Hello I am wondering if u were to run pex in the wall by heating it will that increase r value? If u were to heat that 6inch of concrete does r value increase? Does heated concrete provide higher r value????

No.

No, the conventional R-value does not change. However, the effective R-value can change if the concrete is cooled/heated by the environment. This is why the effective R-value of ICF can be significantly higher than the conventional R-value in a diurnal climate where the average outdoor temperature is near the desired indoor temperature causing the concrete core temperature to hover near the desired indoor temperature resulting in less heat gain/loss than would otherwise occur which can be thought of as being a higher effective R-value.

I have worked on a project that ran heat lines inside the concrete core of an ICF house. A temperature probe was installed into the concrete and each wall was run as its own zone off the boiler. The designer required the concrete temp be kept at 17 Celsius all year (don't ask me why that is the magic number....other than it is close to the likely interior temp). This is Canadian Prairies remember - we just got out of a week and half of -30 Celsius.

The theory is that keeping a mass of concrete warm is easier that heating a large mass of air inside. If the concrete is the same temp as the interior air, there is no heat loss through the walls. The only heat that is needed for the house is that which is lost through doors and windows.

I have tried to get energy info on this project is subsequent years, but the homeowners have not been willing to take the time to share it with the designer/builder (other than to say they are happy with the results).

No, that heat perpetual motion concept was dismissed over a 100 years ago... Yes, you can actively heat the concrete core to the indoor temperature, but this will actually consume more total heat energy than by just heating the building interior. The reason being that there is now a larger heat loss through only half the R-value than by just just heating the building interior. You don’t need to test this to prove this to be true. Only a knowledge of thermodynamics is necessary.

The only way to get ICF to have a higher effective R-value than its conventional R-value is to heat the concrete core using the environment. So you need a diurnal climate, solar heated water or hot springs that can be put to use to play this game. In other words, you need to steal heat from someplace else to achieve over unity heat performance like is done with heat pump systems.

Several years ago we developed software to ascertain precisely how ICF performs in different climates. Effective R-values range from the conventional R-value to infinity depending on the actual outdoor temperature profile. ICF companies often cherry pick this data to make some wild ICF performance claims that are not entirely untrue, but are also not likely to ever be realized in actual practice. We are very happy that our ICF buildings in our southern OR diurnal climate have an effective R-value that are nearly three times higher than the conventional R-value during the summer months making AC unnecessary. However, the effective R-value of our ICF buildings are nearly the same as the conventional R-value during the winter months.

Borst ICF Performance Software

If the thermal mass of the concrete is held at a constant temperature and isn't allowed to change temperature it's as if it isn't really there- it would have no effect on the heat transfer rates. But when it is allowed to heat & cool in response to outdoor temperatures it inserts a time delay between the peak exterior concrete surface temperature to outdoor temperature difference relative to when the peak interior concrete surface to interior air temp difference occurs. This makes the heating & cooling loads dynamic, with peaks decoupled in time from when the temperature difference peaks occur. That time delay reduces the peak heat rates heating & cooling loads, as well as the average energy use needed to stay in a comfortable range.

With EPS insulation on both sides of the wall, raising the concrete temperature would DECREASE the R-value of the EPS. Like most insulating materials, EPS will have higher performance when the mean temp through the foam layer is colder than when it is warmer. The labeled R-value of Type-II EPS (the most common ICF material) is it's performance performance when the mean temp through the foam is +75F, and is about R4.2 per inch of thickness. When the mean temp through the foam is +40F it's about R4.5/inch. When the mean temp through the foam layer is +25F it's closer to R4.7/inch. So if the temperature of the concrete is raised the EPS on both sides of the concrete are higher, and would be taking a performance hit (even in steady-state performance, independent of dynamic effects.)

While a total R2.5 change or 11% difference for the 5" of ICF EPS insulation is not insignificant, it isn’t particularly exciting either. While the reduction of peak heating rates that occur when ICF thermal mass effect can be taken advantage of is interesting, I think it is the reduction in average daily heat transfer rate that is much more significant and note worthy. Having our ICF wall assembly reduce the average daily heat gain from 9.4 Btu/day/sf to 3.3 Btu/day/sf or 285% difference during the summer months is a very worthwhile benefit.

Would a lower amount of energy input be required for heating the solid mass of concrete vs. heating the air inside? Would the situation change if the ICF used had a larger amount of insulation outside the concrete vs inside the concrete? Or if there was no insulation on inside face of the concrete?

