See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/34284632
Moisture control and enclosure wall systems [PhD Thesis].
Thesis · January 1998
Source: OAI
CITATIONS
46
READS
1,334
2 authors, including:
John Straube
University of Waterloo
71 PUBLICATIONS480 CITATIONS
SEE PROFILE
All content following this page was uploaded by John Straube on 04 January 2017.
The user has requested enhancement of the downloaded file.
Moisture Control and Enclosure Wall Systems
by
John Frederick Straube
A thesis submitted to the University of Waterloo
in the fulfilment of the
thesis requirement for the degree of
Doctor of Philosophy
in
Civil Engineering
Waterloo, Ontario, Canada, 1998
John F. Straube, 1998
ii
I hereby declare that I am the sole author of this thesis.
I authorize the University of Waterloo to lend this thesis to other institutions or individuals
for the purpose of scholarly research.
I further authorize the University of Waterloo to reproduce this thesis by photocopying or
by other means, in total or in part, at the request of other institutions or individuals for the
purpose of scholarly research.
iii
The University of Waterloo requires the singatures of all persons using or photocopying
this thesis. Please sign below, and give address and date.
iv
Abstract
Moisture Control and Enclosure Wall Systems
Moisture is one of the most important factors affecting building performance and
durability, especially in countries with cold climates. Understanding and predicting
moisture movement within and through the building enclosure is crucial to the control and
the avoidance of moisture-related problems such as corrosion, freeze-thaw, and biological
growth.
This thesis comprehensively investigated the control of moisture in above-grade enclosure
walls. Emphasis was given to driving rain deposition, rain penetration control, ventilation
drying, and pressure moderation. A major review of liquid and vapour moisture storage
and transport in porous building materials was undertaken, and the results summarised.
The experimental program involved the temperature, humidity, and moisture monitoring
of 26 full-scale test panels exposed to the environment of South-western Ontario for 30
months. Driving rain was measured in the free wind and at 14 locations on a test building.
High-speed pressure measurements, of interest to ventilation and pressure moderation,
where simultaneously collected at many points. The water permeance of brick veneers
under air pressure differences and the moisture absorption of brick were studied in the
laboratory.
A method of predicting driving rain was developed and validated with field measurements.
The distributions of driving rain event duration, intensity, and direction were investigated.
An approximate means of estimating rain deposition on buildings was also developed,
supported by measurements and other researchers’ results. A rational rain control theory
was conceived which led to a useful enclosure classification system. A probabilistic model
of rain-building-enclosure interaction was produced which incorporates all of the
important variables.
Extensive pressure measurements showed that instantaneous pressure equalisation does
not occur. It was also shown that realistic air pressure differences have little effect on the
permeance of brick veneers. It was concluded that pressure moderation is not an effective
rain control strategy for most walls, especially brick veneers.
The physics of ventilation flow and ventilation drying of walls were formulated. Field
measurements of wind pressures and air space moisture content and temperatures behind
brick veneers demonstrated the importance of ventilation as a drying mechanism and as a
means of resisting inward vapour-drive wetting. It was found that the sun and wind have
a large and beneficial influence on ventilation drying. Summer condensation wetting due
to inward vapour drives from solar-heated rain-wetted cladding was shown to be a
potentially serious performance problem.