the answer is no it will not withstand freezing. they work by the amount of water being sent through the tubing, when water is not flowing the unit is idle and not producing any heat. They mount on the wall and take up about 2 feet of width and stick out less than a foot. I have one and it works quite well. If you were to look at the construction of one you would quickly understand why they will freeze, and in fact the installation instructions tell you NOT to install it in an unheated area.

The Takagi gas tankless units have built-in freeze protection.

The heat exchanger is encircled with heaters controlled by a freeze-stat. But you must protect pipes as well.

Try www.endlesslyhot.com

Winter's here folks, have your heating systems checked out.

Cheers from Brian in Swampland.