When we build a house, from start to finish we are trying to escape the elements.  The home is basically a box sitting in the outside air.  The air pressure  outside the box (atmospheric pressure)  is usually greater than inside the box so the air is constantly trying to get in.  This force is greater at the base of the home and as the air comes in it is forced upward by a phenomenon called the Stack Effect.
The stack effect works in both winter and summer. Cracks and openings throughout the building shell allow the pressure difference between indoor and outdoor spaces to drive air out of the top floor and to suck air in through the first floor. The best way to remedy the stack effect in most houses is by air-sealing the house to minimize gaps between indoor and outdoor spaces.
My task in the Test House is to find the leaks and let the guys who are going to seal them know where they are, how big they are and what materials are needed to fix them and what the cost will be to do this.
Now I'm off to inspect some of the usual places these leaks occur and I'll share that with you in my next post.

Calculating the volume of a home is pretty simple math.  You measure the length  x width x height of all the interior spaces.  I'm going to use a Test House which measures 20ft x 30 ft and has 2 floors which are 8 ft tall.

The volume of the home is 9,600 cubic feet. My Blower Door reading was 5,400.  I can now print a report translating what that all means to the owner of the home.
The test shows an air exchange rate of 33.75 per hour @  -50pa.  That rate of air leakage represents a hole in your home of about 3.75 sfT. The Blower Door reading for a house of this size (if it was built today ) should be about 480.  I would recommend this house be "tightened up" approximately 90%.
That "tightening up" process is called Air Sealing and I'll  start that conversation tomorrow.

 Now that I have the Blower Door and Manometer setup in the door and I have the home in "winter conditions" I can start the test.

  I'm testing to see how leaky the home is and there are two ways to do this.  The first method is to force the air out of the house.  The blower door fan sucks the air out and the manometer gives a reading of how much air is being forced out.  Basically I'm  relieving the pressure in the home.  The scientific pressure reading is calculated in Pascals of pressure. I can see your eyes rolling back -  you don't need what a  Pascal is just know that it's  a sensitive unit of measurement. I'm relieving the pressure of the house down to a negative 50 pascals ( -50pa).  This -50 pa is an industry standard pressure reading.
I simply read the cubic feet of air  (cfm)  being forced out of the home @ -50 pa and record that measurement.  The cfm reading is on the right side of the manometer.
This reading is related to the volume of air in the home. 
So I'm now off to  measure all the interior rooms and spaces that are being heated or cooled i'll discuss that process tomorrow.

In my last post I was plugging tubes into a control box.  What is that control box?  It's called a MANOMETER.  It is a very important tool needed to document the air leakage as it is at the time.  Conditions can change in the home so we need to record the conditions as they are now and then again after any changes.
 



Before operating the equipment I need to prepare the home.
by doing this:

• Close all exterior doors, windows and attic hatches
• Close fireplace dampener and cover ash with damp newspaper and tarp or seal off the fireplace with tape
• Open all interior doors
• Shut off any air handling units (AHU), dryer and exhaust fans
• Put water heater on pilot to prevent back-drafts while running

This is called  "putting the house in winter conditions".
I'm now ready to operate the blower door and the manometer.
Let the testing begin !!

This is one of our  Blower Door  air leakage testing units.
We use this to check the volume of air "leaking" from a home.

These units are used during

• an Energy Wise audit
• an air leakage test on a newly constructed home as required by the Rhode Island building codes.

The setup process is fairly simple.

• The red insert you see here is attached to an expandable frame that adjusts to the length and width of the door jamb.
• A flexible tube is poked through a little opening in the insert and placed outside and attached to the white fan that was set into an adjustable hole that surrounds the fan making it air tight.
• Another tube is attached to the fan and then to the manometer (I'll describe what the manometer does in a future post ) control unit in the upper left.
• The control unit turns the fan on and off and also controls the speed of the fan. 
  
• The fan is usually setup to push the air out of your home.  This negative pressure is adjusted to -50 pascals of pressure. ( I'll get to the definitions of pressure and pascals later on). 
  

That is it for the setup.  Pretty simple, no damage to door jamb, setup takes about 5-6 minutes.
This unit is going to suck all the air out of your home, it's safe around kids and pets.
That's all for today-  Happy Thanksgiving !!!!!