BRE Atrium Sizer

Sizing openings for naturally ventilated buildings

Stack ventilation Based on outside - stack temperature difference(s)+optional wind effects

This is a restricted version of the model and assumes a storey height of 3.5 m

The model assumes that there is office accommodation either side of a central atrium with openings on both

the windward and leeward sides of the building

Input item Units Input value(s)

Building definition

Number of floors - 3

Building height (roof level) metres 10.5

Inlet location Windward Leeward Windward Leeward Windward Leeward Windward Leeward

For each floor Floor no. 1 1 2 2 3 3

Floor area naturally ventilated sq m. 480.00 480.00 480.00 480.00 480.00 480.00

Room temperature deg C 20.0 20.0 20.0 20.0 20.0 20.0

Required air change rate achr-1 0.9 0.9 0.9 0.9 0.9 0.9

Wind pressure coeff for inlet - 0.65 -0.45 0.65 -0.45 0.65 -0.45

Height of outlet above ground metres 19.500

Wind presure coefficient for outlet - -0.60

Stack definition

Number of stack slices - 1

For each slice (starting from bottom) 1

Vertical length of slice metres 21.000

Temperature of slice (normal design) deg C 24.0

Temperature of slice (fire condition) deg C 80.0

Height of NPL above ground metres 17.750 Recommended between 10.750 19.250

Weather conditions

Outside temperature deg C 20.0

Windspeed m/s 0.0

Local or meteorological? L or M L

Terrain (Open,Rural,Urban, City) urban

Parametric analysis

Windward Leeward Windward Leeward Windward Leeward Windward

Results Floor no. Outlet Floor 1 Floor 1 Floor 2 Floor 2 Floor 3 Floor 3

Opening size (no wind) sq.m 5.5927 0.3071 0.3071 0.3478 0.3478 0.4105 0.4105

Opening size (with wind) sq.m 5.5927 0.3071 0.3071 0.3478 0.3478 0.4105 0.4105

Opening sizes (user outlet + wind) sq.m 18.6424 0.2928 0.2928 0.3274 0.3274 0.3781 0.3781

Allowances for internal resistance

Windward Leeward Windward Leeward Windward Leeward Windward Leeward

Floor 1 Floor 1 Floor 2 Floor 2 Floor 3 Floor 3

Fixed size of façade/stack opening sq.m 0.5000 0.5000 0.5000 0.5000 0.5000 0.5000

Req'd size of stack/façade opening sq.m 0.3613 0.3613 0.4332 0.4332 0.5778 0.5778

0.00

1.00

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6.00

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Op

en

ing

siz

e (

m2

)

Alternative combinations

Outlet

Floor 1

Floor 2

Floor 3

Floor 4

Floor 5

Floor 6

Requirements under fire conditions

Windward Leeward Windward Leeward Windward Leeward Windward Leeward

Floor 1 Floor 1 Floor 2 Floor 2 Floor 3 Floor 3

Additional door opening area m2 0 0 0 0 0 0

Door in parallel with fixed area? Y/N Y Y Y Y Y Y

Flowrate through floor ach-1 3.096 3.096 3.057 3.057 2.991 2.991

Required outlet area m2 5.7225

Windward Leeward Windward Leeward Windward Leeward Windward Leeward Windward Leeward Windward Leeward

Leeward Windward Leeward Windward Leeward Windward Leeward Windward Leeward Windward Leeward Windward



Windward Leeward Windward Leeward Windward Leeward Windward Leeward Windward Leeward

Leeward Windward Leeward Windward Leeward Windward Leeward Windward Leeward Windward Leeward



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A B C D E F

Calculation sheet units

Reference data

Reference temperature K 298.16

To convert deg C to K, add 273.16

Reference density kg/m3 1.18

Gravitational constant m/s2 9.807

Discharge coefficient - 0.61

Room data 1 1 2 2

Volume cu.m 1512 1512 1512 1512

Opening height above datum metres 1.85 1.85 5.35 5.35

Stack pressures

Slice no. 0 1 2 3

Height at top of slice metres 0 21 21 21

Relative pressure at top of slice Pa 0 -3.3269922 -3.3269922 -3.3269922

Pressures at inlet heights 1 2 3 4

Index of slice in which the opening is 1 1 1 1

Height of bottom of slice metres 0 0 0 0

Relative pressure at bottom of slice Pa 0 0 0 0

Height of top of slice metres 21 21 21 21

Relative pressure at top of slice Pa -3.32699222 -3.3269922 -3.3269922 -3.3269922

