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HVAC - Sizing | Residential | Contractors Summary Heating and cooling consume a large portion of building energy use. Properly sized heating and/or cooling equipment is critical to reducing inefficiencies. HVAC sizing requirements help improve occupant comfort through appropriate conditioning of indoor air.
Current Code The 2009 IECC Section 403.6 states that HVAC systems must be sized in accordance with Section M1401.3 of the International Residential Code (IRC). This requires the use of ACCA Manual S and J calculation procedures.
QUICK FACTS HVAC Sizing – Section 403.6 2009 IECC Detailed sizing instructions can be found in M1401.3 of the International Residential Code Mandatory for all climate zones Software is available to compute sizing calculations Detailed information can be found at:
Previous Code HVAC sizing requirements in the 2006 and 2009 editions of the IECC are identical. Prior to the 2006 version, the requirements specified the use of the ASHRAE “Handbook of Fundamentals.”
DOE EERE information on HVAC sizing PNNL “How to Size HVAC Systems Correctly”
Exemptions
Ten key factors to help keep HVAC sizing calculations on target
Requirements covered in the 2009 IECC Section 403.6 are mandatory for all climate zones.
Professional Remodeler article “When Size Matters”
Requirements Contractors and sub-contractors must be aware of the requirements covered in the 2009 IECC and need to ensure that: The HVAC systems are sized using ACCA Manual S and J and that it is included in their bid They are able to demonstrate Manuals J and S calculations either by hand or applicable software
Typical Problems Standard issues/concerns that arise include: HVAC contractor or sub-contractor does not include IECC requirements in bid Contractors are unable to provide code officials with sizing calculations and other energy-related HVAC requirements
BCAP
Figure 1: Software for Manual J Calculations
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