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ORIENTATION

 The greatest pressure on the windward side of a

building is generated when the elevation is at rightangles to the wind direction, so it seems to beobvious the greatest indoor air velocity will beachieved in this case.A wind incidence of ! degree would reduce the

pressure by !"#.E$TERNA% &EAT'RE(

)ind shadows created by obstructions upwind,should be avoided in positioning the building on the

site and in positioning the openings in the building.E*ternal features of the building itself can stronglyin+uence the pressure built up.

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RO(( -ENTI%ATION

In the absence of an outlet opening or with a full

partition there can be no eective air movementthrough a building even in case of strong winds.

&or e*ample, if the air +ow is at ! deg. To anelevation, a wing/wall at the downwind end or apro0ecting wing of an %/shaped building can more than

double the positive pressure created.

)ith a windward opening and no outlet, a pressuresimilar to that in front of the building will be built up

indoors, which can ma1e conditions even worse,increasing discomfort.

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%ac1 of cross ventilation

Eect of opening

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2O(ITION O&O2ENIN3( To be eective, the air movement must be directedat the body surface.

In building terms this means that air movementmust be ensured through the space mostly used bythe occupants4 through the 5living 6one7.In the 8gure, it is shown that a larger solid surface

creates a larger pressure build up and this pushes theair stream in an opposite direction, both in plan andsection.

2ressure build/up at inlet

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As a result, air +ow on the ground+oor may be satisfactory but onthe upper +oor it may be directed

against the ceiling.One possible remedy is anincreased roof parapet wall.

(I9E O& O2ENIN3(

)ith a given elevational area and a given total windforce:pressure * area;/the largest air velocity will beobtained through a small inlet opening with a largeoutlet.

 This is partly due to the total force acting on a smallarea, forcing air through the opening at a highpressure, and partly due to the 5venturi eect74in thebroadening funnel :the imagery funnel connecting the

small inlet to the large outlet;the sideways e*pansionof the air et further accelerates the articles.

Air +ow in a two storeybuilding

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 This could serve a useful purpose in hot climates,although if the tall bloc1 is not fully closed but ispermeable to wind, these eects may be reduced.

Air stream seperation at the face of buildings

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Reverse +ow behind a tall bloc1