ICF or Concrete Block w/ Ext. Insulation
mrieken
| Posted in Energy, Heating & Insulation on
I am planning a house in the Hill Country of Texas. I am debating between ICF construction and concrete block with external insulation. One of my primary drivers is energy efficiency and large thermal mass. I plan wrap around porches and wish to leave the windows open as much as possible. The building site is on a hill and gets a good breeze. ICF looks good, but it seems that the insulation on the inside of the house somewhat negates the advantage of the large thermal mass. My question is, what are the comparitive advantages of ICF versus concrete block with external insulation?
Replies
I'm not sure thermal mass has much benefit in a mild climate. In cold climates it can store up heat from sunlight during the day and release it during the early part of the night, but I don't imagine you'd have many days where you'd want the sun baking in and store up heat. Besides, the insulation is so good you'll need very little heat anyway.
The pros of ICF's include these.
Depending on the brand, ICF's can deliver an R-value around 25 or so. That's much higher than is recommended even for homes build in the cold parts of the U.S., so it will be very much more insulated than anything anyone in your area already builds.
>I'm not sure thermal mass has much benefit in a mild climate.In general, thermal mass with exterior insulation will have the greatest effect where there meaningful daily fluctuations and where those fluctuations range above and below the desired interior temp. If the fluctuations are from 85 to 110, the mass won't have much of a chance to dissipate the heat energy. If the fluctuations are from -20 to 10, it won't ever absorb much heat energy. But from 50 to 90 would be work well, as the moderating effect of the mass would significantly help to limit the interior temp fluctuation.I also would prefer the poured ICF wall to the CMU wall for disaster resistance. For energy concerns, I don't favor the interior insulation at all. Over each of these, I'd consider a poured wall with exterior insulation, or the sprayed/poured sandwich walls--concrete/insulation/concrete.
Thanks for the information.
Hi,
One way to get an idea how much difference the thermal mass would make in your climate is to model the house with HEED. HEED is a free download here:
http://www2.aud.ucla.edu/heed/
Its a very easy to use (written for homeowers), and the newest version has the ability to add thermal mass inside the structure -- I think under the "advanced" tab. Try it with and without the thermal mass, and see how much difference there is. Also good for making other insulation and solar decisions.
Gary