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Reducing the Energy Burden of Fume Hoods for New and Existing Facilities

Howard Westerdale, DaleFlow Ltd.

Reducing the energy cost of fume hoods without compromising safety is far simpler and cost effective, than is perceived. It is not a question of CAV or VAV, but of making small modifications to fume hood design, balancing, and operating, which can create the significant savings desired. This concept can be applied equally to existing hoods as to that of new and refurbished labs.

In the United Kingdom, modern fume hood design has allowed new facilities to operate safely at 80 ft per minute (0.40m/sec) or even lower. This has been proven with extensive containment testing (AM and AI) using both static and dynamic tests that address the robustness of fume hood performance not only at factory but also on site in real world conditions. The use of lower velocities has now become standard by many major pharmaceutical companies, who quite rightly have seized the opportunity when designing new labs to operate at reduced flow rates.

With fume hoods having a life span of 15 to 20 years, the existing stock of hoods will take years before they are replaced; as such, the energy losses associated with these inefficient systems desperately need addressing if real overall improvements are to be made. Many hoods even 20 years old, can achieve much improved containment performance by small changes to their design, which do not necessitate fundamental and expensive changes to the extract and supply systems or major capital investment. These inexpensive modifications or additions at the face to improve entry flow, coupled with rebalancing of the air systems, would allow lower velocities to be used and can often achieve 20% or more savings in energy use.
Experience has shown existing cupboards, are often operated over design i.e. over 100 ft/min (0.50m/sec) either due to erring on safety or poor commissioning and/or maintenance. Establishing and improving containment performance can reduce those reduced to at least their design flow rates with the potential to reduce even further.

The arguments for using VAV, which provide capital cost as well as operating savings, are well founded, but this is not the only solution. CAV systems can benefit by simply reducing their operator flow rate, and the savings made could even fund converting to VAV. By the use of fume hood design modifications, containment performance and if possible VAV as well, we do not need to wait 20 years to make the reduction in energy use for all hoods whether past, present and future.

Biography:

Howard Westerdale graduated in 1992 and was introduced into the fume hood industry working for the then largest UK hood manufacturer. In late 1993, he joined the leading UK independent fume hood test house and until the beginning of 2008 was Operations Director of all site operations including containment testing, and commissioning fume hoods and laboratories. As the UK distributor of TSI VAV and CAV monitors and controls, Westerdale was responsible for testing and commissioning many of the largest research and design facilities, universities, and nuclear sites in the UK, Ireland, and the Middle East. These include Pfizer; Sandwich with over 1500 hoods; GSK; Harlow; and Stevenage with around 1000 hoods; and the Universities of Oxford, Reading, Bristol, Newcastle, Dublin and Kuwait. With 15 years experience he has tested to the world's foremost fume hood containment standards, including ASHRAE 110, BS 7258, XPX 15203 and the new European Standard EN 14175. Now he is CEO of DaleFlow Ltd, an independent fume hood test house, energy consulting, and maintenance company serving the pharmaceutical, nuclear, and university sectors all over the UK Europe, India, and China.

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