On a sweltering summer night, the Music Shed can feel like a steam bath. The acoustics may be perfect, the performers electrifying and the architecture deeply satisfying, but the place can be just too darn hot.

The building originally had a cupola that, like a vent at the apex of a tepee, allowed hot air to escape. Fresh air was drawn in through the screened windows on either side of the long building, wafting over the seats.

That cupola, which disappeared in the 1930’s or 1940’s, is now being rebuilt at Rosewood Millwork in Killingworth, Conn. Calling it huge, James Nelson, general manager of the Norfolk Chamber Music Festival, describes the cupola as an octagon 16 feet in diameter, whose top, excluding the lightning rod, will stand 20 feet above the existing ridgeline. Delivery is expected in early April, with the cupola arriving on two trucks. A crane will lower it in place.

A public unveiling of the new cupola will be held on June 21.