Blower Door - Slight Disappointment

Ok, we had what was supposed to be the second and LAST blower door test, but I am not happy with the result and I may have Dean Benton of Benton Green Energy come again after I have fixed some problems. 

Blower door reading on August 6, 2014

You may recall that a blower door test helps determine how much air leakage you have through the building envelope. The test involves putting a fan in an outside door frame and depressurizing the home to accentuate the air leaks. The house is depressurized to a level of 50 pascals which is about equivalent to the force of a 20 mph wind on the home. There are 2 main values that you get from the test - one is directly from the manometer as shown above and one is calculated based on the volume of the house. This article, Blower Door Basics by Martin Holladay on Green Building Advisor (GBA) explains it much better than I ever could.

Blower Door Set-up while we were at the rough-in stage. 

The number shown on the manometer above is called cfm50 or the amount of air that moves through the home at 50 pascals of pressure. The other number is ach50 or air changes per hour at 50 pascals.

Our previous reading was 98 cfm 50. The above reading is 235, but I think it leveled out at 220. In any case, the number has more than doubled - 2.4 times greater than the last blower door.

What happened??

Well, I have some ideas.

What do you think about this dryer vent? Do you think that there is some leakage around this pipe?

Dryer vent through the wall, not sealed around the vent pipe. This was installed AFTER the first blower door test.

What about the vent cover for the kitchen fan? Do you think that those little plastic louvers seal out air?

This flimsy plastic piece covers one of the fan vents. A similar cover was on the dryer vent. 

Now the photo below may show a less important air leak. This is the inside view of the Lunos e2 - a heat recovery ventilator (HRV) that exchanges outside air for inside air. It does go through the wall in large tube. We did seal the tube to the sheathing inside and out before the walls were closed in. Still it is designed to move air through the home. You may wonder why we go through all the trouble to seal up every possible hole in the building envelope and then deliberately install a fan to exchange air. Well, when you have a very well air sealed home, you need to move more fresh air through for the inhabitants, but it needs to be filtered, conditioned air, not random leaks. That's what the HRV provides.

Lunos e2 Heat Recovery Ventilator (HRV)

The reason I did not calculate the ach50 is because I am confused about the volume of the house. The house is a Cape Cod design with kneewalls and sloped ceiling upstairs so I don't really know what counts as the house or not.

For example, the space above the bathroom and the bedrooms is not really sealed off from the rest of the house. It is within the thermal envelope of the building. Do I count that? I think so, but I am not sure. I am going to post a questions on Green Building Advisor to get their advice.

Area above the bathroom. You can see the Intello Plus smart vapor retarder from 475 High Performance Building Supply. The ceiling joists are insulated with dense pack cellulose. There will be a small door that fits in the opening. It does not set tightly to the frame, however. Is this within the thermal envelope?

So, the big change from the rough-in stage to almost completion (I know, almost completed at 18 mos later - crazy ) is the vents. We taped cardboard over the area where the vents were during the first test, but I don't know if you tape over vent covers when you go for the final test. That's another question for the knowledgable people at GBA.

I'll let you know more later. Thank you for visiting here. 

An Air Sealer's Work is Never Done

Well, we are back at it - working on the house again.

No, we do not have our construction loan yet.

Yes, the house is gradually nearing completion.

Yes, this drives me crazy. But we do have assurances that the construction loan will go through. Our contractor is willing to go ahead and get back on the house despite not having the actual loan yet. Thank you, Randy.

Anyway, so I am trying to get to some additional air sealing details. These photos show the water supply Pex tubing in the kitchen which runs from the mechanical room under the floor to the kitchen. In other words, this tubing bridges the thermal envelope. The plumbers sealed it with the orange foam in a can. You can see that the Pex tubing is not completely sealed to this extreme air sealer's standards. The orange foam doesn't cover the entire side. In addition if the tubing moves as in the 3rd photo, it opens up and fails to maintain the seal with the tubing.

So what does a good Air Sealing Specialist do? The choice is tapes or flexible sealants. For this area I choose tapes to make a good seal with the tubing.

I used Pro Clima Unitape with a flexible hole in the center to run the pipes through. 

Then I reinforced the seal with one of my favorite tapes - Pro Clima's Tescon Vana.  Love this stuff. I also use it on holes in my work jeans. 

For the vent pipe, I went with Siga Wigluv tape. 

One area I have to air seal and I don't really know how is around the electrical boxes.

It's not really needed because the boxes are in a space in front of the insulation layer and do not penetrate the thermal envelope. (Remember the thermal envelope on this house is sealed at 3 levels - taped on the exterior,  taped and caulked on the inside every single stud bay, then the dense pack cellulose was blown into the stud bay covered with a completely air sealed vapor permeable membrane, Intello Plus. I still like the idea of having redundant layers of air sealing layers so I do want to seal around the boxes. Not to mention that the inspector said we have to because that is where the thermal envelope is usually sealed and that is what they expect. But I don't really know how to do this. More internet study.

We are getting ready to tile the mechanical room because we need it so we can have some heat. We've chosen a wood look tile from Home Depot that is only $2.39 sq. ft. John really likes it. 

I'm going to install it over Schluter Ditra membrane to uncouple the tile from the floor to help prevent cracking. I figure in the laundry room I need to do that.

Well, that's sort of where we are now. Lots more going on - 4 inch red oak floors have already been  installed, doors will probably be installed tomorrow, followed by window trim. So we are getting somewhere. I'll try to keep you better informed the last half of this month. 

Proposed Wall assembly

Here is a drawing of the proposed wall assembly.

The R values (resistance to heat flow) of each layer of the assembly are outlined below:

2" x 6" stud wall = 5.5 inches x 3.5 R value/inch = 19.25
2" layers Roxul Comfort Board* = 2 inches x 4.2 R value/inch = 8.4
1.25" layer of Roxul Comfort Board or insulation in service chase = 1 inch x 4.2 R value/inch = 4.2

Total R value = 19.25 + 8.4 + 4.2 = 31.85

*I just looked at the Roxul website and the thickness of the Comfort Board is listed at 1.25", 1.5", 2", 3" so we may have an R-value about 2 higher if we use 2 layers of the 1.25" board.

Also we will probably use HardiPanels rather than HardieBoard sheathing.

3 postings in a 24 hour period. Pretty impressive, huh? I even skied a little bit today. Last day of skiing is tomorrow which always makes you a little sad.