Relative pressure at opening Pa -0.29309217 -0.2930922 -0.8475909 -0.8475909

Presures at outlet height

Index of slice in which the outlet is 1

height at bottom of slice metres 0

Pressure at bottom of slice Pa 0

Height at top of slice metres 21

Pressure at top of slice Pa -3.32699222

Pressure at outlet Pa -3.08934992

Temperature of outlet air deg C 24

Presures at NPL

Index of slice at which the NPL is 1

Height at bottom of slice metres 0




Pressure at NPL Pa -2.81210057

Calculate sizes - zero wind 1 2 3 4

Volume flow for room m3/s 0.38388 0.38388 0.38388 0.38388

Room air density kg/m3 1.20012553 1.20012553 1.20012553 1.20012553

Mass flow rate kg/s 0.46070419 0.46070419 0.46070419 0.46070419

Pressure difference at inlet Pa 2.5190084 2.5190084 1.96450969 1.96450969

Opening size m2 0.30714905 0.30714905 0.34780587 0.34780587

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A B C D E F

Mass flow at outlet kg/s 2.76422513

Density at outlet kg/m3 1.18397092

Volume flow at outlet m3/s 2.33470693

Pressure difference at outlet Pa 0.27724935

Opening size m2 5.5927163

Adjustments for wind

Terrain class City Urban Rural Open

K-value - 0.21 0.35 0.52 0.68

alpha-value - 0.33 0.25 0.2 0.17

user K - 0.35

user alpha - 0.25

Windspeed at building height m/s 0

Air density at outside temperature kg/m3 1.20012553

1 1 2 2

Wind pressure at inlets Pa 0 0 0 0

Wind pressure at outlet Pa 0

Pressure available (inlet to outlet) Pa 2.79625775 2.79625775 2.24175905 2.24175905

Pressure loss across inlet Pa 2.5190084 2.5190084 1.96450969 1.96450969

Revised inlet size sq.m 0.30714905 0.30714905 0.34780587 0.34780587

Min path pressure loss Pa 1.68726034

Parametric variation

Input value % across out 0 Opening sizes --------------------------------------------------------------------------------------------/

Outlet loss Outlet Floor 1 Floor 2

Data table Equn 0.2772 5.5927 0.3071 0.3071

0.0000 0.2772 5.5927 0.3071 0.3071

0.2000 0.5424 3.9986 0.3247 0.3247

%=0.282 for NPL case 0.4000 0.8075 3.2771 0.3457 0.3457

0.6000 1.0726 2.8434 0.3713 0.3713

0.8000 1.3378 2.5461 0.4037 0.4037

1.0000 1.6029 2.3260 0.4462 0.4462

Adjust outlet area to user value

Outlet size sq.m 18.6424

Outlet loss Pa 0.02495241

Inlet 1 Inlet 2 Inlet 3 Inlet 4

Pressure loss across inlet Pa 2.77130534 2.77130534 2.21680664 2.21680664

Revised inlet size sq.m 0.2928342 0.2928342 0.32741614 0.32741614

Allowances for series resistances

user fixed inlet 0.5 0.5 0.5 0.5

required series resistance 0.36127806 0.36127806 0.43321951 0.43321951

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G H I J K L M N O

3 3 4 4 5 5 6 6 7

1512 1512 0 0 0 0 0 0 0

8.85 8.85

4 5 6 7 8 9 10 11 12

21 21 21 21 21 21 21 21 21

-3.3269922 -3.3269922 -3.3269922 -3.3269922 -3.3269922 -3.3269922 -3.3269922 -3.3269922 -3.3269922

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1 1 #N/A #N/A #N/A #N/A #N/A #N/A #N/A

0 0 #N/A #N/A #N/A #N/A #N/A #N/A #N/A

0 0 #N/A #N/A #N/A #N/A #N/A #N/A #N/A

21 21 #N/A #N/A #N/A #N/A #N/A #N/A #N/A

-3.3269922 -3.3269922 #N/A #N/A #N/A #N/A #N/A #N/A #N/A

-1.4020896 -1.4020896 #N/A #N/A #N/A #N/A #N/A #N/A #N/A

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0.38388 0.38388 0 0 0 0 0 0 0

