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Building envelope testing4/13/2023 The leakage target is typically a percentage of the total envelope area. Flow is read as cubic feet per minute at a pressure of 75 Pa induced by the blower door fan (CFM75). Since the gauge knows each inlet hole size the fan can be set to, it can calculate flow once it reads a pressure. The blower door can be set to various hole sizes on the inlet side of the fan which can be changed as needed to maintain pressure. ![]() The gauge works by reading the fan pressure and converting it to flow. ![]() A blower door system consists of a calibrated fan that is installed in an exterior doorway using an adjustable frame and cloth or a rigid hard panel with a hole for the fan to fit into.Ī digital pressure gauge is connected to the fan and reads the fan pressure with respect to the outside pressure and the pressure inside the building. To accurately test a building enclosure for air leakage and comply with any building enclosure test standards, a blower door system will need to be used. Leaks at the ceiling and floor have the largest impact as these are the areas where air is most likely to infiltrate and/or exfiltrate. Not all leaks have the same impact in a building. This happens without any wind or fans moving air. This is caused by warm, buoyant air moving up and escaping out of the top of the building which draws in outside air at the bottom. Stack effect is the one driver of air pressure that few people consider and has a large impact on energy use and comfort. Fans also manipulate air pressure in buildings whether it is a fan from the HVAC system, exhaust fans, etc. Wind can have the largest impact on buildings that are particularly leaky, causing drafts and pressure changes in various areas of the building. When relative humidity gets too high, it can cause condensation, mold and comfort issues.Īir can move in, out and through buildings in any of three ways: wind, fans and the building’s natural stack effect. This can cause drafts in certain rooms and bring in moisture which can increase the relative humidity of the conditioned space. Air leakage can affect these items by allowing air of an undesired temperature into the enclosure. ![]() Building science is the study of how heat, air and moisture move through buildings. ![]() When conducting a leakage test on a building enclosure, it is important to know some basic building science concepts. Much of this can be prevented by designing a proper building enclosure and testing it to ensure it is working as designed. These issues include shrinkage (nail pops and cracked concrete), water intrusion from poor grading, cracks and bad flashing details, interior finish damage from stains and joint movement, condensation within wall assemblies, squeaky flooring and wet framing and exterior finish damage. According to the Building Envelope Technology Access Centre in Canada, most warranty callbacks for commercial new construction are due to moisture. The presence of a tighter building enclosure allows for lower utility bills, provides the ability to size mechanicals correctly, improves indoor air quality and reduces issues due to moisture brought in by outside air. There are also several third-party standards that require tighter building enclosures such as LEED and the Army Corps of Engineers. Some states are adding air tightness and testing requires to their building codes. As building codes and owner expectations evolve, more commercial buildings across the United States are being designed to meet standards that reduce air leakage through the building enclosure.
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