Shaping the Energy Efficiency in New Buildings - Building Energy ...

This study selects the midpoint score levels for comparison (specifically, thesecond score level for roofs and walls, and the fourth to sixth levels forwindows). 30 Japan’s building energy codes place heavy emphasis on SHGC. Forexample, the highest score for SHGC is 90 (for most of Japan), 50 (in the coldzone), and 170 (in the tropical zone), while the highest score for U-factors ofwalls and windows, respectively, is 30.South Korea also uses a point system to measure building performance in theBDCES. The minimum score should be 60 for the whole building (includingconstruction and mechanical and electronic design criteria). For the buildingenvelope, there are five levels of thermal requirements. South Korea providesminimum R-value by region for roofs, walls and floors for all buildings. For theenvelope of large building, there are five levels of thermal requirements (overallenvelope U-value) that are calculated by averaging the U-value both window andwall which varies depending on window to wall ratio. The RBFCO providesadditional prescriptive requirements for insulation; the envelope analysis relies onthe RBFCO requirements. The maximum U-factors in the United States commercial building energy codesare categorized by building materials. U-factor and SHGC are two indicators forwindow thermal insulation.Four countries have jurisdictions in the hot climate zone including Australia, China, India,and the United States. In this zone, Australia has the most stringent requirements forroofs and floors, while India has the most stringent requirements for walls. The UnitedStates has comparatively stringent requirements for roofs and solar heat gain coefficientin windows. It has a wide range of requirements for walls, and the least stringentrequirements for floors. China has relatively weak requirements in all categories, but it isnot the least stringent in any single category. Figure 1 shows a comparison of the roofrequirements in this zone, while Table 10 provides a more comprehensive comparison ofall the key envelope requirements in this zone. Each of the comparative tables in thissection highlight one country under each component. This is the country that has the moststringent requirements (for the majority of its commercial buildings) in a given category.Several factors can affect the stringency of envelope requirements in different countries.Energy prices vary among countries. Most countries conduct cost-benefit analyses of therequirements before adopting them; differences in energy prices can lead to differentrecommendations on cost-effective requirements. Stakeholders can also play an importantrole, particularly in countries that use some type of stakeholder process or allow publiccomment before revising their standards. Insulation manufacturers may play aparticularly active role in one country, while windows manufacturers may be moreprominent in another. In some cases, if an industry like insulation is less vocal, it mayalso indicate that there are few products available on the local market. The productsavailable and the role of industry can thus affect the requirements adopted.30 We selected the midpoint levels instead of the maximum U-factors because Japan’s commercial code hasno maximum in most categories. In addition, since Japan does not have prescriptive commercialrequirements – only trade-off ones – it was important to pick numbers that would lead to a building thatcomplied, but did significantly exceed the compliance level in order to provide a good point of comparison.38