DT018

Stephen Agunbiade

Rory Conlon

Paul Derwin

Paul Dunne

What is Natural Ventilation?

A system that relies on natural sources such as wind and temperature difference between a building and its environment in order to flow fresh air through a building

Most Suited

Open plan Layouts

Areas of minimised noise pollution and external air

Not Suited

Buildings containing small spaces

Buildings that need a consists air temperature

What are the benefits of a Natural ventilation system?

Energy Savings

Reduce environmental impact

Robustness

In order to work effectively you must

Plan at the earliest stage of design

Team approach

Work out the clients desired objectives

Q=C * A * V

Q = Air flow

C = Effectiveness factor 0.5-0.6 for openings perpendicular to wind direction and 0.25-0.35 for openings diagonal to wind direction.

A = Area of opening ft2

V = Wind velocity ft./min.

Ref: “Natural Ventilation in non-domestic buildings” CIBSE guide.

Q= 60 K A √ G * H (TI – TO)/TI

Q= Airflow cfm.

K= discharge coefficient of an opening 0.6

A= Area of opening ft.2

G= Gravitational constant 32.2 ft./s2

TI = Indoor temperature

TO= Outdoor temperature

Ref: “Natural Ventilation in non-domestic buildings” CIBSE guide.

When both forces combine without obstructions resulting air flow, is not equal to the two flows estimated separately.

Wind velocity and direction, outdoor temperature and indoor distribution cannot be predicted with certainty.

When the two flows are equal the actual flow is 30%greater than the flow caused by either the wind or stack effect.

Openings must be accessible so occupants can operate them manually.

Openings in areas of neutral pressure are not desirable.

For temperature difference to produce a motive force its important of maximum vertical distances between openings.

Inlets should not be obstructed by buildings, trees externally and walls internally.

Openings of larger areas than calculated are more desirable.