We’re making progress!
We’re completed the footers and Logix foundation. The factory built walls panels are also finished, awaiting delivery. Production of the Bieber windows is underway in France. The framers are installing the wood I-beams and floor deck. We still have to add some 4″ of EPS/Roxul insulation to the exterior of the Logix, but that’s not pressing. After the main floor deck is completed, the walls will be delivered and erected.
So it’s time to think about the remaining major component to the building shell – framing and sheathing the roof to get the building dried-in.
I rarely see new homes being built with anything other than factory built roof trusses. A Google search cited a 2008 National Association of Home Builders study that said 4 out 5 homes were being built with pre-manufactured roof trusses instead of traditional rafters. I suspect that percentage is even higher today. It’s easy to understand why:
- Trusses are factory built concurrently with other construction chores, shortening the overall construction timeline;
- Trusses allow much larger unsupported spaces than traditional rafters. The need for interior bearing walls is greatly reduced and perhaps eliminated;
- As roof shapes get more complicated, so does the skill level for calculating and cutting complicated rafter angles. It’s a task CAD + automation completes in the blink of an eye;
- A job-site crane easily and safely places the roof trusses on the walls, allowing for much quicker dry-in of the interior space, and avoiding potential damage to interior building components from prolonged exposure to the elements;
- A factory built truss is engineered and optimized to meet local building codes and load conditions such as wind and snow here in Maine;
- It’s green building friendly. The factory can optimize lumber usage. Trusses use more readily available 2 X 4 stock vs the larger, more expensive, older growth 2 X 10s or 2 X 12s used in stick framing a roof. It is also much easier to collect, recycle or reuse sawdust and lumber cutoffs in a factory setting than at a job site;
- Like factory built walls, factory built truss are assembled to the architectural design, so it puts a premium on the accuracy of the foundation and walls.
There was no question in our mind that we would use factory built trusses, and had several fabricators to choose from in the area. Hancock Lumber made our factory built wall panels, and often works with Aroostook Trusses in Presques Isle Maine.
Aroostook Trusses Inc. is a family owned small business in operation since 1996. It is located in a large aircraft hanger on the former Presque Isle Air Force Base, which closed in 1961. I was very impressed in my initial phone conversations with Sheldon Hyde, one of the Aroostook Trusses designers. Sheldon briefly described the CAD software he uses to design the trusses, and how the software is fully integrated into the manufacturing process. The software Sheldon uses to design the trusses is linked to the cutting machines on the shop floor to quickly measure and accurately cut the stock lumber. The software also configures a template on the assembly table where a seemingly random array of 2 X 4s magically morphs into a truss in minutes. I would later learn that there’s a full time quality control person who randomly inspects trusses under the protocols of the Truss Plate Institute. All sawdust and wood chips are collected and processed into playground mulch. Cutoffs are provided free to employees or the public for firewood. Metal scraps are recycled.
Sheldon incorporated several Passive House elements in our trusses:
- Raised Heel truss, and then some. Many trusses feature a raised heel (that portion of the truss that bears on the exterior wall) to accommodate more attic insulation at the eaves. We’ve got “stiletto heel trusses” with a 5 1/2″ higher heel than typical.
- Field applied soffit. The soffit return is typically included as part of the truss. We deleted it from our trusses, and will apply the soffit return on site. The framers will run the Adventech sheathing right to the underside of the top plate of the truss, then install the soffit return. That will greatly simplify air sealing the exterior wall and avoid wind washing of the loose fill cellulose insulation at the ventilated soffits in the attic.
- Abbreviated roof overhang along the south facade. The width of the roof overhang was calculated to shield the house from the high summer sun. But to achieve Passive House certification, we needed to optimize heat gain from the south facade. So Chris “sawed off” much of the roof overhang above these windows. In a northern climate, additional heat gain in the winter and shoulder seasons trumps occasional summer overheating. Our mini split HVAC system will economically keep us comfortable when the temps turn torrid.
I decided it would be fun to drive up to Presque Isle and watch them build our trusses. Yes, it’s a 300 mile, 5 hour drive north into Aroostook County, the largest county in the U.S. east of the Mississippi. Between Bangor and the end of I-95 in Houlton, there’s 110 miles of driving time to contemplate the mysteries of life and appreciate how heavily forested is the state of Maine. Once in Houlton, it’s up Route 1 through a succession of tiny towns and family farms to reach Presque Isle.
I had picked another glorious summer day in Maine for the trip. Presque Isle is in the heart of Aroostook County, best known as one of the top solanum tuberosum aka potato producing areas in the US. Many of the fields were in full blossom. Driving up there was a bit of a walk down memory lane for me. I had worked in Presque Isle with potato farmers for over two years….more accurately….three winters after I graduated from college.
It was a most pleasant trip. Oh yeah, here’s how Aroostook Truss designed and assembled our roof trusses.