The Modular Approach to Building Affordable High Performance and Net Zero Homes
We will not change the carbon footprint of housing in the US until we make high performance homes truly affordable. Modular construction offers the most promising way to get there.
A modular home is simply a home built in a factory. Like standard site-built houses, it can be built of studs, or it can be built of structural insulated panels (SIPs) and other structural systems. What makes it modular is that it is assembled nearly completely in a shop and shipped down the road in modules sized under 16’ x 64’. These are then sealed together at the site. A small house can be made up of one or two modules; a larger house can be made up of six or more modules.
We define a High Performance Home as a home built to meet at a minimum the Architecture 2030 Challenge benchmarks for energy efficiency.
A Net Zero home is a home that, through energy conservation and the use of photovoltaic panels or wind power, puts as much energy into the electrical grid as it takes out. It basically uses the power grid as a battery, charging when the sun is out (or the wind is blowing) and discharging when it is not.
The modular approach to building high performance and Net Zero homes makes sense a number of reasons:
- Tolerances. The most critical part of a high performance home is the exterior envelope. With a typical site-built home this part is built first, before there is any protection from the weather or a decent working environment. Tolerances for assembling these critical components are thus far lower on a construction site than on a factory floor.
- Moisture control. Most of the structural components of a site-built house get wet many times before the house is closed in from the weather. Long after the painters have left and the owners have moved in, it is still drying out, with the consequent shrinkage and movement of wood. Shrinkage and cracking are not such an issue with a house built in a climate controlled factory.
- Working conditions. People do higher quality work when they work in better conditions. Light, ergonomics, temperature and humidity are all optimized in a proper factory setting.
- Labor. Labor costs are considerably lower in the rural areas where modular factories are located than in the metropolitan regions. And in a factory setting, labor time is reduced by efficiencies of the production process. Most houses built in a factory are assembled in a matter of days, not months.
- Ordering in bulk. A factory can order lumber, cabinetry, and many other components of a home in large quantities, affording discounts unavailable to the contractor building a single home.
While fees for a custom high performance home will run around 15% of the construction cost, modular design fees can be lower. If you choose a modular design that we have already had built, you will incur a much lower fee for the reproduction of the design. Customization of the design to fit your site, your building program and your tastes will incur additional fees based upon the scope of those changes.
- Thousands of miles are driven by gas guzzling pickup trucks in the process of building a site built home. Just think of all those workers creeping in rush hour traffic every day for months at a time. Then compare that to three or four big semis making one trip from the factory to the site. Oversimplified, but you get the point in terms of the amount of greenhouse gases released into the atmosphere.
- There is virtually no construction waste associated with factory built housing. Every scrap of wood is ground up for the creation of engineered lumber. No matter how assiduous the contactor, this kind of efficiency cannot be duplicated with site built construction.
With construction costs what they are today, and with the growing importance of healthier and more energy efficient homes, an industry-wide move toward modular housing seems almost inevitable. We want to be in the vanguard of that movement. Our first modular Passive House is now built and occupied. That design is now available for construction in the mid-Atlantic region.