Thanks for the education/clarification on this!

If the objective is to heat and keep the interior living space at some desired temperature using the minimum Btu/day, you want to create the maximum R-value you can between the interior living space and the outdoors. Whether you heat the interior space directly or heat the ICF concrete core, you still have to heat the interior air. If you moved the 2.5” of interior ICF EPS insulation to the exterior ICF side so as to have 5” of insulation there, then heating the concrete would use about the same amount of Btu/day as heating the interior living space directly if one doesn’t account for the thermal mass effect. However, if you want to properly design and build using ICF, it is helpful to accurately account for the thermal mass effect. We developed the aforementioned ICF performance software to better understand and answer these sort of questions. Here’s an excerpt from the software instructions:

“Here are some ICF performance observations based on varying the various ICF design parameters from the calculator default values and using our Rogue River, Oregon indoor/outdoor temperature profiles:

When the interior EPS thickness is reduced to 0.1” and the exterior EPS thickness is increased to 4.9” (i.e., essentially putting all the insulation on the exterior side, but keeping the total conventional R-value the same), the summer effective R-value went from R66.15 to R44.05. In this case the concrete temperature stays very close to the indoor temp. The effective R-value remains the same (i.e., R44.05) when all the insulation is put on interior side. However, in this case the concrete temperature stays very close to the outdoor temp. This would imply that both these non-symmetrical ICF designs result in an equal, but lower performance than the standard, symmetrical ICF design for this summer outdoor temperature profile. When this is repeated for the winter outdoor temperature profile, the winter effective R-value went from R21.34 to R21.96, i.e., a slight performance improvement.

When both the interior/exterior insulation thickness is reduced to 0.01” (i.e., essentially removing the interior/exterior insulation), the effective R-value went to R0.77 (i.e., 1.12 times higher than the new R0.69 conventional R-value). This would imply that even an uninsulated, 6” thick concrete wall will exhibit some degree of increased effective R-value. When the insulation is retained, but the concrete thickness is reduced to 0, the effective R-value went to R22.50 (i.e., exactly the same value as the new conventional R-value). This would imply that as the concrete thickness is reduced, the effective R-value tends toward becoming equal to the conventional R-value. When the concrete thickness is then increased to 4”, the effective R-value went to R63.40 (i.e., 2.77 times higher than the new conventional R-value). When the concrete thickness is further increased to 8”, the effective R-value went to R67.79 (i.e., 2.91 times higher than the new conventional R-value). When the concrete thickness is further increased to 12”, the effective R-value went to R69.99 (i.e., 2.95 times higher than the new conventional R-value). When the concrete thickness is further increased to 36”, the effective R-value went to R78.48 (i.e., 3.01 times higher than the new conventional R-value). When the concrete thickness is further increased to 360”, the effective R-value went to R177.12 (i.e., 3.03 times higher than the new conventional R-value). When the interior/exterior insulation is then removed from this 360” concrete thickness, the effective R-value went to R109.25 (i.e., still 3.03 times higher than the new conventional R-value). This would imply that as the concrete thickness is increased, the insulation thickness becomes increasingly less important in achieving the higher effective R-values. Furthermore, for this summer outdoor temperature profile, this would imply that the absolute maximum possible effective R-value is 3.03 times the conventional R-value and we are achieving 2.86 times the conventional R-value with a standard ICF design.

One might expect that higher effective R-values might be achieved by having some portion of the indoor temperature profile be the same as the outdoor temperature profile. For example, having that portion of the indoor temperature profile be the same as the outdoor temperature profile during the summer cooling season when the outdoor temperature is below 70 degrees Fahrenheit to simulate having open windows or using increased ventilation during these times. However, this is NOT the case. While doing this will reduce some of the Thermal Mass Temp output parameters, doing this will result in some of the Conventional Heat Flow Rate output parameters becoming 0 (where they were previously providing a building heat loss cooling effect), will reduce some of the Thermal Mass Heat Flow Rate output parameters (where they were previously providing more of a building heat loss cooling effect), will increase both the Total Conventional Heat Flow and Total Thermal Mass Heat Flow output parameters (i.e., provide increased building heat gain), but will increase the Total Thermal Mass Heat Flow output parameter more than the Total Conventional Heat Flow output parameter, and this will REDUCE the Thermal Mass Effective R-value output parameter. Doing this for the summer profile resulted in the effective R-value going from R66.15 to R39.06. One needs to keep in mind that this calculator only determines the effective R-value performance for just the ICF for the entered input/output temperature profiles and this calculator does NOT determine the HVAC system performance of the building. Or perhaps another way of thinking about this is that when you run the building AC system, the building cools down to a lower temperature than it would otherwise be, however, the heat transfer through the walls increases because of the increased inside/outside delta temperature. More thermal mass heat transfer is equivalent to having a lower thermal mass heat transfer resistance or a lower thermal mass effective R-value. Obviously, opening windows or increasing ventilation during the summer cooling season when the outdoor temp is below 70 degrees Fahrenheit is a good thing to do as this provides increased building cooling with minimum HVAC energy usage.”

