I’m a Mechanical Engineer working on replacing (3) dual duct variable volume air handling units and (1) single duct variable air volume boxes for the Questar Gas Company. In the past, these types of units were designed w/ higher external static pressures requiring higher horsepower motors. Under today’s Energy Code, the motor requirement is quite a bit more strict and for the most part, we would need to design to much lower external static pressures. Because the system is existing, and the external static pressure cannot be reduced without a significant redesign to the ductwork, is a direct replacement of the air handling units acceptable without showing compliance w/ the ComCHECK report?
Please note that at this time, I have run a preliminary report and I’m having issues w/ trying to get the units to pass.
Provided by Brent Ursenbach
The IEEC (or ASHRAE) requires compliance with the specific requirements defined in the code. Further, the code requires documentation on plans and other documents sufficient to show code compliance.
The DOE (Department of Energy) provides the Building Energy Compliance Programs at no charge. Quoting the DOE website, www.energycodes.gov:
The COMcheck software product group makes it easy for architects, builders, designers, and contractors to determine whether new commercial or high-rise residential buildings, additions, and alterations meet the requirements of the IECC and ASHRAE Standard 90.1, as well as several state-specific codes. COMcheck also simplifies compliance for building officials, plan checkers, and inspectors by allowing them to quickly determine if a building project meets the code.
COMcheck and REScheck basically simplify showing compliance with the energy code.
Addressing this specific question:
- The code does not include any references to COMcheck or REScheck. It is not mandatory to use the software package.
- If the design professional chooses to not use COMcheck, he/she must provide documentation showing the project complies.
- This replacement of air-handlers and/or VAV boxes on this project is considered an alteration and must comply with IECC Section C503 Alterations.
- 1 General. Alterations to any building or structure shall comply with the requirements of the code for new construction. Alterations shall be such that the existing building or structure is no less conforming to the provisions of this code than the existing building or structure was prior to the alteration. Alterations to an existing building, building system or portion thereof shall conform to the provisions of this code as those provisions relate to new construction without requiring the unaltered portions of the existing building or building system to comply with this code. Alterations shall not create an unsafe or hazardous condition or overload existing building systems.
- Per the underlined text above, an alteration of a portion of the building system does not require unaltered portions to comply.
- After spending a little time in COMcheck, specifically in multi-zone systems, I don’t see where the software recognizes installation of only VAV boxes, or only an air-handler. It asks for fan system details, economizer information, which may be unaltered.
- In a new project, fan hp limitations are met through the efficient design of the duct systems. It’s unreasonable to expect existing duct systems to perform as a new system will.
- If I was reviewing your project, I would except a COMcheck, even if it fails, with a statement attached/included, justifying code compliance based on the referenced section in Chapter 5, noting the supply fans and/or the duct systems are unaltered; therefore, compliance is not required for those existing components. A similar written justification, without a COMcheck would also be acceptable. Bottom line, replacement of air handling fans or VAV boxes does not trigger duct replacement.
Further discussion or questions are welcome.