Applying ASHRAE Standard 62. 2 to Existing Buildings Paul Francisco Building Research Council
ASHRAE 62. 2 Ventilation Requirements n Whole-House ventilation n n Bath Fans Kitchen Fans n Can choose continuous or intermittent q Both CAN count toward whole-house rate Intermittent may require greater flow
ASHRAE 62. 2 Requirements Minimum Ventilation Air Requirements, CFM Floor Area (ft 2) Bedrooms 0 -1 2 -3 4 -5 6 -7 >7 <1500 30 45 60 75 90 1501 – 3000 45 60 75 90 105 3001 – 4500 60 75 90 105 120 4501 – 6000 75 90 105 120 135 6001 – 7500 90 105 120 135 150 >7500 105 120 135 150 165
Whole-House Ventilation n Mechanical rate = 7. 5*NP + 0. 01*Afloor q q q n NP default is number of bedrooms + 1 Use actual occupancy if higher Assumes infiltration rate of 0. 02*Afloor No differentiation between mechanical ventilation system types
Local Exhaust Ventilation n Bathrooms (not half bathrooms) q q n 50 CFM on-demand, or 20 CFM continuous. Kitchen q q 100 CFM on-demand, or 5 ACH continuous, based on kitchen volume.
Existing Buildings n Can comply using a single fan through alternative compliance appendix n Three steps q q q Base fan flow rate Adjustment for local exhaust “deficits” Infiltration credit
Base Fan Flow Rate Floor Area (ft 2) Bedrooms 0 -1 2 -3 4 -5 6 -7 >7 <1500 30 45 60 75 90 1501 – 3000 45 60 75 90 105 3001 – 4500 60 75 90 105 120 4501 – 6000 75 90 105 120 135 6001 – 7500 90 105 120 135 150 >7500 105 120 135 150 165 or can use 7. 5*NP + 0. 01*Afloor
Local Exhaust “Deficits” n In each room where local exhaust should be, determine deficit relative to intermittent rate q q n How much less than 50 cfm in bathrooms How much less than 100 cfm in kitchens For each room with a deficit, reduce room’s deficit by 20 cfm if that room has an operable window (not to drop below 0)
Local Exhaust “Deficits” n n Add up deficits, divide by 4 Add the result to the whole-house requirement q This becomes the new whole-house requirement
Local Exhaust “Deficits” n n For existing fans being used, sound and ducting requirements not applicable Must measure flow if ratings don’t exist or duct sizing can’t be verified q If only have rating at 0. 10 in. wc but not 0. 25 in. wc, can reduce rating at 0. 10 in. wc by 25%
Local Exhaust “Deficits” n Example #1 KIT -100 3 BR, 1500 sq. ft. house -50 BT BR BR Deficit = 100+50+50 = 200 Add 200/4 = 50 -50 MBT BR Whole-house requirement = 45 + 50 = 95 cfm
Local Exhaust “Deficits” n Example #2 KIT -80 -30 BT BR BR Deficit = 80+30+50 = 160 Add 160/4 = 40 -50 MBT BR Whole-house requirement = 45 + 40 = 85 cfm
Local Exhaust “Deficits” n Example #3 KIT -80 -30 BT BR BR Deficit = 80+30+18 = 128 Add 128/4 = 32 -18 MBT BR 32 cfm Whole-house requirement = 45 + 32 = 77 cfm
Local Exhaust “Deficits” n Example #4 KIT Add whole-house fan here -0 -80 BR BR BT Deficit = 80+0+18 = 98 Add 98/4 ≈ 25 -18 MBT BR 32 cfm Whole-house requirement = 45 + 25 = 70 cfm
Infiltration Credit n IF q q q n House built before adoption of 62. 2 Blower door test done Estimated infiltration using Standard 136 is greater than 2 cfm/100 sq. ft. THEN q Reduce whole-house rate by ½ of the excess above 2 cfm/100 sq. ft.
Infiltration Credit n Example #5 KIT BR BR BT Std. 136 estimates inf. = 70 BR ½ * (70 -30) = 20 MBT Whole-house requirement = 45 - 20 = 25 cfm (plus any “deficit” adjustment)
Infiltration Credit n Example #6 KIT BR BR BT Std. 136 estimates inf. = 120 BR ½ * (120 -30) = 45 MBT Whole-house requirement = 45 - 45 = 0 cfm (plus any “deficit” adjustment)
Std. 136? n Requires q q q n CFM 50 Number of 8 -foot stories (e. g. a 12 -foot ceiling counts as 1. 5) Weather factor “w” Weather factors can be found in BPI-101 standard
Std. 136 Approximation n From Workforce Guidelines Appendix n Assumes that volume = floor area * 8 # stories 1 1. 5 2 2. 5 3 S 1 1. 13 1. 23 1. 32 1. 39
QUESTIONS?
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