Innovative Housing Grants Program : [report summaries]

2 Pages·1991·0.73 MB·English

by  Alberta. Innovative Housing Grants Program

Innovative Honsing Grants Itogram
PASSIVE DEHUMIDIFICATION AND AIR CIRCULATION
VENTILATION SYSTEM FOR NORTHERN RURAL
HOUSING IN ALBERTA
Prepared by
J.J. Hamilton, P. Eng.
INTRODUCTION METHOD
The worked commenced with an
Many small wood-framed and wood-
heated homes in northern rural areas extensive literature review. It also
of Alberta suffer from extreme interior focused on theoretical analyses of
condensation problems. Many have humidity problems to establish a basis
limited or intermittent hand-fired for developing new approaches. Site
heating systems, partially insulated and visits to houses In the Chipewyan and
poorly sealed exterior envelopes and Peerless Lakes areas helped to provide
high levels of occupant-generated an understanding of the lifestyles and
water vapor. Condensation problems, construction environment in which the
including mould and mildew growth system (s) must operate.
cause degradation of finishes and
structural elements, and create a need The first phase of the work led to the
for a simple and cost effective moisture development of a design for a
removal strategy. ventilation system driven by air
pressure differentials between the
OBJECTIVE windward and leeward sides of the
home.
The objective of this project was to
explore unconventional approaches to The second phase of the work involved
ventilation and moisture (humidity) a comparative analysis of ventilation,
diffusion and condensation plates as
removal that respect the resident's
lifestyle while not imposing an dehumidification strategies. Based on
unrealistic economic or maintenance
the analysis, five alternate wall
burden. The study focused on assemblies were developed and tested
ventilation /dehumidification systems in a laboratory setting to determine
which are driven by natural and free their ability to diffuse moisture vapor to
forces such as the stack effect and the exterior. The general assembly
differential wind and vapor pressures consisted of a 600 mm x 600 mm wood
between the interior and exterior frame in which different insulation batt
environment.
configurations and vapor/air barrier
coverings were placed and tested.
Copies of this report and manual are available from Innovative Housing Grants Program, Report: 43 Pages
Alberta Municipal Affairs, 16th Roor, CityCentre, 10155 - 102 Street, Edmonton, Alberta Plus Appendices
T5J 4L4 (403/427-8150). Please refer to the order number shown in box at right, when Date: June 1991
requesting copies of the completed report or manual.
ISBN: 0-88654-337-1
V J J
In two of the test panels, oriented glass CONCLUSIONS
fibre insulation board was placed near
the top of the wall, where most frost Oriented glass fibre insulation board
buildup occurred, to test its appears to be a feasible method of
effectiveness in channelling moisture channelling the moisture vapor to the
to the exterior. Four configurations exterior with limited interruption.
employing the oriented glass fibre Moisture that condenses out as frost in
insulation board were tested. the board is held hygroscopically until
it evaporates and escapes the board
FINDINGS
as vapor; consequently no problems
occur as the moist interior air vents
Test assemblies without oriented glass past the dew point in the wall. Based
fibre board were found to be upon the findings It w as calculated that
inappropriate because of high rates of in order to vent the moisture generated
frost accumulation. For those panels by the average family, the insulated
incorporating the oriented glass fibre board vents would only need to expel
board, the exposed oriented glass 4% of the total home air volume per
fibre insulation board suffered frost day. When translated into heating
accumulation at a much slower rate costs, it was estimated that the
than the associated batt insulation. dehumidification costs for a large
For one panel, after a 7.9 day duration family would be approximately $15 per
test, frost increased the insulated month.
board weight by 16.8% and the batt
insulation weight by 98.1%. Further, The report contains proposals and
air flow and vapor transmission at 5Pa construction details for a field trial and
remained fairly constant through the evaluation of the vent concept. This
oriented glass fibre insulation board. report will be of interest to those
individuals and agencies engaged in
When allowed to thaw at room the research and evaluation of
temperature, the batt insulation frost alternate, efficient, low-technology,
was released as water while no water low-maintenance moisture control
was collected from the insulation strategies.
board.
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