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NUMBER OF FLOORS ( N ) = 4 FLOOR

STAIRWELL WALL AREA = 139.4496FT

2PER FLOOR

EXTERIOR BUILDING WALL AREA = 18496.44FT

2PER FLOOR

OUTSIDE DESIGN TEMPERATURE = 115OF 574.67

OR

STAIRWELL DESIGN TEMPERATURE = 85OF 544.67

OR

Exterior building walls Tight N A/Aw 0.00021

Average Y Average

Loose N b

Very lose N

Stairwell walls Tight N A/Aw 0.00011

Average Y AverageLoose N b

STAIRWELL WALL HEIGHT = 12FT

PER FLOOR

THE

FOR

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880

CFM

DONE BY:EngineerHasan Kayed

MOUNT OF CFM

EACH FLOOR:

E

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N: Numberof Floors = 4 Floor

As : Stairwell Wall Area = 139.4496FT

2PER FLOOR

Aw: Exterior Building Wall Area = 18496.44FT

2PER FLOOR

To: Outside Design Temperature = 115 OF 574.67 O R

Ts: Stairwell Design Temperature = 85OF 544.67

OR

Y: Stairwell Wall Height = 12FT

PER FLOOR

Max. design pressure differences when all stairwell doors are closed is 0.551 in of Water

The minimum aloowable pressure differences is 0.052 in of Water.

Using the leakage ratio for Table-1: Typical Leakage Areas for Walls and

an exterior building wall of Floors of Commercial Buildings

Average tightness from Wall Area Ratio

the table: Construction Element Tightness A/Aw

Abo = Aw x b Exterior building walls a-Tight 0.70x10-4

= 3.88 FT 2 b-Average 0.21x10-3

c-Loose 0.42x10-3

Using the leakage ratio for d-Very loose 0.13x10-2

stairwell wall of

Average tightness from Stairwell walls a-Tight 0.14x10-4

the table = As x b b-Average 0.11x10-3

= 0.02FT

2c-Loose 0.35x10

-3

The value of flow area between stairwell and building (per floor) equals the lekage area of the stairwell

wall plus the gaps around the closed doors ( 0.26 FT2 ), Asb = 0.02 .+ 0.26

= 0.28FT

2

The temperature factor B = 7.64 x ( 1/Ts - 1/To)= 0.00073 in.of Water

The pressure difference at the stairwell bottom is selected as Psbb = 0.080 in. of Water to

provide an extra degree of protection above the minimum allowable valueof0.052 in. of Water.

The pressure difference from stairwell to building at stairwell top Psbt is calculated by the equation:

Psbt = Psbb + [ ( B x Y x N ) / ( 1 + ( A sb / Abo )2

) ]

= 0.115 in. of Water

Thus, Psbt does not exceed the maximum aloowable pressure

The flow rate Q of pressurization air is calculated from the equation:

Q = 1740 x N x Asb x {[ (Psbt)3/2

- (Psbb)3/2

] / [ (Psbt)- (Psbb)

]

= 896 CFM

224 04.075571 220 230 220

305 05

STAIR CASE PRESSURIZATION UNIT CALCULATIONS