If you spend any time searching Google for “flow rate tests” or “part F airflow tests“, you’ll quickly come across references to a piece of kit called a “vane anemometer”, and probably “vane anemometer with hood”. What is this esoteric piece of equipment, and do you need one?
As we know, Part F of the Building regulations requires us to measure the flow rate of every extractor fan installed in new dwellings. This means we need to calculate the volume of air flowing through the fan, and also measure the time taken. To help us, we must measure the speed of the air flowing through the fan – and this is what an anemometer does. It was originally created to measure wind speed for sailing ships. Unusually, this tool was invented twice – once in Italy by Leon Batista Alberti, and then again in 1664 by the better-known Robert Hooke.
There are now many different types of anemometer for different purposes, e.g. weather forecasting, wind tunnel measurements, car engine air intakes, etc. However, most of them are useless for extractor fan flow rate tests! It’s so important to get the correct one, or you’ll find you’ve wasted your money. (PEATA members can get advice and recommendations on the best models. We’ll also lend you one for free for your first test!) The most common type used for airflow tests is a Vane Anemometer, being robust, simple to use, and suitable for extractor fans. This is a freely-rotating propellor with a digital display, from which can be calculated wind speed, flow volume, and airflow rates. (The PEATA web app will do the calculations for you and create the Commissioning Notice – also known as the Airflow Test Certificate or PEATA Certificate).
Although it is possible to measure flow rates without a hood, in practice using a hood is the best option. The hood is a large funnel which fits snugly over the vane anemometer, and has a known area and known windspeed resistance.
If all this sounds complicated, you’re not alone! It’s not tricky with the right training and knowledge – our simple online course takes only an hour or two to complete, and will have you completing flow rate tests immediately. And we’ll even lend you a vane anemometer with hood – for free!