Humidity and Steel Buildings: What You Should Know

Published August 6, 2015 by Whirlwind Team

While humidity may feel like a summer season issue for many areas of the country, it's actually a year-round problem for most architectural structures - especially if they lack proper insulation and ventilation. Elevated interior humidity levels will lead to condensation - or water droplets that collect on hard surfaces - compromising both your steel building structure as well as its interior air quality.

During the steel building's design phase, you have the ability to plan the measures to protect your building from humidity and condensation, using vapor barriers, adequate insulation and ventilation and a property sized heating and cooling system. Together, these systems will keep your steel building at optimal temperatures and humidity levels.

Smart Design Prevents Humidity & Condensation Build-Up in Steel Buildings

Humidity refers to the amount of water vapor in the air. Typically, we think of it as an environmental problem, something that you can check on the local weather channel. In fact, building interiors are also prone to elevated humidity levels due to excess moisture build-up from the respiration of building occupants, hot water usage, cooking, and so on.

The warmer air is, the more water vapor it can hold. When that warm, humid air meets a cool surface, the water vapor becomes a liquid again in the form of condensation. Condensation is most visible on glass surfaces since these are often the coolest surfaces in the house. However, it also accumulates on hard interior surfaces, or concealed areas, where condensation and the ensuing moisture damage isn't visible. This is the type of humidity/condensation that is the most dangerous for steel building owners.

Over time, that moisture can seep into interior wall surfaces, providing a ripe environment for mold and mildew to bloom. This leads to the rot of any interior wood or organic trim material as well as compromised interior air quality. Once that moisture reaches steel and metal building elements, it can lead to corrosion, which completely undermines the durability and longevity that steel and metal buildings are known for. Fortunately, planning ahead of time and purchasing products designed to maintain optimal humidity levels inside your building will prevent this.

Vapor barriers. Also called vapor retarders, these materials mitigate the flow of warm, moist air to cooler inner regions of interior wall or roof spaces. Metal roofs are notorious for condensation issues is regions of the country with higher year-round humidity levels, combined with temperatures that often reach dew point, so vapor barrier options are highly recommended for most metal roofing systems, as well as interior wall spaces. Vapor barriers can be used alone and paired with insulation or you can select an insulation product with a built-in vapor barrier, like reflective insulation.

If you use a separate moisture barrier system, be sure to seal it properly. The Metal Building Manufacturer's Association (MBMA) recommends sealing the seams, including rolling and stapling the side-laps, peeling and sticking tabs at side-laps, and sometimes using insulation tape. Although using insulation tape alone is not advisable.

InsulationAdequate insulation is another weapon against condensation and moisture build-up. It is both a temperature regulator (reducing heat transfer) as well as a vapor barrier. As mentioned above, some insulation products are more vapor retardant than others so your metal building manufacturer can help you select the best product for your building and its application.

Make sure your entire building, from the roof and attic space to interior wall spaces, is appropriately insulated - free of gaps or spaces - using insulation with the recommended R-value for your location and climate. Also, only consult insulation R-Value guidelines for steel and metal buildings, rather than wood-framed buildings, as these values and quantities may differ. The more insulated your building is, the less prone it is to temperature fluctuations, which reduces vulnerability to interior humidity and condensation.

Ventilation. One of the most natural ways to prevent condensation is to make sure water vapor is able to escape the building so it doesn't accumulate indoors. Because condensation is so prevalent in poorly designed roof spaces, roof ventilation is a top priority. Today's homes and businesses are tightly sealed to increase energy efficiency and interior comfort in combination with their HVAC systems. However, these tight seals mean moisture can't escape, so additional ventilation needs should be accounted for. After roof ventilation has been taken care of, consider features like louvered wall ventilation and an HVAC system with adequate fresh air intakes to further leverage ventilation benefits.

The right HVAC system. Your HVAC system is also a key element in controlling interior humidity levels. Make sure you work with a qualified HVAC contractor who will correctly size the HVAC system for your building to provide efficient heating and cooling as well as humidity control.

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