I don't want to hijack your thread, but I have the exact opposite question! We are thinking of air krete foam in our existing walls and blown in cellulose in the attic. Is the air krete (a cement based foam) much better than dense pack cellulose in the walls? It's about $1200 more. Any help with insulating info would be greatly appreciated. We currently have next to none in both attic and walls. Thanks.

midwest- can you be more specific? Midwest has 2 main climate zones, 5 and 6. While they are similar, 6 has more IECC requirements. I design for 6 all the time, even though some of my projects may be in zone 5. I sit directly on the line between the 2. Either way, house wraps are NOT, repeat NOT an air barrier to provide a tight home. Depending on the climate 5 or 6, the easiest way to get a tight, energy efficient is to use typical framing with an exterior air barrier plane, and insulating sheathing. The climate zone will decide how thick the exterior foam sheathing is. My go to wall structure is as follows: air tight drywall on the interior, NO vapor barrier/plastic sheet, blown fiberglass insulation, 2x6 framing (24" o.c.) with rubber gasketing to the subflooring, Huber ZIP sheathing caulked to top and bottom plates, seams taped, 2" XPS insulating sheathing (2 layers of 1" with the seams offset and overlapping), 3/4" vertical strapping drainage plane, siding of your choice. The exterior thickness of insulation will adjust in thickness up or down based on your climate zone to eliminate condensation on your sheathing/within your wall. Another cost effective, highly efficient wall type that I also like to use is the double stud wall. I have found it has a similar price as the one above, but has a higher r value, but it is a thicker wall and you lose interior floor space. Either solution, caulking and air sealing is your first priority. Insulating second. There is a ton of info out there. I would suggest you check out Green Building Advisor website for a ton of great information. Also check out the Build Science website for wall assemblies, pros and cons, etc.

When you are looking at new construction. Blown in fiberglass is the better choice over blown in cellulose. For one R-factor is clear when you look at each individual manufacture's spec. Blown in fiberglass in 2x6 walls get an R-23 vs. cellulose gets an R-20.6. You can get a better R-factor in a ideal setting no wires, in cavity with high density fiberglass blanket/batts R-21. Blown in fiberglass is maybe a fraction of extra cost but no more if you go with dense pack cellulose with a netting. Which by the way if you do insist on going with cellulose make sure they install dry pack with netting. I don't know how many times I have seen mold law suits that have involved wet-spray cellulose. Wet spray you have to wait in ideal setting 72 hours (that's by the way 70 + degrees and almost zero humidity) before you can cover. How many times will the ideal setting happen during that stage of building? Which is not even the worst part, if you are planing to have cabinets installed on the exterior wall, guarantee if you went with wet spray cellulose you will have a mold issue there. I have been around insulation for over 14 years and for some reason a lot of people have never even heard of blown in fiberglass almost every one associates fiberglass as being the preformed batt/blankets. And if you look at most fiberglass versus cellulose side by side comparisons they always show the blanket/batt form of fiberglass why? Because that is the only thing cellulose is better than is the blanket/batt form because of the perfect fit scenario. In fact in studies from fiberglass companies show blown in fiberglass is up to 70 percent better than standard blanket/batt form fiberglass in air infiltration. They even have a sample where one side of cavity is blanket/batt then other side is blown in tight and you have a hair dryer attached blowing through both materials at the same time. The blanket/batt side reaches temps of 130 degrees while the blown in tight fiberglass only gets to 85 degrees. But blown in fiberglass you get both worlds perfect fit and highest R-factor. As to the case which products works best in ceilings. Again there is no specific studies that I have found in my research that is non-biased that says Cellulose is better than Fiberglass. Why is that? Because cellulose is not better than blown in fiberglass. If both products are installed to manufactures spec in inches then they will perform the same, until cellulose settles 20 percent as it says on the actual bag of material. In all the thousands of attics I have looked in almost every one that was installed with cellulose had settled below original suggested R-value at least 20 percent. The only time fiberglass need to be fixed is because of contractors or tradesmen have been up in attic and they never replace the insulation or they stomp all over it until there is nothing left but the depth of the bottom cord of truss. Also the rumor of cellulose being better in extreme cold temperatures I personally have found to be amusing. My brother lives in Alaska 40 degrees below zero and I asked what kind of insulation does he have in his house? Guess what it was fiberglass insulation. Bottom line fiberglass is better in exterior walls new construction and it performs the same at first in ceiling until cellulose settles then in the long run fiberglass is preferred between the two most common blown in insulation. Now if you have at least double the normal budget for your house then I would strongly recommend at least 1" thick sprayed closed cell urethane then covering the 1" spray with either blanket fiberglass or blown in fiberglass. Blown in still being the better option over blanket because of the perfect fit concept. This application completely shuts off any air movement in the wall cavity thus helping the fiberglass do its job to a better ability. One more word to the wise make sure you go with closed cell when you go with foam insulation. Open cell is no good it will absorb water like a sponge, and the R-factor is not there you can get better R-value per inch in blown in fiberglass in exterior walls. Well this has been my experience the past 14 plus years in the insulation industry. Take it for what it's worth. I hope this helps people. I feel I may have done a little to much rambling. Sorry for so much confusion that is out there. I really am only doing this to try to help combat all the confusion.

Here is my response to a similar question on one of the other boards. I reasearched this a lot, and though I'm not in a cold climate, most of the recommendations would hold for your situation: I had a similar situation. Some genius had put 3 inches of blown fiberglass in the attic (over the knob and tube wiring!) and that's it. The room was hot in the summer and cold in the winter. Here is what I did: - r13 on the floor between the soffits and the back of the kneewall - this was over conditioned space down below (I didn't cover it, but I could have if needed for storage)- rafter vents at the soffit-end of the insulation keep the soffits open - r13 kraft faced insulation on the back of the kneewalls (2x4 wall construction) - 2" isocyanate foam insulation (r14)with reflective surface on the angled portion of the ceiling, leaving 1.5" air space up to the unfinished part of the attic. My rafters were true 2"x6", so I didn't need the fancy channeled insulation. This insulation is R7 per inch, so I got R14 on the slanted portion. - R38 faced insulation in ceiling of the finished space, with eyebrow roof vents to keep air moving through there. - seal up all penetrations (electrical boxes, pipes, etc) with caulk or spray foam) The principles you need to follow are that you should insulate any of the unconditioned space where air from the outside is flowing. Any vapor barrier (e.g. the kraft facing)should face the INTERIOR - don't put insulation then vapor barrier, because then any moisture from the interior will reach the cooler air of the unconditioned space and condense, leading to mold. If you use the foam insulation, you have to cover it with a fire rated material (e.g. sheetrock). You could also consider using the new reflective sheets on the bottom of the roof sheathing - I didn't do this, but apparently it has a huge impact on heat gain. The impact - the upstairs is comfortable all year. It has no dedicated heat or AC, but never gets below 65 during the winter or above 72-73 in the summer. If it gets stuffy on the hottest days, I open a couple of windows to get a cross breeze. Hope that helps.