The factory-built efficiencies and controlled-environment quality provided by modular homes have been attracting growing attention from green building professionals for a few years. Now two leading architects specializing in green pre-fab—Michelle Kaufmann Studio in San Francisco and Kaplan Thompson Architects in Maine—are furthering the cause even more by announcing new net-zero modular designs, each with features and products intended to promote efficiency, performance, and longevity while producing as much energy as they use.

Kaufmann’s Zero Series homes range in size from 422 square feet to 2,643 square feet and start at $66,500, which the architect says targets the need for more affordable options for architect-designed green homes. The houses, available through Studio 101 Designs and factory partner Blazer Industries, offer flexibility in module configuration, size, and product selections: The modern Vista0 design, for example, allows for easy expansion through the addition of attached or detached modules. Some core structures and systems, such as HVAC and soy-based spray-foam insulation, come pre-specified, but customers can then select from a wide range of product options, each pre-vetted “for the optimal balance of beauty, longevity, sustainability, and cost,” says Kaufmann, AIA.

The three designs in Kaplan Thompson’s Modular Zero Collection, which will be built by Keiser Industries, range in size from 960 square feet to 2,200 square feet and start at about $140 per square foot. Features include cellulose-insulated R-40 double-stud walls and R-60 roofs, FSC-certified lumber, CFL lighting, and low-flow fixtures. Careful attention was paid to window placement to ensure cross ventilation and passive solar gain while increasing visual size and maximizing views. Blower-door tests will be performed while the modules are being built at the factory as well as after assembly on site.

And, perhaps the most important detail of all: “It doesn’t feel like a modular house,” says principal Phil Kaplan, AIA. “It just feels like a house.” —Katy Tomasulo