![]() ![]() The higher outside air pressure then flows in through all the unsealed cracks and openings. The fan pulls air out of the structure (or pushes air in), lowering the air pressure inside. In a smaller building a powerful fan, or ‘blower door,’ is mounted into the frame of an exterior door. This can be accomplished with exhaust fans, specialized blower/fan doors, or, in larger buildings, by temporarily altering the HVAC system (if central) to create a negative pressure inside. In general, building envelope air leakage inspections are best conducted when air flow is directed and controlled. Decoupling floors involves sealing junctions between walls, as well as floor-to-floor vertical penetrations such as elevator shafts, doors to emergency stairs, garbage chutes, and plumbing and electrical penetrations. Interior compartmentalization involves sealing units from one another, and sealing service or common areas from the rest of the building. The separation of floors from one another is called decoupling. Sealing off areas in a building - such as separate units or rooms from one another - to help equalize pressure differences is called compartmentalization. High-rise building compartmentalization is critical because these areas of air leakage exacerbate life-threatening hazards such as smoke spread. They represent a successful approach to controlling previously uncontrolled airflow.įloor-to-floor and same-floor air leakage cause many of the same problems as infiltration and exfiltration. If the air pressure creates higher pressure on the inside of the building envelope, air leaks outwards, or air exfiltration.Ĭompartmentalization and decoupling are relatively new words in building envelope commissioning. ![]() When higher pressures act on the outside of the envelope air leaks inward, an effect called air infiltration. ![]() The resulting gradients and cycles cause many structural and moisture problems, such as moisture penetration and condensation within the construction cavities of roofs, exterior walls, and within or around windows.Īnother significant effect of air pressure difference is air leakage through openings, cracks and joints in the building envelope. There are significant differences in air pressure between the interior and exterior of a building envelope and between the lower and upper levels of multi-storey buildings, according to Quirouette.įive forces - stack effect, fan pressurization, wind cycling, barometric cycling and thermal cycling - induce air pressure differences. Test method standards exist to deal with these (for examples, see sidebar). To commission a newly constructed or retrofitted building envelope, four areas need to be tested, according to Quirouette: heat loss, air leakage, rain penetration and vapour diffusion. Similarly, with a mechanical ventilation system all it takes is a flow meter to confirm the correct cfm of supply air. He quotes the example of an office floor fluorescent lighting layout, where turning a switch on and off proves to an electrical commissioner that the work has been completed satisfactorily. He uses electrical/mechanical commissioning practices to illustrate to the construction industry that the same can be done for the envelope. is a long-standing Canadian champion of building envelope commissioning and has published many papers on the subject. Rick Quirouette of Mississauga, Ont.-based Quirouette Building Specialists Ltd. The science is known and so are the preventive approaches for new construction and the remedial measures for retrofit. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |