043 -- Field Measured Data on Ventilated Attic Performance to Validate the Code Requirements ✓ Most Recent

Ventilating attic is a common practice to control moisture built-up inside the attic. Factors influence the effectiveness of attic ventilation includes venting area, attic volume, air sealing of attic from indoor living space, roof coverings, attic insulation type and equally exterior weather conditions. Investigating the hygrothermal and energy performance of ventilated attic is gaining research focus as Canadian homes moves towards Net Zero Energy Construction. National Research Council of Canada (NRC) initiated a research project entitled, “Energy Performance of Residential Roofs (EPRR)” to answer the following questions: 1) Whether the attic ventilation ratio recommended by NBCC2015 (1 square foot of net free vent area for every 150 or 300 square feet of attic space (1:150-1:300) are adequate to ensure energy performance without unintended consequences? 2) What are the requirements to permit sealed attic in NBCC? Whether using Spray Polyurethane Foam (SPF) provide adequate insulation without unintended consequences? An in-suit experimental platform is designed to measure temperature, relative humidity, air flow, heat flux, and pressure differences to evaluate the performance of ventilated attic under typical Canadian weather conditions. A two story typical residential house built in 2012 with a hipped roof structure was selected as the experimental site. The ventilation ratio is 1ft2 (0.09m2) of net free vent area for every 125ft 2 (~12m2) of attic space which is higher than 1:150 ratio specified by NBC2015. Findings from the current study indicated that the temperature, air flow, and humidity are, to some extent, constant with a minimal changes inside the attic throughout the day showing a static condition. During heating degree days, the vent exhaust air is nearly 10oC (50oF) warmer than the air coming in through the soffit indicating that the indoor hot air penetrates into the space. The dew-point temperature falls within the insulation temperature gradient, indicating that there is no condensation between insulation layers. See more