Table Of Content

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. 2/2 337-1