A platform for research: civil engineering, architecture and urbanism
A platform for research: civil engineering, architecture and urbanism
Condensation in Attics: Are vapor barriers really the answer?
Abstract Calculations of water vapor flow through walls and ceilings are frequently based on the permeabilities of building material, and implicitly assume that most of the vapor transport takes place by diffusion. In order to determine the validity of this assumption, a model for vapor transfer between two spaces by diffusion and convection is first developed. Measurements in a number of houses reveal that, for normal construction practices in U.S. wood frame houses, the transfer of water vapor from living space to attic is almost entirely by air movement. “Kraft” paper “vapor barriers”, frequently attached to batt insulation, do not effectively hinder air (or moisture) flow into attics. Even after numerous cracks and openings in the attic floor, below the insulation, were plugged, significant air flow from living space to attic remained, and evidence of condensation of water vapor within the attic was observed. In new housing, a continuous sheet placed between the ceiling and the framing of the attic floor should effectively hinder air and moisture flow. In existing housing, where it may not be possible to install a continuous sheet under the attic insulation, adequate opening for ventilation with outside air should be provided to prevent moisture build-up and condensation.
Condensation in Attics: Are vapor barriers really the answer?
Abstract Calculations of water vapor flow through walls and ceilings are frequently based on the permeabilities of building material, and implicitly assume that most of the vapor transport takes place by diffusion. In order to determine the validity of this assumption, a model for vapor transfer between two spaces by diffusion and convection is first developed. Measurements in a number of houses reveal that, for normal construction practices in U.S. wood frame houses, the transfer of water vapor from living space to attic is almost entirely by air movement. “Kraft” paper “vapor barriers”, frequently attached to batt insulation, do not effectively hinder air (or moisture) flow into attics. Even after numerous cracks and openings in the attic floor, below the insulation, were plugged, significant air flow from living space to attic remained, and evidence of condensation of water vapor within the attic was observed. In new housing, a continuous sheet placed between the ceiling and the framing of the attic floor should effectively hinder air and moisture flow. In existing housing, where it may not be possible to install a continuous sheet under the attic insulation, adequate opening for ventilation with outside air should be provided to prevent moisture build-up and condensation.
Condensation in Attics: Are vapor barriers really the answer?
Gutt, G.S. (author)
Energy and Buildings ; 2 ; 251-258
1979-05-15
8 pages
Article (Journal)
Electronic Resource
English
Use of Passive Radiation Barriers in Ventilated Attics
| British Library Conference Proceedings | 1996
Use of Passive Radiation Barriers in Ventilated Attics
| British Library Online Contents | 1996
How to overcome condensation in building walls and attics
| Engineering Index Backfile | 1939
| Engineering Index Backfile | 1941
Hygrothermal Performance of Attics
| Online Contents | 1998