The Ridge-Vent Bat House

For decades, a colony of little brown bats lived in our roof between the corrugated metal roofing and an older layer of cedar shingles underneath. We appreciated having fewer insects around, but we needed to replace our old roof. Rather than lose our bats, we wanted to incorporate a bat house and attic ventilation directly into the new roof. We succeeded by combining the two into a "ridge-vent bat house."

Our 72-foot-long, one-and-a-half story house, located in rural Vermont, was built in the 1840s. We replaced the old roof with galvanized metal, which also covers the new bat house and vent. To avoid disturbing the bats during the maternity season, construction began in late September of 1995. The layout and design of our unique bat house took about one afternoon, while the prep work took approximately one day, and construction took two. Our cost for labor and materials was about $600.

When most of the new roofing was in place, a one-inch-wide vent was cut across most of the roof peak (ridge) to ventilate the attic. The vent was covered with a layer of fine mesh screening, then a layer of hardware cloth. Sharp edges were covered to prevent injury to bats.

The bat house was assembled in place over the vent (see Figure 1). It consists of a series of 1-inch thick by 12-inch wide rough-cut boards, laid end to end. One-inch-thick spacers were added, followed by sections of 1/2-inch-thick by 16-inch-wide plywood above. After assembly was completed, the bat house was covered with metal roofing painted dark green to absorb heat.

The next year, we eagerly awaited the return of our bats. In June and July 1996, we saw only a few; but in early August, we observed approximately 50 bats, and we believe the same number returned in 1997. Some bats exit from the end of the bat house, but most exit along the bottom. We have trouble estimating the number of bats because we never know where the next bat will emerge. We succeeded in keeping our bats, and we have a new roof and attic vent too! For more information, contact Mack Gardner-Morse, Cold Spring Farm, HC 32, Box 27, Calais, Vermont 05648.

• 1-inch by 12-inch by 20-inch rough-cut boards (~150 linear feet)
• 1-inch by 2-inch rough-cut strips (~200 linear feet)
• 4-foot by 8-foot, 1/2-inch-thick exterior plywood (6-7 sheets)
• 1/4-inch mesh galvanized hardware cloth (~40 linear feet, 36 inches wide)
— prevents bats from entering attic or tearing the fine insect mesh
• #18 x 16 fine mesh screening (~40 linear feet, 36 inches wide)
— keeps insects out of attic
• galvanized nails
• wood screws
• staples

COURTESY MACK GARDNER-MORSE