When talking energy efficiancy, you have to be careful of what you are hearing. It is very common to twist ratings around to make something seem better then something else. In a house, there are two different things happening when talking insulation and energy efficiency. The first, and easiest is that heat rises, so insulating the attic is the easiest to understand. Foam is the best because it also seals off air. If you can afford it, and if you will be in the house long enough to see the return on your investment, it's a great product. It's also very good if you have vaulted ceilings or a thin distance between your exterior roof and interior ceiling. For a lot less money, I like blown in insulation in an attic. The latest standard is R60, which is about 2 feet thick. It should look like fresh snow when done, and it should never be disturbed. This is also why I never like putting the AC system in the attic, and never store anything up there. Attic space should only be used for insulation in my opinion.
I'm also very much against skylights. While there may have been an argument at one time that it's cheaper to have a skylight to light up a room during the day then to turn on a light bulb, that argument doesn't work anymore with LED lights. There is never a good reason to have a skylight. It's just a massive hole in your ceiling that has almost no R value. And while people selling skylights like to tell you they have solved all the leaking problems, or it leaked because it was installed wrong, I believe that they will all leak sooner or later. Just say no to skylights.
Wall insulation is where things get really confusing. It's actually very simple, but people selling products have muddied it up so much that it's easy to over think and confuse what's happening with the exterior walls. First, the force that you are fighting with the walls is wind. Wind gets through your walls and defeats the insulation that you have there. The number one goal of an exterior wall is to keep the wind out. Bricks allow a massive amount of wind through them. House wrap is pretty good at stopping the wind, but it needs to be taped and sealed up everywhere. Zip siding is better then house wrap, but it's quite a bit more expensive then standard OSB and house wrap. My house has Zip siding and when I build my addition, it will have Zip siding. I feel that expense is worth it.
From what I'm reading in the trade magazines that I get, rubberized paint type products are probably going to be the future in home building. They are using it more and more around windows instead of tape. I'm also reading that they are rolling it on the entire exterior of the the OSB or plywood, covering every inch to achieve the highest level of efficiency. There have been all sorts of studies done on double framed walls with foam between the studs to stop therm jumping, and then building with SIPS to get an even higher R value, but none of those very expensive methods actually achieve anything above a certain point that you already get when super sealing the exterior walls with something like Zip system or rubberized paints. Another huge consideration is that every double pained window has an R value of 3 or less. What good is making your wall R30 when you have a big opening that is only R2.5? You can get three pane, and I know one guy who lived close to a major airport that got 4 pane glass. The price is crazy, but you do notice a difference in sound. He didn't see any change in his energy bill after those windows where installed, but the rest of the house was well insulated, and he really didn't have any issues with his 2 pane windows before going to 4 pane. It was all for sound.
In all reality, you will never notice any difference in your wall insulation going above R19 if your walls are air tight and able to keep out the wind. If the wind can get through your walls, it wont matter what you use on your walls, they will not insulate.
Solid logs are not great at insulating for walls. But that's not that big of a deal if they are able to keep the wind out. Your chinking, or sealing off the air is all that matters. Log companies claim that the thickness of their logs is what does the job, but that's just a sales gimmick. Keeping the wind out is all that matters.
Going with alternative building methods is for those who want something special and unique. Not for somebody wanting to build an energy efficient home with limited funds.
I had a friend back in CA who was into riding mountain bikes. He was fifty pounds overweight and not what anybody would consider an athlete. But he really liked riding and he didn't think he was overweight at all. So to make up for not being able to keep up with his friends, he spent a fortune on things to make his big better and lighter. His seat cost him $600 and it was several ounces lighter then anybody else's. He spent more, felt better about it, but that didn't make him any better and keeping up with is friends. Houses are the same way. You can spend a lot more on products that sound good, may be the latest "thing" and you see on TV, but they don't actually make any real world improvement to your home.
When planning your home, focus on the floor plan, storage, usable square footage, curb appeal and resale value. Read up on what's available to make it something you will enjoy living in, and last the longest with the least amount of work. You mentioned vinyl siding, what about going with Hardie siding instead? Rock is becoming more and more affordable. Exposed beams, cedar posts, and trim add a lot to the look of a home without adding a lot of expense. Forget the alternative building methods, they will just lead you down a hole that is impossible to get out of.
