I’m an architect and I’ve got a client that wants to have exterior concrete walls that show up on the inside, that is they want to see the concrete on the outside and also have concrete on the inside. I understand their aesthetic desires, but concrete will be terribly cold here in the Colorado winter. I’ve thought of pouring two walls with a layer of rigid insulation in between, but that seems excessively expensive and we also want a high R value. Anyone have any experience, advice or suggestions?
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I am not an architect or engineer just to qualify my opinion but I have had some experience as a builder in this area.
The two experiences I would draw from would be building in Alaska (non-tundra) and building recording studios. Both share your problem: a need for insulation in a concrete wall.
The answer is concrete block. You can place a lot of insulation in it, it can be built up by masons rather than the expense and time of building forms and then stripping forms. And in most area's code requirements you can build higher walls.
You might have already thought of this option and rejected it because many people do not like the aesthetic value of concrete block, to which I cannot entirely disagree. But there is an amazing variety of styles and colors now, many are quite attractive. There is also the option of parging or stucco on the interior or exterior to create a different color texture.
Another idea would be to add pearlite or another insulating medium to the concrete/in-form mix to increase R-value but I don't know the parameters for this in a structural sense.
Another consideration for both concrete and concrete block walls is your infrastructure: i.e. plumbing and electrical having to be placed on the surface of walls or in the floor.
Have you thought about straw bail construction?
I had thought about using straw bale as an insulator between two 6" poured concrete walls, with a 6 mil poly barrier to keep the concrete out of the straw, but that just seems way to "over the top". I know the client won't go for a stucco or plaster wall, they want the look and feel of real concrete in some (not all) of the walls. I do plan to use the concrete walls for thermal mass in a passive solar design, but it will ot be a trombe wall on the south.
But thanks to all for the suggestions. I'll keep my thinking cap on for awhile longer.
Look into the tri-d-panels. http://www.tridipanel.com/ Concrete only? No way.
I was curious about this technology too but the website is having some problems and the page wouldn't open.
Edited 8/28/2004 8:27 pm ET by Spike
Hmmmm, all works for me...
The tri-d-panels just might do the trick. They already have reinforcing and could be used as an interior insulation for the wall. Thanks!
Try Composite Technologies Corporation 525 east 2nd st. POBox 1888 , Ames Iowa 50010 800 232 1748
This is ten year old info ,but they had pour in place foam insulation products . Plastic tys that held the XPS foam in the "center" of the concrete form and the 'crete was poured on top of the foam to split the flow and fill both sides at the same time.
You mention aesthetics but is it possible they intend to make this a tromb wall, I think that is the term. A south facing wall to absorb heat and release it to the inside at night.
In that climate I read that this has some advantages if a greenhouse structure, to limit convective heat loss and contain the heat during the day, and a removable insulation system, to keep the heat from flowing back out at night, is installed over the exterior.
If they are just into the concrete bunker look, no accounting for taste, and there is no structural reason to need a full concrete wall perhaps you could use insulated forms for the concrete and finish both sides with a good stucco system. Stucco at most of an inch thick and applied over a steel mesh has a resemblance, look and feel, to solid concrete. If put on with a smooth hard troweling I have seen look very much like solid concrete.
Of course the insulated forms are just one base. Steel or wood framing and various panels, including concrete board, might provide a good base and allow plenty of space for insulation.
Cement block, 6" perhaps, with rigid foam insulation on one or both sides and finished with stucco would be an idea.
I'm not sure any of these ideas are good or if they might work on your project but maybe they will bet the juices flowing. In the mean time ... well ... bump.
I think Spike had a good idea with insulated concrete block walls and parging. Dry stacked block was a rage several years ago, is it still available? Haven't heard anything about it recently. When that's done, it has the look of poured concrete. I'd be inclined toward two block walls with insulation between (if I could afford it) because the webs of the block conduct heat out past the insulation in the cores. Perhaps do it like veneer brick, only use 4" masonry units as exterior "veneer" wall and 8" as the interior and stuff the space between with insulation. I'm just sort of thinking "out loud".
I don't know if this will help much but I remember reading about lightweight concrete that has good R-Value and can be structural. I did a quick Google search and found several different web sites I will link on here I guess you can do some cool stuff with it.