Oh, sorry, I forgot to answer your house size question. It's a townhouse in the middle of the row and I believe is 1500 square feet, but about an eighth of that is a garage.
Hi, Phil -- the walls are siding over wood. The side walls are common with neighbors. I live in the Washington, DC area so there are plenty of contractors available, just all with that pesky diagnosis fee. The climate here is generally in the 80s and 90s and humid in the summer; 20s to 40s in the winter. I grew up here and it seems to me it's hotter in the summer now and not as cold in the winter, though we do get an occasional cold winter, like the second Reagan inauguration when they had to cancel the parade because it was just too darn cold.
I'm north and west of the city, over the District line in Maryland, but most contractors in the MD/DC/northern Virginia area serve the whole area. Your tip about not needing a diagnosis but just an estimate is very good; hopefully that will save me some money!
Phil, you're my hero! Yes, please keep it open. I plan to construct a matrix when I get home so I can compare the offerings side by side. I love any excuse to construct a matrix; I even make one for Christmas baking!