Posted by: Scott McCullough | May 30, 2013

Zehnder Commissioning & Blower Door Test

During the past week or two we have been getting the last few things completed that relate to the blower door test that would be done by Horizon Residential Energy Services on May 29th. One major part of that was getting the ventilation system commissioned by the engineer from Zehnder.

Since we installed the system ourselves I would be the only one to blame if something wasn’t installed correctly.  Fortunately everything looked fine minus a few minor adjustments.  Commissioning the system is primarily dealing with balancing the flow of the air throughout the house.  Aubrey uses a flow meter at each supply and return to make sure each has the appropriate cubic feet per minute flowing for each level of ventilation.  The whole system is controlled by a digital display that we installed discretely in our Kitchen pantry where it’s convenient to the cooktop.  Each bathroom has a wireless controller where the ventilation level can be changed.


The process took about an hour and a half.  I’ll probably mess around with the programming features to vary the ventilation to fit our work schedules.  The commissioning included a report showing a summary of measured flow rates:

3-0174-02.13 McCullough Residence Zehnder Commissioning Report

Before our blower door test we went around the house and addressed any air leaks that we hadn’t filled already.  We have a cord wood door that I added rubber weather sealing to.  Jess spray foamed where ventilation duct-work and hosebibs exited the house.  And although I closed the dampers on our woodstove, I knew that it would be a source of air leakage for the test.

Kevin and Andy from Horizon arrived and set up on the basement door, which was a bit of a curveball.  I was hoping they would use the front door that hadn’t been weather sealed yet, but it is too large for their blower door equipment.  But they allowed me to tape off the front door, I’ll send them pictures of the double layered rubber sealing that I’ll install later.


As the fan got going reducer rings were added which was a good sign.  The final reading came to 490 CFM, or .98 ACH at 50 pascals.  Not Passive House, but we were pretty satisfied with the number.  I think that if we did not have the woodstove we would have done better.  But if we were to do it again we would still have the woodstove.  The endless supply of free heat is not something to eliminate just for a better leakage rate.

Kevin walked around with his thermal imager to see how the envelope looked.  This is something I would have liked to spend more time on as we could have found where we had weak spots in our insulation.  The imager did show the obvious difference in temperature between the double pane and triple pane windows which was good to see.


In a few weeks we will have our final Energy Star Rating and we will also know how much of a rebate we can expect from our utility.


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