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Indoor airPLUS

Technical Guidance to the Indoor airPLUS Construction Specifications

1. Moisture Control

Sections 1.11 - 1.13: Interior Water Management

1.11 Moisture-Resistant Materials and Moisture-Protective Systems in Wet Areas

Install moisture-resistant materials and moisture-protective systems in vulnerable areas. For example:

  • Install water-resistant hard-surface flooring in kitchens, bathrooms, entryways, laundry areas, and utility rooms. Do not install wall-to-wall carpet adjacent to toilets and bathing fixtures (i.e., tubs and showers).
  • Install moisture-resistant backing material (i.e., cement board or the equivalent, but not paper-faced wall board) behind tub and shower enclosures.
  • Install all condensate discharge according to IRC section M1411.3.
  • Insulate piping installed in exterior walls.


The purpose of each of these measures is to prevent the growth of mold by preventing sources of moisture. For example, water-resistant hard surfaces dry quickly after becoming wet, unlike carpeting, which holds water for long periods and thus fosters mold growth. An improperly installed condensate line from a cooling coil can allow large quantities of water to enter a building’s ceiling, wall, and foundation components. While the International Plumbing Code requires the insulation of water pipes concealed in outside walls (or other locations) subject to freezing, in warm climate conditions cool pipe surfaces (without an insulation covering) exposed to warm temperatures will form condensation and wet surrounding building materials.


Follow the requirements as stated in the specification.

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