Code Proposals for HVAC Equipment Could Be Significant for Window Industry
The 2013 International Code Council Group B Code Development Hearings recently took place in Dallas, where code officials reviewed numerous proposals for changes to the 2015 International Residential Code, 2015 International Energy Conservation Code and 2015 International Existing Building Code, among others. Following is a report on the more significant results of these hearings, with regards to residential construction.
AAMA Standards for Flashing
Members of the flashing industry successfully introduced proposals that reference two AAMA standards for flashing approved for the IRC.
AAMA 712 was approved for mechanically attached flexible flashing of window and door openings. In addition, AAMA 714 was approved for fluid-applied membranes in exterior walls.
The 2012 IRC requires all self-adhered membranes used as flashing to comply with AAMA 711. No action was taken at the hearings to change this in the 2015 IRC. An AAMA-supported proposal that added a definition of “shingle fashion” was also approved for the IRC. Section 703.8 of the IRC requires flashing in exterior walls to be installed in “shingle fashion.”
Design Wind Speed Model
A proposal to convert the design wind speed model of the IRC from allowable stress design to strength design was approved. The 2010 edition of ASCE 7 uses a strength design model for wind speed, which was incorporated into the 2012 IBC. This change will align the wind load provisions of the 2015 IRC and the 2015 IBC.
Comparative Analysis Provisions for Fenestration
A proposal to add comparative analysis for skylights to the IRC was approved. The proposal added language consistent with that permitted for vertical glazing as one option. A second option requiring compliance with WDMA I.S.11 was also added.
Comparative analysis for vertical glazing has been permitted since the first editions of the IRC and IBC. The comparative analysis provisions permit a unit smaller than that initially tested for labeling to be rated to a higher design pressure, if accepted engineering analysis determines it's appropriate to do so. When comparative analysis is used, the components of the smaller unit that is rated for a higher design pressure are to be identical to those of the originally tested unit, and the performance of the unit rated at the highest design pressure is to be verified by testing. A proposal to permit use of WDMA I.S.11 as a second option for comparative analysis of vertical glazing was also approved.
For the fenestration industry, one of the most significant proposals approved for residential construction under the IECC actually deals with HVAC equipment. The proposal defined the equipment efficiency assumed for HVAC equipment in residences as the federal minimum standard when performance-based design is used. This provision had been contained in earlier editions of the IECC, but the 2009 and 2012 IECC require equipment efficiency to be assumed as proposed rather than as the federal minimum standard.
The federal minimum standards were developed in the mid-1970s and require furnaces to have an efficiency rating of at least 78 percent. Most residential furnaces on the market today have an efficiency rating of 90 percent or greater. Similarly, the federal minimum equipment efficiencies require residential air conditioning equipment to have a Seasonal Energy Efficiency Ratio rating of 13 or greater. Most residential air conditioning units on the market today are rated at 15 or higher.
The approved proposal is significant to fenestration manufacturers because it allows for tradeoffs between the building envelope and equipment efficiency. The extent to which tradeoffs can occur will continue to be limited by performance caps on both fenestration U-factor and SHGC, as it is in the 2009 and 2012 IECC.
For example, the 2012 IECC sets a maximum U-factor for fenestration in Chicago of 0.32 when the prescriptive design path is used. If the proposal approved during the 2013 hearings is upheld, a builder or designer could install a furnace with an efficiency rating greater than 78 percent, or an air conditioning unit with a SEER rating greater than 13, and trade that off with a window that has a U-factor higher than 0.32.
But the extent of tradeoff permitted will still be limited by the fenestration caps. In Chicago, which is in Climate Zone 5, the maximum fenestration U-factor permitted under performance-based design would be 0.48, as it is for all of Climate Zone 5, and 4 as well. In Climate Zones 6 through 8, the maximum fenestration U-factor permitted under performance-based design would be 0.40. In Climate Zones 1 through 3, the maximum SHGC under performance-based design is 0.50.
Thermally Isolated Sunrooms
Also approved at the 2013 Code Development Hearings was an AAMA-supported proposal that provides a higher maximum U-factor of 0.45 for thermally isolated sunrooms in Climate Zones 2 and 3. Without this provision, the maximum U-factor for vertical glazing in sunrooms in Climate Zone 2 is 0.40 and in Climate Zone 3 is 0.35, while the maximum U-factor permitted for vertical glazing in Climate Zones 4 through 8 is 0.45. By definition, the wall between a thermally isolated sunroom and the interior conditioned area of the home must meet the requirements for the exterior building envelope in the applicable climate zone.
Another proposal that was supported by AAMA, and approved at the hearings, establishes criteria for the evaluation of dynamic glazing in residential construction. Dynamic glazing shall be considered as satisfying the prescriptive maximum SHGC requirements of the IECC for residential construction if the ratio of highest SHGC rating to lowest SHGC rating is at least 3, and the dynamic glazing is automatically controlled to modulate the amount of solar gain into the space in multiple steps.
This range of solar heat gain coefficients allows for a low SHGC on hot summer days when it is desirable to block the sun's heat and light, in addition to allowing for more heat and light transmission on bright winter days when appropriate. In order for this type of glazing to contribute to the energy efficiency of the home in a passive manner that does not depend upon the homeowner, it must be automatically controlled.
In addition to the approved proposals described above, there were a number of proposals of potential interest to our industry that were disapproved, as noted below:
- Reduce or increase the maximum SHGC permitted under the prescriptive path
- Establish minimum SHGC in northern climate zones
- Add provisions for consideration of orientation or projection factor in determining maximum SHGC permitted
- Remove or change the fenestration performance caps
- Add additional performance-based compliance paths, including one based upon RESNET
- Add a footnote to increase the maximum U-factor and SHGC permitted for impact-resistant glazing in Climate Zones 2 and 3
- Permit up to 75 square feet of replacement fenestration to have a higher SHGC in Climate Zones 1 through 3
- Require all glazing in a home to be safety glazing
- Require windows that are of sufficient size to serve as Emergency Escape and Rescue Openings (EERO), to be so labeled by the manufacturer
- Raise the minimum sill height of operable windows in single-family homes, including above fixed seating, to 36 inches.
At this point, anyone who would like to challenge the results of the 2013 hearings can do so via public comment. Public comments are due July 15, 2013, and will be heard during the Final Action Hearings, Oct. 2-9, 2013, in Atlantic City, N.J. AAMA members will meet to discuss possible public comments from the association over the course of the next few months.