Tuesday, February 2, 2016

1st Blower Door Test

The Initial Blower Door Test

Airtightness is of a building is related the the overall comfort of a building. The tighter the house, the less drafty it is and the more comfortable it is. In this Blower Door test we will be verifying the tightness of the primary air barrier, and sealing any holes we may have. It is much easier to seal them now, than after the insulation is in and the drywall is up.

The blower door is a diagnostic tool used to measure how tight (or leaky) a structure is. You should see a blower door done when you have an energy audit done on your home or if you own a Certified Energy Star, LEED or NAHB Green Homes you have had this test performed on your house (probably before you moved in). 

A few acronyms before I move on:
ACH50 - Air Changes Per Hour at 50 Pascals - With a blower door running at 50 Pascals (forcing a 20-25 mph wind on all 6 sides of the house at once). The number time time you will entirely replace the air inside the house in 1 hour
CFM50 - Cubic Feet Per minute at 50 Pascals - With a blower door running at 50 Pascals (forcing a 20-25 mph wind on all 6 sides of the house at once). The number of cubic feet of air moving though the blower door fan (and thus the amount of air being drawn into the house) in 1 minute

There are limits to each of the above programs
 - NYS Building Code is 7 ACH50 - or - Visual Inspection (99% of homes is a visual inspection)
 - LEED and NAHB Green are on a sliding scale (the tighter you are, the more points you get - and you may not need any of those points to achieve the certification) - so just because you have a Green Home, or a LEED home does not make it a Tight Home
 - EPA's Energy Star (in our area of the country) is 4 ACH50

However none of the is even close to the Passive House Standard. 

To meet Passive House Standards the house has to be 0.6 ACH50 or lower.

The blower door test will give you a CFM50 (cubic feet per minute at 50 Pascal's pressure difference between the inside and outside). Then the volume of air in the house must be calculated.

Calculating the Volume:
RESNET, BPI and ASTM standards calculates the Volume fairly similarly:
Measure the house from the outside, Measure the height from the basement slab to the upper ceiling and boom you have your volume. Pretty Easy, pretty straight forward

Passive House does things a little different. The measurements are all taken from the inside (since walls are so thick) and excludes the area's for interior walls. 

How much of an impact does this have on our house??
RESNET, BPI and ASTM standards has a volume of:                                      38,698 CUFT. 
Passive House Standard has a volume of:                                                         27,299 CUFT.

That is almost a 30% difference! 

This impacts the calculation quite a bit since:

So the Passive House Standard is even tighter than you'd expect!

OK - So enough "Technical Information" Lets see house we did!

Test Results:
We need to be under 273 CFM50 at the end of the build, our Goal for this test is 150 CFM50.

Here is our prep:
We sealed off the:
Front Door

Large Basement Window

Plumbing Penetrations

Small Basement Window

We chose to run the test out of the small basement window using the "Minneapolis Duct Blaster"
 

Here is our test result for today:

83 CFM50
0.129 ACH50 - per RESNET Standards
 0.182 ACH50 - per Passive House Standards

We determined the test to be a HUGE Success. We also did a little bit of air sealing and brought the test down to 73 CFM50

With the initial Blower Door test complete we can now continue installing all of the windows - my next post will discuss the installation procedure

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