Bath exhaust fan in cathedral ceiling: problem
Our second story bathroom fan exhausts (via the usual flexible tubing) downward between two roof rafters and terminates in the cavity above the roof soffit. The tubing undoubtedly compresses the insulation and carries warm air which causes a loss of heat which inevitably leads to roof icing during our cold New Hampshire winters. You can easily see the limits of the two rafters caused by melting from the heatloss. As a result an ice dam forms at the dripedge and icicles hang from there. Even when the fan is not running I'm sure the tube continues to act as an avenue for warm inside air to excape.
Are there any bathroom fans designed to exhaust directly upward through the roof? One which is energy efficient and that closes off effectivly so house heat just doesn't go up a "chimney"? Can a bath be successfully dehumidified without an exahaust fan, say, with a small dehumidifying unit?