Exhausting hot air in warm climates....

Are Extractor Fans the best solution?

Everyone knows that warm air rises because it is lighter than cool air. In commercial buildings such as factories, warehouses, retail space and workshops, the warm air generated by machinery, workers and customers rises into the roof space. In addition, the sun can heat the air in the roof space to over 60C (140F). In turn this superheated air heats both the structure of the building and the cooler air below. If the roof is not properly insulated, the problem is only amplified.

Many designers decide that the most effective way to remove the hot air trapped inside buildings is to install extractor fans to exhaust the superheated air rom the ceiling. The simplest way to control the extractor fan is to install a thermostat in the roof space set at 40C (104F). Once the temperature exceeds this, the fan will start, removing the hot air. In addition, since air is being exhausted out of the building, an equal amount of fresh air must also be supplied into the space using some type of air intake such as louvers, vents or dampers.

While fitting extractor fans and fresh air intake vents to remove the hot air that gathers in the roof space is one way to remove the hot air trapped inside commercial buildings, it does very little to make employees and customers feel more comfortable at ground level. Is there a better solution? Yes! BladeTec High Volume/Low Speed (HVLS) Ceiling fans!

Why is there hot air at the ceiling? Because it is trapped! By installing fresh air supply intake fan(s) and a HVLS Ceiling fan(s), you can better mix the air inside the space preventing the build up of hot air in the first place. At the same time, a HVLS fan will provide a breeze that effectively cools people at ground level. A BladeTec HVLS fan, which covers an area of 30 meters in all directions, provides movement of air that can decrease the perceived temperature felt by workers, customers and employees by as much as 8 degrees C in large spaces.

BladeTec HVLS fan layout is based on the concept of how air velocities can produce a perceived range of temperature drops at varying distances from the center of the fan. To help define theses ranges, BladeTec has introduced the concept of Areas of Influence. Figure A defines the Area of Influence as four distinct areas (A1, A2, A3, and A4) using concentric circles to represent average air velocities, distances, and perceived temperature drop.

Each BladeTec model has its own Area of Influence. The larger the fan, the larger the Area of Influence. Each area of influence is based on air velocity and the change in perceived temperature drops from 2.0°C (4°F) to 8.3°C (14.4°F). For example, the A1 Area of Influence is defined at a distance from the fan center where the velocity is 2.8 m/s (550 fpm), A2 is 1.3 m/s (250 fpm), A3 is 0.9 m/s (175 fpm), and A4 is 0.5 m/s (100 fpm). (See Figure B.) The real benefit of the BladeTec selection methodology is a more scientific analysis of the relationship between fan diameter and perceived temperature change.

What if you already have an extractor fan installed in your facility? In retrofit applications, a HVLS fan can be used in conjunction with an existing fan. The extractor can be controlled to exhaust any buildup of hot air in the space during unoccupied times. When the building is occupied, simply switch off the extractor fan and allow the supply and the HVLS fan to better circulate the air and provide a cool breeze to the people in the space. In addition, a HVLS fans operates at very low revolutions per minute, therefore, they are extremely energy efficient.

When used in conjunction with fresh air supply fans, the BladeTec HVLS fan not only help better mix the air and lower the overall temperature in the building but also provide effective cooling for everyone in the space. A much better solution in this Extreme Application

For more information, visit www.bladetecfans.com.