Concrete ICF home continues

[dfkrug]

Patrick:

There is nothing wrong with concrete backer board. I prefer
Hardi-backer myself. Have you worked with it? Tough to cut
and screw, and comes in funky sizes. I did my walk-in shower
with the 3x5 Hardi-backer and it was a lot of work. The seams
also need to be taped. For the exterior, wire lath and conventional
stucco would be easier, IMO.

[Paddy]

dfkrug,

My main issue with wire lath besides the cost and effort is attachment. I plan on installing an additional 2" of foam over the ICF existing 2-5/8". I feel this additional insulation is well worth the investment. I will glue and randomly use screws/fender washers to attach this extra foam. The wire lath I assume would require some major attachment. What was your attachment method?

Patrick T

[dfkrug]

Attachments (interior and exterior) were a major challenge to
the development of ICFs. The early products were all foam and
required that all attachments adhere with glue. Not impossible,
but difficult to properly apply and hard to proof-test. So virtually
all ICFs have gone with a metal or plastic tie that is integrated with
a web that holds the 2 sides of the form together. On the outer
surface, these ties formed mechanical attachment points, aka
"furring strips". The furring strips are flush with the surface or
embedded in the foam 1/2" or so. Spacing is 12" on some forms,
and as little at 6" or 8" on others. Early plastic tie forms had
flush strips and suffered from easy screw pull-out and the plastic
deteriorated in the sun. My first forms had flush sheet metal furring
strips (folded 26-guage sheet metal), 12" o.c. I use an impact screw
gun (like those used by steel framers) and 1/2" sharp-point sheet metal
screws to attach paper-less wire stucco lath. I see that some
ICF manufacturers have now moved to wider and thicker plastic
furring strips (e.g. Fox).

Patrick, if you add insulation to your ICFs, adding to the INterior will
result in better energy performance, and adding to the ceiling will
help more than to the walls. Furthermore, if you still want to go thru the
extreme efforts of attaching insulation to the outside, the best panels
you can use are polyisocyanurate, not EPS. The former are around
R7/in, while the best EPS is only R4.5-. Gluing to them may be a problem,
however.

[Paddy]

dfkrug,

The most ideal concrete/foam wall is all the insulation on the outside of a concrete wall.
Thermal Mass Discussion Forum

The ORNL site shows this in their real testing results. But in the big picture, ICF are easy to build with, i.e. foam distance for ele. Keeping the thermal mass on the inside is the goal to stablize the daily temp cycle. I know there are beter foams out there but they also cost as much as twice as much. For example; The blue DOW Extruded foam is $22.5 a sheet at R-5/in. The white stuff, Expanded foam is $10 a sheet at R-4.5/in. Do you know the source and cost for polyisocyanurate?

I do plan on much insulation in the roof as well.

I like your statement at the bottom of your posts. I am an engineer who used to be a builder, go figure!

Patrick T

[dfkrug]

Originally Posted by Paddy

The most ideal concrete/foam wall is all the insulation on the outside of a concrete wall.

There are many variables involved here, incl climate, sun exposure, thermal
siphoning footers, choice of heating/heating methods, etc. I am familair with
the Oak Ridge whole wall performance studies and experiments. They were a
factor in my deciding not to insulate under my floating slab. Little benefit in
my mild climate. In some very real-world cases, it is desireable NOT to have
the thermal mass exposed directly to the interior. In other cases, it could
be more beneficial to insulate more on the ext vs. the interior, I will give
you that. But that is too big a discussion for TBN.

As for types of PU insulation board, even HD has it, but expect to pay
2x what EPS costs. Many buliders in hot climates (e.g. Las Vegas) went
with this kind of exterior sheathing to supplement f/g ins in the stud cavities
in recent years. Often it was stucco-ed over. Thermal performance of
tract houses in LV has dramatically inproved.

[Tororider]

Paddy, you are killing me, I am dying for pictures. I suppose things are going to start slowing down with the weather.

I will throw my thoughts into the exterior siding. Was brick ever a consideration. I would think that brick has a good insulation rating and it would definitely add to the thermal mass.

I am just throwing that out there. Don't know much about building... yet. Trying to learn as much as possible in the next couple years. Cost probably is a consideration, I have no idea how much bricks cost in comparison to hardi board or stucco.

Btw, I would assume that cement floors, if possible, would be a plus in keeping heat in with r value?

[Paddy]

Tororider,

Brick is expensive and it does not fit the design style. The home is modled after the Spanish style. I really like the look of stucco. Also, brick is not a good insulator. I will have plenty of thermal mass with the concrete walls and floors. I estimate 450 cubic yards of concrete. We have slowed for the Winter season but also hoping to sell my existing home first. So far I have not gone to the banks for construction loans and I'd like to keep it that way! My goal would be to get the first floor, suspended, poured before Winter. This way I can back fill and buttom her up.

Patrick T

[mjncad]

Brick is a wonderful and almost maintenance free material; but as Paddy says...it's a bad insulator. A brick veneer gets hot in the summer and cold in the winter. Building a wall system correctly can minimize these effects, and I would never shy away from brick if the budget, design and energy efficiency warrant its use.

[Paddy]

Here is the look I'm going for inside. This photo came from Mexico on a biz trip. My open space is 30' by 30'. Not as big but I hope it will get the feel.

Patrick T

[mjncad]

Nice...I was wondering what your house's style was going to be. If you have any sketches or renderings of the intended result, I hope you'll post them here.