Decisions! Decisions!

Brabble Insulation Fills the Gaps

Who has seen the wind?

Neither you nor I,

But when the trees bow down their heads

The wind is passing by.

Christina Rossetti

Writing this entry about insulation and its effect on the comfort of the house evoked some wonderful memories of growing up in North Carolina in a time before air conditioning was the norm. I do remember living with storm windows when I was a teenager, but I can’t think when it was that we first had air conditioning at home. In the summer, it was common to close the blinds against the heat of mid-day, opening them again when the sun was lower in the sky. At my own childhood home, summertime meant that the windows were always open, and the sound of the screen door slamming cheerfully meant that the arrival of summer was official. We had oscillating fans and cardboard fans and community pools…all of which worked fine for my home town. I remember waking up to the sound of my neighbor trimming her rose hedge and the smell of mown grass. During summer evenings, the grown-ups sat outside drinking sweet iced tea and talking while we children ran the neighborhood and played. That was a wonderful time, and I miss the freedom of having the outside and the inside blending together.

In the early years on the Outer Banks, most houses were summer homes and had no insulation. The houses were built to stay cool with balloon framing, which also contributed to their being able to dry out. The first cottages in Nags Head were faced with either juniper or cypress shingles, and interior walls would be made of knotty pine. Although things might get wet over and over again, the sea air and the sun dried it all again. I sometimes wonder if it is crazy for us to want to live by the sea all the time and to do all of these things to make that life possible. From my personal perspective, I often think that simpler is better and that most of the time we can be fine with what’s what, but at the same time we want to house to stay in place with us in it for a very long time.

Our house is now fully insulated, thanks to the great guys at Brabble Insulation. They used a combination of closed cell spray polyurethane foam and unfaced fiberglass batts to get to R50 in the roof, R40 under the house, and R28 in the exterior walls. Unfaced fiberglass batts were used alone between the floors and in the interior walls, primarily for sound reduction. For the exterior shell of the house, we would have preferred to use only foam insulation, but that would have been extremely expensive for not an incremental gain in insulative value.

What is spray polyurethane foam, and why is it such a good idea for a coastal environment? For our application, Brabble used InsulStar, a 2 lb/ft3 closed-cell foam from NCFI, a North Carolina company based in Mt. Airy, NC. NCFI produces spray polyurethane foam by “mixing two chemicals, polyol and isocyanate, in the presence of catalysts and other additives using a specially engineered spray applicator system.” When the chemicals are mixed, they expand to form adhesive foam that sticks to everything it touches, hardens, and seals the surfaces. The foam expands 20 to 30 times its liquid state to fill cracks and crevices, providing a solid air and moisture barrier that “stops air leakage in and out of your home, reduces noise, and blocks dust, pollen and other airborne pollutants.” For us, the application of a moisture barrier was the primary reason for choosing the closed-cell foam, especially since we sealed the outside of the house with the Grace Perma-Barrier House Wrap. Not following through with a low permiance barrier inside the house would have risked the integrity of the sheathing, knowing that any moisture that penetrated the sheathing would be stuck there rotting the wood.

An equally important benefit of SPF is that it reinforces the exterior sheathing and studs, increasing resistance to “racking” from hurricanes and other strong wind events. Racking is a structure’s response to a shearing force, causing the house to distort its shape from a rectangle to a parallelogram. For example, a strong wind blowing hard against the front wall of a house applies a shear force to a side wall, literally pushing or pulling it out of shape so that the house can topple over. Simply put, SPF makes the walls harder to push or pull. That is an amazing benefit!

Because there are no penetrations in the roof and a conditioned attic, Vince wanted to use 3 ½” of SPF covered by 10 inches of unfaced fiberglass batts. This specification for insulating the roof deck became quite a challenge. It was important that the two types of insulation abut, both for the accumulated R value and to be sure there was not an open space to accumulate condensation. Since the roof was constructed of open web trusses, there was no good way to attach the batts. Karl had the great idea for Currituck Construction to fur down the rafters to provide a support web, and Brabble used nylon webbing to strap the batts in place. It was a terrific system. There are alternate methods for doing a job like this, as in long stick pins that go through the batts and adhere to the roof deck, but this was a much easier and cleaner method. Vince and I really appreciate Brabble’s willingness to do this extra step to give us what we needed in the roof. As in so many of the house systems, not being able to have the correct R value in the roof would have resulted in stressing the HVAC system, skewing the application of Steve Jenkins’ Manual J calculations and leading to less energy efficiency.

Because of his particular interest in energy efficient homes as well as in the quality of his own work, Pat Brabble offered to conduct a Blower Door Test on the house, even though the house was newly insulated and neither drywall nor woodwork had been installed. Pat is no longer a credentialed Blower Door test GUY, but he is trained in its administration and able to “score” the results. A Blower Door Test is basically an energy audit to determine a home’s airtightness. Establishing the building tightness shows how to lessen energy consumption due to leakage, avoid moisture condensation problems, and eliminate uncomfortable drafts. Basically, a Blower Door consists of a frame and flexible panel that fit in an exterior doorway, a powerful variable-speed fan that mounts into the frame, a pressure gauge to measure the pressure differences inside and outside the house, an airflow manometer and hoses for measuring airflow. The fan either pulls air out of the house, lowering the inside air pressure OR pushes air into the house, increasing the inside air pressure. Pat did the test for us both ways. Here’s how it works: If the house is DE-pressurized, the higher outside pressure pulls air in through all the unsealed cracks and openings. If the house is pressurized, the higher inside pressure forces air out. Auditors sometimes use a smoke pencil to detect air leaks, but Pat’s guys were happy to use lit cigarettes instead. By following the smoke and listening to the sound of the air flow (it’s LOUD!), the leaks can be found and then sealed. Blower Door Tests can be either calibrated or uncalibrated. An uncalibrated test only detects air leaks but doesn’t measure the overall tightness of a building.

The Blower Door Test measures the air exchange rate for the total volume of the house, expressed as Air Changes per Hour (ACH). A good score for a completed house is .35, which means that all of the air in the house is exchanged with outside air every 3 or so hours. That is roughly the equivalent of having a small window open all the time. A good score would qualify a home as an Energy Star House and make available various tax credits. Our test results came back as .08, which is phenomenal, especially considering that the house is not complete. Pat will come back and do a “final” Blower Door Test for us when the interior is finished just for his own satisfaction, but BC Custom Builders may also want to have an official test done by Dominion Power to help in green building qualification assessments. Having a score of .08, which will surely be less the next time, lets us know that the house is very tight, which is good, but also that the use of the Energy Recovery Ventilation system is really important in providing good indoor air quality.

Here’s a little video that shows the Blower Door Test:

Vince and I would highly recommend Brabble Insulation for any job. These people were just great to work with, and the work was beautiful and neat. They even put straps on the fiberglass batts under the house so that it would stay in place until the underpinning could go on. There was a level of hard work and professionalism that is gratifying to see and to enjoy.