Transcript Applying ASHRAE Standard 62.2 to Existing Buildings

Applying ASHRAE
Standard 62.2 to
Existing Buildings
Paul Francisco
Building Research Council
ASHRAE 62.2 Ventilation Requirements

Whole-House ventilation


Bath Fans
Kitchen Fans

Can choose continuous or intermittent

Both CAN count toward
whole-house rate
Intermittent may require greater flow
ASHRAE 62.2 Requirements
Minimum Ventilation Air Requirements, CFM
Floor Area
(ft2)
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

Mechanical rate = 7.5*NP + 0.01*Afloor




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

Bathrooms (not half bathrooms)



50 CFM on-demand, or
20 CFM continuous.
Kitchen


100 CFM on-demand, or
5 ACH continuous, based on kitchen volume.
Existing Buildings

Can comply using a single fan through
alternative compliance appendix

Three steps



Base fan flow rate
Adjustment for local exhaust “deficits”
Infiltration credit
Base Fan Flow Rate
Floor Area
(ft2)
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”

In each room where local exhaust should be,
determine deficit relative to intermittent rate



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”


Add up deficits, divide by 4
Add the result to the whole-house
requirement

This becomes the new whole-house requirement
Local Exhaust “Deficits”


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

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”

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”

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”

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”

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

IF



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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

Reduce whole-house rate by ½ of the excess
above 2 cfm/100 sq. ft.
Infiltration Credit

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

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?
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Requires
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CFM50
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

From Workforce Guidelines Appendix
I CFM  0.0508* w * S * Q50

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?