Energy Recovery Drives Nonresidential Gains

DOE projects (PDF) that ASHRAE 90.1-2019 will generate savings of over 4% in each of four categories: site energy (4.7%), source energy (4.3%), energy cost (4.3%), and carbon emissions (4.2).

Those reduction represent meaningful results given the scale of U.S. nonresidential building stock.

Energy use intensity in hospitals emerges as the biggest gainer in the DOE’s projections, achieving over 12% savings. This is presumably due in part to a new requirement for condenser heat recovery in acute care inpatient hospitals.

Large hotels stand to top 8% savings in all four categories. Small hotels and standalone retail stores also do well, with estimated savings of between 7% and 8%.

Small and medium offices join primary schools as spaces expected to enjoy meaningful gains nearing 6%.

The latest version of ASHRAE 90.1 may do the least for quick service and full service restaurants, projected for savings at or less than 1%.

Of 88 addenda affecting various sections of ASHRAE 90.1, the HVAC-related section comprised 32 addenda covering a range of equipment.

As ASHRAE outlined at the time of the update’s release, ASHRAE 90.1 includes pump definitions, requirements, and efficiency tables for the first time.

The latest version also pays some attention to fan power for ceiling fans and to load-matching variable-speed fan applications. As previously reported, the fan efficiency grade (FEG) efficiency metric has been replaced with the fan energy index (FEI).

High-rise residential buildings, which fall under ASHRAE 90.1, also face new energy recovery requirements.

Pumps Make The Cut, Duct Exception Dropped

While the projected savings under ASHRAE 90.1 are meaningful, the expectations are even bigger (PDF) for residential dwellings under IECC 2021.

DOE’s technical analysis finds room for 9.38% site energy savings, 8.79% source energy savings, 8.66% energy cost savings, and an 8.66% reduction in carbon emissions.

IECC 2021 includes various updates regarding windows, lighting, and insulation that will of course have corresponding impacts on HVAC loads.

HVAC-specific changes include the following:

• Increased whole-house mechanical system ventilation fan efficacy requirements for inline fans and bathroom/utility fans.
• Heat or energy recovery requirements for ventilation systems in climate zones 7 and 8. According to the determination’s map, those zones include certain high-elevation parts of other states but largely represent upper portions of North and South Dakota, Minnesota, Wisconsin, and Michigan, as well as northern regions of New York, New Hampshire, Vermont, and Maine.
• A requirement to implement at least one Additional Efficiency Package, with the target of an additional 5% energy reduction. The menu of additional package categories is building envelope, HVAC, hot water heating, thermal distribution, and “improved air sealing with efficient ventilation.”

Another measure that generated some disagreement within the industry removes the previous duct testing exception for ducts located within the building thermal envelope. Under IECC 2021, ducts are subject to leakage testing regardless of whether they are in conditioned or unconditioned spaces.

Speaking of air leakage, IECC 2021 revises the air leakage threshold from a mandatory to a prescriptive requirement while preserving an absolute leakage rate of 5.0 air changes per hour, according to the analysis.

Local Flavor

States must certify that they have reviewed and updated their own codes to meet or exceed ASHRAE 90.1-2019 and IECC 2021. They do, however, have the latitude to adapt their own codes to their own climate and other particular circumstances.

States must make those certifications by July 28, 2023, so HVAC contractors should monitor that situation and any resulting meaningful changes for codes in their service territories as updates take effect.