I am looking for the most cost effective way to provide a very efficient home.   I have been reading all the great things about straw bale.  However this company that is willing to do a passive/active solar design for me told me to look into ICF so that is why I am here.  I would like to get opinions on which is better for heating and cooling straw bale or ICF.  I am only going to be building a 1350 sq ft home to start that I would like to be designed for easy additions as well.  The company that is going to be working on the design that asked me to look into ICF is http://www.wisehomedesign.com.  I appreciate everyones help in advance.

This is just my opinion, but I wouldn't build a strawbale home, there is just something about making exterior walls out of a perfect material for bug food and mice homes doesn't sit right with me. Other people may feel otherwise. I don't want to argue over this, I just state this as my opinion. In my way of thinking, there are other types of insulation that are inexpensive besides strawbales.

ICF's are a nice system, but very pricey. Reinforced concrete isn't cheap. And, you can build a stick frame home just as tight if you will pay attention to the details.

You can get a lot more R for the dollar using a double stud walls and stuffing them full of insulation. Construction is easy, just put up a 2*4 wall, leave a 4" (or more) gap and put up a second wall. The gap eliminates the direct wood thermal bridge that is in most stick frame homes.
Fill with batts (easy), spray foam(pricy but seals well), or blown insulation(cheap but can settle). If you go with dry blown insulation, I would leave a way to top off the wall cavities from the attic, and make the bottom of the window casing removable to top off those cavities under the windows.

Don't overdo the windows, as they are you biggest losers. If you can, put most of them on the south side and use fewer larger windows instead of a lot of small windows. Also, don't go cheap on the windows, as a window with a bad R value can ruin a wall, no matter how the wall is insulated.

Here we go again, the infamous "double framed stud wall" with all of the insulation options. The only thing "green" about this system (this forum is titled "green building talk", isn't it?) is that it will be more energy efficient than a single framed "stick built" wall, and you'll probably be framing with "green" lumber (really green, like in high moisture content which usually twists and warps when it dries, resulting in walls that are not plumb, straight, and square.) Ok so, use KD framing lumber, or, better yet, engineered lumber, that'll take care of that problem, won't it? Of course, you won't just be buying 2 x 4's, you'll be buying 2 x 8's, or 2 x 10's if you leave a gap between the 2 walls for the foam sheets (For plating, wrap, etc.) And, this only address the walls, if you don't put a nice tight "lid" on your virtually airtight walls, your conditioned air is forced right through the roof openings that are inherent in conventional "stick" construction. How much is all of this going to cost?)

I apologize if my above statements appeared to be contentious, or argumentative, these are my opinions based on about 35 years in the construction industry, with the last 15 years solely involved in the field of "green" building, primarily with SIPs and ICFs, but with some experience with strawbale, and other related "green" building materials.

Some brief personal observations in connection with the 3 "green" systems being discussed in this thread (I'm aware that I'm the one who added the 3rd, SIPs)
1. Stawbale: Very "green", organic, energy efficient, etc. However, for anyone who's seriously considering this system, read up on it, and be sure that its a suitable way to build in your area. Hire an "expert", check his references thoroughly, and tour examples of his work. Also, when you're considering your square footage, be sure that whomever has jurisdiction over the permit process in your area allows for a variance for the 2' thick walls, otherwise you could lose a lot of your planned 1350 sq ft, or you'd have to build a larger footprint.(If you go this route, consider a SIP roof)
2. ICF's: A great way to build, but bottom line, probably only a little more costly than starwbale "done right". One caveat, in connection with all of the building systems discussed in this post, I'm assuming that you're going to use a licensed "pro" who is experienced with whichever sytem that you elect to use. The whole equation changes with owner builders as some put a value on their time, and some do not, so speed, and ease, of construction will be of value to the former, and maybe not to the latter. (Again, if you build your walls with ICF's, consider a SIP roof)
3. SIPs: Less expensive than either of the above systems, relatively simple to install, super energy efficient, along with many other "green" benefits. Can be used for walls and roofs, and sometimes, floors.

