There are many ways to do everything. In Seattle, there are many houses built this way, especially in Mountlake Terrace (hundreds). They suffer many issues, but mostly dampness from the indoor warm water vapor. Having researched this issue in trying to decide what to use for my next house, this is what I would do, and opinions vary, so use common sense.

I would insulate on the outside if possible. By doing this, you can take advantage of what you already have....high thermal mass. Use either spray foam or rigid polyurethane on your exterior block, even if you have to remove the siding and put it back on. If you don't have siding you are in good shape. Use furring strips that are insulated from the blocks with a thin foam to create some thermal break to hold your siding. Glue the foam panels or spray between the furring. Put your siding back on, or use stucco, plank, etc. You can now hold your siding off of the insulation so it can breathe if you use wood, per standard methods.

This insulation envelope will allow the high thermal block mass to warm up to room temperatue and radiant some of the heat back into the house. It is argueable how much this will help in terms of energy cost, but it will make the house temperature more stable and therfore more comfortable. Since a wall is only as good as the total 'system', think about doing a blower test to find all of your air inflow and outflow weaknesses. Caulk and foam all of these areas. Use the best doors and windows you can afford. Ensure that your attic is properly ventilated if you have one, and insulated to what you can afford. If you make your house very tight, you should invest in a ERV system to be healthy. If you are on a slab, and their is no thermal break between the foundation and/or the ground, you have a more difficult situation.

This is why in my new house, I have decided to use ACC blocks, after researching almost every other system on the planet. My next choice is a monolithic dome, but my wife doesn't think 'round'. :)

I just received this letter from StyroNews. It sounds like you may have a need for this type of product. Outside envelope and this on the inside.

http://epsdrywall.com/index.html

Thanks for the reply, Jim, and thanks for the link to the EPS drywall. Cool stuff.

I liked the idea as far as insulating the exterior of the home. But I am hesitant because of what I would be giving up / trading off. The masonry block seems so resiliant / impervious to the elements and termites.

For now, I will be addressing the issue from the inside of the walls. I realize that it likely will not be as affective as insulation on the outside. Maybe someday we will be in a position to do that at a later time.

Do you think it would be best to fir out the walls with 2X lumber, or can the EPS go directly onto the block walls? What do you think about a radiant barrier such as a product like Refectix foil/bubble/foil?

How to get the best of what we have to work with is my goal!

thanks again

Mark

I would fir out the inside block wall. Create a thermal break by putting a "gasket" between the wood and the wall. I furred out my garage wall that is buried on the West side with 1x2 treated lumber (code), and put a thin insulation film under it. I used a non-VOC adhesive and nailed the sheetrock to it. It has made a huge difference with this, even after installing the insulated garage doors. I use part of the garage for a study/office. In your situation, you will get a huge benefit by doing the basics, and this might be the best cost/benefit ratio for your situation. Sometimes, the simplest method is the best approach. Ideal situations are rare, except in new construction. You have to be conscious of the potential for vapor condensation because of the temperature delta inside and outside with a concrete wall. This is why I am a believer in the high thermal mass approach and insulating on the outside. Siding is not supposed to be a thermal barrier. It is a system disigned to protect the house, and it must breathe to avoid rot. Even stucco has to be held off the exterior wall to allow for the inevitable water intrusion. Breathing allows it to dry without rot. Insect barriers can be incorporated into any siding system. :))

Quadlock has a new product for retro fitting that does not need furring check them out... E retro i think it's called

If it were me, I would install a 2*4 wall on 24" centers inside the walls, leaving a 2" gap between the new wall and the old block wall. Then you can stuff the cavity with 6" R-19 Insulation, letting it fill the gap as well as the stud cavity. This also makes it very easy to run all your wires and such, as well as not having any thermal bridges. If your block wall is not already waterproofed, you should definitely waterproof it first to prevent any mold/dampness problems.

InSoFast is the only way to go!!!! InSoFast.com

It sounds perfect for you installation, has about R-8 but has no thermal-bridging like a 2x4 wall and will not mold like a 2x4 wall. Easy to install. Quadlock has something similar but InSoFast is better.