WOW! Great info.

I have previously read that the ratio of insulation inside vs. outside the thermal mass (ie concrete core) varies depending on local climate to get best performance from the wall assembly. IIRC - cooling climate (eg southern states) should have all insulation outside concrete, heating climate (eg, northern Canada) should have even insulation inside/outside, climate with cooling in summer/heating in winter (eg, Canadian Prairies) should have 2/3 outside and 1/3 inside.

Any thoughts? Agree/disagree?

I don't mean to sound overly dismissive or sarcastic but I can't help wondering about software and/or statistics that are alleged to "prove" that they were right all along. Many times the same statistics can be used to either prove or disprove the same thing. I'm not attempting to do either in this case but rather to question the relevance of the information. The "R" value or the concept of heat loss or gain through the wall seems almost irrelevant unless you live in a cave. Most heat loss and gain is through windows and doors either from radiation or infiltration. Climate dictates the most appropriate choices for locating windows and insulation but Most people desire a lot of natural light and south facing double pane glass can provide substantial heat gain on sunny days that can be stored in any exposed thermal mass but is largely wasted without such access. Active solar radiant heat can also be stored in walls as well for additional capacity. Insulted and/or reflective shades are a good idea for nighttime heat retention in northern climates and to reduce heat gain in summer. I know this is the 2 sided insulation club and while there are places or cases where insulation on both sides may be a superior method - it surely isn't every case. Someone mentioned at least one ICF manufacturer who makes a product that uses removable plywood for the interior of the form.

This thread and discussion is about ICF effective R-value performance and NOT about passive solar heating. Yes, windows and air infiltration can contribute to significant heat gain/loss, but this discussion isn’t about that either. Our aforementioned ICF performance software models the ICF heat transfer physics and isn’t statistics based. We developed it several years for precisely the reason you indicated, unrealistic claims about ICF performance and general ignorance about how ICF performed in different climates. We use it to perform more accurate heat loss/gain analysis (e.g., ACCA Manual J8) for the ICF buildings that we design/build. TF Systems, which is a vertical ICF panel system, has the option of eliminating the interior or exterior ICF insulation and the vertical panels also facilitate easily placing PEX tube to allow creating HR heated walls.

I figured you'd probably take offense at someone not drinking the cool-aid. The thread "IS" about house building and "NOT" cave building or cellar dwelling isn't it? - with windows being the major difference. The OP seemed to be questioning the viability of a wall as a heat storage or transfer medium in spite of how it was worded and thermal mass whether used actively or passively is usually a great asset so why isolate it on the wrong side of some insulation? "Windows and infiltration can contribute"??? Compare the "heat transfer physics" through a window and it makes a fiberglass filled 2x4 stud wall look good never mind a foam covered concrete one. Someone with a wall that is half R50 and half R1 to R3 where the windows are is in need of more than just a new heat transfer physics program. Probably just a coincidence that your program "proved" that you were right all along with traditional icf. Who could have guessed? Polycrete, logix, nudura and buildblock all make one sided forms as well. I much prefer empirical data to "calculator default values". One is true and one is theoretical.

No, I don’t take offense with anything you wrote and I actually fully agree with most of it. However, this thread and discussion is certainly about ICF effective R-value performance. Please note that it is in the ICF forum section. There are separate forum sections for window and energy efficient building design/construction discussions. So you are hijacking this thread with your digression from the principal subject. I recommend you start you own thread in a more appropriate forum section if you want people to respond to your line of inquiry.

If you don’t like windows, please be aware that you can get an engineering deviation from building code and not use any windows at all in masonry buildings. We have several clients who used outdoor video cameras and flat screens mounted on the interior walls in lieu of windows. Egress requirements are satisfied by alternative acceptable means.

