Specifiers are becoming more attuned to the need to design buildings to higher standards than the minimum requirement. John Kelly explains why.
If targets set out by the Government to reduce carbon emissions and improve the efficiency of the UK's building stock are to be met, the whole design of a building has to be challenged.

As technically good as any new product is in the development laboratory, in practice it will only be as good as the way it is installed and maintained. A case in point is the increased awareness of the benefits to be obtained from the specification of ventilation with heat recovery systems.

These units are becoming increasingly efficient by recovering over 90 per cent of the heat from what would normally be the waste, damp extract air from the wet rooms. Air that would normally be lost is, in fact, a valuable resource to warm the fresh, filtered incoming air from outside and distribute it to the occupied areas of a building.

However, it makes no sense to invest in energy efficient products to improve indoor air quality, prolong the life of the building enhance the occupants' well being if the benefits to be gained are lost through leakage from poor quality, badly fitted ductwork.

Traditional methods like flexible ducting are easily torn, high on system resistance and are often squeezed around bends and between joists, further reducing airflow. Likewise plastic flat ducting is often ill fitting with sharp bends causing dust traps and time consuming to install with much wastage of material.

There is now a viable alternative. Semi-rigid ducting provides a quicker, more hygienic and zero leakage method of ductwork installation for ventilation with heat recovery units (MVHR). Recently assessed by BRE, our own Airflex Pro Semi-Rigid ducting, for example, is supplied on a roll and just 75mm diameter.

It is measurably faster to install as it is flexible while still being durable. In fact, it has a higher degree of 'crushability' than flexible and plastic ducting, enabling it to withstand higher external pressures.

Fewer parts required

Instead of wasting time cutting and taping plastic ducting like a jigsaw puzzle, fewer parts are required and the pipe can be manoeuvred between joists with ease. It is also easier to fit in refurbishments as it can be run vertically down the walls to connect with low level wall and floor grilles. It is even possible to bury it in the concrete screed between floors.

A saving of up to 75 per cent on installation time on-site is possible for contractors, making them more competitive when tendering for MVHR installations.
Each room is connected individually to the ventilation unit. This reduces the issues of inter-room noise transmission.

The double skin, low resistance piping is connected to the heat recovery unit via a central plenum box where air is smoothed out and conditioned for either extraction through the unit or for delivery into living areas within the dwelling. With a simple push-fit sealing ring at the ceiling termination and the ventilation unit there is no possibility of leakage because there are no other interim joints. Depending upon the amount of balanced air to be extracted or delivered to a particular room, it is a simple matter of doubling the length of the delivery pipe to provide higher volumes of air into larger spaces.

Indoor air quality and hygiene issues are growing dramatically. The UK has the highest rate of asthma sufferers in young people in Europe and with increasingly airtight dwellings, moist, stale and stuffy air abounds.
Semi-rigid ductwork systems can ensure the air in circulation should be as fresh and as clean as possible as the possibility of dust traps within the ductwork system are almost eliminated.