A New York-based retailer is offering a pull-down attic stair designed to solve a knotty problem in high-performance houses with unconditioned attics.

Unless a builder cobbles together a well-sealed attic hatch, or builds an insulated and air-sealed door and stairwell, the hole in the attic floor will mean a lot of wasted heating and cooling energy as well as serious air leaks.

The Klimatec 160, made by the Austrian company Wippro, offers builders a way to insulate the opening with 6.3 inches of extruded polystyrene insulation for an advertised R-value of 26 and an installed whole-unit R-value (taking the frame into account) of about R-17. An optional hatch adds 2 3/8 inches of insulation for another R-9.7.

The retailer, 475 High Performance Building Supply, sells the unit for $1,195; the optional lid is another $300.

The stair is certified by the Passivhaus Institut in Germany. It fits in a rough opening 55 1/8 inches by 27 9/16 inches, and has a staircase length of 98 1/2 inches to 118 1/2 inches.

A full set of specs is available at the 475 website. The Passivhaus Institut certificate is available here.