Condensation Control

The condensation process occurs when warmer moist air comes in contact with cold surfaces such as framing members, windows and other thermally conductive accessories, or the colder region within the insulation itself (if moisture has penetrated the vapor retarder). Warm air, having the ability to contain more moisture than cold air, loses that ability when it comes in contact with cooler surfaces or regions. When this happens, excessive moisture in the air is released in the form of condensation. If this moisture collects in the insulation, the insulating value is decreased.

In dealing with condensation, air may be considered to be a mixture of two gases-dry air and water vapor. One thousand cubic feet of air at 75°F can hold up to 1.4 pints of water. At 45°F, it can hold only 0.5 pints.

Relative Humidity is a percentage measurement of the amount of water vapor present in the air in relation to the amount it is capable of holding at that temperature. Therefore, 50% Relative Humidity would mean that the air is carrying only one-half of the total amount of moisture that it could be holding at that particular temperature. Cold outside air is usually much drier than warm inside air. Therefore, you can lower the Relative Humidity by bringing in outside air to mix with and dilute the moist inside air. At 100% Relative Humidity, the air is "saturated."

The temperature at which the air is saturated and can no longer hold additional moisture is called the dew point temperature. Whenever air temperature drops below its dew point, excess moisture will be released in the form of condensation. Condensation problems are most likely to occur in climates where temperatures frequently dip to 35°F or colder over an extended period of time.

Recommended Installation Methods of Insulation

Roof insulation rolls are cut to lengths that will cover the distance from eave to eave, leaving a one-foot overhang on each side of the building.

1) Start at the end of the building and temporarily secure one end of the roll by attaching the insulation to the eave strut with double-faced tape.

2) Pull the insulation across the purlins with the vapor barrier toward the building interior. Double-faced tape attached to the opposite end of the insulation will keep tension on the roof roll while the metal panels are being attached over the insulation.

3) Install the next roll in the same manner, making sure the rolls are stretched tight, aligned properly and closely butted.

4) Fasten tabs using one of the methods described on the following page. Any rips or tears must be covered with matching facing tape to ensure a tight vapor seal.

5) Trim excess insulation flush to prevent it from acting as a wick and moving water into the building.

Frame Features

Connection Clips - Specially fabricated clips are designed to securely connect structural components. Many companies supply only blank plates that must be cut, drilled and/or welded to components before assembly can begin. In some cases it may require many hours of work to connect required clips. Metal Building Depot details and supplies each clip and placement to every building manufactured. We factory weld all clips onto rigid frames and guarantee the correct placement of all component connections. Don't waste your time and money attaching clips that should have been factory located.

Structural Bracing - Most buildings under 60' have sufficient diaphragm action or "panel shear" that provides all the bracing needed to stabilize the building. In some cases of high winds, seismic or snow loads may cause more stress than panel shear can handle, so additional reinforcement may be required. In these extreme cases we will employ the use of X bracing to reinforce the frame. In situations where X bracing cannot be used a wind column is an excellent addition to strengthen a vertical rigid frame column. A portal frame is sometimes used in extreme load circumstances. Portal frames are fairly expensive and only necessary in rare circumstances.

Temperature Control

Your geographic area will, to a great extent, influence the type of insulation that will provide the best performance. If you live in a mild climate and your building is used for farm equipment storage, insulation may not be necessary. If you are planning to have employees working in a building, you should probably install insulation, particularly in areas where temperatures are extreme. Energy savings will quickly pay for insulation if the building will be climate controlled.

Controlling Condensation

Two things must be present for condensation to occur: warm moist air and cool surface temperatures below the dew point. The proper control of these two factors can minimize condensation.

In metal buildings, we are concerned with two different areas or locations: visible condensation which occurs on exposed surfaces below dew point temperatures, and concealed condensation which occurs when moisture has passed through the vapor retarder and into interior roof and/or wall cavities and then condenses on a surface below dew point temperature.