Mounting the sink in a bump out is a great idea since the view while working at sink is better. Nothing special is required to prevent pipes freezing but it must be done right. If you must tell plumbers how to do it you need new plumbers.

klem1, so we know that the plumber we select knows what they are doing, can you give us some ideas as to what should be done to prevent frozen pipes? Thanks in advance for your input.

I would love to share ideas but without knowing details about construction of home,ideas would be idle conversation. Is d room on slab,crawl space,pier &beam or other? Pertinent measurements and material specs for wall and foundation. Overhead clearance beneath dr and window. Type of water and drain lines presently. Winter ambient temperatures. Heated or unheated crawl space/basement. Insulated or non insulated floor between crawl/basement? To name a few,and we can take it from there.

The size of the area is 2'x11.5'x10"(high). Full cinder block foundation for the non-cantilevered part of the room, this area is heated. No insulation in the cantilevered area. 1/2" exterior plywood and vinyl siding. If we put the sink, 2 1/2" feed pipes for the water and 1.5" drain pipe. Possible feed and drain for dishwasher. Because there is no exterior insulation, currently the cantilevered area is insulated from the basement. Living in Central NJ, we can have a week or more of nights in the single digits and days only reaching the 20s. For most of 2-3 months, we get nights in the 20s and days in the 30-40's.

Ok,I'm sure I am not seeing the complete picture but briefly,it would be wise to insulate all sides,floor and roof/ceiling of cantilevered room,esp floor and wall with plumbing,keeping all plumbing on living area side of insulation. Use copper supply lines,metal drains if possible or double wall DWV drains. Insulate lines within room/cabinet but expose lines in heated area. Again,you must realize talking about this without seeing it first hand is akin to shooting in the dark. If you will be standing on present floor while working at sink,bringing toe kick inward a few inches might ease job of bringing plumbing from basement to under side of sink base where line continue's to rear wall of sink base. Custom building sink base inside present living space without disturbing exterior wall would undoubtedly afford excellent freeze protection. Having said all that,as a contractor I always hated to hear customers begin a sentence with "somebody on the internet said,,,,,,,,,,,,,,,"

Bruce and klem1, thanks for taking the time to respond to my question. We have some things to think about and talk about with the plumber if we go with the sink in that area. BTW, the cantilevered areas already exist, we don't notice them being particularly cold when you stand on them, maybe a little colder than the area next to them. Maybe because there are vents in those walls and the heat coming out of them keeps the floors warm enough. In the DR where we are thinking about putting the sink, there are two vents in the cantilevered wall.

Keep pipes on the warm side of the insulation. Dont cover pipes with spray foam (heat cannot get to it). The cantilever obviously needs to be insulated, spray foam advised in this area to seal common drafty rim joist and sill plate.

We faced a similar situation with the cantilevered kitchen at our cabin in Ohio. We ran the hot and cold lines right up against the kitchen floor, and we brought them up into the cabinet about a foot inside of the exterior wall. As Bruce suggested, we also ran a duct for the heater in that same joist bay, and brought the heat out a toekick register under the sink. We put 3 inches of polyiso foam between the duct and the outside of the floor. Works fine when we are home (well, the cold water comes out warm for a few seconds). When we are going to be gone for extended periods of time we turn off the water and drain the kitchen lines.