Blower door test protocol for certification

Everything I've read says you can seal the HRV intake & exhaust ducts - as in plastic bag & tape, super tight, and I understand why (its continuous operation). However, what's not clear is if I can seal off other vents, like a clothes dryer exhaust - this answer depends on the source. The way I understand it is that you can't - and this makes sense because these intermittent vents are potential leaks when the device is not in operation. But of course reaching a certifiable level of air tightness is easier if you can seal these others off. Can you clarify?

A:  You ARE allowed to seal the intake and the exhaust of the MHRV system for the purposes of the blower door test. Unlike these any other openings, designed or unintentional, contribute to heat losses and thus presents an extension of the airtight building envelope, that will cause infiltration depending on its level of airtightness. For this reason, they may NOT be temporarily sealed during the blower door test. For example, the exhaust from a dryer or the supply/exhaust air flue system for a room stove should be in the normal operational state during the blower door test. Obviously these should be 'room sealed' and thus airtight but often they are not - this is partly what we are testing. Similar to the windows, they are supposed to be airtight but we must check and verify this with the blower door test and if there are leaks we amend them until we at least achieve an n50 of less than or equal to 0.6ach@50Pa.

If a damper is present in the flue system this can be closed over during the test but not sealed and when the house is in use it should also be closed when the system is not in use - thus the blower door test is mimicking a realistic scenario.

You ARE allowed to seal the intake and the exhaust of the MHRV system for the purposes of the blower door test.

 

Unlike these any other openings, designed or unintentional, contribute to heat losses and thus presents an extension of the airtight building envelope, that will cause infiltration depending on its level of airtightness. For this reason, they may NOT be temporarily sealed during the blower door test. For example, the exhaust from a dryer or the supply/exhaust air flue system for a room stove should be in the normal operational state during the blower door test. Obviously these should be 'room sealed' and thus airtight but often they are not - this is partly what we are testing. Similar to the windows, they are supposed to be airtight but we must check and verify this with the blower door test and if there are leaks we amend them until we at least achieve an n50 of less than or equal to 0.6ach@50Pa.

 

If a damper is present in the flue system this can be closed over during the test but not sealed and when the house is in use it should also be closed when the system is not in use - thus the blower door test is mimicking a realistic scenario.

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