Why slab on grade? You get pretty good winters out your way so footings will need to be dug below frost line. A crawl space offers you a better ability to insulate and run utilities.
MarkV
Most people around here prefer to have a basement. Slabs on grade and crawl spaces are not nearly as popular. A lot of people here simply won't buy a slab on grade house due to their history of frost heaving and cracking when constructed poorly.
80% of homes in Maine are heated with oil. About 90% of those have a 275 Gal. oil tank and oil burning furnace in their basements. Even in old houses, they had basements with roughly cut granite foundations and walls and a dirt floor. They may have used them as root cellars. Some have a bedrock (ledge in NE) 'feature' sticking up out of the basement floor. Some very old houses had beehive oven/fireplaces with a massive 10' square chimney foundation in the middle of the basement.
My house is a passive solar design. It has 8' tall concrete walls on the north, east and west. These are earth bermed to about 6" below the top of the wall. The south wall is built on a standard frost wall such as a crawl space would use. The frost wall wraps around 12' on the south east and south west corners to prevent frost penetration below those walls. For those 12', the 8' concrete wall is poured on top of the 4' frost wall. All the concrete walls have footers below them. They all have continuous inside and outside perimeter drains made of 4" slotted flexible pipe in a bed of washed stone. Moisture is your enemy because it wicks heat away.
My floor is a concrete slab poured inside the 8' walls and covers the top of the south frost wall. The floor slab stores a lot of heat provided by sunshine through south facing windows. For heat conservation the slab needs to be in the ground as much as possible.
The concept of a passive solar system is that your baseline temperature is the same as the earth around and below the foundation, walls and slab. You are adding heat to a structure that 'wants' to be about 50-55 deg. in winter, compared to a regular frame house exposed to the much colder outside air.
Having my plumbing below a slab does not give me the warm fuzzies. I considered trying to come up with a design where all my fixtures and drains would run in horizontal chases in the concrete with some sort of removable cover, or to centralize all the plumbing around a small service room. I never was able to come up with a layout that accomplished that and also had a decent floor plan. I am still convinced it is possible
The plumber I used , who is a really nice old guy, told me I should quit worrying about it, so I did. He said that would be the last thing he would worry about with PEX tubing. So far, he has been right.
Getting back to the drainage discussion, the stone drainage bed below my slab is well below the finished grade level. Moisture that collects there has to go/be sent somewhere or there will be dampness problems and heat loss.
Sorry for the long winded answer. But, I realize this is quite a bit different than typical TX/Southwest construction and thought it might help to add some detail.
Dave.
