All depends on the temperature of the concrete as it cures. Lots of references regarding this.

JMaGill; thanks for stating and opposing some of the bias i have observed here. Thermal mass is useful in keeping a house cool where there is a diurnal swing; since I am in CA, it applies to me. I have asked similar questions to this OP, and got the same line of nonsense, even after specifying Ca location. With ICF's heat that creeps in during the day can not be absorbed by the mass because there is foam surrounding it. No difference from drywall and stickbuilt, so air temp increases. Concrete walls exposed on interior absorb the heat, keeping it cooler inside, then radiate it back out to a cooler night time temp.

I have never said it works in humid areas, cloudy areas or in cold winter heat needs. But the ICF spokespeople (sales) talk like it works everywhere. I've quit asking questions, because straight answers that are well supported are hard to find. So thanks for being a voice.

With ICF's heat that creeps in during the day can not be absorbed by the mass because there is foam surrounding it.

The interior heat DOES pass to the mass. The inner layer of styrofoam just slows it up, like any other insulator would.

Posted By ICFHybrid on 09 Nov 2011 07:45 AM

With ICF's heat that creeps in during the day can not be absorbed by the mass because there is foam surrounding it.

The interior heat DOES pass to the mass. The inner layer of styrofoam just slows it up, like any other insulator would.

The problem is that the insulation slows it enough that there is little or no benefit from the daily thermal flywheel in solar homes.

Did you have some studies you could direct us to that would support that contention?

Do you have studies that support your contention?

You might want to read this.

http://arch.ced.berkeley.edu/vitalsigns/res/downloads/rp/thermal_mass/mass-sml.pdf

Or this

http://www.ecospecifier.com.au/knowledge-green/technical-guides/technical-guide-4-thermal-mass-its-role-in-building-comfort-and-energy-efficiency.aspx#radiant interaction

Do you have studies that support your contention?

You may be confusing me for someone else. I don't have a contention here save for the basic laws of thermo.

http://www.ornl.gov/sci/roofs+walls/research/detailed_papers/thermal/index.html

Look at figure 6

http://www.ornl.gov/sci/roofs+walls/research/detailed_papers/thermal/figures/figure6.pdf

Figure 7

http://www.ornl.gov/sci/roofs+walls/research/detailed_papers/thermal/figures/figure7.pdf

The above reports do not even take into account Solar

http://www.ornl.gov/sci/roofs+walls/research/detailed_papers/thermal/index.html

"CONCLUSIONS

Experimental and theoretical analysis of the energy performance of light-weight and massive wall systems was presented in this paper. Dynamic thermal performance of sixteen wall assemblies was investigated for residential buildings and the potential energy savings were presented for ten U.S. climates. It was found that some massive building envelope technologies can help in the reduction of building annual energies.

Several comparative field experiments have demonstrated that in many U. S. locations, heating and cooling energy demands in buildings containing massive walls of relatively high R-values can be lower than those in similar buildings constructed using equivalent R-value with lightweight wall technologies.

The thermal mass benefit is a function of wall material configuration, climate, building size, configuration, and orientation. From ten analyzed U.S. locations, the most beneficial for application of thermal mass are Phoenix, AZ and Bakersfield, CA.

Comparative analysis of sixteen different material configurations showed that the most effective wall assembly was the wall with thermal mass (concrete) applied in good contact with the interior of the building. Walls where the insulation material was concentrated on the interior side, performed much worse. Wall configurations with the concrete wall core and insulation placed on both sides of the wall performed slightly better, however, their performance was significantly worse than walls containing foam core and concrete shells on both sides.

Potential whole building energy savings, available when lightweight walls are replaced by massive walls of the same R-value, were calculated for 143 m2 (1540-ft2 ) one-story ranch houses located in Minneapolis, Minnesota and Bakersfield, California. For high R-value walls, up to 8% of the whole building energy could be saved in Minneapolis and 18% - in Bakersfield when wood-framed walls were replaced by massive wall systems. Thermal mass layers must be in good contact with the interior of the building in these walls.

Whole building possible energy savings in houses built with ICF walls were estimated as well. Three houses with 74 - 279 m2 (800-3000 ft2 ) of floor area were simulated for this purpose. It was found that for ten U.S. locations, ICF walls of R- 2.6 and 3.5 m2K/W (15 and 20 hft2F/Btu), the average potential whole building energy savings (ICF house vs conventional wood-framed house) can be between 6 and 8%. "

Comparative analysis of sixteen different material configurations showed that the most effective wall assembly was the wall with thermal mass (concrete) applied in good contact with the interior of the building.

But note that their results will change completely if you change the assumptions regarding how widely you allow the interior temperature to vary. No interior temperature variation (what most people like) leads to practically no thermal storage or savings with interior mass. Temperature setback is another issue - evidently most people with high interior mass homes don't use it - missing out on a ~10% (also varies widely) savings that negates "6 and 8%".

"Potential", "up to", "possible" and "can be lower" are very important parts of the quote. You can correctly add "can be higher" and "can be the same". Something to think about before proceeding with high mass.

Greetings,
I have found, by experience, that if you install a single reflective foil on the exterior of the ICF wall before siding, steel siding best, or bricking and install an advanced 3 layer RI sys in the ceiling that the performance is enhanced. One customer who did this had the local utility company changing the meter because the usage was TOO LOW.

However ICF may not be the only choice for incorporating mass thermal effects. In the late 80's I had a contractor who install 1 1/2", 1.25#, t and G foam on the exterior of the basement walls. I installed a 3 layer RI sys ceiling and walls. The operating costs were very low. In one house he built in a solar room and used the hot air to warm basement stored rocks that were used to heat the house. Worked very well. The house never exceeded 81 degs in summer without ac, so the ac bills were low too.

It is just that kind of incorrect information that does the ICF a disservice. If you are going to stretch the truth on that what else are you going to stretch the truth on.

Greetings,

You shouldn't make comments on something you know nothing about.

Now that you have accused me of lying, I now know that you do the same.

I have over 30 yrs experience as a reflective insulation (RI)contractor. How many RI jobs have you done?