This week, the American Council for an Energy Efficient Economy (ACEEE) published its annual State Energy Efficiency Scorecard, reporting that 2019 “was a whirlwind year for energy efficiency at the state level.” ACEEE ranks the performance of states based on several energy efficiency public policy areas including building energy efficiency, utility programs and transportation. Topping the list of states for overall performance is again Massachusetts, followed closely by California. Digging down into the data to focus on building energy efficiency, these states remain the leaders. However, there are some surprises in the top states for code stringency, which has some interesting implications for high-performance fenestration adoption.
According to ACEEE, the latest version (2018) of the International Energy Conservation Code (IECC) including ASHRAE Standard 90.1-2016 has recently been (or is just about to be) adopted by Nebraska, Illinois, Massachusetts, Maryland and Nevada for commercial buildings. This raises their performance close to that of states such as California, which we typically associate with high code stringency, and leapfrogs Washington and New York states.
ACEEE also looked at compliance and enforcement of codes, and the use of benchmarking and transparency strategies to drive the market to higher efficiencies. The top-rated states for compliance were California, Connecticut, Massachusetts, Oregon, Pennsylvania and Texas.
As we discussed in a previous blog, there is data indicating that building energy benchmarking and transparency requirements have resulted in significant energy use reductions. This is where the management tenet of “you can’t manage what you don’t measure” can be applied. The very act of having to measure and record energy use promotes actions to change them. The need to disclose these numbers also can prompt actions to improve performance, especially if current performance is worse than the real estate competition nearby.
While ACEEE notes that benchmarking and transparency requirements have been driven largely at the city level, with over 25 already enacting such laws, it recognizes Washington, D.C.; California; Washington and New Jersey for their commercial building transparency requirements.
When all aspects are combined, the top-ranked states driving building energy efficiency are:
- California
- Massachusetts
- Connecticut
- Pennsylvania
- Texas
- New York
- Oregon
- Washington
We are hearing questions and concerns from architects in Massachusetts about how they can meet the new 2018 IECC fenestration requirements, especially with curtainwall systems. We expect architects in Illinois, Nebraska, Maryland and Nevada, which have recently adopted this version, have similar questions.
NGA Code consultant, Tom Culp of Birch Point Consulting, noted that the change from 2015 IECC to IECC 2018 in climate zones 4 and 5 is not very dramatic for fenestration. Table 1 below shows the current 2015 IECC and 2018 IECC requirements (and equivalent ASHRAE Standard 90.1 requirements, since this is a compliance pathway).
Table 1:
According to Richard Braunstein of Oldcastle BuildingEnvelope®, widely available higher performance curtainwall framing systems can already comfortably meet a 0.38 U-factor with a standard air-filled, double silver low-E coated, dual pane insulating glass unit (IGU) having a center of glass U-factor of 0.29 Btu/of.hr.ft2. He also asserts that improving the frame performance rather than the center of glass is typically the most cost-effective and reliable strategy of achieving this thermal performance in a curtainwall. Further improvements in U-factors can then be achieved using additional glass strategies (see below). Also, better thermally broken frames, followed by the use of warm-edge spacer, have the added benefit of improving condensation resistance performance.
The challenge for architects using 2018 IECC is more likely encountered when designing with higher window area than the prescriptive 40% baseline. Since the baseline performance of all the other building systems (e.g. lighting, HVAC) has increased, there are less opportunities to trade off higher glazed areas with better performing internal systems in the performance paths.
Specifying higher performing walls and fenestration is the optimum solution. The following table (Table 2) gives some very approximate guidance* (Source data: Tom Culp, NGA code consultant) for how to meet a range of fixed fenestration U-factor targets that may be needed to achieve higher window areas. In addition to the strategies in the table, pressure plates made from non-metals, such as polyamide, can also be used to reduce the overall U-factor by up to 20% depending on the system.
Table 2:
With several states, and some large cities (Philadelphia, St. Louis, San Antonio), adopting the latest revision of the IECC, there comes an opportunity for us to consult with design teams on how to achieve the needed higher envelope performance targets. Using higher performing fenestration allows increased glazed area to provide needed views and daylight, without compromising comfort or energy performance. A win-win.
* This information should be used as a guide only. Calculations according to NFRC 100 using the actual fenestration system components are required to confirm the actual performance.