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Guideline I.2: Moisture Control

Intent

To ensure the prevention of exterior water intrusion, leakage from interior water sources, or other uncontrolled accumulation of water.

Required Performance Criteria

Guidelines apply to all projects designated New Buildings and for Major Renovations with exterior envelope included in project scope.

  1. Design the building envelope to resist moisture penetration. Since all buildings have potential for moisture penetration, and since Minnesota is a heating dominated climate, provide drainage planes to the exterior.
  2. During the coldest portion (99.5% cold temperature design value) of the heating season, keep the indoor dew point below 35°F (2°C).
  3. Specify maximum moisture content of materials used in construction to assure that subsurface layers are dry enough to prevent moisture trapping by surface finish materials.

Implementation in the Design Process:

In the program document, note any unusual water uses in the building for this occupancy class. As the site is selected, note any potential water intrusion potential associated with the site(s).

As the project proceeds through design, incorporate building envelope and mechanical systems to meet the performance criteria for I.2. Calculate dew points for interior surfaces of all exterior wall elements according to winter-day design conditions.

In bid documents, describe how materials at construction site are to be stored for protection against moisture damage during construction. Describe procedures to be followed to remove moisture-damaged materials from the construction site.

During construction, store materials appropriately to prevent water damage. Do not accept moisture sensitive materials with evidence of moisture damage, including stains. Remove them from the site and dispose of properly. Replace any moldy materials with new, undamaged materials. Sequence drying of construction materials appropriately during the construction process to prevent future problems.

During occupancy regular inspections should be conducted to ensure there are no visible signs of moisture intrusion or accumulation and to conduct regular testing of exterior wall construction to detect moisture in the exterior wall system. Remediation of identified exterior water intrusion should be corrected as soon as it is identified to lower the likelihood of mold growth.

 

Final Design:

  • I.2A: Verification of design of building envelope to resist moisture penetration.
  • I.2B: Verification of indoor dew point within guideline limits.
  • I.2C: Verification of specifications requiring maximum moisture content of materials within guideline limits.

Lstiburek, J, and J Carmody (1993) Moisture Control Handbook, New York, Van Nostrand.

Lstiburek, J. (2002) “Moisture Control for Buildings.” ASHRAE Journal 44(2): 36–41.

Lstiburek, J. (2006) ”Understanding Drainage Planes.” ASHRAE Journal 48(2): 30–35.

Harriman, L. I., G. Brundrett, et al. (2001.) Humidity Control Design Guide for Commercial & Institutional Buildings. Atlanta

ASHRAE Standards 62.1 and 62.2: https://www.ashrae.org/resources–publications/bookstore/standards-62-1–62-2

Minnesota Department of Commerce Guide for Managing Indoor Air Quality: https://mn.gov/admin/assets/Minnesota_Guide_for_Managing_Indoor_Air_Quality_tcm36-207630.pdf

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