Special delivery: rethinking modular construction
By Tim King
SINCE HENRY FORD started his first assembly line, people have understood that the most efficient way of consistently constructing a high-quality product was to do so in an environment that was designed specifically for accomplishing those tasks.
Not only is this method of manufacturing efficient – producing the highest number of widgets with the least amount of effort and energy – but when highly trained, specialized workers are adequately supervised and parts are regularly inspected, factory assembled products also deliver consistent quality, and typically at an affordable price.
Throughout our history, the ability to affordably produce large quantities of high quality products such as automobiles, clothing, tools and electronics has given many more people the ability to purchase them and enjoy the benefits they provide.
Slowly, this same model is being used to help wring some of the cost out of producing another complex product – healthy, high performance homes.
As concerns about residential energy use and its connection to climate change continue to affect how homes are designed and built, an increasing number of homeowners are demanding that their new homes not only look good on the outside but use less energy on the inside, too.
While many builders and homeowners are perfectly satisfied to build and live in homes constructed in accordance with the Maine Uniform Building and Energy Code (MUBEC), others are taking matters into their own hands. Instead of building “up-to” code in order to obtain an occupancy permit, forward-thinking homeowners and building professionals are designing homes with a fundamentally different approach.
Builders are focused on better ways to keep the heat inside the home where it belongs. With less heat loss, less new heat needs to be produced, greatly reducing the energy needed to produce it.
Heat. Keep more, use less. Be happy.
Offsetting the never-ending force of heat energy that always wants to go “from where it is to where it ain’t” requires a keen attention to detail. Think of it this way: instead of trying to visualize a scattered collection of small, insignificant channels of invisible heat energy flowing OUT of a home, imagine that these same tiny channels are letting water IN.
In order to achieve a high level of tight-fitting precision, builders are installing pre-built walls, ceilings and roof systems into their projects. These components, typically prebuilt offsite under near perfect conditions by highly skilled craftsmen, allow contractors to form a tight, weather-proof building envelope in just a fraction of the time it would take to build the same structure on site.
It’s not that the general contractor (GC) no longer has to sweat every little detail to make sure that the wall-ceiling-windowroof is made perfectly – it’s that somebody has already done the sweating for them. And for many GCs that’s a welcome relief.
Homeowners see the light
Over the last several years, as concerns over high energy costs increased and homeowners shifted away from burning environmentally unfriendly fossil fuels for heat, people have turned to new technologies not only to see inside their walls, but then actually measure their ability to retain heat.
Today, using small, handheld thermal imaging cameras, professional energy auditors (among others) are able to precisely determine where homes are failing to keep the heat in and the cold out.
As access to this type of “x-ray vision” has increased to the point where an average homeowner can buy a thermal imaging device that clips onto their cell phones for under $300, so has the visibility of the structural and material deficiencies that have hidden behind walls of sheetrock, sheathing, floors and ceilings for decades.
In response to the increased accessibility of these tools for home inspectors, energy auditors and homeowners, contractors are feeling the pressure to build tighter, better insulated structures. And, while some homeowners are comfortable with the notion that this may result in an incremental increase in construction costs, others could argue that building to the highest energy efficiency should be standard practice – and have no impact on the cost of building the house.
As a result, contractors find themselves in a tight spot. They need to build increasingly better performing houses without increasing the price that a homeowner is willing to pay for the home. Homebuilders are now realizing that trying to accomplish this without adjusting how, where and when they construct homes can be a major challenge.
The search for developing a more efficient and more effective way of constructing homes led some companies in Maine and New Hampshire to experiment with incorporating pre-built building components into their projects. A few are providing entire home packages that are first constructed offsite, then delivered, assembled and permanently installed at the homeowner’s lot.
Your new home, delivered. Some assembly required.
It can vary by manufacturer, but typically pre-fabricated building components are delivered (flat) well labeled, carefully shrink wrapped, then covered with heavy duty tarps to protect them from the weather and stacked precisely on a flatbed truck according to how they will later be installed at the home site.
These pre-built sections are fully functional units, with insulation, electrical, plumbing and drywall already in place. Some off-site providers will also install windows, doors, siding, floor systems and trim before shipping.
