North Carolina Passive House: Spray Foam, A blower door test, more spray foam, and another blower door test

At the end of last week we had most of the roof spray-foamed and conducted our first blower door test and found that the envelope wasn't holding air to that Passive House standard (which is .6 air changes per hour under 50 Pascals of pressure). We had the spray foam experts back yesterday to attack the trouble spots. In particular there were 5 places where for structural integrity the BCI (I joists) were doubled up in the roof system. Well, by doubling those up it creates a void between the two joists and since those joists run from the ridge of the roof all the way to the outside of the soffit, they were acting as a perfect channel for air into the house. The spray foam troubleshooter blew foam into the gap through knock-outs in the beams and filled them to stop the airflow. He also attacked a corner of the house where the apparent leakage was highlighted by "natures thermal imaging" - the frost formation on the roof yesterday morning showed us where the leakages were occurring in a pretty amazing way.

Yep, that's the spray foam tech laying on his back in the rafters spraying foam into the smallest of crevices he can find.

And when you can, you use scaffolding to get into the right position.

The left side is before appcliation, the right is after.

And the contortionist continues - he's hidden a bit by that vent pipe but he's there hitting the space above the stairwell window.

In addition, there were a few small areas that were missed on the initial application of foam, including along the sill place between the walls and the knee wall and gable ends. Again, the troubleshooter foamed over all those missed areas.

Today we ran another blower door test and the numbers (depressurization and pressurization) averaged out at .62 ACH at 50 Pa. The average is from the pressurization at .70 ACH at 50 Pa and depressurization at .53 ACH at 50 Pa Still not what we hoped for so we used smoke to find the leaky areas. A couple areas that turned out to be problems were the corners where the roof and soffit meet at the tops of the concrete walls. Tomorrow we'll attack those sections with a combination of housewrap, caulk, and GreatStuff sealant to seal them up properly. Once that's done we fully expect to drop the numbers below the required Passive House standards - and that's before the caulking/painting and before the roof goes on.

The blower door installed and ready to go - basically a flexible frame that replaces the door with a variable speed fan that adjusts to get to the desired pressure (in our case 50 Pascals)

Jamie at the controls of the test station - this computer samples the pressure differential between inside and outside as well as calculating all the variables to provide the results. You have to change the fan physically to change from pressurization to depressurization.

Speaking of the roof, the panels were delivered today- they came in 8 crates and are cut to size to fit the roof. The longest sections are 37 feet long and the shortest are about 3 feet. Minimal cutting will be required on the panels but some will be necessary for the angles where the garage roof meets the front of the house under the clerestory.

Today the septic field installation also got underway - they started by meeting with the County inspector to discuss the field location and then started clearing paths through the trees to lay down the pipe. Tomorrow they'll finish clearing a couple more trees and then trench for the lines and dig the tank into place.

Though it's still not fully light, it's evident by the lines running up the front section of roof to the skylight that there's a problem with the air sealing at the double BCI points in the roof.

This is a section of the spray foam that was inadvertently missed the by the first spray foam tech.We knew this was going to get reapplied but it validated the "frost test." The left to right line of dark is where the overhang/soffit is - no insulation there and therefore the frost pattern is different.

Here's another double-BCI but the more interesting thing is the small section at the corner that has a n obvious insulation problem.

THis is a picture of the back from the best vantage point to see the frost lines. Harder to see problem areas but there is one in the lower left corner of the roof.

A view with a bit more light and from farther away - note you can clearly see the "problem areas."

East end of the North section of the roof.

North Center section of the roof - note the two lines leading to the skylight and one leading to the inner wall of the clerestory. You can also see the bump in the wall section near the front door which shows the same frost line differences where the roof is insulated.

In honor of Halloween - this was Dee's entry into the Bynum pumpkin display. Pumpkins provided for folks to carve and it's amazing to see what you can do with a pumpkin - from faces to animals, a brain, houses, Battlestar Gallactica, and even one where "people" were sitting inside the pumpkin enjoying the warmth of the fire (the candle).