The Agency for Natural Resources and Energy, part of the Ministry of Economy, Trade and Industry (METI), has opened a public comment period on proposed amendments to two sets of rules governing energy efficiency standards for sashes, or window frames, used in buildings ^[1]. The proposals would revise the enforcement regulations of the Act on Rationalizing Energy Use and Shifting to Non-Fossil Energy, as well as the criteria that sash manufacturers and other building material makers must meet regarding measures to prevent heat loss and improve sash performance ^[1].

According to the notice, the draft amendments are based on Article 154, Paragraph 1 of the Act, together with Article 21, Item 2 of its enforcement order, and also Article 156 of the same Act ^[1]. The proceeding falls under the Administrative Procedure Act ^[1]. METI states that the proposals reflect a summary report compiled by a working group on judgment criteria for building materials, which is listed among the reference documents ^[1].

Public comments can be submitted from October 16, 2026 at 0:00 until November 16, 2026 at 17:00 ^[1]. The case is filed under reference number 620340009 and is categorized under construction and housing ^[1]. Materials for review, including comparison tables showing the old and new text of both the draft ministerial ordinance and the draft public notice, are available as PDF documents, and copies can also be obtained at the counter of the Energy Conservation Division at METI's Annex Building, 4th floor ^[1]. METI advises that anyone wishing to submit an opinion must first check the full text of both the submission guidelines and the draft rules to avoid errors ^[1].

Inquiries should be directed to the Energy Conservation Division's Building Materials Top Runner System desk within the Agency for Natural Resources and Energy ^[1]. The sources do not specify how individuals should submit comments beyond directing readers to the published submission guidelines, nor do they detail what specific numerical performance standards for sashes would change ^[1]. As this is a proposal open for public input rather than a finalized rule, the exact effect on sash products sold in Japan, including any changes to costs or specifications for homebuilders and renovators, cannot yet be confirmed and will depend on the final version adopted after the comment period closes ^[1]. Readers involved in construction, renovation, or building material manufacturing should consult the official documents linked in the notice for full details.

Source credit 出典：「「エネルギーの使用の合理化及び非化石エネルギーへの転換等に関する法律施行規則（案）」、「サッシの性能の向上に関する熱損失防止建築材料製造事業者等の判断の基準等（案）」の改正に対する意見募集について」（e-Govパブリックコメント）（https://public-comment.e-gov.go.jp/servlet/Public?CLASSNAME=PCMMSTDETAIL&id=620340009&Mode=0）、PDL1.0（https://www.digital.go.jp/resources/open_data/public_data_license_v1.0）を加工してJapan News (j.apan.news)が作成 This article is Japan News's own English summary of the Japanese original. It has been translated and edited by Japan News; it is not an official translation, and the e-Gov Public Comment did not write or review it.