Asymmetrical shelves filled with books, records, and other beloved possessions lend color and texture to an otherwise minimalist background of white paint, tigerwood flooring, and vapor-proof light fixtures.

RELAXING at his dining table and sipping green tea on a gray evening in late May, typically soft-spoken designer Matt Kirkpatrick notes—with more than a hint of incredulity—that the average size of a newly built single-family house in the United States in 2009 was 2,438 square feet. “In 1950,” he says, “it was less than a thousand.” Although Kirkpatrick, 31, was born on the cusp of the bigger-is-always-better 1980s, his own home, nicknamed the Harpoon House, appears to have taken a page from the Leave It to Beaver decade, if only in terms of size.

The first project of his solo company, Design for Occupancy, and a collaboration with his girlfriend, communications designer Katherine Bovee, 30, the Harpoon House has 704 square feet of living space and 448 square feet of unconditioned basement, with three tiers of eco-roof, one bedroom, and one bathroom—no garage. And to leave the smallest possible footprint on their half-size lot (2,500 square feet), the house was built 16 feet wide, 28 feet deep, and 28 feet tall.

For the two young creatives, this über-modern urban tower is a dream home. It’s also the product of both necessity and a desire for economy—of space, of budget, and of impact on the planet. With a budget of $192,700, a smaller home was cheaper to build, says Bovee, “but smaller homes also take less time and money to maintain and naturally require far less electricity and resources.”

To maximize space, the couple chose fixtures and furniture that frequently could serve dual purposes, and carefully curated possessions in which a high-design aesthetic allows them to easily double as art. Every square inch of the property was considered in the design process, always with an eye to usability, efficiency, and an uncluttered look.