Steady state R-values don’t apply since thermal mass is acting as a hot/cold storage vehicle. The complex thermal dynamics equates up to several dimensions of flow. The computer models will try and simplify to one dimensions. The new metric is DBMS (Dynamic Benefit for Mass Systems) that gives mass walls a comparative r-value to lightweight construction. ONRL (BTRIC) has a calculator based on three house prototypes in 10 climate zones.

 http://web.ornl.gov/sci/roofs+walls.../index.htm

So basically, thermal mass is all about loading/unloading hot/cold concrete from a source such as the sun or HVAC systems, preferable from the sun a free renewable source. The biggest bang for the buck are in areas where the temp fluctuates diurnal(daily) temperatures of say 50F with respect to the internal building set point. Mass performs equally well in hot a cold climates if the walls are able to load and unload.

According to a 2001 ORNL hot box test a CIC (Concrete Insulation Concrete) due to the above out performed ICFs (ICI),

“This data shows that the most effective wall assemblies were walls with thermal mass (concrete) being in good contact with the interior of the building (Intmass and CIC)”

SCIP (Structural Concrete Insulated Panel) is CIC and despite myths that a thermal bridge is created by the metal W-truss there are test and utility bills to the contrary.

 Contrary to popular believe ICF (ICI) by insulating the ability to load and unload performed much worst in the ORNL hot box test as seen by low DBMS value in the graph, http://web.ornl.gov/sci/roofs+walls...igure4.pdf

 “Wall configurations with the concrete wall core and insulation placed on both sides of the wall (ICI)/ICF performed slightly better than Extmass (foam on inside) configurations. However, their performance was significantly worse than CIC/SCIP and Intmass configurations. “

Due to day/night temp fluctuations the ICF/SCIP walls performed better in hot climates, not cold like popular believe has it.

 “The most favorable climates for both wall systems were in Phoenix and Miami and the worst locations were Minneapolis and Chicago”

 Click “conclusion” on left/bottom,

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

Conclusion, the most efficient predictable wall is CIC/SCIP with constant DBMS in adequate delta “T” climate zones. Thermal loading/unloading concrete drive weight/thickness/size design criteria with respect to passive solar gains that determine HVAC and structural load requirements.

Other References:

http://web.ornl.gov/sci/roofs+walls/AWT/HotboxTest/PCP/Metal&Concrete/index.htm

 http://www.bibm.eu/Documenten/ECP%2...%2009).pdf

 http://www.rci-online.org/interface...gatski.pdf

 http://www.homeenergy.org/show/article/nav/walls/page/3/id/1503

Texas Tech did ballistic testing on heavy mass vs light weigh construction. The weight and speed of the missiles (2x4s) were determined with a 220 mph wind and average projectiles speeds found in over 200 storms. Light weight construction and wood SIPs don’t survive debris penetrate walls, mass concrete walls shatter the missile. They tested helix added to concrete (not noted) but it is hard to analyze since concrete cannot be penetrated. I would think helix is not necessary although the thickness of the helix reinforced concrete may allow less structural thickness if the thermal properties could be maintained.

Concrete roofs are another unproven dilemma since most storms such as Moore, Joplin, OK lost the stick roofs even with hurricane ties from up lifting. Now rebuilding with eve vents to relieve internal pressures yet to be proven. A monolithic roof/wall concrete design would make sense here. Using the TX tech data in 90 degree wall ballistic and blast test one could assume greater impact resistance from debris force with a sloped roof, less slope, less force but, more snow loads and rain accumulations and perhaps unappealing esthetics that come with low or flat pitched roofs.

References:

Ballistic Video: http://www.depts.ttu.edu/nwi/research/DebrisImpact/

ICF Blast Video: http://www.tfsystem.com/Benefits/DisasterResistance.aspx

http://en.mdue.it/files/2012/07/May...rt_ING.pdf

Got it fixed with Fire Fox......I put the same post on CT/JCL got no response. I been reading some out here some of you are pretty good. Questions,

The ORNL test shows that mass benefits most in a CIC (SCIP) type configuration in locations that have diurnal temperature swings around the inside set point, how do I determine how much swing? Further,how do I determine the number of days the temp swings occur in a year?

