Overall Heat Transmission Coefficient (U-Value)

A unit used to express heat passage through a complete building section, including air films. U-Values serve as a basis for determining transmitted heat loss. The lower the U-Value, the higher the insulation value.

Heat Transfer

Effectively controlling temperature in a steel building requires insulation to be present along exterior walls and roof. When a temperature differential is present in an enclosed steel building, heat will work from warmer areas to colder areas until the temperature in the building has stabilized. At the point of thermal stabilization, the cooler (and heavier) air will be present at lower elevations and warmer air will be present at the roofline. The function of insulation is to help stabilize air temperature at more desirable levels. When it is hot outside, preventing heat from transferring into the building is the goal, and of course in the winter we want heat to remain inside.

Heat transfer occurs in three ways:

Conduction : Occurs in a solid or liquid when heat from one object is transferred by touch to another object. An example of this occurs when a pot on a stove will heat up by conductive heat transfer from an electric coil.

Convection : Occurs with the physical movement of air. There are two types of convectional heat movement. The first is natural, where hot air rises displacing the cold air and moving it down. The second type is forced or mechanical convection. This occurs when an object, like a fan, physically moves or "forces" the air to move.

Radiation : Occurs when an object is warmer or hotter than the air around it. For example, the sun, which is hotter than everything around it, radiates heat waves that travel through the air and is either absorbed by or reflected by the surface it comes in contact with.

Facings as Vapor Barriers

The main function of facings is to act as a vapor barrier. While a vapor barrier may not necessarily be able to stop the flow of water vapor, it does an excellent job of minimizing the rate and volume of the flow. This prevents moisture from accumulating within the insulation blanket and the structure, which translates into consistent thermal values and lower heating and cooling costs.

Facings intended to serve as vapor barriers should be installed on the inner, heated surface of the insulation, where vapor pressure is the highest. This helps in preventing vapor from reaching the cooler air and condensing.

VAPOR BARRIERS PREVENT VAPOR FROM REACHING COOLER AIR AND CONDENSING.

Ridge Vent

Ridge vents come completely assembled for ease of installation. Ridge vents supplied by Metal Building Depot are of a low profile design to provide gravity type ventilation. Because gravity ridge vents are designed to allow free airflow, some penetration of water during blowing rains is to be expected. Standard available finishes for the ridge vents are polar white and galvalume. Other colors may be available at an additional cost. Nominal ridge vent length is 10'-0". Ridge vents are available with 9" and 12" throats. Bird screens are provided as a standard. The ridge vents can be ordered as continuous or single units. Exterior parts are 26 gage painted or galvalume. Interior parts are all made of G90 galvanized steel. The substructure consists of 10 gage saddle straps with interior baffles of 24 gage steel. Lifter arms and damper slides are made of 18 gage steel. Manual operation is through activation of a pull bar which is attached internally to bell cranked type lifter arms connected to the damper with Teflon coated pins through the damper slides. Dampers are spring loaded to remain in the open position until the pull bar is operated and locked in the closed position. Dampers operate in a vertical manner. Each vent is opened by a pull chain that extends approximately 12" below the roof unless noted otherwise on the order documents. Other opening mechanisms are available at an additional cost upon special request. Ridge vents should not be placed closer than 5’-0" to the endwall steel line to allow room to properly flash the building. For example, a 90’-0" long building with ridge vents required the entire length should have no more than (8) units. The ridge vents are available with the following accessories:

Installation and Selection of Insulation

We provide the highest quality products available. However, proper installation and selection is imperative for maximum effectiveness. Please refer to installation instructions to ensure correct procedures are used. Facings that have been torn or punctured are no longer capable of blocking water vapor and may eventually do more harm than good. Be sure to quickly patch any holes in the vapor barrier.

When selecting a facing, special consideration should be given to its reflective quality. A facing with high reflectivity reduces the need for high light levels in work areas. This results in reduced energy costs and increased productivity.

Although the fiberglass insulation itself is not affected by cold weather, the facing is. Colder temperatures can cause cold crack, a situation where the facing becomes brittle and if handled can crack. Bay Insulation recommends that vinyl faced fiberglass products never be installed in temperatures below 40 degrees.