1.20012553 1.20012553 1.28799531 1.28799531 1.28799531 1.28799531 1.28799531 1.28799531 1.28799531

0.46070419 0.46070419 0 0 0 0 0 0 0

1.41001099 1.41001099 #N/A #N/A #N/A #N/A #N/A #N/A #N/A

0.41053741 0.41053741 #N/A #N/A #N/A #N/A #N/A #N/A #N/A

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G H I J K L M N O

3 3 4 4 5 5 6 6 7

0 0 0 0 0 0 0 0 0

1.68726034 1.68726034 1000000 1000000 1000000 1000000 1000000 1000000 1000000

1.41001099 1.41001099 999999.723 999999.723 999999.723 999999.723 999999.723 999999.723 999999.723

0.41053741 0.41053741 0 0 0 0 0 0 0

Opening sizes --------------------------------------------------------------------------------------------/

Floor 3 Floor 4 Floor 5 Floor 6 Floor 7 Floor 8 Floor 9 Floor 10 Floor 11

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

Inlet 5 Inlet 6 Inlet 7 Inlet 8 Inlet 9 Inlet 10 Inlet 11 Inlet 12 Inlet 13

1.66230793 1.66230793 999999.975 999999.975 999999.975 999999.975 999999.975 999999.975 999999.975

0.37810137 0.37810137 0 0 0 0 0 0 0

0.5 0.5 0 0 0 0 0 0 0

0.57783856 0.57783856 #DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0!

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P Q R S T U V W X

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0 0 0 0 0 0 0 0 0

13 14 15

21 21 21

-3.3269922 -3.3269922 -3.3269922

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#N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A






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0 0 0 0 0 0 0 0 0

1.28799531 1.28799531 1.28799531 1.28799531 1.28799531 1.28799531 1.28799531 1.28799531 1.28799531

0 0 0 0 0 0 0 0 0



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P Q R S T U V W X

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0 0 0 0 0 0 0 0 0

1000000 1000000 1000000 1000000 1000000 1000000 1000000 1000000 1000000

999999.723 999999.723 999999.723 999999.723 999999.723 999999.723 999999.723 999999.723 999999.723

0 0 0 0 0 0 0 0 0


0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

Inlet 14 Inlet 15 Inlet 16 Inlet 17 Inlet 18 Inlet 19 Inlet 20 Inlet 21 Inlet 22

999999.975 999999.975 999999.975 999999.975 999999.975 999999.975 999999.975 999999.975 999999.975

0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0 0

#DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0!

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Y Z AA AB AC AD AE AF AG

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0 0 0 0 0 0 0 0

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#N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A






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0 0 0 0 0 0 0 0

1.28799531 1.28799531 1.28799531 1.28799531 1.28799531 1.28799531 1.28799531 1.28799531

0 0 0 0 0 0 0 0



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Y Z AA AB AC AD AE AF AG

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0 0 0 0 0 0 0 0

1000000 1000000 1000000 1000000 1000000 1000000 1000000 1000000

999999.723 999999.723 999999.723 999999.723 999999.723 999999.723 999999.723 999999.723

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0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

Inlet 23 Inlet 24 Inlet 25 Inlet 26 Inlet 27 Inlet 28 Inlet 29 Inlet 30

999999.975 999999.975 999999.975 999999.975 999999.975 999999.975 999999.975 999999.975

0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0

#DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0!

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AH

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AH

Floor 30

0.0000

0.0000

0.0000

0.0000

0.0000

0.0000

0.0000

Calculations for wind driven cross flow

This option is only valid for single storey case with no stack slices defined

Available driving pressure

Stack pressure based on room - outside Pa

Room air density kg/m3 1.20012553

Stack pressure difference Pa 0

Driving pressure per opening Pa 0

Opening size (stack only) sq.m #DIV/0!

Wind pressure difference Pa 0

Total driving pressure (stack + wind) Pa 0

Driving pressure per opening Pa 0

Opening size sq.m #DIV/0!

User specified exhaust size sq.m 18.6424

Exhaust pressure drop Pa 0.00068379

Pressure drop across inlet Pa -0.0006838

Inlet size sq.m #NUM!

Adjustment for internal area

User specified internal area sq.m 0.5

If user exhaust is blank, apply fixed opening to

both sides of corridor

Required area sq.m #DIV/0!

