Newsletter

2019 Nonresidential Performance Method is not a Magic Bullet

In the past we have used the performance method to get anything we want in our projects. No matter the details, we’ve used our “Magic Bullet” on the project. Under the 2019 code cycle however, a lot of projects are going to learn the hard way that the magic bullet they’ve been using, is now, in many ways, the norm.

There are several changes to how the Nonresidential Energy Code looks at mechanical systems, hot water systems, lighting and envelope. All the changes will affect compliance, but some changes will be harder to overcome than others. Note that the “Nonresidential” Energy Code covers nonresidential, high-rise residential and hotel/motel buildings, but has somewhat different requirements for each type.

2019 Nonresidential Indoor Lighting

The 2019 changes to indoor lighting requirements for nonresidential buildings will make possibly the most noticeable difference in performance method compliance results. Currently, selecting high efficacy LED fixtures for nonresidential indoor lighting offers large amounts of performance compliance credit. In the 2016 code, reduced energy use from LED lighting has been used to offset mechanical and envelope choices that result in penalties to compliance (not adding rigid to walls, poor window U-factor and SHGC, minimum efficient DHW and HVAC).

However, under the 2019 code the prescriptive baseline that sets the performance energy budget assumes high efficacy LED lighting and has gotten more stringent. “Complete Building” lighting allowances have gotten 36% more stringent; “Area Category” allowances have gotten 31% more stringent; and “Tailored” allowances have gotten 18.5% more stringent. In short, the credit we have been taking for nonresidential indoor lighting the last few years is going to disappear. Lower power allowances will require lower wattage bulbs and will require more thought going into envelope and mechanical choices as the credit we get from lighting will be drastically reduced.

2019 Code Changes for Mechanical Systems

There have been several changes to the way the Energy Code looks at mechanical systems as well. Some will seem like heavy hitters while others may seem like small potatoes. However, all the changes will have an impact on the way projects are designed, and some of them may impact performance method compliance.

  1. Dwelling units cannot meet ventilation requirements by using operable windows. In 2016 the Energy Code trusted inhabitants to open their windows and assist with ventilation. That is no longer the case and ventilation must be met through mechanical means.
  2. Nonresidential and hotel/motel spaces using natural ventilation must also use mechanical ventilation unless openings are permanently open or controlled with easily accessible controls.
  3. MERV 13 filters are required for supply only ventilation systems and the supply side of balanced ventilation systems. MERV 13 filters will also be required for any HVAC system with over 10 feet of ducts. This may not seem like a big change, but it is one that you should pay especially close attention to as the MERV 13 filter is 2” wide. Not only will appropriate mechanical attachments be required to accommodate the larger filter but the increase to the HVAC system’s static pressure will need to be considered to ensure the system can handle the increase strain.
  4. Multifamily systems serving 1+ dwelling units must be balanced systems that provide ventilation air.
  5. There are now two methods for minimum ventilation for multifamily attached dwelling units: Use a balanced system, or use an unbalanced continuously operating supply or exhaust fan with HERS verification of building envelope leakage. (See the article “Multifamily Ventilation Strategies: Balanced Ventilation” for details.)
  6. Kitchen hoods must be HERS verified as being in the HVI directory (see the article “Highlights of New HERS Measures in the 2019 Code Cycle”).
  7. Occupancy sensing zone controls are now required to have acceptance testing done.

Fan power associated with the 2019 ventilation system changes has to be modeled for performance method compliance. Depending on the efficiency of the proposed fans, it may be a surprisingly large compliance credit or penalty.

2019 Code Changes for Water Heating, Envelope and Solar Ready Area

Finally, we have a few changes to hot water heating, envelope and solar ready requirements.

For domestic hot water, the prescriptive method and the performance baseline now include heat pump water heater options for high-rise residential and hotel/motel guest rooms. This will provide some flexibility for projects that would like to reduce their carbon footprint. To avoid incurring performance method compliance penalties, it is recommended to spec heat pump water heaters that are NEEA Tier 3 rated or higher (see “Client Questions & Gabel Answers” Q9/A9).

As for envelope, the main changes to be aware of are the reduction of amount of “site-built fenestration” and the way we look at glass doors.

Energy Code Reference Appendix NA6 includes equations to calculate overall site-built fenestration U-factor and SHGC based on center of glass values and frame type, but for 2019 the amount of site-built fenestration allowed to use those equations has been reduced from 1,000 ft² to only 200 ft². Any site-built fenestration over 200 ft² either has to be assumed to have the very poor default values from Standards Tables 110.6-A and 110.6-B, or else it has to be NFRC-rated.

Doors will now count as glazed surfaces if 25% or more of the door is glazed (down from 50%). Doors come in all different configurations, but most doors with glass in them will fall into the “glass door” category now and will need to meet all those U-factor, SHGC and VT requirements. Depending on the kind of glass door, this can hurt or help your performance method compliance.

When thinking of how to meet the required solar ready areas on the roof, you may now locate solar ready zones on steep sloped roofs oriented between 90 degrees and 300 degrees. This is a change from 110 degrees through 270 degrees. This change won’t affect performance method compliance, but it is important because you now have more roof area to work with when trying to design your solar ready areas!

 

Article written by Jim Hurley, Energy Analyst
First published in the Gabel Energy Summer/Fall 2019 Newsletter