How many do I need – easy calculator?
Calculate your most effective installation of RoofWhirlys4Africa ventilation. Use the size of the building and what activity is happening in your building. Of course the number of people per square metre in your building will affect how much air you need. Furthermore if your activity in your building is producing excessive fumes, odours, heat or moisture it needs more frequent air changes. These factors affect how many you RoofWhirlys4Africa will give you the best ventilation solution. However it is always better to have some rather than none!! Since your RoofWhirlys4Africa ventilation solution does not need to be installed on a single day… you can buy and install in stages.
Here are some easy calculator examples to assist you
If a building is 2m long x 2m wide and 2m high then the volume of air in the building is 2x2x2 = 8m3
If the building is an outside toilet then it requires 20 air changes per hour i.e. 20×8 = 160 m3 per hour to replace stale air with fresh air. You can use the table below for recommended air changes per hour.
You will then choose a roof whirly that extracts 200m3 per hour. A single roof whirly will provide sufficient fresh air and remove fumes and odours.
If a building is 5m long x 5m wide x 5m high then the volume of air in the building is 5x5x5 = 125m3
If the building is a restaurant kitchen then it requires at least 20 air changes per hour. You will then need 20 x 125 = 5000 m3 per hour to remove the heat, moisture, fumes, and CO2 and replace this with fresh air.
If the selected roof whirly extracts 1000m3 per hour then the kitchen will require 5 RoofWhirlys4Africa to provide your fresh air requirement. (extraction rates at the bottom of the page).
Air Changes per Hour
The air changes per hour is the number of times the entire air in a room is completely replaced with new air in one hour. A minimum air change rate for a space used for human habitation is 4 per hour. The more congested the space the higher number of changes is needed per hour. Other factors that increase the required number of air changes per hour in a building include the removal of fumes, excessive heat and moisture. The chart below shows typical spaces and the required amount of changes per hour.
The size, number and installation all depend on different factors which include average wind speeds, temperature difference between the inside and the outside of the building, number of people who use the building, environment conditions, and the size of the building.
Air Extraction Rates