With a single floor home, the wall assemblies are attached to each other using rugged screws, bolts and adhesives, and can be set directly on a foundation that may or may not also include a basement.
A simple 2,000 sq ft home arrives in modules as large as 16’x60’ and are assembled into “boxes” before being placed into their final positions. Although a general contractor is onsite to oversee the assembly, manufacturers often design components to only fit together in a specific way, following a pre-determined sequence.
Once the boxes are in place, work begins on joining the seams, attaching a roof, adding insulation where needed, and connecting the plumbing and wiring conduits together. A fully weather-tight exterior can usually be completed in a few days, allowing the bulk of the on-site finish work to occur inside, protected from the elements.
Here in Maine, we are fortunate that some of the most recognized green home design and building professionals in the country also choose to call this home.
In fact, several Maine companies have found a niche by designing and constructing pre-fabricated building panels that – when assembled to create a “regular looking” house – achieve energy efficiency performance standards that are many times more efficient than a newly constructed “code built” home.
In many parts of the world, including Scandinavia and much of Europe, the vast majority of homes are built using these “panelized” construction methods.
Although modular construction currently accounts for only 3% of all home starts in the United States, a shift is beginning as new materials, processes and technology have helped to reduce costs enough to make the upfront expenses deliver a reasonable ROI over time.
So, it stands to reason that some of the pioneering efforts that are taking place here in Maine have strong ties with European countries, and Sweden in particular.
“The heart of our company is about reducing energy consumption and our carbon output through the built environment,” says Chris Corson, the technical director of Ecocor High Performance Buildings of Searsmont.
Ecocor focuses entirely on designing healthy, resilient, low-carbon, net-zero-ready homes built to meet the Passive House standard, one of the most stringent home energy rating systems in the world. The company was the first Certified Passive House building component manufacturer to be located outside of Europe.
“Our panelized wall systems are built in our shop and engineered with a unique assembly method that creates a truly airtight, highly insulated connection from one panel to another,” says Corson.
The company has also developed a proprietary method of constructing the corners of a home, traditionally one of worst performing areas in terms of heat loss.
“The corners of our homes are designed to completely eliminate any heat energy from being transferred through thermal bridging,” which is the process of heat travelling from one object to another through physical contact.
Where the typical new home in Maine is required by current building codes to achieve an insulated (R-Value) of R-20 (R-13 insulation added to R-5 for the wood sheathing), Ecocor, along with many panel manufacturers, greatly exceed CONTINUED ON PAGE 50 these standards. The Ecocor wall panels, in addition to being airtight, achieve an insulated resistance to heat loss (R-value) of approximately R-59.
“Our wall systems are filled at a much higher density with specially treated, fiberized cellular insulation, then reinforced and sealed using a combination of Zip System sheathing and Pro Clima’s airtight weather resistive barrier,” says Corson.
To help put this into perspective, a common 2x4 piece of wood has an R-value of just under 2. It would take a stack of 2x4s nearly 4 feet tall to achieve the same insulation value as the Ecocor wall panel.
“We use a panelization construction process because we found it to be the most effective way to deliver the type of high quality, high performing, customizable homes to the market,” explains Corson. The company has sold several dozen homes throughout the northeast, in cold weather climates such as Maine, New York and in New Brunswick, Canada.
Ecocor’s complete lineup of homes, named Solsken (a Swedish word meaning “sunshine”) are designed to reduce the energy consumption of the house by 80-90%.
To accomplish this, Corson and his team researched and evaluated many of best practices that builders have developed both here and overseas. They adopted what they thought would also work for ecocor and where no suitable solution was found, they developed their own.
Customers start by choosing from several different types of home models and then work with ecocor to customize the design. Once the final plans are set, construction of the home can begin almost immediately.
This is just one of the major differences between the offsite and site built construction processes.
Unlike building a traditional stick-built home, offsite construction typically occurs in a separate, climatecontrolled building in a factory type setting. This means that construction can occur simultaneously while site-specific activities such as surveying, permitting, excavation, grading and foundation work are being completed.
“We put in a foundation in the spring for a new home in Brunswick last year. We were delayed because of an issue with our window supplier in Europe, so we didn’t begin construction in our shop until August. Still, just after Labor Day (September) we showed up to the site with a crane and the completed panels. The owners moved into their new home in mid-November,” Corson said.
