Gutters help in some cases. We have them along two sides of the house. We had to install a scupper and downspout for an area where two valleys meet. For other valleys without gutters I place river rock below them. Much less erosion with the rock.

It was nice to look at your build twice worthy! In my area foam is much higher than conventional insulations, ROI is 15+ years, and in cases of foam on the roofline for a semi conditioned attic ROI can reach 20+ years, depending on pitch of roof. IMHO that is a long long payback for any one building componet. My answer to the yes or no questioin would be no. locate hvac system in conditioned space..use R-8 ductwork in attic and radaint barrier roof decking is a more cost effective for my area install. if in design stage..locate ducts with in conditioned space also. Like worthy I like the foam to the exterior, and use a foil faced closed cell sheating board behind brick, t&g blue board behind other materials that don't have an air space. conventional insulation in walls, air tight drywall approach to interior of wall. We have stick built homes built as described above with wall R values of R-5.6 sheathing, plus R-15 insulation for an overall R-value of 20.6. not shabby for the price. with proper air sealing these homes achieve same lowered infiltration rates as foam insulated homes, and in some cases better. .25 ach (air changes per hour) is the goal. once infiltration rates fall below this number fresh air is needed. filtering the air, controlling how much air in introduced,cooling and dehumidifying the air before it enters the conditioned space is what we do here. it is not at all inefficient if done correctly. many people assume that their home is tight enough to need fresh air (make up air). it is only with testing that the amount of air changes per hour is determined. houses leak in the damndest places! testing various methods of buildings with a blower door shows how same results can be achieved with different materials and costs. it is not a crapshoot if you know what you are doing and take the steps in the building process to achieve the end means. better building practices consiter the house as a whole and how componets function with each other..low e windows..lower heat gain..smaller hvac.. savings from building a tighter home is not only lower utility costs, but smaller hvac systems. unfortunately most people spend big bucks on lots of things but do not feel the need to pay for a load calculation, duct design or duct sizing calculations. there in lies the problem. built tight and ventilate right.. best of luck.

There is not " a single "correct " way of doing a metal roof but here are a few thoughts for your consideration. I am taking you at your word about being familiar with construction because much depends on your ability to apply experience to which way to go. Be certain the one saying two layers is honest as well as experienced before sighning a contract with him. Most properly installed composition shingles look like 2 layers at drip edge because of starter strips. Can you install metal over one layer of composition? Maybe. The main consideration is wherther the deck and frame will support the extra weight. Then there is the question of how smooth and level surface the shingles afford. Regardless of other underlying material,decking must be capiable of holding screws. 1x deck is strong but usually has many gaps between edges and ends of boards that if a screew gos through,a leak is likly. OSB and plywood are flat and smooth but must be thick enough to prevent flex between rafters. I have installed metal over a few compostions with no problem after several years. On a couple where shingles were aged and deck was strong, we layed tar paper between the shingles and metal. Another had heavy truss framing with questionable decking so we installed 2x4 laths over tar paper making certain to hit rafters with lath fasteners. If your husband is a healthy 70 yo,you might consider hireing laborers to work under his supervision. I agree with Hollysprings about metal not being difficult compared to other construction tasks. A word of warning about roof tearoff. Think twice about putting old shingles in anything without dump. The shingles interlace and make the intire load act as a single blob that resists shoveling off. If you use a non-dumping truck or trailer, lay a cross tie or similar on floor at front with heavy chain on it. If bed is more than 8 feet long, put another drag half way to back and leave enough chain slack between the drags to alow first to move a few feet and pull some material off before chain tightens on other drag. In farm and ranch country you may find people who have installed metal as part of thier farm work. A farmer or rancher who has built thier own barns might welcome extra or off season work. If that sounds interesting,in addition to other means of asking,check out the people on "Yesterday's tractor forums". The board you want is "tractor talk" . If you go with diy ,you can buy or rent the specialized cutters. If your husband decides to supervise labor and isn't comfortable on a ladder and/or walking on the roof,rent a lift to alow him safly going to roof level as well as saving time lifting materials.

I think black shutters on the single windows, as you mention, would add interest/contrast since your roof and siding color are so similar. However, I'd have them sized correctly for the window, mount them on hinges and use shutter dogs to make them more authentic. Your previous shutters looked flat mounted directly to the siding outside the casing. I recommend Timberlane shutter company. You can also hold off on the shutters for now and see if the look without them grows on you.