Where can I find out how much and what type of insulation I need for the home that I'm going to build?

How large a space are you hoping to cool? One room? One LARGE room? One SMALL room? One floor of a two-story house? A whole four-story house?

What's your climate like where you live? Very hot, dry, year-round? Cool most of the year but two weeks of hot during the summer? Just a little too warm in summer? Blazing hot all summer, including nighttime?

How's the insulation in the building you want to cool? Is it a plain steel building with no insulation? Is it a trailer? Is it a frame house with 4" walls and R13 fiberglass insulation? An old frame house with no insulation? An adobe building? A timberframe house with 8" of polyisocyanurate foam insulation?

All these are important to know when you select an air conditioner.

For most of the USA, assuming a frame house with 4" of fiberglass insulation, a 10,000BTU air conditioner will cool one large room or two small rooms pretty well, or a 5,000BTU AC will do one medium-sized room. Different places, and different house designs, and different types & amounts of insulation, will all have a profound effect on how much AC you need/want.

It seems to me that a reliable source would be this site from the Department of Energy. You just enter your zip code along with some other info and it provides recommendations for your building:
http://web.ornl.gov/~roofs/Zip/ZipHome.html

Urea-formaldehyde foam, which is know to release poisonous gas. Avoid at all costs.

The flue is just 1 pipe inside another, no insulation. But has lil support brackets holding the inner pipe in its place, centered to the outer pipe. I googled Nordyne Flue Pipe, and it is available online. And HELLO from the heart of Texas! Hope this helps!

Hi - Romex is a brand name for NM type cables, and is acceptable wiring method in the 2012 National Electrical Code for use anywhere that is not a wet location in residential buildings; unless your state, county or town specifically prohibits its use.

When you say "12/2" or "12/3" all you are telling us is that you have some type of cable that consists of 2 insulated wires and a second cable type that consists of 3 insulated wires (and possibly a ground wire - but you didn't say "12/2 with Ground" as it would be indicated on the packaging. This same "12/2" or "12/3" designation is used to describe BX, AC, MC, NM, UF, and other cables, too. Since I do not know what cable type you have, I can't say that you can use it or not with any certainty. I can tell you that based on the 12/2 or 12/3 info you provided, it can be used on 20 amp circuits without a problem.

Please provide the cable type or description for a better answer.

Depending on the type of building and insulation. For building with good insulation and not many windows, you could manage with a 18000BTU, but if your insulation not so good, you should need 24 to 26000btu unit.