How to shut down three nuclear reactors
The reduced air leakage possible with LindabSafe presealed ductwork can reduce ventilation operating costs by 35%.
Against the background of increased global demands for energy efficiency, DUNCAN McGREGOR believes that property owners should raise the standards of duct systems for ventilation, heating and air conditioning. Across Europe this could not only save energy equivalent to the output of three nuclear power stations — and also result in lower installation costs, shorter assembly times and better air quality.The importance of energy-efficient buildings will increase in the future — not only in response to rising energy prices but also because of increased environmental awareness. One example of this is the Kyoto Agreement, which indirectly forces countries to review their energy use with the aim of reducing carbon-dioxide emissions. A real output is the Energy Directive from the EU, which basically increases the demands on energy planning and on the energy performance of buildings. One way of satisfying the stricter energy rules, which is currently neglected, could be to make tougher demands on the specification of ventilation air duct systems. Four classes
The UK industry standard DW/144 defines three classes of airtightness for ventilation duct systems. The most stringent is Class C, and the least airtight is Class A. Class C is three times more airtight than Class B, which in turn is three times more airtight than Class A. To enable the specification of even higher standards, Lindab has introduced the concept of ‘Class D’ — which is three times more airtight than Class C. Most modern ventilation systems struggle to achieve airtightness to Class B, so there is a vast scope for improvement. If ventilation duct systems are ‘leaky’ a larger fan is installed to maintain the required air-flow at the furthest parts of the installation, increasing energy consumption. If ducting systems across Europe could all be uprated to just class C, an annual energy saving of around 10 TWh, (100 000 000 MWh), which is comparable to the annual production of three nuclear power plants. ‘Class D’ is rarely specified and is three times as leak-free as Class C, but it can readily be achieved with a properly-fitted pre-sealed ductwork system such as LindabSafe. — so imagine the long-term energy savings that could be achieved if this type of ducting was more widely specified. Leaky and inefficient ducting makes a ventilation system hard to pressurise, and fans have to work much harder to deliver ventilation air to where it is required. An airtight ducting system needs less power, so you may even be able to use smaller and less expensive fans that require less space in the building. Practical considerations
In practice, ventilation systems often consist of a mixture of pre-sealed and conventional ducting — with the latter often making it more difficult to satisfy strict demands on airtightness. If we aim to use as much pre-sealed ‘Class D’ ducting as possible it will still be possible to achieve an overall Class C rating. The combination of LindabSafe’s airtight joints and a range of bends, connectors and accessories designed to minimise pressure drop, mean that overall ventilation operating costs can easily be cut by 35%. A further advantage of a high-quality duct system is the positive effect it can have on people’s health and well-being. In a poorly sealed system there is often inadequate air flow at the remotest parts of the building, and research shows that good air quality reduces absence through illness and increases productivity. A system that goes together quickly, simply, and is right-first-time, every time, is the secret of cost effective installation. Because each section of the LindabSafe ductwork comes with a high-performance seal already applied, the elements of the system simply push together for an airtight fit. All that is then required is to fasten the elements together using self-tapping screws or blind rivets. There is no need for taping or adapting the parts. On a like-for-like project such ducting components may cost more than unsealed duct components. The cost of accessories such as hangers will be about the same. However, installation time and labour could be reduced by around 40%, giving an overall saving of more than 10% on the installed cost — plus significant lifetime savings in energy demand by using less powerful fans. Spelling it out
Not only does an ‘Class D’ system save a huge amount of energy — which could be expressed as lower carbon-dioxide emissions — but it also costs less to install. Indeed, I find it surprising that this simple way of reducing carbon-dioxide emissions is not being written into legislation. Even without legislation, architects and planners with a stake in the long-term running of a building should be paying keen attention to the financial benefits. It is therefore crucial to define your requirements for airtightness as early as possible in the planning stage of a building. If you do not spell it out, and make sure that you get what you have specified, you can look forward to years of unnecessarily high and escalating energy costs! Duncan McGregor is managing director with Lindab Ltd, Units 9-10, Riverside Business Park, Northampton NN3 9HG.