Porous insulation in HVAC systems

Porous insulation used to line the air stream surfaces of HVAC equipment provides a locus for the accumulation of dirt and debris. Dirt and debris are hydrophilic and the insulation on the air stream surfaces of mechanical cooling systems thus provides a niche for mold growth. The mold growing on porous insulation unlike moldy debris on a hard surface such as sheetmetal cannot be removed by duct cleaning. Actions for proactively preventing biocontamination of HVAC insulation include the following. (1) Porous insulation shall not be used to line the air stream surfaces of HVAC plenums where wetting is likely such as in the vicinity of cooling coils, water spray systems, humidifiers, and other sources of water. Porous insulation may, however, be used in these HVAC components provided that the insulation is separated from moisture sources by a barrier that is both air and water tight. (2) Because of possible mold growth, the use of porous insulation should be minimized on the air stream surfaces in mechanical ventilation systems where the relative humidity consistently exceeds 65%.