Mechanical and Building Envelope Changes from 2014 to 2016
The New York City Energy Conservation Code aligns with the city’s 2050 emissions reduction target: 80% with respect to 2005 levels. The original version of the code was published in 2011, and two updates have been carried out in 2014 and 2016. The main difference introduced in 2014 was mandatory system commissioning, and the 2016 edition introduced more demanding energy conservation requirements while clarifying portions of the code subject to ambiguous interpretation
This article will provide an overview of the main changes to the energy conservation requirements that affect mechanical systems and building envelopes, in both residential and commercial buildings.
Residential Buildings: Mechanical and Building Envelope Changes
The changes introduced between the 2014 and 2016 editions of the NYC Energy Conservation Code are expected to increase energy savings by 23.5% in residential buildings. Both mechanical systems and building envelopes are subject to changes, but in the residential section of the code most changes focus on envelope performance.
General Building Envelope Performance
One of the main changes deals with air leakage testing. In the 2014 code a visual inspection of the air barrier was enough, but the 2016 edition makes infiltration testing mandatory, to ensure that air leakage does not exceed 3 air changes per hour (ACH). The test must be according to the ASTM E 779 o 1827 standard, at a pressure of 50 Pascals. Infiltration testing by a third party may be required at the discretion of a code official. Another major change is that open-air combustion fuel-burning appliances must now be located outside the building’s thermal envelope.
The 2016 NYCECC also adopted Climate Zone 6 prescriptive requirements for building envelopes, which is expected to increase overall performance by 5% with respect to the 2014 edition of the code.
Insulation and Fenestration
Most changes in the 2016 edition of the NYCECC focus on this area. There are many minor changes that have a significant effect on building envelope performance when added together:
- Visible transmittance criteria were added for fenestration. The 2014 edition of the code did not address the topic.
- The code now states that wall assemblies in the thermal envelope must meet the vapor barrier requirements of the NYC Building Code, Section 1405.3.
- Many insulation options in the 2014 of the code have been deleted. For example, unvented attic assemblies are no longer allowed, and the use of siding over foam sheathing has been eliminated now that vapor barriers are mandatory.
- The 2016 NYCECC makes eave baffles mandatory to minimize air leakage in vented attics. They were not required explicitly in the 2014 edition.
- The performance requirements have been eased for vertical doors between conditioned and unconditioned spaces. In the 2014 edition they were subject to the same requirements as opaque walls, but since the 2016 edition they are subject to fenestration performance requirements.
- Dynamic glazing is now a valid option to comply with solar heat gain limitations. It was not mentioned in the 2014 code.
- In walls that require constant insulation thickness, and where structural sheathing covers less than 40% of the gross area, variable thickness is allowed as long as the total thickness remains constant. However, the R-value must not be reduced beyond R-3.
- Sunrooms that enclose conditioned spaces are now subject to more demanding energy performance requirements, but those that do not enclose conditioned spaces are now exempt.
In the 2016 edition of the code, most changes that affect residential mechanical systems focus on ventilation and hot water. Space heating and cooling equipment is not subject to major changes.
Hot water boilers in one- or two-pipe systems are now required to have outdoor temperature setback, to lower their operating temperature based on outdoor conditions and save energy. In addition, the control requirements for circulating hot water systems have been expanded; a manual or automatic switch was enough in the 2014 edition. Hot water piping insulation requirements are also more demanding in general.
Mechanical ventilation requirements were very basic in the 2014 ECC, but the 2016 edition has introduced a new section dedicated to the topic. Ventilation systems compliant with the NYC Mechanical Code are now explicitly requested for each dwelling, loads must be calculated based on ACCA Manual J, and equipment must be selected according to ACCA Manual S. The code also introduced minimum efficacy requirements for fans, in CFM per square foot.
Commercial Buildings: Mechanical and Building Envelope Changes
Under the 2016 NYC Energy Conservation Code, commercial building efficiency is expected to increase by 8.5%. In this section of the code, there are major changes for both building envelopes and mechanical systems.
General Building Envelope Performance
One of the main changes is that insulation has become mandatory for all below-grade walls. Open-air combustion fuel-burning appliances are now required to be outside of the thermal envelope, just like in residential buildings. The code has also expanded the list of buildings that are exempt from building envelope requirements, to include greenhouses, equipment buildings and similar unconditioned occupancies.
The thermal envelope must now account for the performance deficiency caused by some types of mechanical equipment that cross the wall and interrupt the thermal barrier. If their total area exceeds 1% of the opaque wall area above grade, they count as a separate wall assembly with a U-factor of 0.5.
