According to Tom Culp of Birch Point Consulting, “These walls are assumed to have steel stud framing 16 inches on center with fiberglass insulation in the cavity and continuous insulation across the face.” That means that in order to comply with the prescriptive U-factors in ASHRAE 90.1-2016, for example, spandrel must reach a U-factor of 0.064 btu/ oF.hr.ft 2 (R15.6 *) in climate zone 4 (New York) and 0.055 btu/ oF.hr.ft 2 (R18) in climate zone 5 (Chicago). Photo: Stéphane HoffmanĪSHRAE Standard 90.1 treats spandrel as a steel-framed wall. SOMA Towers in Bellevue, Wash., was designed by Bohlin Cywinski Jackson and used a unique window wall design in which the thermal performance was maximized by using full-height 10-foot spandrel panels (to maximize the center-of-panel relative to edge-of-panel performance), adjacent to large slab-to-slab glazed expanses. Here lies a large performance gap which, if unaddressed, could have serious long-term ramifications. Initially I was confused, since with opaque insulation placed in the spandrel assembly, shouldn’t the spandrel thermal performance be better than the transparent areas of the curtainwall? As it turns out, it is not the comparison between spandrel and adjacent transparent areas that is important it is the comparison of the spandrel with a typical opaque wall assembly.
#ASHRAE 90.1 2016 WINDOW U FACTOR CODE#
Culp notes it would mostly affect colder climates.Ĭulp will provide additional information on energy code updates during the upcoming NGA Glass Conference.Over the past few years, I have heard several people talk about spandrel as the weakest link in the curtainwall system. New proposals would require identifying and addressing of thermal bridges on a system to improve whole-system performance. Thermal bridging refers to the more thermally conductive-or thermally inefficient-sections or components of a system or wall. Proposals for new thermal bridging requirements are up for ASHRAE 90.1-2022. (Read Tom Culp’s recent column about envelope backstops and what they mean for the glass industry.) 4. Requirements for envelope backstops are complete and will appear in the 2022 version of ASHRAE 90.1, according to Culp. The implications-both positive and negative-are significant for the glass and glazing industry. Envelope backstops will require a minimum level of envelope performance no matter what else is done in the building. Envelope backstopsĮnvelope backstops are coming in the latest energy codes, placing limits on what can be “traded off” to meet performance requirements. The next edition (ASHRAE 189.1-20 IgCC) will include a new above-core requirement for minimum views in offices, classrooms and patient rooms. The ASHRAE 189.1-2017 and the 2018 IgCC expanded daylighting requirements for more spaces, including classrooms, offices, patient rooms and more. Requirements for daylighting and views have come, or are coming, to the green codes-ASHRAE 189.1 and the International Green Construction Code. The report includes ASHRAE’s revised climate map along with indications about roughly what glass and glazing products might meet the new requirements.) 2. (For complete information on the recent updates to ASHRAE 90.1, see Glass Magazine’s Glass & Metals 501: Guide to Glazing Performance. The change marks roughly a zone shift between the U-factor requirements in the 2016 version and the 2019 version, according to Culp. More stringent U-factor requirementsĪSHRAE 90.1-2019 was published in October, and the updates in the standard will also be referenced in the 2021 IECC. In a June 18 Thirsty Thursday webinar from the National Glass Association, NGA Code Consultant Tom Culp, owner of Birch Point Consulting LLC, provided a rundown of recent code changes and important proposals on the horizon. Building energy codes continue to increase in stringency, with tougher requirements for thermal performance and new calls for daylighting and views, envelope backstops, thermal bridging and more.