Condensation Part 2: Prevention is better than cure

New build properties - especially those in the social housing sector - are built to stringent environmental guides such as the Code for Sustainable Homes and of course, 2010 Building Regulations. This has inevitably led to ‘sealing’ the building to prevent heat loss, which in turn results in dramatically reduced ventilation opportunities.  As a result, such homes require a mechanical form of ventilation, often used in conjunction with a heat recovery system which preheats fresh air drawn into the building with the internal waste stale air using a heat exchanger. It’s an effective and sustainable solution.

You would think that with such measures in place, issues of condensation would be resolved; unfortunately, not always the case.

Where the ducting used in the ventilation system passes from a warm room through to unheated areas and voids, such as loft spaces (where heat recovery units are usually located), condensation is likely to form on the inside of the duct. This can then run down the duct and create a potential hazard, such as dripping onto the electrical connections of a fan, as well as creating stains and mould over a period of time. So new technology brings with it its own set of problems?

 One solution is to use a condensation trap that collects the moisture and releases it through an overflow port externally to address this issue. Quick and simple to install, the traps are installed in the loft space as low as possible on vertical ducts but high enough to allow for a slight fall in the overflow pipe.

 Alternatively you could aim to prevent the formation of condensation in the first place. To accomplish this, the inside wall temperature of the duct mustn’t fall below the dew-point of the humid air entering the duct.

 The first step to achieving this is to only use quality rigid ducting with a smooth internal surface area, rather than the cheaper flexible hose. This is because air itself has very good insulating properties when flowing smoothly over a surface. When the reverse happens, ripples are created and insulation is reduced.

 Furthermore, ensure the ducting has a uniform profile and the joints fit tightly. Our Polypipe Ventilation Domus rigid duct systems, for example, are designed and manufactured to exacting tolerances, guaranteeing a uniform shape and superior fit.

 Secondly, use insulation around the ducting in those colder areas that are likely to be affected. The new Domus Thermal duct insulation, from Polypipe Ventilation, has been specifically engineered to meet the revised Building Regulations. Manufactured from silver EPS (expanded polystyrene) incorporating carbon particles to further improve performance, Domus Thermal has high insulating properties yet remains a cost-effective and simple solution to prevent the formation of condensation.

Of course whatever form of insulation you opt for there are other considerations to be taken into account. Firstly, if it’s an insulation system specifically designed for use with ducting, ensure there is a full range to insulate both round and rectangular duct systems and it is available in suitable lengths. Secondly, make sure the insulation fits snugly around the duct and fittings with no air gaps. Thirdly, check how easy it is to fit and secure once on. Domus Thermal is designed with a gripping interlock so the pieces stay together without the need for taping or gluing joints, throughout the range of round and rectangular, significantly reducing installation time. The straight length sections are also moulded with a cutting guide every 10mm for added simplicity.

Condensation is a part of everyday life in this country, particularly so in the winter months, but with good ventilation practices in older properties and mechanical ventilation systems in new builds, condensation can be prevented from being a problem