Air leakage testing has also become mandatory for buildings with an floor area of 25,000 square feet or more.
- If the building area is below 50,000 square feet, the air barrier must be tested according to ASTM E 779 and any applicable rules from the NYC Dept. of Buildings.
- Buildings 50,000 or greater require air barrier testing, according to a plan developed by a NYC Registered Design Professional.
A new U-factor compliance calculation method has been introduced for the overall building envelope. It is detailed in the C401.1.5 article - Component performance alternative.
Minor Insulation and Air-Tightness Changes
Just like in residential buildings, there is a series of minor changes that affects different building components, but when added their effect is significant.
- Radiant heating system panels are now required to have R-3.5 insulation between them and unconditioned areas.
- When the area under a floor is unconditioned, the code now requires the installation of floor framing cavity insulation or structural slab insulation.
- The code now specifies an air leakage limit for high-speed doors - 1.30 CFM / ft2
- Solid or hollow masonry made from clay or shale now meets air barrier requirements.
- All building entrances opening into an area of 3,000 ft2 or less were exempt from having a vestibule in the 2014 code. In the 2016 edition, the maximum area is reduced to 1,000 ft2 if the building is at least 75 feet high.
- Since the 2016 ECC, air curtains are allowed instead of vestibules.
- The code now presents a method to calculate the U-factor of cold formed steel wall assemblies.
- The maximum fenestration area allowed above grade can be increased from 30% to 40% if the building is at least three stories high and at least 25% of floor area is within daylight zones. Other exceptions apply, but they were already present in the previous code.
- In the 2014 code, skylighting was mandatory for all areas directly under a roof with a floor area exceeding 10,000 ft2. Since the 2016 edition, the requirement applies for all areas greater than 2,500 ft2.
With respect to mechanical systems, the main change introduced in the 2016 NYCECC is that there are now efficiency requirements for refrigeration systems; the 2014 edition limited its scope to HVAC. All walk-in coolers and freezers must include automatic doors, a minimum insulation value, ECM motors, anti-sweat controls and lighting controls. Refrigerated display cases are required to have lighting controls, defrost termination and anti-sweat heaters.
In general, the efficiency requirements for all types of HVAC equipment previously covered and their controls have been increased, and turndown is now mandatory for all boilers and boiler plants with a capacity of one million BTU/hour or more. The number of applications where energy recovery is required has been increased as well.
Most of the changes introduced in the 2016 edition of the NYC Energy Conservation Code affect HVAC control systems. The following are some of the main changes introduced:
- Auto-start capabilities are required in systems exceeding 6.8 million BTU/hour.
- Zones greater than 25,000 ft2 or covering more than one floor must be isolated.
- Hot water boilers with one- or two- pipe systems must have outdoor temperature setback, just like in residential buildings. >
- The 2016 code adds ventilation control requirements for enclosed parking garages, modulating fans to 50% of installed capacity or 20% of occupied time.
Energy recovery ventilation systems are now required in a wider range of applications. If a ventilation system exceeds 8,000 hours/year or 80% outdoor air, ERV is mandatory. For all other cases, tables are provided in the code.
Kitchen exhaust systems were not addressed in the 2014 of the code, but are now covered in article C403.2.8. When system capacity exceeds 5,000 CFM, it must use a minimum of 50% transfer air from other areas, or be equipped with either demand-controlled ventilation or exhaust ERV.
The 2016 NYCECC also added a section on fan efficiency requirements: all fans with a capacity above 5 hp that are not part of packaged units must have a fan efficiency grade (FEG) of at least 67 according to the AMCA 205.
Boiler turndown is now required for all boiler systems with at one million BTU/hour of heating capacity. The turndown ratio required is as follows:
- Up to 5 MMBTU/hour = 3 to 1
- Up to 10 MMBTU/hour = 4 to 1
- Above 10 MMBTU/hour = 5 to 1
The turndown ratio requirement can be met with multiple single-input boilers, one or more modulating boilers, or any combination of both.
The 2016 edition of the NYC Energy Conservation Code provides efficiency tables for all service water heating systems, but now makes it clear that all systems with a capacity equal or greater than one million BTU/hour should have an efficiency above 90%. In addition, the code now establishes hot water flow rate limits and provides two accepted calculation methods, one based on piping length and the other based on the water volume contained.
The NYC Energy Conservation Code establishes high performance standards for mechanical systems and building envelopes, and compliance is mandatory for legal use of a building. The best way to ensure code compliance is to work with qualified professionals - making sure that all building systems meet the applicable codes from the design and specification phase is much simpler than carrying out expensive changes during construction or commissioning.