If user exhaust is set, apply only to one side sq.m #NUM!

return value sq.m #NUM!

Calculation sheet units

Reference data

Reference temperature K 298.16

To convert deg C to K, add 273.16

Reference density kg/m3 1.18

Gravitational constant m/s2 9.807

Discharge coefficient - 0.61

Room data 1 2 3 4 5

Volume cu.m 1512 1512 1512 1512 1512

Opening height above datum metres 1.85 1.85 5.35 5.35 8.85

Stack pressures

Slice no. 0 1 2 3 4

Height at top of slice metres 0 21 21 21 21

Relative pressure at top of slice Pa 0 -41.991548 -41.991548 -41.991548 -41.991548

Pressures at inlet heights 1 2 3 4 5

Index of slice in which the opening is 1 1 1 1 1

Height of bottom of slice metres 0 0 0 0 0

Relative pressure at bottom of slice Pa 0 0 0 0 0

Height of top of slice metres 21 21 21 21 21

Relative pressure at top of slice Pa -41.9915481 -41.991548 -41.991548 -41.991548 -41.991548

Relative pressure at opening Pa -3.69925543 -3.6992554 -10.697847 -10.697847 -17.696438

Presures at outlet height

Index of slice in which the outlet is 1

height at bottom of slice metres 0




Pressure at outlet Pa -38.9921518

Temperature of outlet air deg C 80

Density of outlet air kg/m3 0.9962306

Presures at NPL

Height of NPL metres 17.75

Index of slice at which the NPL is 1

Height at bottom of slice metres 0




Pressure at NPL Pa -35.4928562

Windspeed at building height m/s 0

Air density at outside temperature kg/m3 1.20012553

1 2 3 4 5

Wind pressure at inlets Pa 0 0 0 0 0

Stack available from inlet to NPL Pa 31.7936007 31.7936007 24.7950094 24.7950094 17.796418

Pressure across inlet Pa 31.7936007 31.7936007 24.7950094 24.7950094 17.796418

Door opening area at this level m2 0 0 0 0 0

Equivalent area of inlet path m2 0.2928342 0.2928342 0.32741614 0.32741614 0.37810137

Flow through inlet m3/s 1.3002389 1.3002389 1.28384832 1.28384832 1.25604745

Mass flow through inlet kg/s 1.5604499 1.5604499 1.54077915 1.54077915 1.50741461

Air changes through inlet ach-1 3.0958069 3.0958069 3.05678172 3.05678172 2.99058917

Wind pressure at outlet Pa 0

Stack available from NPL to outlet Pa -3.49929568

Pressure drop at outlet Pa 3.49929568

Volume flow at outlet m3/s 1.56635411 1.56635411 1.54660893 1.54660893 1.51311815

Exhaust area to match flow from floor m2 0.96880135 0.96880135 0.95658882 0.95658882 0.93587453

Exhaust area required m2 5.7225294

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1512 0 0 0 0 0 0 0 0

8.85

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21 21 21 21 21 21 21 21 21

-41.991548 -41.991548 -41.991548 -41.991548 -41.991548 -41.991548 -41.991548 -41.991548 -41.991548

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1 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A




-41.991548 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A

-17.696438 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A

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0 0 0 0 0 0 0 0 0

17.796418 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A

17.796418 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A

0 0 0 0 0 0 0 0 0

0.37810137

1.25604745 #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE!




0.93587453 0 0 0 0 0 0 0 0

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0 0 0 0 0 0 0 0 0

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21 21 #REF! #REF! #REF! #REF! #REF! #REF! #REF!

-41.991548 -41.991548 #REF! #REF! #REF! #REF! #REF! #REF! #REF!

15 16 17 18 19 20 21 22 23







15 16 17 18 19 20 21 22 23

0 0 0 0 0 0 0 0 0



0 0 0 0 0 0 0 0 0

#VALUE! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE!




0 0 0 0 0 0 0 0 0

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0 0 0 0 0 0 0

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#REF! #REF! #REF! #REF! #REF! #REF! #REF! #REF!

#REF! #REF! #REF! #REF! #REF! #REF! #REF! #REF!

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#N/A #N/A #N/A #N/A #N/A #N/A #N/A






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0 0 0 0 0 0 0



0 0 0 0 0 0 0

#VALUE! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE!




0 0 0 0 0 0 0

Documents

BRE Atrium Sizer