A proposed addendum to the “ASHRAE 189.1-2017 Standard for the Design of High-Performance Green Buildings Except Low-Rise Residential Buildings” identifies requirements from Section 8 that are appropriate for local jurisdictions to consider excluding from their adopting ordinances.
The proposal suggests adding [JO] to Section 8.4.1.3 “Shading for Offices” to indicate that it is a jurisdictional option.
The code requires that for office spaces larger than 250 square feet, each façade be designed with a shading projection factor (PF) that should not be less than 0.5 for the first story above grade and 0.25 for other aboveground stories. Shading can be external or internal using the interior PF. According to the “User’s Manual for ANSI/ASHRAE/IE Standard 90.1-2010,” the PF is “the ratio of the horizontal distance that the overhand projects from the surface of the window to the vertical distance from the windowsill to the bottom of the overhang.”
Shading devices are limited to:
- Louvers;
- Sun shades;
- Light shelves;
- Building self-shading through roof overhands or recessed windows; and
- Any other permanent device.
The code also specifies that any vertical fenestration that employs a combination of interior and external shading is allowed to be separated into multiple segments for compliance purposes. Each segment must comply with the requirements for either external or interior PF.
There are also several exceptions to 8.4.1.3, which include the use of dynamic glazing. The exceptions are:
- Facades facing within 45 degrees of true north in the northern hemisphere or facades facing 45 degrees from true south in the southern hemisphere;
- Translucent panels and glazing systems with a measured haze value greater than 90 percent when tested according to ASTM D1003 or other test method approved by the AHJ, and that are entirely 8 feet above the floor do not require external shading devices;
- Where equivalent shading of the vertical fenestration is provided by buildings, structures, geological formations or permanent exterior projections that are not horizontal, as determined by sun-angle studies at the peak solar altitude on the summer solstice and three hours before and after the peak solar altitude on the summer solstice;
- Vertical fenestration with automatically controlled shading devices in compliance with Exception (2) of Section 7.4.2.5;
- Vertical fenestration with automatically controlled dynamic glazing in compliance with Exception (3) of Section 7.4.2.5; and
- Existing buildings undergoing alteration, repair, relocation or a change in occupancy.
This proposed addendum is under a 30-day public review from March 8 to April 7. For more information about commenting on the public review draft, click here.
