Air movement & ventilation Distribution
grilles
Well-prepared
By specifying inappropriate grilles, louvres and diffusers for an air distribution system, you run the risk of condemning the entire system to poor performance, resulting in energy inefficiency, high costs, compromised comfort and unhappy occupants, says Ian Vallely
A
s pressure mounts on consultants to meet the twin challenges of reducing costs and increasing the energy efficiency of the systems they design and specify, there
is an inevitable temptation for them to focus on big- ticket items in a heating, ventilation or air conditioning (HVAC) system that appear to have a greater payoff than the smaller commodity-type components. So, for example, when designing large, expensive
air movement systems, they might concentrate on the air handling units and fan coil units and dismiss as relatively unimportant air terminal devices (ATDs) such as grilles, louvres and diffusers. However, although understandable, this is a mistake
because neglecting ATDs can adversely affect comfort levels in a building and is potentially expensive both in terms of the system’s running costs and the building’s energy efficiency. Indeed, many industry experts assert that ATDs have
an impact on the efficiency of the air management system that far outweighs their size and apparent significance. That, says David Fitzpatrick, sales director, Ruskin Air Management, is why it is worth spending time and effort on their specification. He believes this could be an issue affecting, perhaps,
one in four projects: ‘Consultants rightly spend a large percentage of their time designing the system to get the right products in place and [ATDs] are often the last-minute items that don’t always get thought about enough. ‘The problem arises because consultants have so
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many different jobs to do within a building, and grilles, louvres and diffusers are such a small part of the overall project. However, they can have a disproportionate impact on the effectiveness of the system as a whole.’ There are many different types of ATDs on the
market and that is why Fitzpatrick believes it makes sense for consultants to seek the advice of manufacturers on their specification. As he says: ‘The problem is not always the quality of the product; it can be down to specifying the right type of product for the particular application.’ A failure to address this can devalue all the effort that
has gone into designing and installing the system. Ian Thomas, product manager for components at TROX UK, puts it bluntly: ‘The wrong £50 diffuser can ruin a million-pound air conditioning system.’ Craig MacFadyen, applications manager at Fläkt
Woods, compares ATDs in an HVAC system to loudspeakers in a hi-fi: ‘It is important to have high- quality design and components throughout the system. This, of course, applies as much to air distribution as it does to hi-fi.’ For MacFadyen, ATDs have a particular significance because they are the air distribution system’s customer interface: ‘They are the product that affects people’s perception of the installation as a whole because they are all that people feel, hear and potentially see.’
Ductwork
But ATDs are not the only air movement accessories that tend to suffer when it comes to specification.
Grilles, louvres
>
and diffusers can have a disproportionate impact on the effectiveness of the system as a
whole – David Fitzpatrick
May 2010 CIBSE Journal
55
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