I'm not an HVAC expert, just a home remodeler, so I get to see a lot of what's out there, and I also hear from quite a few people who have spent a lot of money to save money, and not seen those savings.
With all things mechanical, you have to be VERY CAREFUL in figuring out what is hype, and what is reality. What actually provides MEASURABLE results, and what is there just to make you feel better.
If I was building new house today, my focus would be on insulation and almost more importantly, wind proofing a house. I subscribe to several trade journals on home building, and where I'm seeing the biggest band for the buck is in keeping out the wind. House wrap was a big step forward, but it's full of leak points. Worse is around windows. Tape has gotten better at sealing windows, but the new paint on membranes are where the results seem to be really showing up. ZIP siding is far superior to OSB or plywood, and then house wrapping because of the membrane already on the exterior side. It's a much higher grade of OSB then what most people are used to, which is really evident when you cut it. You get it in 4x8, 4x9 and all the way up to 4x12 sheets. It's awesome stuff. Then you seal it with ZIP tape, which is really nice. I use it for everything now, it's what most people used to think Duct Tape was for, except Zip Tape really lasts and sticks to everything. Anyway, instead of the tape, the new membrane paints work even better. I've been using it in showers for years to waterproof everything. It's still expensive, but the results have been so good that more and more builders are starting to paint the entire exterior of their sheeting with it!!!
Heat and Cold go up and down. Here, the goal is to have R60 in your attic, which is about 2 feet of blown insulation. Foam is even better, but you still want the max R value that you can get. So far, anything after R60 doesn't seem to have any benefit.
In the walls, the R value isn't as important because of the up/down path heat and cold travel. This is why it doesn't really matter how many windows you have, it's how they are sealed that makes all the difference. Remember, most double pane windows are only going to be in the R4 range. Ignore all the gimmicky extras that are added to increase the cost of the window, all you want is ones that seal the best to keep the wind out.
Wind eliminates are R value from insulation. If you foam, the wind wont matter except around your openings in the walls, which are mostly windows and doors. If you use fiberglass, the wind will go right through it regardless of what you siding is. In just about every brick house that I've worked on, dirt is on the inside of the sheetrock,from where the wind went through the mortar, the gaps in the siding, and through the fiberglass and paper, to the sheetrock. Some houses are worse then others, but it's always there.
In houses that are 100% insulated with closed cell foam, and all the windows are taped, or painted, it takes almost nothing to heat and cool them. Insulation never wears out, never breaks down, and doesn't cost anything to operate. Put your money there first, then install what your HVAC expert in your area recommends.
As for finding an HVAC expert, good luck. I can't even count how many there are in my area, and over the years, I only trust and recommend one. Time and time, they have proven to be there when needed, and in every case, my clients where taken care of, not taken advantage of.
