SAFETY Another important consideration before any work is carried out in restoring property, whether historic or modern, is safety. Modern buildings will often have services, including electricity, carried through ducting along fairly logical pathways. However, a heritage building can be more haphazard as wiring will often have been fitted many hundreds of years after the original design and before the implementation of rigorous safety regulations. If this is the case, then work must be undertaken to locate where wiring and pipework runs before any drilling or ripping out gets underway. Furthermore, if there has been any amount of water in the fabric of the building, then it is advisable to switch the power off before investigations begin (always use a qualified electrician). Failure to locate services could lead to a life threatening accident if a cable is drilled through. If a pipe is ruptured during work, because the team were unaware of it, then further flooding could result or there could be a dangerous escape of gas. Anyone carrying out restoration work also needs to be aware of other risks of injury such as structural failure and falling plasterwork. Workers must always wear appropriate protective clothing for the job in hand. Gloves are essential in the case of removing timber in order that workers do not suffer cuts and abrasions. Masks are advisable whilst ripping out materials as there can be airborne health hazards. Despite a building being damp after a flood, there can still be pockets of dry material that comes away with the moisture damage. Though dry materials such as plaster can cause a cloud of benign dust, a worker must also be aware of the potential hazard of asbestos. DRYING A HERITAGE STRUCTURE Once a risk audit has been performed and the location has been surveyed for moisture, then work can progress to the drying stage. For this to be effective, any freestanding water must be removed from the property. Once dewatering is complete, a directed air flow across the surface of wet materials is used to promote evaporation. This is combined with creating the movement of air to carry the water vapour from the property. During drying, technicians can enhance evaporation by the use of heat. This accelerates moisture released as a vapour that can then be collected by a dehumidifier. However, as evaporation occurs, the temperature of the air falls in the same way as we cool down by perspiring. Because heat has been taken out of the system by this process, lost energy needs to be replaced with further heating in order to maintain the drying action. This cycle should be 20 FEBRUARY 2016 CLEANING HYGIENE TODAY carefully monitored, whether in person or remotely, to be sure that the air flow, temperature, and resulting drying action are all working at the correct rate for the type of materials being worked on. SELECTING THE RIGHT METHOD Much scientific study into the properties of building materials has enabled damage management technicians to choose the right type of drying technology for varying situations. A dryer comes in many forms, from desiccant to refrigerant to trailer mounted dryers. These all work at different ambient temperature levels and use different amounts of power to operate. A trailer-mounted drying unit will be the most expensive to use as it is designed to have a fast effect by providing a large volume of warm air to cause faster evaporation. However, many heritage properties would suffer damage if such a method were used. Many situations, where a historic building needs drying out, have to be dealt with by applying gentle heat over a longer period. An important element in creating the right conditions for drying is good ventilation. There is no point in applying heat to a surface and evaporating the moisture if it has nowhere to go. A flow of air through a building is needed to be able to remove the excess moisture. Thus, opening doors and windows is the best way of creating the conditions necessary. INJECTION DRYING Creating natural ventilation through a building can help the drying process but it will not work on moisture trapped in voids in floors or walls. This is where more targeted techniques are employed. Give the moisture less than half a chance and a day or so then it will start to cause problems – starting with a slightly strange smell which grows stronger by the day and hour. Without appropriate intervention, this situation can result in the need to rip out and replace materials, significantly extending the project duration and overall claim cost. The employment of the injection process, where warm and dry air is introduced into the structure, means that a wall can be totally dried within a matter of days. FEATURE HISTORICAL CLEANING “the damage becomes worse the longer it takes to begin remedial drying”
CHT February 2016
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