Corson explains how his company can move homebuilding projects from frame to finish quickly while also maintaining high quality levels.
“We build our super insulated building enclosures here in our Searsmont shop using an integrated computer aided design (CAD) and computer aided manufacturing (CAM) process. Every piece of material is precisely measured, cut and labeled, insuring that the final assembly matches the computer modeled design.”
Definitely NOT your Grampy’s double-wide
One reason that off-site, modular construction hasn’t taken off as quickly as some have hoped here in the U.S. is because it is often mistakenly associated with the lower quality methods and materials that have historically been used to construct mobile homes.
A mobile home is a self-contained, fully finished home that is (by code) allowed to be built to lower standards. It’s delivered to its owner by truck - fully assembled and fully furnished. Although a mobile home may or may not remain on its wheeled frame, it typically is not attached to a permanent foundation.
On the other hand, a modular home is constructed off site, delivered to the customer in large sections and assembled on top of a permanent foundation. Attached to the foundation just as a traditional stick-built framed house, these homes may or may not also include a basement.
Still, confusion exists in the marketplace, and several key players in the industry have set out to try and reframe just what modular means.
Here’s a bright idea: Build better, use less
Phil Kaplan and his firm, Kaplan Thompson Architects, introduced many Mainers (including myself) to the idea of combining pre-fabricated building components as an effective way to create super-efficient, net-zero energy structures (without going broke in the process) when they introduced the BrightBuilt Barn project in 2008.
At that time, the thought of building an affordable home in Maine that would be able to maintain a comfortable indoor temperature without relying on a large, combustion type furnace as a source of heat seemed farfetched.
Most assumed that such a building would either require the home to be so small that it could not reasonably accommodate more than 1 or 2 occupants at a time or be so ridiculously expensive to build that a person would need to live three lifetimes as a recluse before breaking even.
For me, the BrightBuilt Barn project was the first “real world” example that proved it was possible to create a building – built right here in Maine, by a Maine company – that could supply more energy than it consumed.
Today, nearly a decade later, thanks to the tireless efforts of residential building companies such as Kaplan Thompson, Briburn, GO Logic, Taggart Construction, Kolbert Building and others, the idea of designing and constructing homes that do not need a gas or oil fired furnace for space heating is no longer a foreign concept.
On budget. On time.
One reason why the popularity of off-site, modular, pre-fab and panelized construction has finally begun to gain traction here in the U.S. is that it enables builders to effectively remove many of the uncertainties (about weather, quality of materials and the availability of skilled labor) from the equation.
“Our buyers know all of the costs associated with the project before construction begins,” says Kaplan, who also leads BrightBuilt Home, a high performance modular home company based in Portland. “So, there should be very minimal (if any) cost surprises with the finished product. Providing this level of price predictability significantly reduces the ‘money pit’ anxiety that many people experience when building a new home.”
Part of BrightBuilt’s mission of creating attainable high performance homes is achieved by having conversations early and often with customers to educate them about the short-term and long-term costs of homeownership, including forward-looking information about maintenance costs and energy use.
BrightBuilt delivers a detailed report explaining exactly how a customer’s new home will perform, before a single board is cut. Computer models track every customer requested modification made to any of BrightBuilt’s stable of nine customizable home designs and automatically predict how the modification will affect construction costs today – and energy costs tomorrow.
Kaplan explains, “The price of one of our BrightBuilt Home models incorporates all architectural design, structural engineering, construction, site preparation and assembly costs. We’ll also include line item details about quality assurance and performance measurement costs, such as blower door testing and commissioning, which ensures the long-term value of the home at no added cost.”
What’s more, building a modular home doesn’t come with a pre-determined set of limitations as some may think. BrightBuilt’s designers work with customers to create virtually any layout, size and exterior finish.
Homeowners can also shift the size and location of windows and doors, as long as the overall energy performance of the home is not impacted.
Foundations and panels feature foam insulation built-in
In addition to modular panels providing a cost effective, highly insulated solution for home builders, the same concept is being applied to the foundations these homes are built on. Insulated concrete forms (ICF) are interlocking foam blocks that can be pre-assembled and installed in less time than a traditional wood framed form. The foam cavities are filled with concrete to produce high performing foundations that greatly reduce heat loss through basement walls.