 Looking at the ORNL test tables attached I can get close to my climate (IE: Denver) but if I am in KS and want more specifics how to determine the benefit?

 “The ASHRAE Handbook of Fundamentals lists “mean daily temperature range” data for hundreds of U.S. climates in the chapter on climate data (see attached). These values can be helpful in figuring out how significant mass-enhanced R-value might be for a particular climate, but they do not tell the whole story; also significant is the percentage of days during the heating and cooling seasons when the outdoor temperature cycles above and below the indoor temperature. “

 How do you determine mass effect or the mass enhanced r-value to calculate a specific DBMS? If you look at the tables attached you see a significantly higher DBMS for walls CIC/SCIP 2 say compared to 1, where wall 2 has more internal mass. Same for ICI/ICF that has less foam to the inside & more to the outside. You can see in both walls shifting mass inward with respect to insulation yields higher DBMS values.How do you determine how much internal and external mass shift based on a zip code?

 I downloaded and played with ONRL new CMAS calculator that does this I think by using test results but I am not sure what it is outputting (see attached).

 I’m amazed how many people are building popular ICFs in locations that have little to no benefit they should have put their money somewhere else.

 References:

ONRL Test Write-up: http://www.homeenergy.org/show/arti.../3/id/1503

Mass affect & DBMS Explained: http://www.buildinggreen.com/auth/a...ing-Issue/

ORNL Calculator: http://web.ornl.gov/sci/roofs+walls/AWT/home.htm

I’ve played and studied the c-mass calculator understand more. It is based on field test (prototype homes) built dated back over 15 years, 19 wall configurations, and 1000’s of computer model simulations validated further by protected hot box test. There is no update to the 2001 test report, but this new model captures history. The model simulates the r-value needed to match 2x4 light construction with different concrete heavy mass construction configurations (ICI, CIC, CMU, etc) by rewarding the mass walls with an  enhanced “dynamic r-value” DBMS. If anyone knows of a better calculator or rating system please inform me. You can tell ORNL spent a lot of time and money in this research.

It should stand to reason and no surprise (as validated by the model) that insulating the density and specific heat storage capacity of a mass wall such as an ICF yields worse results than exposing concrete to hot/cold daily temp swings with the proper storage lag time. Also, if you expose the thermal properties to greater fluctuations around the homes internal set point to say temperature swings found in Phoenix for example, concrete will perform better at in-taking and exhausting hot/cold air to drop heating loads, worse in the Minneapolis.

I think the calculator is a good tool (I have not seen being used on forums anyway) to justify a comparative cost study of construction of stick framing to ICF/SCIP for example. I think many are assuming too basically that mass will produce lower energy bills in all climate zones and is cost effective. There is also a myth that mass performs better in cold climate zones when as you can see by the ORNL test that is not true. What I find baffling is why ICI/ICF is growing in popularity more than CIC/SCIP that out performs it. Appears to me either the public is not educated or the ICF manufactures are doing so good marketing, or both. No offense to ICF owners there are other benefits to mass such as burn rate, sounds, ballistic, blast, etc…

The attached shows in Bolder if I built ICF I’d see a reduction in cooling loads of around

15% to stick, SCIP over 50%. Comparing SCIP to stick heating not much of a difference in gas bill, a much lower electric bill, and a very small percentage saving’s in annual energy bill.  If I went to a stick build I would need an R-36 wall, an R-16 increase to R-20 used to compare stick-to-mass when I ran the model which I may find stick is cheaper to build than ICF or SCIP.

Run the calculator in Phoenix annual saving’s improves from lower heating loads better swings, gets worse in Minneapolis higher heating loads worse swings. As far as I can tell and assume, the calculator is taking averages and not getting into specifics or improvements arising from shifting more exposed concrete mass to the interior, less to the exterior. I guess one could look at the hot box test report and interpolate a reduction in energy bills by doing so. It's still not clear to me how to design to mass and lag times, I guess by hand wish I could find a model.