INTELLIGENCE
FEBRUARY 2021
W
BUILDING ENGINEER
22
ith heavy rain a normality and summers getting hotter each year in the UK, high humidity is likely to be an issue that will continue to present itself. For building engineers, moisture doesn’t just make working conditions on-site uncomfortable. It can also spell disaster for building materials and the finished product if not properly mitigated. As the UK is often struck by cold, rainy weather, many tradespeople believe winter months present the only periods of high humidity levels, whereas summer is drier so the problem is reduced. This is a key misconception. During the summer months, the warmer weather expands the air, allowing it to have a larger humidity capacity. This means the relative humidity may show a lower percentage, yet the physical volume of moisture is still the same as under cooler conditions. It is, therefore, vital to understand that humidity is a yearround challenge for building professionals. When it comes to relative humidity – the percentage of water within an air particle – it averages at 76% in the UK’s largest cities. Considering that the comfortably dry range for relative humidity falls between 40% and 60%, it is clear that moisture in the air is a significant issue.
Types of moisture Free moisture can be the surface water or water that has been absorbed into a material, or water that is chemically bound into the cells of materials in the room. There are several sources that are found on construction sites. The following are the most common: water vapour diffusion – water vapour from outside a building can permeate into the space through cracks or by being absorbed into materials. The moisture coming from outside to within the room does so through this water vapour diffusion water evaporation – any water that is introduced into a space for cleaning or mixing with building materials can evaporate and contribute to moisture in the room evaporation from materials – building materials that have been brought on-site can release water absorbed in their cells into the space intended ventilation – ventilation systems that have been installed may not be able to keep up with high moisture levels in a space, so humidity in the room remains high unintended ventilation – leaving windows and doors open on a construction site can allow moisture-filled air from outside to permeate a room through unintended ventilation human-derived emissions – those working on-site release moisture from breath and perspiration plant and machinery emissions – any equipment used in a space on-site can produce moisture from its exhausts, particularly in enclosed, poorly ventilated spaces. Premature deterioration of building materials is something any building engineer wants to avoid. In particular, poor humidity can affect things such as electrical components – the moisture can find its way
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Vapour trails Ryan Stanley, Moisture Control Sales & Product Manager, Northern Europe, at Aggreko, explains why humidity is unwanted on-site and how to avoid common errors in its removal into the smallest areas and spaces. This, in turn, can leave behind corrosive deposits that continue to cause damage after drying, not to mention prolonged time for paintwork, adhesives and cement to dry or cure. Improper drying and moisture control can also exacerbate such problems while creating new ones, which could lead to further damage and potentially higher costs. In particular, building engineers working
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