2. INSULATION MATERIALS AND PROPERTIES

2.5 PROTECTIVE COVERINGS AND FINISHES

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The efficiency and service of insulation is directly dependent upon its protection from moisture entry and mechanical and chemical damage. Choices of jacketing and finish materials are based upon the mechanical, chemical, thermal and moisture conditions of the installation, as well as cost and appearance requirements.

Protective coverings are divided into six functional types.

1. WEATHER RETARDERS

The basic function of the weather-barrier is to prevent the entry of water, ice, snow or atmospheric residue into the insulation. Sunlight and ozone can also damage certain insulations. Applications may be either jacketing of metal or plastic, or a coating of weather-barrier mastic. Jacketing must be over-lapped sufficiently to shed water. Avoid the use of plastic jacketing materials with low resistance to ultraviolet rays unless protective measures are taken.

2. VAPOUR RETARDERS

Vapour retarders are designed to retard (slow down) the passage of moisture vapour from one side of its surface to the other. Joints and overlaps must be sealed with a vapour tight adhesive or sealer free of pin holes or cracks. Vapour retarders take three forms:

a. Rigid jacketing – plastic fabricated jackets to the exact dimensions required and sealed vapour retarding.

b. Membrane jacketing – laminated foils,treated or coated products and plastic films which are field or factory applied to the insulation material. (Additional sealing beyond the factory seal may be necessary depending on temperature/humidity conditions of the installation.)

c. Mastic applications – solvent types which provide a seamless coating but require time to dry.

3. MECHANICAL ABUSE COVERINGS

Rigid jacketing provides the strongest protection against mechanical abuse from personnel, equipment, machinery, etc. The compressive strength of the insulation material should also be considered when designing for mechanical protection.

4. CORROSION AND FIRE RESISTANT COVERINGS

a. Corrosion protection – can be applied to the insulation by the use of various jacket materials. The corrosive atmosphere must be determined and a compatible material selected. Mastics may be used in atmospheres that are damaging to jacket materials. (see Section 3).

b. Fire resistance – can be applied to insulation systems by the use of jacketing and/or mastics. Fire resistant materials are determined by flame spread, smoke developed and combustibility. The total systems should be considered when designing for fire resistance. (see Section 3).

5. APPEARANCE COVERINGS AND FINISHES

Various coatings, finishing cements, fitting covers and jackets are chosen primarily for their appearance value in exposed areas.

6. HYGIENIC COVERINGS

Coatings and jackets must present a smooth surface which resists fungal or bacterial growth in all areas. High temperature steam or high pressure water wash down conditions require jackets with high mechanical strength and temperature ranges. (see Section 3).