Monday, March 18, 2013

Steel Buildings and Condensation–Understanding the Causes and Recommended Solutions

Condensation is a common problem in wood-framed buildings, but it could also affect structural steel. If left unattended, this could cause the structure to succumb to corrosion and eventually its early deterioration.

Builders in both commercial and industrial sectors have long acknowledged the excellent characteristics that steel buildings exemplify. They are light weight, easy to construct, consistent in quality, offer design flexibility and ensure long term use by resisting a number of damaging elements.

Despite such special qualities, however, steel buildings are not perfect. In fact, they are susceptible to condensation–a very potent source of moisture intrusion which if left unaddressed could lead to a number of potentially damaging problems, including steel corrosion, mold and mildew growth, cracks on foundation and ruined finishes.

Condensation and Steel Buildings

Condensation is a process where water vapor changes into liquid. This happens when warm, moist air touches the cold surfaces, such as a building's steel framing members and components that are thermally conductive. Since warm air has the ability to hold more moisture compared to cold air, it could eventually lose that ability when it comes in contact with cold surfaces. As the warm air cools down, it will eventually reach a temperature where it can no longer retain moisture (dew point) forcing it to give up some of the water it is holding. This is what is known as condensation.

In steel buildings, condensation can be both visible and concealed. Visible condensation occurs on surfaces that are below due point temperature, while concealed condensation occurs when the moisture reaches the interior regions of the building and then condenses on a surface below dew point temperature.

One can tell if a steel structure is encountering visible condensation if there are water, ice or frost forming on windows, doors, ceilings, walls , floor, skylights, insulation and cooling ducts. The presence of concealed condensation, on the other hand, can be known through the formation of stains, damp spots and mold and mildew on walls or ceilings, damp insulation, splitting of laminate surfaces, peeling paint and bubbles and blisters on asphaltic surfaces.

Between the two, concealed condensation is more difficult to deal with since it is not easily seen. Over time, as it is allowed to sit in the inner regions of the structural steel, it could cause more problems that could affect the integrity of the building.

Consequences of Condensation in Steel Buildings and its Occupants

As many are aware, steel and water do not make for a perfect pair. Thus, the presence of condensation could have serious consequences not only to the building but to its occupants as well.

Although the components of steel buildings are protected against corrosion through their zinc coating, their exposure to moisture for extended periods of time can lead to oxidization, making them more susceptible against rust. Corrosion, of course, will not only shorten the life expectancy of the building but can also negatively affect its integrity.

Excessive condensation, either on the interior or exterior finish of the structure also attracts dust, dirt as well as mold and mildew. The formation of these things can lead to a pattern of staining which, in turn, impacts the aesthetics of the building.

In addition, as most steel buildings use fiberglass as their primary thermal insulation, the formation of condensation on such insulating material will significantly increase its thermal conductivity and decrease its insulating value. This then reduces the energy-efficiency of the steel building.

Recommended Solutions
Existing steel buildings

Condensation in existing steel buildings is often the result of the absence or insufficient insulation. It may also be due to old or damaged insulation which allow for air leaks. For damaged insulation, the best solution is retrofitting. Retrofitting insulation between the purlins or wall girts of the structure is not only an energy-saving solution, it could also help address any existing condensation problems within the building.

Experts recommend that in insulation retrofitting jobs, the entire cavity of the building's roof purlins or wall girts should be filled with insulation to prevent the formation of air pockets between the insulation and roof panel. This is vital because the presence of air pockets can cause condensation to form inside the cold surface of exterior panels.

Vapor retardants or also referred to as facings should be used in conjunction with insulation. These materials restrict warmer, moist air from passing toward the cold inner regions of the building's roof or wall system. The rating of facings are determined by the amount of moisture that can pass through them. The lower the rating the vapor retardant has, the more effective it is in inhibiting vapor transmission.

There are a number of vapor retarders available today, such as impermeable structural membranes like steel sheets, vinyl siding, tilt-up concrete panels; flexible membranes like coated papers, foils and plastic films; and coating membranes like paints, epoxy and urethane foams and trowel-on bituminous coatings. Picking the right type of vapor retardant is critical to ensure its performance. Hence, proper care and research should be taken when choosing a facing.

New steel buildings

For a new structural steel, building it right for the first time is critical to ensuring long-term savings of ownership and will prevent the occurrence of condensation. Thus, any possibility of condensation should be thoroughly addressed during the design and construction phase of the structure.

Proper provisions for adequate ventilation and insulation should be followed when designing the steel structure, especially if it will be climate-controlled. At the most, dead air spaces should be reduced in locations that are prone to gather warm, humid air, such as under roofs. Nonetheless, good quality and continuous insulation and vapor retardants should be put in place to prevent condensation from making its way into the cold inner regions of the building.

Generally, condensation can be especially damaging to steel buildings. So it is particularly important for steel building owners and would-be owners to ensure that adequate attention is given toward controlling this element to ensure that it does not affect their structures. Following best practices when designing and constructing the steel building as well as addressing the ventilation and insulation needs of the structure combined with ongoing maintenance could greatly help in avoiding condensation.

This article was written by one of the regular contributors of Steel Buildings Design is a premier company that designs, supplies and erects high quality steel buildings

1 comment:

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