The completed structure before roof membrane and strapping. The …
The completed structure before roof membrane and strapping. The trusses were set with a crane. In this view, you can see the diagonal 2×4 bracing for the truss system, and the metal spacers used to stiffen the top chords of the trusses.
A view of the truss system from below shows how the raised heels…
A view of the truss system from below shows how the raised heels of the trusses butt to the OSB skin of the second-floor wall panels. Strips of membrane hanging down from the wall plate will be used to tie the air barrier of the occupied space (created with smart vapor-control fabric), into the wall system air barrier (formed by taped OSB sheathing over the 2x wall frame). In this view you can also see the metal bridging used to space and stiffen the trusses, as well as the diagonal 2×4 truss bracing.
A closer view of the raised heel detail on the trusses shows the…
A closer view of the raised heel detail on the trusses shows the 2×4 bracing applied to the inboard side of the truss tail, and the wall system’s OSB skin (which extends up to cover the truss heels).
Another view of the diagonal bracing applied to the truss web ch…
Another view of the diagonal bracing applied to the truss web chords.
A view of the roof eave juncture shows the first course of Pro C…
A view of the roof eave juncture shows the first course of Pro Clima Solitex Mento Plus applied to the roof framing, and taped to the Solitex Mento Plus on the wall panels to create a continuous weather-resistive barrier for both wall and roof. The wall panels’ strapping was applied in the shop; similar strapping for the roof will now be applied in the field.
This view shows the first vertical strapping pieces applied to t…
This view shows the first vertical strapping pieces applied to the roof truss top chords through the Solitex Mento membrane.
A carpenter applies horizontal 2×4 strapping to the roof over th…
A carpenter applies horizontal 2×4 strapping to the roof over the 1×3 vertical strapping. This creates a space allowing air movement in all directions. Solitex Mento membrane is air-tight but highly vapor-open. The insulated space beneath the membrane will be able to dry into the vented air space created by the strapping. The horizontal 2×4 strapping will provide nailing for the metal roof, to be installed next.
Using the lower courses of 2×4 cross-strapping for footing, a ca…
Using the lower courses of 2×4 cross-strapping for footing, a carpenter extends the vertical 1×3 strapping farther up the roof, working towards the peak.
Using a spacer block, a carpenter applies more courses of 2×4 cr…
Using a spacer block, a carpenter applies more courses of 2×4 cross-strapping to the roof.
This view of the roof ridge shows the completed strapping system…
This view of the roof ridge shows the completed strapping system extended all the way to the roof peak.
A view from the ground shows the completed roof strapping system…
A view from the ground shows the completed roof strapping system.
Last month, JLC traveled to the job site in Blue Hill, Maine, to see a panelized Passive House wall package being set up on site by the Belfast, Maine, company EcoCor (click here for last month’s slideshow). Those were the walls — but what about the roof?
According to EcoCor owner and technical director, Chris Corson, EcoCor has invested in a 50-foot framing table that will let the company build roof panels on a design similar to their concept for wall panels: an inner air-tight assembly made with dimensional lumber and sealed with OSB taped at the seams, married to an outer I-joist frame that can be packed with dense-blown cellulose.
But that panelized cathedral roof system is the plan for the future. For the current job, EcoCor built a truss roof the old-fashioned way, booming in trusses one by one and stiffening the structure with 2×4 diagonal braces. Then the crew attached highly permeable Pro Clima Solitex Plus weather-resistive barrier membrane to the top of the truss chords, taping the roof membrane to the wall membrane to create a continuous wind-tight and water-tight skin for the entire shell. Then, working their way up the roof, the crew attached a cross-hatch system of strapping to the roof, making an airflow space above the membrane and creating nailing for the building’s metal roofing. The result is a roof that sheds water and dries to the outside. For a closer look, click through the slideshow (all photos courtesy of EcoCor).
