Analysis of Professionals’ and the General Public’s Perceptions of Passive Houses in Korea: Needs Assessment for the Improvement of the Energy Efficiency and Indoor Environmental Quality

Despite the economic and environmental benefits of passive houses, their market penetration has been low, which is partially due to misperceptions regarding their cost. This study examined the perceptions of building-related professionals and the general public regarding Korean passive houses to explore strategies for spurring passive house concepts and practices. The participants took an online survey on their interest in and reasons to reside in passive houses and their expected construction costs. The results from two separate groups of participants, including 162 professionals and 130 members of the general public, were analyzed using descriptive and inferential statistics. Both the professional and general public groups expressed a strong interest in passive houses because of the comfortable and healthy indoor environment, energy efficiency, cost savings, and sustainability that they provide. However, the expected construction costs of passive houses were perceived differently by the two groups: They were believed to be less expensive by the professionals and more expensive by the public respondents. This difference seems to result from their prior knowledge or experience regarding passive houses. Both groups were willing to pay more and assumed that the high expected costs were related to the construction products, systems, and labor costs of passive houses. The results showed that the lack of information or education on passive houses could be a major barrier to accessing passive houses, especially with the general public, while the cost could pose less of a barrier to the overall growth of the Korean passive house market. Further efforts by the government and industry are needed in order to provide more educational programs and to identify and manufacture more reasonably priced construction materials.

Reducing linear thermal bridging in passive house details

This Major Research Project focuses on reducing the linear thermal bridging coefficient (ψ-value) in junction details in Passive Houses in North America. By analyzing a sample of details from existing Passive Houses in North America, the range of ψ-values was found to be between -0.154 and 0.124 W/mK. A process was outlined to lower the ψ-value in junction details. Strategies that can be used to reduce the ψ-value include: localized overcladding, thermal breaks, alternative material, and alternative construction. The first and last strategies were found to be most effective at reducing the ψ-value. Comparing the results of PHPP simulations for several houses, with and without linear thermal bridging, showed that the impact on the specific heating energy intensity can be large. The PHPP models showed that savings of 6-25% on the specific heating energy intensity can be achieved by applying the reduction process to details above 0.01 W/mK.

Reducing linear thermal bridging in passive house details

This Major Research Project focuses on reducing the linear thermal bridging coefficient (ψ-value) in junction details in Passive Houses in North America. By analyzing a sample of details from existing Passive Houses in North America, the range of ψ-values was found to be between -0.154 and 0.124 W/mK. A process was outlined to lower the ψ-value in junction details. Strategies that can be used to reduce the ψ-value include: localized overcladding, thermal breaks, alternative material, and alternative construction. The first and last strategies were found to be most effective at reducing the ψ-value. Comparing the results of PHPP simulations for several houses, with and without linear thermal bridging, showed that the impact on the specific heating energy intensity can be large. The PHPP models showed that savings of 6-25% on the specific heating energy intensity can be achieved by applying the reduction process to details above 0.01 W/mK.

Analyzing the Impact of the Phius HRV/ERV protocol on North American Passive House Certification

The stated heat recovery efficiency of HRV and ERV units in North American passive houses is dependent on the testing procedures and calculation methods established by several pertinent performance testing standards. This project highlights major differences between the applicable HRV/ERV standards for North American passive houses: the European Passive House Institute standard, the Canadian CSA-439-09 standard, and the American HVI-920 standard. It further examines the proposed PHIUS protocol which established ɳPHUIS, a modified HRV/ERV heat recovery efficiency rating to more accurately reflect the North American climate. Simulations were performed to quantify its effect on the modelled annual heat demand for 31 certified passive houses. The results yielded two key findings. First, the margin of error for the new rating, ɳPHUIS, relative to the existing rating, Ɛ, is a function of the regional climate given by the equation: y = 0.00001x + 0.0012. Locations with a colder climate have longer winters, thereby increasing the heating demand and intensifying the margin of error. Second, small to medium sized houses with floor areas (<250m2), which formed 90% of the sample study, have the largest impact on the margin of error up from 3.8% to 12% compared to large homes (>250 m2) from 2.8% to 4.2%. The results validate the necessity for PHIUS’ proposed ɳPHUIS for North American HRV/ERVs.

Analyzing the Impact of the Phius HRV/ERV protocol on North American Passive House Certification

The stated heat recovery efficiency of HRV and ERV units in North American passive houses is dependent on the testing procedures and calculation methods established by several pertinent performance testing standards. This project highlights major differences between the applicable HRV/ERV standards for North American passive houses: the European Passive House Institute standard, the Canadian CSA-439-09 standard, and the American HVI-920 standard. It further examines the proposed PHIUS protocol which established ɳPHUIS, a modified HRV/ERV heat recovery efficiency rating to more accurately reflect the North American climate. Simulations were performed to quantify its effect on the modelled annual heat demand for 31 certified passive houses. The results yielded two key findings. First, the margin of error for the new rating, ɳPHUIS, relative to the existing rating, Ɛ, is a function of the regional climate given by the equation: y = 0.00001x + 0.0012. Locations with a colder climate have longer winters, thereby increasing the heating demand and intensifying the margin of error. Second, small to medium sized houses with floor areas (<250m2), which formed 90% of the sample study, have the largest impact on the margin of error up from 3.8% to 12% compared to large homes (>250 m2) from 2.8% to 4.2%. The results validate the necessity for PHIUS’ proposed ɳPHUIS for North American HRV/ERVs.