A thick concrete wall can keep your house cool. Steel will make your house hot unless you insulated the walls well. Insulated walls don't work very well in a flood zone. When they get wet, you need to tear them apart. You will need concrete for the foundation most likely unless you are driving steel pylons. There is probably a combination of the two that will suit your needs best. It would be helpful to know what you want to achieve by using steel. There are advantages to both. Steel floors can be cantilevered further. It is easier to make bigger window openings. Floor and roof spans can be lighter and quicker to build with steel, but the roof will get hotter and therefore need good insulation and need to be well ventilated. These are just general assumptions of certain building practices so that you know what to ask people where you live. The practices and resources vary from place to place and building something for a specific purpose can change the benefits of one material or the other. My best guess is that you will probably want to use both.

This arrangement works much better, but some adjustments are needed to make it work. First, the fireplace grouping needs to be tightened. It crowds the dining area and you need a passageway behind the couch. Turn the rug lengthwise, parallel to the fireplace. Pull the large couch about 2 1/2 feet closer to the fireplace, and place the two chairs and loveseat on the ends of the rug, and pull them closer together. This will give you a more intimate conversation area, and not impose on the other areas of the room. Remove that floor lamp from behind the couch. If you need the light in that area, put it by the fireplace. Also, the stereo system on the mantel needs to find another home. Maybe it can go IN the fireplace instead. At the other end of the room, I think the arrangement would look better if the seating were rotated 90 degrees. Keep the rug and coffee table in its current configuration, place the sofa either facing the window or with its back to the window, and put the two chairs opposite it. Finally, the dining area. Now that you've moved the big leather chairs, you should have enough room. Your rug is too small. It should be big enough to give you at least a 2 ft. border all the way around when the chairs are pushed in. And it's a really beautiful table; please uncover it. I can't see what kind of lighting that area has. It really needs a pendant or chandelier hanging directly over the table.

I think a comfortable distance between the island and the counter is around 42". It seems that you have only 30" between your cook top and the counter. I might be a little too tight. The wall between the entrance and the kitchen could be 4' long instead of 6', you would then be able to move the island a foot which would give you more room between the cook top and the island. Could you switch the location of the toilet and vanity in your dad's bathroom so your enter facing a vanity instead of a toilet which is a lot nicer.

How do you decorate your place, what kind of style, colors, and feelings? That will greatly influence the type of door you might want. Also, think of your budget, and whether you want to install it yourself or hire a professional (you don't need to tell us, just keep that in mind). Then look around Houzz, in the products page, they have lots of interior sliding doors and hinged ones, from elegant frosted glass in a dark wood frame, to rustic reclaimed wood planks. You may not want to purchase that exact model, but it might give you a better idea of what would fulfill your airflow needs without sacrificing style.