If there’s something growing on your roof, it might actually be a good thing.

No. Not mold or mildew, but plants that can serve to cool your home or business and offer other benefits.

You can see for yourself Saturday on the Annual Solar & Green Building Tour & Expo, put on by the Wilmington nonprofit Cape Fear Green Building Alliance.

One of eight stops on the tour is Mott Landscaping’s green roofs – atop a front porch and a Segway garage.

Also on the tour are homes that incorporate environmentally friendly and energy- and cost-savings designs and technologies.

One of them, near Greenfield Lake, is owned by architect Gordon Hall and his wife, Tanya.

The Hall home – a wood frame house on a concrete block foundation – is described as “a new infill house featuring daylighting, green materials and a highly efficient space-saver layout.”

“Daylighting principals were employed to reduce the requirement for electric lighting,” Hall explained Thursday. “What we did in this house was to employ a lot of skylights and a really open envelope around the perimeter to let natural light in.

“To reduce problems of solar heat gain, we have broad (roof) overhangs.”

Hall said there were altruistic and practical reasons for building the house, the Halls’ personal residence.

“I think that anything that anybody can do to reduce to their ecological footprint on the world is a good thing. But a lot of strategies we’ve employeed on this house make common sense: natural light and natural ventilation, lots of windows that open, outdoor spaces,” he said.

“One of the things that I think is important is the strategy for the design: compact form; minimizing materials and redundant structures, using local materials when we could. Also many of the appliances and electronic and mechanical systems are really high-efficiency.”

Tickets for the tour – which runs 10 a.m. to 5 p.m. – are available online at www.cfgba.org or at the alliance’s Green Expo Saturday at Bailey Park on Front Street. Cost is $10. Cost is $5 for members of the Green Building Alliance or N.C. Sustainable Energy Association as well as students and teachers.

The Green Expo, 10 a.m. to 4 p.m., will showcase and discuss sustainable products and services offered in the Wilmington area. Expo admission is free.

The following sites are on the tour:

The Monteith Construction office. The first LEED-certified building on the annual tour.

The Hall residence.