A newcomer to this site can spend countless hours perusing the "Green Building Talk" forums, and, by doing so, will hear many different opinions in regard to the pros and cons of the various building systems discussed herein, and, also, with patience and fortitude, can probably find the right combination of materials and services the meet his/her specific needs.

Good luck with your search for the "perfect way to build your home" That's what this is all about, isn't it?

I could sit here and list problems with any construction system. I could pick though the post you made about the system you suggested and make comments. But I'm not going to.

In the posters original post he mentioned he was looking for the best R value for the least cost, and behind strawbale, a double stud wall with dry blown insulation filling it fits the bill. You can use a 16" gap between the walls and have an R-(3.5*24)=R84 wall for the cost of 2 2*4 walls and a bunch of dry blown insulation. Any other system that can get into that ballpark? No, it won't withstand 300mph winds, and yes you have to take precautions to make it air sealed well, but look at the bang/buck.

I know a lot of people on here will disagree with me, but just notice that most of them are selling the product that they say is better for a living. I don't sell anything for a living, and I don't get any money if a bunch of people buy double stud walls. I am just trying to help people realize there are other options out there.

Aardvarcus, I stand by my comments in response to the orignal poster's questions,eg: strawbale is a great way to build, certainly "green", but requires unique expertise, which is usually espensive; ICFs are hard to criticize, and while they are costly, they're sometimes the absolute best choice (I included the caveat of "professional" installation in regard to these two building systems) Then I added SIPs as something to consider when factoring in cost. I also stand by my contention that a SIP building envelope will perform as well, or better, than the most elaborately concieved framing system, at comparable, or less, cost. Then there are all of the other "green" benefits of SIPs (Double 2x4 walls with a 16" airspace? give me a break!) Also, on one of your posts you even advocated sheathing the interior of a double stud wall because it would result in a "giant box beam" (maybe not your exact words, but close, what do you think a SIP is, with the sheathing on both sides?)

Yes, I do "sell" SIPs and ICFs, and provide all needed related services to my clients through an association with like minded GBIPS (Green Building Insustry Professionals). I "sold" conventionally framed systems for about 20 years before I discovered SIPs, and later ICFs. As another of the regular "professional" contributors to this site once said, and I'll paraphrase "I don't sell these products because this is my business, I chose these products as my business".

In closing this post I do want to express my agreement, to a degree, with the following statements "Using lumber from managed forests is one of the few ways to actually reduce the amount of co2 in the atmosphere" I don't know whether that statement is technically correct or not but I do believe that the utilization of well managed timber resources, in a responsible manner, is an enviornmentally sustainable, or "green", thing to do. However, if everyone built with double 2 x 4 walls, with plates and "wrap" requiring 2 x 8' to double 2 x 12's (or equivalent) we'd probably run out of these resources in pretty short order) And, absolutely no quibble with the statement regarding "The green benefits of reducing the energy used by a building over its lifetime".
Having said that, I'll stick with my contention that SIPs and ICFs are the best way to achieve this goal, with the technology at hand, on a large scale basis.
While Strawbale, Cobb, Rammed Earth, Earth Sheltered, Earthships, etc etc are all certainly green, and more organic, and I never discouage people who are interested in these building systems (I've put a number of SIP roofs on strawbale walls) However, put them all together, and they won't make a dent in the overall "big picture".

Also, I always have to add "a building is more than walls........remember the roof, and the floor system, or, the entire "building envelope".

OK, enough for now, that's my story, and I'm sticking to it! (This is not an "argument", Aardvarcus, just a "friendly discussion, right?)

Thanks for your replies.  Can someone point out the what makes ICF more energy efficient than strawbale. 

you have to consider that an icf/sip home will have good resale value and a strawbale home may be very tough to sell in the secondary market.imho a home like that would probably require a 30-40% discount to sell.

My wife, for one, would not consider living in a straw bail house yet she likes SIPs!