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Infiltration: Leaky buildings are lousy buildings
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You can't control it - if you can't enclose it...to achieve high performance standards (in addition to
improving
insulation and
windows) you have to seal up
the holes and cracks!
Description: Illustrated above is the trends in air leakage
rates in air changes per hour (ac/h) at 50 Pascal's (ach50) differential. One Pascal (pa) is equivalent to 0.00401463 inch
H2O or about the weight of a single paper currency,
i.e. a $5 bill. 50 Pascal's would be a stack of 50 bills or
about 0.20 inch H2O or 5.1 mm H2O. It doesn't take much to move air!
Here's an example, an 8ach50 equates roughly to 0.6
air changes per hour. Put another way, the entire volume of air
in the home will have been replaced in just under two hours. Now
just imagine that its -40 deg F outside and you have to heat
that up as you bring it inside - can you see how inefficient
that would be? Not only that, when you bring this air in
uncontrolled, it's coming through cracks which are on both
sides of the insulation which now makes the insulation a filter...so
asks yourself if you would be willing to wear a fiberglass face mask?
No? So it's probably a good idea to control the incoming air -
so seal up the house properly to reduce the uncontrolled leakage
(1.5ACH50 is a good target)
and bring the air in thorough the ventilation system with a
proper filter and if it makes sense a ventilation system with
heat recovery...and in my not so humble 40 grit opinion - dedicated
ventilation systems are better than combined systems; i.e.
separate the thermal comfort from the ventilation system. To
learn why, read:
Dedicated Outdoor Air Systems (DOAS).
Air Leakage Testing: Pre drywall and pre occupancy.
Below are three photo's of a new home. At the far left you are looking at a ceiling mounted light fixture and next to it are multiple support rods which are part of the structural system for the suspended staircase. These rods are attached to a steel beam. In the middle photo you are witnessing what the image on the far left looks like with a thermographic camera. The thermographic camera permits us to see undesirable heat flows. The photo on the far right is the same image except with the house under negative pressure which is accomplished using a blower door instrument. Notice the diffusion from the middle image to the right image...this tell us that there is a problem area at the light and steel beam that went undiscovered prior to putting up the drywall. Now you might thinking "who is to blame". The reality is leakage failures are a team effort which can be mitigated by doing air leakage testing before putting up the drywall.
Here's why pre drywall leakage testing is valuable. On the right side you are looking at the ceiling of a walk in shower and the right is the thermographic image of the same ceiling under negative pressure. Imagine showering on a cold winter day where hot water vapour leaks into the ceiling spaces and condenses into water...its a recipe for water damage and mould...again preventable with pre-drywall air leakage testing.
 
Whether a building is tight or leaky is a team effort and even the best most conscientious teams believe they did a great job until we show up with the testing equipment. You get one chance - just one - to check and correct...it is an option but it is money well spent. |
