Home stays naturally cool

Mary Spear doesn't hold back when she talks about her new house. She describes working with an architect as "a dream come true" and calls her house a "gift," one that makes her feel "supremely grateful."

The 2,400-square-foot house in St. Peter, Minn. -- which Mary shares with her husband, Jack, and teenage son, Michael -- does seem to have it all.

Designed by Minneapolis architect Sarah Nettleton as a "lantern on the prairie," the house has a curved, reclaimed-fir ceiling that sits low, but is lighted by more than a dozen small sconces. At night, the house lights up like a beacon on its bluff-top perch overlooking the Minnesota River.

The house is essentially one oversized room. (Nettleton's architectural term for it is "continuous volume.") The shape was inspired in part by Jack Spear's upbringing in rural Vermont, where his family hand-shanked their own log cabin.

"If a one-room cabin is the Baby Bear size, and a luxury house with a cavernous great room is the Papa Bear size, then this house is the Mama Bear size," says Nettleton. The house also has whole-house in-floor radiant heating and solar-thermal heating; its interior was designed by Doran Thayer and Sasha Thayer of Minneapolis.

What the house doesn't have is air conditioning. Not even a window unit.

"We talked about it, and it was going to be $35,000 with all the machines and ductwork, and Jack and Mary said, 'Let's not,'" said Nettleton, noting that the A/C would have been especially expensive because the homeowners opted for in-floor heat, which doesn't use traditional ductwork.

To make that happen, the architect first used a "sun model" to study daylight patterns on the Spears' 14-acre parcel. After an exhaustive amount of homework, Nettleton decided the house would be best ventilated if she turned it slightly to the southeast and added a sloped-roof screened porch to shade the west side.

On the long south side of the house, closest to the bluff's edge, she added sliding metal sunshades to all the doors and windows, designed to block 60 percent of the sun's rays. It works well, said Nettleton, because the house sits in a sweet spot where breezes can ride up from the river and sweep directly through the house.

"Every window and shade was designed to maximize nice breezes," says Nettleton. "This house is not some air-conditioned box out in nature."

Going natural

Although Nettleton counts "natural ventilation" as one of her design specialties -- the architect says she's incorporated the idea into almost every project she's designed -- the Spear house is highly unusual in that there is no backup system. In her 22 years as a working architect, Nettleton has designed only one other residence without A/C, and that was a 945-square-foot cabin in Tofte, Minn., on the North Shore.

Nettleton says it's possible to design a comfortable, un-air-conditioned house anywhere, but it isn't easy. Air currents, sun movement, window shapes, overhangs and terrain all play roles in the equation.

And even after the design is finished, the homeowners need to be willing to pay attention to the sun and air currents, and open and close the house to keep things cool.

For the Spears, that was the most enchanting part: building a home that is experiential in an old-fashioned way.

"There's something really lovely about tuning in to where the sun is, where the breezes are, opening and closing up the house," said Mary Spear. "There's a kind self-satisfaction to it, like growing your own tomatoes."

Still, the A/C-less Spear house is a bit of an experiment. The family moved in at the tail end of last August, and got only a few hot-weather teasers.

But if the experiment turns out to be more than the family can handle this summer, they do have a fail-safe: a built-in spot in their bedroom for a ductless air conditioner.