Empirical data are first used to understand the phenomena and develop the physics/mathematical software models. Empirical data (i.e., actual test measurements) are then subsequently used to validate the mathematical software models. Mathematical software models are needed to forecast how a building design will perform BEFORE it is constructed. Our aforementioned ICF performance software uses a 0.01 hour (i.e., a 0.6 minute or 36 second) sampling rate over a twenty four hour period using finite element time/temperature numerical differentiation/integration analysis. All of our software has been extensively validated using actual test measurements.

Outdoor cameras and flat screens???? SEVERAL clients????

I would love to see some pics of this.....

sailaway, You are mistaken on a number of accounts. I am certainly not "hijacking" this thread any more than you are - probably less. I have no line of inquiry. I am responding to the OP. You should please note the number of ICF manufacturers that make forms with the insulation on one side before you dismiss the concept as not being ICF. The concept is valid and you should embrace it. If anyone has something against windows, it would be you and your BTU-phobic clientele with the outdoor cameras and flat screens. I won't bother to rewrite my above post but I noted how most people - and I include myself there - desire natural light - sunlight - and a direct connection to the outdoors - not a video feed. Unfortunately this comes with a loss of efficiency that almost everyone can live with - save for that "aforementioned" clientele of yours. What are the acceptable egress alternatives to those who eschew windows? Escape hatches? Perhaps this is the same clientele that is so impressed with your software. Most people like and want windows - lots of them - even though they are only R-1 to R-3 so why not show and tell about how to make the most of them and gain what benefits there are - like being a potential heat source during the heating season - and how best to use them - like to charge exposed thermal mass? In your dismissive critique, while erecting false straw men to topple, you completely ignored my main point about so much R-1 to R-3 window area mixed in with your potentially marginally higher R value walls achieved at the expense of so much thermal mass. That mass stores cool temperature in summer as well. I liked that at the end of your software pitch you admitted that even though the software couldn't grasp it, it is a good idea to open the windows when the temp is below 70 in the summertime. That must be some empirical data.

Mojoe,

No, the software does “grasp it” and indeed does provide the correct solution. The explanation at the end of the instructions is to explain why the software provides the correct solution even though it may be counter intuitive to some.

We love using windows, passive solar cooling/heating and thermal mass in our designs and builds. We even have a suite of free DIY design software just for that purpose:

Borst Passive Solar Altitude Angle Software

Borst Passive Solar Roof Overhang Design Software

Borst Passive Solar Fenestration Exposure Software

Borst Passive Solar Heat Gain Software

Borst Passive Solar Thermal Mass Performance Software

If you don’t like our software, don’t use it. I may be mistaken, but I get the distinct impression that you have some other agenda or ax to grind. Perhaps break up your responses into separate paragraphs so they don’t read like an angry rant. In any event, I am way too busy and I have learned there is little point in endlessly debating anonymous people (who are often just anonymous trolls with some warped personal agenda) on forums. So please feel free to be helpful and better answer the OP and anyone else as this is my last response to this thread. Good luck.

Gayle Borst

Sorry, your distinct impression is wrong again. No need for name calling - I'm no "troll" and have no axe to grind. I said exactly what I meant and usually do. You got insulted and felt compelled to respond in a way that seems less than your professed motto at the end of each of your posts. I'm not selling anything and I'm not your competition. I didn't invent any of the concepts I am suggesting and I don't profit from promoting them but I have seen them work and they do work. My only impetus is the sharing of information in fields where I have enough experience to know what I'm talking about. I would think we all could agree that there is a need for high quality, affordable, energy efficient, yet livable housing and construction methods and there is always more than one way to any end. You're right when you said - If you don't like the software don't use it. You should have left it there or at least answered my main query. I'm not an expert on your software and don't claim to be, I just pointed out the glaring shortcoming that came to my mind. If I was wrong about that you would probably have corrected me by now instead of trying to defend it with the likes of video feeds and flatscreens. It's probably very profitable but that is of no concern to me. Sorry if it reads like a "rant" to you - it's not. I'm just trying to take up as little space as possible. Another one of my observations over the years is a concept I call - It won't be a good idea until I think of it. Seen it a many times. I think pex in the walls and the floors with insulation on the outside is a good idea in climates that have a substantial heating season - esp. when combined with things like active solar or wood fired boilers where there are temporary sources of cheap heat that could be stored for long term comfort stability. Just my 2 cents.