In pursuing green building principles, Saint-Gobain believes that a skillfully executed airtightness and moisture management of a building shell and its thermal bridges is an essential investment in order to protect the longevity of the building fabric.
To limit the potential for bacteria and mold growth within buildings from water infiltration and condensation.
Part 1: Exterior Liquid Water Management
A point-by-point narrative describes how liquid water from outside the building is addressed; responding to the nature and intensity of wetting based on the project's site and climate, and includes the following leading concerns:
- Site drainage, including the impact of any site irrigation.
- The local water table.
- Building penetrations (especially windows and plumbing/electrical/mechanical penetrations).
- Porous building materials connected to exterior sources of liquid water.
Part 2: Interior Liquid Water Management
A point-by-point narrative describes how liquid water from interior sources is addressed, including these leading concerns:
- Plumbing leaks.
- "Hardpiped" plumbing appliances (appliances such as clothes washers exposed to building water pressure even when not in use).
- Porous building materials connected to interior sources of liquid water.
- New building materials with “builtin” high moisture content or building materials wetted during construction but now on the inside of the building.
Part 3: Condensation Management
A point-by-point narrative describes how condensation is addressed, including these leading concerns:
- High interior relative humidity levels, particularly in susceptible areas like bath and laundry rooms and belowgrade spaces.
- Air leakage which could wet either exposed interior materials or interstitially “hidden” materials.
- Cooler surfaces, such as basement or slabon-grade floors, or closets/cabinets on exterior walls.
- Oversized air conditioning units.
Part 4: Material Selection and Protection
A point-by-point narrative describes how moisture-tolerant materials have been selected and/or moisture-sensitive materials (MSP) are being protected, considering these leading concerns:
- Exposed entryways and glazing.
- Porous cladding materials.
- Finished floors in potentially damp or wet rooms such as basements, bathrooms and kitchens.
- Interior sheathing in damp or wet rooms.
- Sealing and storing of absorptive materials during construction.
See detailed requirement for Moisture management
Part 3 and Part 4
One of the main reasons for producing an airtight building is to protect the structure against dampness originating from air leakages. The following two processes lead to the transmission of water vapor through the construction.
The first mechanism is the classical vapor diffusion caused by different vapor concentrations. Within buildings, people, animals and plants continuously release moisture. Because of pressure differentials around a wall, water vapor tends to have an equal concentration on both sides of the surface, moving from the high pressure to the low pressure area. If the material is permeable, diffusion happens and water vapor passes through it with more or less resistance. The diffusion happens all the time and is almost unavoidable.
The second mechanism is caused by the flow of air through gaps, cracks and other openings in a wall.
Condensation effects caused by air leakage have bigger impacts compared to those caused by diffusion. Depending on the location and size of an air leakage, the material affected can suffer damage and lead to it requiring expensive restoration work. In addition, when moisture penetrates insulation material with poor drying potential, its performance can be reduced by up to a sixth compared to dry material. A skillfully executed airtightness and moisture management of a building shell and its thermal bridges is therefore an essential investment in order to protect the longevity of the building fabric. However, it has to be coupled with effective ventilation to remove moisture-laden interior air.