Off-site Construction

Unity’s Better Way to Build is based on a proprietary design system, off-site construction and on-site assembly. Much of the work on each home is done by computer-controlled (CNC) machines in our state-of-the-art panel production facility in Keene, NH. But the people operating the equipment and the highly-evolved processes that we’ve developed to manage the work are just as important as the machines themselves.

A Highly-Evolved System

Before the first piece of lumber for a house has been cut, we know the size, location and material of every part and piece that will go into the building shell. This information is embedded in the 3D computer model of the home. We also know the sequence in which the panels will be assembled into the shell on site, and this dictates the order in which the panels are built in our shop.

Unlike on typical job sites, where materials are delivered sporadically and often exposed to the weather, we purchase our lumber and sheet goods in bulk, and store them inside until needed. Thanks to our practicing the principles of Lean manufacturing, the supplies that we use on a daily basis are stored where the work is happening, and mobile tool carts customized for particular processes mean that time isn’t wasted searching for the proper tool.

The shop setting also allows us to use back-saving equipment such as vacuum lifts, rolling carts and fork lifts that are simply not feasible on job sites.

Computers and Sawdust

Sawdust begins to fly—or rather, it’s captured by our dust collection system—at the CNC milling center called the Speed Cut 3. An automated vacuum lift system loads long lengths of lumber onto the infeed table of the Speed Cut, which then grabs each piece in turn and saws, drills and mills it to the precise size and specifications dictated by the computer model. As a final flourish, the Speed Cut prints a unique part number on each piece, so that it can be cross-referenced to the 3D model as needed.

The various parts and pieces are grouped by component (panel) and transported to one of three production lines: floor panels, roof panels and wall panels.

IN THEIR OWN WORDS
Facility Tour
MIND BLOWING IMPRESSIVE

Mind blowing impressive is the only way to describe your facility. Definitely the future.

Bruce F, Developer

Floor Systems – Our Simplest Panels

Floor panels are built on our “open cavity” line, a basic set-up that includes framing tables at a comfortable working height, nail guns and a vacuum lift. The joists and rim material are nailed together, the framing is squared by the table, and ⅞” Advantech subfloor is installed. The panels are then stacked and bundled for shipping.

Roof Panels – with Insulation and Interior Finish

Our roof panel line is more extensive than the floor panel set-up, because roof panels require insulation and air sealing, and we may install either sheetrock or prefinished boards on the interior surface.

As with the floor line, our roof panel fabrication begins with the kit of parts that have been milled by the Speed Cut 3. The framing is nailed together and squared, and the outer layer of sheathing is installed. We also frame and sheath the roof overhangs, because it’s much easier to do that in the shop than in the field.

The panels are turned over with the help of a bridge crane, and then insulated by our automated Iscocell equipment. Cellulose is packed densely into the rafter bays by being blown through ports in a large metal platen. Thanks to our 3D model of the home, the system knows how much cellulose to install in each bay to achieve the desired density of 3.5 to 4 pounds per cubic foot. Periodically we will double check the density by weighing core samples of cellulose taken from a panel.

Following insulation, we install an inner skin of oriented strand board (OSB), taping the seams to ensure airtightness. If the roof panels will enclose vaulted living space, then we typically install the finish material—either sheetrock of prefinished boards—on the panels. They are then bundled and wrapped, and moved out to our storage yard.

Wall Panels – Automated Fabrication of Complex Assemblies

Our wall panel takes up the bulk of the production space in our shop, and contains the most automated equipment. Wall assemblies for high performance homes are relatively complex, because in addition to providing insulation and an air barrier, walls support second floors and roofs, they include windows and doors, they hold siding, and they need to accommodate electrical and plumbing work.

As with the floor and roof panel lines, all framing members for wall panels are machined by the Speed Cut. These pieces are then fed into the Weinmann framing line, where top and bottom wall plates are automatically nailed to studs that are positioned by stops. Rough openings for doors and windows are pre-assembled on a framing table, and fed into the wall line as needed.

Interior Sheathing

After the wall framing has been “extruded,” the interior sheathing layer is tacked in place, and a multifunction bridge nails off the sheathing. The sheathing is then trimmed at the edges and rough openings by the bridge’s router.

After taping the sheathing joints for airtightness, we install the 2×3 service layer that provides a chase for wires and pipes on the interior face of the panel. The panel is then flipped over using a butterfly table—two adjacent tables that raise the panel to vertical and then lower it down on the opposite side.

The wall panel line has its own Isocell equipment for dense-packing cellulose insulation into the stud bays. When required for third party certification, we photograph each panel after it has been insulated, before we enclose it with exterior sheathing. Unity installs a continuous layer of wood fiberboard insulation as the exterior “weather resistant barrier.” The sheathing is fastened and trimmed by a second multifunction bridge. We then add strapping to create a ventilated “rainscreen siding” detail.

With framing, insulation and sheathing complete, the wall panels are brought vertical by an “upraiser table,” and then slid into a gantry system for the installation of windows and doors.

Windows and Doors

Installing windows and doors properly can be challenging on job sites where bad weather, inadequate training and lack of the proper materials can result in failures. As with all of our processes, we’ve been developing and improving the way in which we install windows and doors for many years. Standard operating procedures, specialized tools and the best tapes, gaskets and fasteners ensure installations that are air- and water-tight.

Whereas floor and roof panels are stacked horizontally for transport, the completed roof panels are organized in vertical bundles before being wrapped and stored prior to shipping. Each bundle is labeled with the job name, the contents and the weight, so that it can be loaded and delivered to site at the proper time.

Parallel Processing

One of the many benefits afforded by off-site construction is accelerated construction schedules that result from parallel processing: while the site is being prepared and the foundation put in, we are fabricating the panels that will become the high performance shell of the home. Typically our work in the shop is completed before the site is ready, and we are able to arrive on site to assemble the shell as soon as the foundation is complete.