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ASHRAE’s Radically New 62.2 Standard

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Up to now, previous updates of the original 2003 version of the standard only required fairly minor and easily accomplished tweaks to the existing calculation procedures. In the 2013 version, there is a radical difference in how outside air calculations are calculated. Some of the major changes in ASHRAE 62.2 for 2013 are:

  • There are new infiltration calculations based on a new weather data table
  • There are new requirements for carbon monoxide alarms.
  • The default leakage rate of 2 CFM per 100 ft of conditioned space is gone.
  • There is now no reasonable leakage rate for multifamily buildings.
  • Single family home leakage rates must be established with a blower door.
  • Climate limitations on pressurization and depressurization are gone.
  • One of the two DOE climate maps and the related instruction set was deleted.
  • The base assumption for calculating the outside air requirements has changed.
  • Table values are universally changed in the Standard

When faced with a document filled with changes, my dad (an attorney) always said “the Devil is in the details.” In the case of 62.2 2013, that appears to be a valid assessment based on the number of individual sections removed and individual changes sprinkled throughout the document. From my perspective, the only thing that remains untouched is the original basic principle: outside air is brought into the building to dilute the level of interior contaminants in the air.

Few Homes Are Exempted From The 62.2 Requirements
Most contractors will never be able to apply any of the exceptions in the ASHRAE 62.2 requirements on a money making job. Those exempted are homes without AC in the southwest, Florida, and along the Gulf of Mexico in zones 1 and 2 on the climate map. Additionally, there are still exceptions to the requirement if local code or the authority having jurisdiction allows the use of windows for ventilation or for any building that is thermally conditioned less than 876 hours a year.

Changes To Watch Out For
Contractors will need new formulas to calculate leakage rates for all new construction, and will need to do blower door tests on existing homes in order to meet the new calculation requirements for retrofi ts. Additionally, during Manual J load calculations, HVAC contractors have a new hurdle. ASHRAE 62.2 2013 differs in instruction from standard residential load calculations that do not allow adding more people into the calculation process. In fact, ASHRAE 62.2 requires it. Thus, for 62.2 compliance, an additional 7.5 CFM is added for each additional person known to occupy the space. For a new home being built by a track builder, the additional 7.5 CFM should probably never be applied. However once invoked, 62.2-2013 requires the addition of extra air to the ventilation rates for: custom built homes or retrofit jobs where it is known that there are additional people in each bedroom. When 62.2 2013 is adopted by ENERGY STAR if additional people are included in makeup air calculations, the additional people in the design will need to be documented in the design as an exception.

Some Good News For Contractors
Even though the calculation process has been completely overhauled, the good news is that professional HVAC contractors do not need to retrain their installation staff as the mechanical methods and airflow measurement requirements for meeting the ASHRAE 62.2 were not changed. Therefore, once the new target CFM for the outside air and the equipment has been determined, the installation practices remain unchanged. Equipment configuration and type should still be selected based on local climate conditions. Ventilation options recognized include the following:

  • Exhaust-only systems
  • Exhaust Fan + Duct Connected to the Return Plenum from the Outside
  • OA Supply-only systems
  • Heat Recovery Ventilator (HRV) or Energy Recovery Ventilator (ERV)
  • OA Supply Fan + Exhaust Fan
  • OA Supply Fan Ducted to the Return Plenum
  • Dehumidifier with Outside Air Supply
  • Duct, From the Outside, Connected to the Furnace / Air Handler Return Plenum

Detailed Information Available For ACCA Members
Some of the options above that work well in one type of climate will cause problems in another. In case you missed it, in IE3 there is an overview on how professional contractors are approaching ASHRAE 62.2 mechanically by region called Creative Solutions For ASHRAE 62.2 Makeup Air Requirements at
The Consumer related ComforTool entitled “You May Need Outside Air In Your Home” is written in layman’s terms so it did not need updating and is available at under “Downloads.”

Recognizing that professional HVAC contractors are all very busy business owners, they seldom get overly enthusiastic when the codes or standard requirements change. This is because digging through additional standards cited in ASHRAE 62.2 to figure out how designs and installations for their jobs will be impacted is not the best way to spend a quiet weekend evening at home. In order to save our members time, ACCA developed a Technical Bulletin on ASHRAE 62.2 2013 as a quick one stop reference covering most applications it is available for free downloading at under “Downloads.”

Don Prather

Posted In: Residential Buildings, Technical Tips

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