Metal walls (or metal sheathed walls) are commonly used in the livestock industry. The metal cladding is adhered to the exterior of the building and provides protection against weather conditions. The metal cladding is secured with vertical or horizontal seams and can act as an effective rain screen, that is, a barrier that prevents wind-induced rain from entering. Metal wall cladding is cost effective and durable. Various colors are available and can be easily cut to desired lengths. Metal wall cladding is the most preferred cladding in modern agricultural and livestock buildings. Buildings used for cattle or poultry can have significant internal moisture production from animals. This moisture can come from manure and directly from animals. Insulating the inside of the metal cladding can prevent surface condensation, but condensation cannot form inside the insulation or between the insulation and the inner metal surface unless vapor barriers are properly used or closed-cell insulations (sprayed or rigid sheet) are used. The vapor barrier on the interior wall must be protected from ingress, so an interior lining is typically added. It should be emphasized that ventilation is the primary means of reducing the potential for condensation. These guidelines assume proper ventilation is available and used. There are several alternatives to conventional wall section construction and their cost effectiveness varies widely. The different wall section construction methods are summarized below:
Metal cladding placed over rigid insulated foam boards: Metal and rigid insulation fixed to the outside of the building perimeter. The metal cladding creates the rain screen and allows the penetrating water to flow down and out of the wall. This type of metal cladding uses horizontal seams that provide continuous drainage lines for any penetrating water. The coating must be installed according to the manufacturer's specifications. Individual rigid insulation boards can be of any thickness required to provide thermal comfort, energy savings and condensation control on interior surfaces; it is impermeable so water vapor from inside cannot get inside. This is the approach used in modern commercial construction and has many advantages. It is also more expensive than traditional methods.
Single-component (panelized) wall sections: Typically called Structural Insulated Panels (SIP) sections are factory-assembled wall sections with seams designed to provide the same water drainage as in the previous example. They combine outer jacketing and insulation in a single panel. If properly installed, condensation cannot form inside the wall. Because the wall panels arrive on site ready to be fixed directly to the perimeter of the building using the fasteners and methods recommended by the manufacturer, the labor to install this system is often less than in the previous example.
Metal outer coating with vapor barrier specially applied on the inner surface: Vapor barrier is a "smart" material that can absorb water vapor at high relative humidity and return it to the interior at lower relative humidity conditions. The use of this material in applications with high internal moisture load on the inside of the exterior cladding will still experience condensation in cold weather and this condensation will create a water problem on the inner floor of the wall. This is especially problematic if some kind of interior lining is used on the inside of its perimeter to protect the wall from animals. Because this can trap moisture that condenses and runs off. This is exactly the problem with the use of uninsulated metal-walled siding, or with insufficient insulation or poor vapor barrier installation. A path must be provided for this drain to condense.
Liquid membranes applied to the inside of the metal coating: Similar to the previous example, this liquid membrane is nearly impermeable. It can be sprayed, brushed or rolled onto the surface. This technique does not prevent condensation from forming, but it can act as a barrier to both water vapor and liquid water and slow down the corrosion process. If used, it is important to take care to drain the condensate from the wall. This system can be useful in some applications with relatively low internal moisture loads where insulation is not desired or required. The metal coating acts as a rain shield.