Modern Building Services

28 MODERN BUILDING SERVICES FEBRUARY 2022 FEATURE INDOOR AIR QUALITY INDOOR AIR QUALITY Managing humidity is an ongoing concern for building professionals working on construction sites that is growing in prominence at certain key parts of the year. With the UK recently struck by Storm Arwen and Storm Barra, many projects have been disrupted by damaging floods, this topic is now rising back in the spotlight. However, the impact of these increasingly common events can be amplified without an effective dehumidification strategy in place, as residual moisture can pose a threat to structures, building materials and electrical equipment. With this in mind, Matt Watson, Moisture Control Expert for Aggreko Northern Europe, explores how to effectively dry out sites without long-term issues. Site Humidity Levels: Riding Out the Storm H eavy rain and increasingly hot summers are staple parts of British life, as our perception of what constitutes ‘normal’ weather shifts due to climate change. Nowhere is this more apparent than with Storm Arwen and Storm Barra at the turn of the year, which buffeted the UK with torrential rain and disrupted travel and services for many. Site and project managers in the construction industry were one such group impacted by this disruption. Indeed, the humidity brought on by excessive rain did not onlymake onsite working conditions uncomfortable – in particularly affected areas, flooding was not just a possibility, but an inevitability. Such events will only rise as British weather becomes more extreme, and in a country already affected by high humidity levels, will require round-the-clock maintenance schedules to be effectively managed. Yet while humidity risks are most commonly associated with extended periods of wet weather, it is important to recognise that this challenge is not exclusive to rainy winter months. Moisture management is not an issue that peaks and troughs with the seasons, but instead presents persistent and varying challenges in different weather. Different seasons, same concerns Indeed, as a nation renowned for its heavy rain, many building professionals may believe winter months present only periods of high humidity levels, whereas summer is drier and so the problem is reduced. Yet this is a keymisconception – during the summer months, the warmer weather expands the air, allowing it to have a larger humidity capacity. This thermal expansion means the relative humiditymay show a lower percentage, but the physical volume of moisture is still the same as under cooler conditions. It is therefore vital to understand that humidity is a year-round challenge for building professionals. When it comes to relative humidity – the percentage of water within an air particle – it averages at around 76% in our nation’s largest cities. When considering that the comfortably dry range for relative humidity falls between 40% and 60%, it’s clear that moisture in the air is a significant issue. Such a concern is further exacerbated by extreme weather events such as Storm Arwen and Storm Barra, which can lead to additional spikes in humidity. Different moisture types Whether its free moisture – the surface water or water that has been absorbed into a material – or the water that is chemically bound into the cells of materials in the room, there are several sources that are found on construction sites. The building materials themselves, for instance, can impact overall site humidity.