Skip to page content
USDA Forest Service
  
Treesearch

Research & Development Treesearch

 
Treesearch Home
About Treesearch
Contact Us
Research & Development
Forest Products Lab
International Institute of Tropical Forestry
Northern
Pacific Northwest
Pacific Southwest
Rocky Mountain
Southern Research Station
Help
 

Science.gov - We Participate


USA.gov  Government Made Easy


Global Forest Information Service

US Forest Service
P.O. Box 96090
Washington, D.C.
20090-6090

(202) 205-8333

You are here: Home / Search / Publication Information
Bookmark and Share

Publication Information

View PDF (290 KB bytes)

Title: Air pressures in wood frame walls

Author: TenWolde, Anton.; Carll, Charles G.; Malinauskas, Vyto.;

Date: 1998

Source: Thermal Performance of the Exterior Envelopes of Buildings VII : conference proceedings : December 6-10, 1998, Sheraton Sand Key Hotel, Clearwater Beach, Florida. [S.l. : s.n., 1998?].:p. 665-675 : ill.

Publication Series: Miscellaneous Publication

Description: Wind pressures can play an important role in the wetting of exterior walls (driving rain). In response, the rain screen concept, including compartmentalization and air spaces, has been developed to provide pressure equalization and limit water entry into the wall. However, conventional construction such as wood lap siding has not been evaluated as to its ability to function as a rain screen. As part of a two-year project assessing the performance of hardboard lap siding, we measured air pressure differences across the siding over extended periods of time in two single-story wood-frame buildings, specially constructed for this study in southern Florida. Three different wall constructions were included in the study. We found that the conventionally installed lap siding provided substantial air pressure equalization. Inward air pressure differences across the siding did not appear strong enough, or long enough in duration, to raise concern about significant water penetration through the siding overlaps, even during windy days. Air leakage has been recognized as an important mode of water vapor transport, and airtight construction is therefore recognized as an important ingredient of designing for high moisture tolerance. As part of the same study, we monitored air pressures across the siding, sheathing, and gypsumboard in two of the walls. We found that wind-induced air pressures across the exterior walls were predominantly exfiltrative, even on the windward side of the building. Infiltrative pressures only occurred near windward comers of the building during short periods of time. We also found significant air leakage past the top plate into the wall cavity. This paper also presents a method for coordinating the design for airtightness (airflow retarders) with the design for control of vapor diffusion (vapor retarders). The calculations show that a vapor retarder of 1 perm (57ng/Pa*s*m2) should be complemented with an air barrier system (ABS) with an ELA of 0.003 in.2/ft2 (2*10-5 m2/m2) or less. Specifying lower-perm vapor retarders (e.g., 0.1 perm, or 5.7 ng/Pa*s*m2) would require specifying an extraordinary level of airtightness.

Keywords: Walls, Building construction, Structural timbers, Pressure, Rain, Moisture, Wetting, Screens, Lap siding, Air pressure, Wood frame walls, Rain screens

Publication Notes:

  • We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
  • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.

XML: View XML

Citation:


TenWolde, Anton.; Carll, Charles G.; Malinauskas, Vyto. 1998. Air pressures in wood frame walls. Thermal Performance of the Exterior Envelopes of Buildings VII : conference proceedings : December 6-10, 1998, Sheraton Sand Key Hotel, Clearwater Beach, Florida. [S.l. : s.n., 1998?].:p. 665-675 : ill.

 


 [ Get Acrobat ]  Get the latest version of the Adobe Acrobat reader or Acrobat Reader for Windows with Search and Accessibility

USDA logo which links to the department's national site. Forest Service logo which links to the agency's national site.