Blower Door Test #1

Big item this week is that we did our first blower door test. More on this below.

Spraying closed cell foam. They did 2.25”+ of this on all of the walls. This provides insulation and seals things up to prevent leaks.B1200BlowerDoor 100

A tool they use to scrape off excess that could interfere with sheetrock.B1200BlowerDoor 101

It’s important to get every nook and cranny where air may leak in or where cold/heat can transmit through. Interesting fact: wood transmits cold/heat better than air. This is why all of the studs are called thermal bridges and why a full layer of exterior insulation is important. Here he’s spraying the rim joist.B1200BlowerDoor 102

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The insulation folks accidentally sprayed closed cell foam on the steel flue for the indoor fireplace. Since the foam is flammable that’s a no-no. So they hired some folks who can ’sand blast’ with dry ice. Here is their compressor, air cooler and air dryer. 
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Blue coolers are filled with dry ice.B1200BlowerDoor 105

They pour the dry ice in to the Cold Jet which grinds it up to a consistency similar to sand, mixes it with the air stream from the compressor and sends it to the gun.
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The gun. He has a number of different tips of various shapes that he can put on here.B1200BlowerDoor 106

Blasting away the foam insulation.B1200BlowerDoor 108

It was a humid day so a lot of water blowing out of the bottom of the dryer.B1200BlowerDoor 109


A blower door test increases or decreases the pressure in the house, typically by 50 pascals, to measure air infiltration. The less infiltration the better.

This first test is sometimes called a prescriptive test because it’s purpose is to find and seal leaks. To do this they raised the interior pressure, filled the house with smoke and then looked for places where the smoke was moving to find leaks. There were a couple of small leaks found but nothing major so everyone was quite cheerful. Later on when they measured the leakage it showed 3.32 @ ACH50. It should have been close to 1.0 so this was disappointing on two levels. First that the house is leaking so much and second that their leak finding earlier in the day clearly failed.

I was once again frustrated that we’d not done exterior insulation as that results in a much tighter house with fewer leaks. Exterior insulation also reduces thermal bridging through studs and problems of frost building up on the interior of the house due to small gaps between adjacent studs.

Our insulation contractor is working to figure out why it is so leaky and fix the leaks. Then we’ll do another blower door test.

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Things that will naturally be sealed after the house is complete had to be temporarily sealed for the test. Here they used cardboard and spray foam to seal off the access to the chimney that is needed for installing the fireplace flue and more recently for blasting foam off of it.
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Why this is called a blower door test. The concept came out of Sweden in the late 1970’s. Folks at Princeton, Lawrence Livermore and the University of Minnesota worked on variations of it but the real breakthroughs came from a company called Minneapolis Blower Door. We had one of the first blower door tests done on our current house. Since it was so new we had the actual developers doing our test which was fun. We also did some interesting explorations on our house like measuring bath fans, clothes dryers and our range hood to see how much air these drew. The bath fans and range hood drew far less air than they should have according to their specs.

We then built a fire in our small fireplace and found that it drew about 400 CFM. That’s a lot. We then added our larger fireplace and it was 600-800 CFM. Later we installed a make-up air system to bring in outside air for our fireplaces. This was in 1989.
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Dan dug out the dirt below the steel angle iron that had to be installed for the stone on the conservatory. (There was a stone ledge but the plans were drawn 7” narrower than the Conservatory called for so they had to put block on the stone ledge to build out the 7” and thus angle iron outside of that to support the stone.) He then put sheets of foam in below the angle iron. This is so that any freezing and thawing will not push up against the angle iron and cause cracks in the stone.B1200BlowerDoor 114

The duct for our range hood. Ideally there should be no bends. Bends introduce static pressure which reduces the effectiveness of the hood and they can cause increased noise. The house had been designed specifically to allow for a straight duct for the range hood so we’ll have to see how much of an issue this is and what can be done to fix it if necessary.B1200BlowerDoor 116

This is the muffler for the range hood duct. It will reduce noise from the blower which will be in the attic. The muffler is about 4’ long and nearly 2’ wide.B1200BlowerDoor 117

Dan installed lintels over the door and window for the sauna.
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Beginning stone on the north end of the porch.B1200BlowerDoor 115

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I’ve spent a considerable amount of time watching these guys. Stonework like this involves a fascinating combination of effort, skill and art to get it right.B1200BlowerDoor 120

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Looking down from my office in to our master bedroom. This and other areas will be filled with insulation to reduce noise when I’m working late and from the HVAC that is behind me. HVAC noise is also transmitted through the wood structure as vibration (the structure and sheetrock effectively become a large speaker) so they’ll use isolation hangers and other bits to isolate the equipment from the structure. 
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