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Depressurization: A Serious Safety Concern

How Safe Do you think your Home is?

Maybe it's time to think again?

Depressurization: A Serious Safety Concern

Winnipeg - Brian Baker, President of Custom Vac Limited, a local Heating, Ventilation and Air Conditioning (HVAC) contractor says, "One area that contracting firms are finding very challenging is the issue of home depressurization." In-home research conducted in Manitoba has proven the levels of depressurization occurring in both, new homes and older homes is potentially a serious safety issue that remains unresolved. In the past technicians were taught that they need only concern themselves with energy efficient new homes as it was believed that they had a greater potential for depressurization problems. "Not true", said Baker. Research conducted has proven many times that any home of any age and style can have and experience serious depressurization conditions.

What is Depressurization?

Depressurization is a condition that is created when air within the home is exhausted by natural or mechanical means. As air within the home is being removed, pressure levels within the home are lowered. This lowering of air pressure within the home increases air leakage into the home around doors, windows and other cracks in the building envelope. With the building pressure reduced, the least restrictive way in which to bring air back into the home is via the chimney and that is typically what happens, air is drawn back down the chimney allowing the products of combustion to enter the home.

"This can create a very hazardous condition that has the potential to cause serious injury and even death in cases where carbon monoxide (co) is being produced", said Baker. Many homes have a 5" or 6" fresh air duct connected to the return air of the furnace and a 5" or 6" combustion air duct supplied to the furnace area. This may not be enough! In some homes just by operating the dryer the home can exceed the -5pascals depressurization limit allowed by the code.

The research in Manitoba has shown that the present codes, standards, installations, and inspection methods have fallen short. Even though installations follow the codes and standards, and are inspected by the authorities, at present this does not guarantee that a home will not experience a serious depressurization condition. The reason why says Baker is, "there is no requirement or enforcement to conduct a depressurization test when servicing, maintaining or installing or replacing a piece of equipment." Some homes in Manitoba have been shown to have depressurization levels well in excess of -20 Pascal's (pa) [-5 pa. = 0.02" water column (wc)] If you have exhaust devices, central vacuum systems, bathroom fans, dryers, kitchen range fans or any other device(s) that exhaust air from the home there is a greater potential for a problem.

Depressurization can also be a problem in homes that have high, large, or multiple chimneys. The reason is that these chimneys create high negative draft conditions that will pull more air from within the home, which again has been proven in actual tests to be a serious problem.

Is Depressurization a Problem in Your Home?

"Testing can be done to determine the level of depressurization and once determined remedial measures if required can be proposed", said Baker. His firm has been working with an independent consultant since this type of research began in Manitoba, and is proud to say that his company is one of a small handful of concerned Contractors leading the way for change in this area.

"There is no way for any technician to know for certain whether or not there is a depressurization problem with a home when performing a service for the homeowner by simply looking at the home. The only way to determine the depressurization limit of a home is to conduct a test, said Baker".

Homeowners tend to think that their homes are not airtight and therefore are not a problem. "This is just not the case and the actual in-home research proves that", said Baker. Just like we need to educate homeowners about the signs and dangers of carbon monoxide we need to spend time to educate them about depressurization and how the two are inter-related. CO and depressurization are similar in that you cannot detect or identify a problem without the proper testing equipment. Approximately, 25% or 1 out of 5 homes tested, exceeded the -5 pa. limit set out in the codes, a real eye opener for all those homeowners who think their homes are leaky, said Baker.

"Homeowners should have a depressurization test conducted to identify any potential safety issues that could affect occupants within the home. The test is performed by independent trained and qualified personnel," said Baker. In addition, Brian suggested, that homeowners that are planning to install an exhaust device or retrofit their homes building envelope regardless of how minor it may seem, should consult with a Heating Refrigerating and Air Conditioning Institute of Canada (HRAI) certified residential mechanical ventilation designer and installer, they have been trained to Nationally recognized standards and undergo training updates to remain current with the changes as they occur.

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R3E 1S5
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