Changes to PA UCC Code: Mechanical Code Changes 2009 vs 2015 IECC/IMC

The change from the 2009 International Codes to the 2015 International codes in Pennsylvania, except for the City of Philadelphia, ushered in many substantial changes when it comes to mechanical system design, construction and operation.

Similar to other code updates, the hike toward sustainable design and operation continues in these common areas: increased equipment efficiency requirements, tighter buildings and better control. However, there are several significant changes that not only effect how systems are designed and built but may require significant capital investments where they weren’t required before.

In this issue of Insight, we outline some major changes taking place, and what you can expect in upcoming projects.

Window Area Limitations

With some notable exceptions, the maximum amount of window area allowed is 30% of the exterior wall area for most building designs. This may seem contradictory to the LEED requirement of daylighting and views, but the industry is still searching for the balance of thermal envelope efficiency and the benefits of daylight. While there are exceptions that allow up to 40% external glazing, there’s no free lunch. Those exceptions, which are generally for multi-story buildings, require an investment in daylighting controls and have strict guidelines for glass performance, which some owners may find too costly for the standard facility.

HVAC Controls

As lighting efficiencies continue to drastically improve when compared to the days of 40-watt fluorescent tubes and 100-watt incandescent bulbs, and as computer equipment moves from 250-watt desktop computers to 20-watt laptops, a significant shift has occurred in the building energy usage toward the HVAC systems. Electricity usage is increasingly dominated by ventilation load incurred on the heating and cooling systems when compared to other building systems, and as such, the codes are now requiring smarter controls to attempt to bring the air conditioning systems better in line with the efficiencies gained in other building systems. Changes in requirements include:

  • Direct Digital Control (DDC) systems are now required for most commercial systems.
  • Economizers are required to have Fault Detection Diagnostics (FDD) to be able to self-diagnose operational issues.
  • Boiler controls now require setback based on outside air conditions.
  • Demand Controlled Ventilation (DCV) requirements have increased.

HVAC Design and Installation

There have also been significant changes that affect design and installation of HVAC systems, some of the most significant include:

  • Parking garage contaminant control is required unless the garage is smaller than 25,000 sq. ft., or the fan is more efficient than 1125 cfm/hp.
  • Energy recovery is now required on systems with more than 1,200 cfm of outside air, but with notable exceptions.
  • Ducts are generally seal class A, which means longitudinal and transverse seams are sealed.
  • Ducts and pipes have significant insulation requirement changes, in some cases up to 5” of insulation on steam piping systems. This will result in tighter coordination tolerances, and potentially larger plenum and chase area requirements.
  • Commercial refrigeration systems are now required to meet set efficiency levels.

And finally, Commissioning is now a requirement for all systems over 40 tons cooling and a combined space and service water heating exceeding 600,000 btu/hr.

While this is not an exhaustive list of all the changes in code requirements, it’s obvious that navigating our changing landscape requires careful application of our new code system. If you have any questions, please do not hesitate to contact Stephen E. Oskin, PE, LEED AP at (814) 237-2180 or