Building For the Future Part III: 2018 IECC Mechanical System Updates

In Part I and Part II of our Building for the Future blog posts we gave a general overview and building envelope updates of the 2018 IECC.

Now it’s time to turn our sights on what 2018 IECC updates lie ahead for a building’s mechanical system. A building’s mechanical system is similar to the human body’s cardiovascular system, it acts much like our vital organs (heart, liver, and lungs), that pump and filter for the efficient passage of fluids and air through the building.

Mechanical System

The mechanical system provides:

• water,
• heating,
• ventilation and
• air conditioning

to meet the interior conditioning and service requirements for the building occupants.

Modern commercial Heating, Ventilation and Air Conditioning (HVAC) systems may be comprised of either rooftop units or air ducts, CO2 sensors, thermostats, fans and dampers. Some systems may even contain humidifiers and dehumidifiers as well as carbon monoxide detectors. Large systems (commercial, healthcare, education) include central plants with chillers and boilers.

In order to keep the building

• comfortable,
• eliminate allergens and mold, and
• prevent toxic gases from building up in the indoor environment,

all of these pieces of equipment must work together.

2018 IECC Mechanical System Updates

• • C403.4.4. As the other sections of the code like building envelope and internal lighting loads improve, our mechanical systems need to react to that, which means more turndown. Variable Frequency Drives (VFDs) are required for fans and pumps with 2 HP and more. This change can be easily achievable because the market for that technology makes it affordable. (Electronically Commutated Motors (ECM) technology takes it to another level.)
  • C403.6.1 When we turn down systems associated with a flow rate, we need to measure that with meters or pressure sensors so controls complexity will continue to evolve. The previous Variable Air Volume (VAV) system turn down with reheat was 30 percent, but is now 20 percent. Easy enough to program, but what about adequate ventilation for indoor air quality? This can be accomplished with more CO2 sensors in high-density occupancies like classrooms or conference rooms.
  • C402.5.3 New requirements for systems that use atmospheric combustion air will continue to push the trend toward sealed combustion for water heaters and other gas-fired systems. The heat traps on domestic hot water systems at the heater were highly effective, so now we will have them at unfired storage tanks, and the pipe insulation will be a little thicker.
  • C402.5.7 Vestibules that are heated or cooled now have their own set-back requirements and Economizer cycles continue to expand to more systems with additional controls to make sure they are functional. Kitchen exhaust is not what it was 10 or even five years ago. Many of the good ideas from engineers and ventilation system manufacturers are now in code language.
  • C408.2 With so much automation in building systems, there are opportunities to combine occupancy, HVAC and lighting controls for simplicity, efficiency, and potential first cost savings. In order to make all this work together, Commissioning is a requirement for systems with 40 Tons of cooling or 600 MBH heating.  

2018 IECC Mechanical Updates At Schemmer

“The changes to mechanical and some domestic hot water systems from the 2009 IECC to 2018 IECC are already standard practice at Schemmer in most instances. Now it has simply become the industry standard in terms of equipment efficiencies and design for the best value in regard to energy and comfort,” said Schemmer’s Bryce Johnson, PE, LEED AP, QCxP, mechanical engineer and associate.

Since Schemmer works on projects in areas outside of Nebraska, the firm’s current mechanical design standard is similar to the 2012 IECC.

“We do this because ASHRAE Standard 90.1 considers real payback based on building type and climate zone. So, Nebraska’s new state energy code really just catches up the enforcement language with what we are already doing. With the 2018 IECC updates, we will take what we are already doing and make it one step better,” said Johnson.

Stay tuned for our next blog in this series to learn more about 2018 IECC and how it will affect electrical systems.

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Sources: Asset Insights; Althoff Industries; Whole Building Design Guide; Upcodes; ASHRAE Standard 90.1