2016 Update for ASHRAE 62.2
At a minimum, every three years ASHRAE updates ASHRAE 62.2 (Ventilation and Acceptable Indoor Quality in Low-Rise Residential Buildings). In the updates, ASHRAE tweaks the ventilation rates and the formulas for calculating and applying them.
In the latest 2016 update, ASHRAE made major modifications to 62.2. The title was changed to Ventilation and Acceptable Indoor Air Quality in Residential Buildings. Thus, adding multifamily buildings of all heights to the scope. Additionally, unvented space heaters as a source of contamination were also added to the scope. The separate section on multifamily homes was merged with the single family home section. Thus, removing conflicting requirements. 17 Interim addendums have been incorporated to include:
- Addendum b: where a minimum calculated ventilation rate of 15 CFM will require the use of a mechanical system in an existing home.
- Addendum c: that separates requirements for range hoods and other kitchen ventilation methods.
- Addendum j: that provides a method for determining infiltration credit for horizontally attached dwellings.
- Addendum v: to address strategies for intermittent ventilation systems.
The ANSI/ASHRAE Standard 62.2-2016 update is divided into eight sections. Sections 1-3 has the Purpose, Scope, and Definitions. The actual requirements start at Section 4:
- Dwelling-Unit Ventilation
- Local Exhaust
- Other requirements
- Air-Moving Equipment
- Climate Data
ASHRAE 62.2 2016 requires upgrading to MERV 6 filters, sealing ducts in unoccupied space, sealing the building’s envelope, adding ventilation openings to bathrooms, and adding ventilation to utility rooms. In a number of cases, it may be prohibitive to meet the requirements in many existing homes. ASHRAE 62.2 2016’s Appendix A provides some advantages and disadvantages for some commonly used compliance strategies.
This time, there is some good news, a new ASHRAE 62.2 2016’s Appendix C allows for more flexibility for automated designs. Flexibility for automated system designs allow contractors to consider efficiency by varying operation times, volumes, air temperatures, and occupant loads. Additionally, the Table values were combined and now are the same for single and multifamily dwellings and the formula method has remained unchanged.
The Table Method (See Table 1)
For estimation purposes, or for basic residential OA requirements, Table 1 can be used to determine the CFM required for all residential applications with 5 bedrooms or less that are 5000 ft2 or smaller. Using the table method, a two-bedroom house with a 1,525 ft2 conditioned floor area would require 83 CFM OA for a 3 occupant rating. As per ASHRAE 62.2, when using Table 1, the values provided are for 2 persons in a studio (or in a one-bedroom), and if the number of occupants is known, and greater than the table values, the additional occupants must be accounted for by adding 7.5 CFM per additional person to the table value.
Figure 1: CFM Required ft2/ Bedrooms
Adapted from ASHRAE 62.2 – 2016 (for all Residences)
|Ventilation Air Requirements in CFM|
|Floor Area ft2||Number of Bedrooms|
|Less Than 500||30||38||45||53||60|
The Formula Method
This method may be used on any size of home with any known occupancy. Calculating the quantity of outside air needed for compliance is based on a relatively simple formula that multiplies 3% of the conditioned floor area, and adds it to the number of occupants multiplied by 7.5. When unknown, the number of occupants, for residential applications used in the formula is generally the number of bedrooms plus 1 with a one bedroom minimum allowed (or 2 people). The formula is:
Qtot= 0.03 Afloor + 7.5 x (Nbr+ 1)
Qtot=Total required ventilation rate in cubic feet per minute (CFM)
Afloor =Floor area in square feet
Nbr =Number of bedrooms. Not to be less than one; used to estimate the number of occupants for design purposes.
Note: When AHJ rules requires a different the Qtot value, that value must be used.
Using the same 1525 ft2 two-bedroom house that was used in the Table Scenario above, OA would be calculated as follows:
OAcfm =0.03 (1525) + [7.5 x (2 + 1)] = 68.25 CFM
For a more complete update download Technical Bulletin 2016-3 at: http://www.acca.org/members/downloads
Or listen to the ACCA Town Hall archived video, ASHRAE’s Residential Ventilation Requirements in the HVACD Technical Issues section at: http://www.acca.org/members/videos
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