Even if you are
There is an unavoidable trade-off between the louvre’s ability to let air through the grilles and to keep water out
less concerned with water penetration, sizing your louvre for maximum energy effi ciency is
something designers should be considering. In fact, the more water you can allow to penetrate, the lower your running costs will be, since there will also be less resistance to air.
Identifying suitable products Once you know your required face velocity and water penetration requirement, you are much closer to making an informed choice as to the best available product option. However, you still need to specify the requirement in meaningful terms and have confi dence that the product you choose will deliver on its promised performance. Speaking the supplier’s language: Suppliers of weather louvres defi ne products in many ways but the most useful indicator of performance is the ratings provided by the test standard, for water penetration and coeffi cient of discharge, as detailed above. Hence you should express the louvre performance requirement in the following terms: ● Water penetration class A-D; ● At face velocity 0-3.5m/s (based on the air volume requirement and louvre face area); and
● Coeffi cient of discharge class 1 to 4. If you are able to express your own requirement in these terms, you should be able to shortlist available products to match. To establish the performance of the weather louvre, make sure it is stated in direct relation to the required face velocity. Product assurance: A robust certifi cation scheme will combine two elements of product assurance to provide confi dence to specifi ers: ● Type testing: Testing (to EN 13030:2001 in the case of weather louvres) measures the performance of a one-off sample but gives no assurance that the design and manufacture of the product are consistently applied to subsequent units; and
● CHRIS MARNEY is manager of BSRIA Cert, whose weather louvre certifi cation scheme, supported by manufacturers, was recently launched. BSRIA has also published its Weather Louvre Specifi cation Guide.
www.bsria.co.uk
● Factory production control (FPC): Factory audits are used to give assurance of consistent and robustly controlled production methods. FPC audits relate directly to the product range and so go beyond the more general audits conducted for ISO 9001 management system certifi cation. Independent type testing and FPC together
provide a higher level of confi dence to both manufacturers and specifi ers that weather louvres are fi t for purpose. CJ
www.cibsejournal.com
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March 2012 CIBSE Journal 53
31/01/2012 15:32
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