Another pre-assembled building component, SIPs (Structural Insulated Panels) are constructed and function in much the same way as ICFs, and can be used for entire house solutions. SIPs are composed of a continuous core of rigid foam insulation, which is laminated between two layers of structural board (OSB) to form a single, solid pane. One Maine company, House & Sun Inc., has been building energy efficient homes and commercial buildings with SIPs for more than 30 years.
While several companies are working to distinguish their modular home solutions from the negative stereotypes that have been associated with mobile homes, one New Hampshire builder wants to do away with the word altogether.
A montage to remember
“We have long been uncomfortable with the terms used for offsite building fabrication methods,” says Tedd Benson, founder of Bensonwood and Unity Homes in Walpole, New Hampshire.
“Describing our building practices as ‘modular’ or ‘prefab’ never seemed to fit us because of the diversity in practice and the baggage that each word has acquired over time. Our lean-manufacturing processes have been fine-tuned to save time, costs and waste, and produce durable, energy efficient homes that are built to joint tolerances as low as 1/32˝.”
In early 2013, Benson adopted a term—Montage—to describe his company’s approach to design and construction methods.
Interestingly, it happens to also be a Swedish word that has been used in a very similar context in German, French, Japanese and English languages.
When translated to English, “montage” means “assemble,” and is defined as “a combination of disparate elements that forms … a unified whole.”
“We chose Montage for its hard-won association of achieving the highest possible building standards through a system of construction that is an efficient, quality-focused assembly process.”
The company even supplies its customers with a guidebook to help prospective homebuyers know what to expect along the way. The 10 Step Guide to Building a Unity Home educates customers about the Montage process and identifies the major project milestones for planning, fabricating and assembling a Unity Home.
“Traditional, on-site home construction involves assembling roughly 50,000 parts over the course of many months, though all types of weather conditions,” says Benson. “A Unity Home arrives on site in just 50 or so precision building components that have been carefully fabricated in a controlled environment and loaded onto a truck in the exact order in which they will be assembled.”
Unity can assemble the basic shell of a new home in a few days. Depending on the amount of interior finish work, homeowners can move in 6-8 weeks later.
Another important issue that modular, offsite construction advocates are trying to address is the amount of waste that is created during a home construction project.
A study from the American Institute of Architects found that up to 40% of the nation’s solid waste in landfills is made up of building material. Sustainable Sources also found that constructing a 2,000 sq ft home will generate approximately 8,000 lbs. of waste, in the form of packaging, new material scraps and other debris.
Alternatively, homes built in modules inside a controlled factory environment are constructed under close supervision and inspected on several occasions to ensure each piece meets a strict building code. This attention to detail also generates less material waste and few labor hours wasted because of bad weather or scheduling issues.
Preferred Building Systems (PBS) is a wholesale modular housing manufacturer that sells exclusively to approved builders throughout New England. The Claremont, New Hampshire company recently opened a new 160,000 sq. ft. factory specifically designed to build energy efficient modular homes.
“Our construction process produces much less material waste because we maximize the use of all raw materials through our design and production planning, leaving very little scrap behind,” says Bryan Huot, president of Preferred Building Systems.
Riding with the wind
The PBS factory is organized in a horseshoe style and uses low-pressure air-pad systems to hovercraft (move) their building modules through their manufacturing process. This allows PBS to adjust its workflow within the factory to meet changes in demand, project scope or production schedule.
To ensure that the quality and integrity of their work carries over to the finished product at the work site, PBS prescreens every builder before they allow them to purchase their modules. Designed to meet current Energy Star new home construction standards, builders and homeowners can then take additional steps to further improve the home’s energy efficiency in pursuit of higher levels of green building certifications.
Since 2007, PBS has completed well over 400 projects with builders in Maine, New Hampshire, Vermont, Massachusetts and beyond.
The quest continues - High quality without high prices
Through ongoing collaboration between builders, architects, designers, product and material manufacturers, the home construction industry is getting closer than ever before to finding the elusive sweet spot where low energy buildings and low cost intersect. The best may still be yet to come. Skål!
This article was reprinted from the spring 2017 issue of Green & Healthy Maine Homes. Subscribe today!