When we built the addition on our house I had only one 40" Norwood 8S loom. Our bedroom was built on the footprint of the 2-car garage--lots of room for our bed, my loom, floor-to-ceiling shelves on two walls for yarn storage and carefully placed spotlights in the 18 foot ceiling. It worked great for a few years, then I bought a 45" 16S computer-dobby Leclerc Colonial II. The Norwood has been moved over to the window between the French doors and the fireplace, the Colonial is in the place of honor with the lighting just right, and the computer is on a yarn storage box by the loom. The Norwood is lit by natural light and by a floor lamp on gloomy days. The yard storage has spilled over into an upstairs bedroom and there is a table loom on the dining room table and an inkle loom next to my chair in the living room. The sewing machine is stored under the TV in the breakfast room where it can be set up in a minute, as soon as we have finished eating. We certainly didn't plan for my weaving to take over the house, but you all know how it is.
Incidentally, the screened porch has made a wonderful dye studio--no worries about breathing in little particles of dye. I think the only room that hasn't been affected by weaving is the kitchen--but then, there are all those handwoven dishtowels and placemats.
The only advice I would add to those who have written about electrical outlet and phone jack placements is to think long and hard about yarn storage. I loved the idea of having all my yarn out where I could look at it and get inspired by the colors. The moths liked it, too. They had easy access and I lost a lot of lovely yarns I was saving for just the right project.