There are stories behind every community member, program and insight we uncover, and here is where you’ll find them. Read on to learn more about how we think, what we’re up to and what drives us.
Innovating the Box
"Our industry is begging for innovation," says Harris Woodward of Finish Werks, a custom builder in the Baltimore, Md. area. He claims to have found that innovation in modular.
Some builders go deaf at the first mention of the M word, with visions of cheap, HUD-code homes and customers fleeing in the opposite direction, but Woodward dismisses such fears. He insists that modular will support any branding message a builder wants to convey.
Finish Werks uses it to support a brand centered on high performance construction. The company builds Net Zero energy homes that are so well insulated and air sealed that a few solar panels on the roof can, on an annual basis, satisfy all their heating and cooling needs.
He doesn't even need a boutique module maker to pull this off. He uses the same manufacturers conventional builders do, although he gets them to customize their boxes somewhat and has a process for air-sealing them on site.
And rather than being complicated, this approach is something any builder who wants to can pull off.
Although Woodward has been a modular builder since 2004, he didn't turn his attention to high performance until '08, when he needed a way to stay profitable in a collapsing market without chasing other builders to the bottom of the price scale. "I wanted to differentiate my company from builders selling on price," he says. "As Wall Street was crashing, I noticed people trading in their SUV's for Priuses, so I decided to go green."
Modular manufacturers were starving for work so they were willing to try details that were new for them at the time. "I showed them how to build zero-energy wall assemblies using standard construction and off-the-shelf materials."
One reason they came around is that he wasn't asking for anything radical. The products and energy details in his modules include:
2x8 studs placed 24 inches on-center
1-inch, R-5 XPS exterior foam board, typically Dow Styrofoam
The industry doesn't make a fiberglass batt for 2x8 walls. His solution is to use high-density R-30 attic batts that, when compressed, deliver an in-place value of R-28. The exterior foam brings the total wall R-value up to 32.
Some module manufacturers have the ability to apply spray foam to the ceiling plane below the attic, while others don't. In the latter case, Woodward recommends specifying modules with un-insulated ceiling joists (attic floor), so that crews can air seal around plumbing vents and wire chases on site. Then the insulation contractor can blow R-49 loose-fill into the attic.
Because good windows are crucial to a zero-energy home, the manufacturer needs to buy the highest quality glazing from their preferred window supplier. "Instead of regular Energy Star, you need to get super Low-E windows with Krypton rather than Argon gas."
The envelope details add about $10,000 to the cost of a 2400 square foot home, but the homeowners typically see their energy bills cut by half before any renewable energy is installed.
Woodward now serves on the board of the Modular Home Builders Association and NAHB’s Building Systems Council, where he is educating manufacturers and builders on the value of high-performance detailing. He says that a lot more factories are willing to provide those details than when he first started. According to Bruce Bingaman, sales manager at Icon Legacy Custom Modular Homes near Harrisburg, Pennsylvania, builders who want this type of customization should help the manufacturer understand why, so they can finish the details correctly. "Harris didn't just ask us for a set of product specs," says Bingaman. "He explained the building science behind those specs, and how they would help him meet his Net Zero goals."
When Woodward first started down this road, some manufacturers balked at shipping walls with 24-inch stud spacing. "Wide spacing stud bays make transportation departments worry about drywall cracks." However, he reports no more problems than with 24 than with 16-inch spacing. "I even offer to sign a hold harmless on drywall cracks." He says that the manufacturers he works with are less hesitant now that they see it doesn't cause problems.
Of course the energy detailing doesn't stop when the modules are loaded on the truck for delivery. Some work needs to be done on site.
Part of this is in the foundation. Maryland homeowners want full basements, and homes appraise better when those basements have finished living space. To keep his basements warm and dry, Woodward uses precast foundation panels from Superior Walls, which come pre-insulated to R-12.5 and have integral studs that will accommodate R-19 batts. His foundation sub also puts 2-inch R-13 Polyiso R Max or Thermax insulation board beneath the entire slab to thermally break it from the ground.
The rest of the site work is focused on air sealing. Low air leakage is a hallmark of an energy-efficient home and Woodward says that modular makes that easier to achieve because the adhesives used to glue drywall to wall studs and ceilings to top plates is a great air sealant. To complete the job, however, crews need to do some additional air sealing during the set.
They apply caulking between the sill plate and the concrete. (It's more effective than conventional sill sealer only because the Superior wall panels are dead flat at the top.)
Wherever modules meet – known as the marriage line – they apply commercial-grade polyurethane spray foam in the floors, walls, and ceilings.
After the modules have been set they foam the area around the sill plate from the inside, and all other penetrations created during the installation of electrical and mechanical systems.
The result is exceedingly tight structures. Since Maryland adopted IECC 2015 over three years ago, all of Woodward’s homes are tested with a blower door to confirm an air infiltration rate of no more than 3 air changes per hour at a negative pressure of 50 pascals (3ACH50). His homes come in at just over 1 ach 1ACH50. They also earn an average HERS rating Index of 40 and need just 7 kilowatts of PV to get to Zero. By comparison, a home built to energy code minimums (IECC 2012 or 2015) would score 75 and require 10-11 kilowatts.
The Bottom Line
How hard is it to get Woodward's results? While none of this is complicated, he admits that it's a different way of building that requires a learning curve. Fortunately that curve is short.
"You need to do three homes," he says. "One the first one, you can expect to have some problems. On the second one, you will get most of the kinks worked out. After finishing the third house, you will have worked out all the kinks and you won't look back."
He says that homeowners love the result and that he hasn't heard negative comments about modular from any of them. They just want a builder they can trust to do good work, which is why he makes it a visible part of the quality message on his website. "If you build a reputation as a high-performance builder, any questions about your quality go away."