The operable window sliders/casements/sashes are leaky, allowing conditioned air to escape or outside air to infiltrate. In either case heating and/or air conditioning energy is lost and comfort is reduced (drafts in winter).
The operable portion of these windows can be weather-stripped to reduce unwanted air leakage and save heating and/or cooling energy.
Install weatherstripping on openable windows.
May greatly reduce window air leakage. Requires careful installation and periodic replacement.
Issues and Concerns
This recommendation is in accordance with Measure BE9 of the CMHC manual on Energy and Water Efficiency in Multi-Unit Residential Buildings and with Section 6.2 Building Envelope of the ASHRAE Standard on Energy Conservation in Existing Buildings.
The CMHC manual on Energy and Water Efficiency in Multi-Unit Residential Buildings can be found online at www.hwbinc.com/495-1003/introduction.html.
ASHRAE Standard ANSI/ASHRAE/IESNA 100-1995 – Energy Conservation in Existing Buildings is an approved standard of the American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., the Illuminating Engineering Society of North America and the American National Standards Institute.
Estimate average crack size on site, and use ASHRAE crack method for calculations. Weatherstripping will reduce loss by 2/3.