Here's another consideration. The ICF wall is also connected to a huge heat sink in the ground. I've talked to a guy in the high desert of west texas and hes says he thinks the temperature swings in the summer are moderated by the concrete in the wall being connected to the COOLER ground temps. Very HOT air temps but very dry air. Much more complicated system than a typical batt insulated wall section. Adobe walls are the same thing.
You are spot on here. There is not only a large thermal mass in the concrete but it is also a thermal sink to the ground. It's as close to the benefits of living in a cave as you can get without actually living in a cave.
I live in a working class neighborhood next to a bad neighborhood in Alabama, USA. ICF stops stray bullets. Our city gets hurricanes and occasional tornados. ICF is not affected by hurricanes. ICF houses will often survive tornados even if all of the openings get obliterated. (we will have a safe room) The ICF walls will give us time to get to the safe room if a tornado hits in the middle of the night.
In Canada the r value is based on a 15 degree temperature difference. Celsius that is. So when you want your home at 20 degrees it preforms like the rating if it's 5 degrees outside. In the north we sometimes get below 40 degrees and a batt insulation will perform at about r 7 drastically less than it's rating while isf or sips lose very little r value.
Its basically like building underground but above. Being able to keep the interior at a constant temperature is a key factor in icf's. The added benefits of storm protection and disaster resistance is also why icf's are a superior building technique. Plus if there is ever a power outage, the interior will remain comfortable for longer. Regardless of time of year.
You are looking for the specific heat of concrete. The amount of energy it takes to change the temperature of 1 gram of concrete, 1 degree Celsius. From that we can basically say it takes x amount of heat to increase the temp. Now that energy has to move to the next gram of concrete and increase that temp. This can be used in the reverse direction as well, to say how much negative energy (cold compared to the temp of concrete) is needed to lower the temp. From that, you can throw in the R value calculations that slow down those changes and losses in temperature.
Going back to specific heat, concrete has a specific heat of 880 j/kg•degree Celsius. So if we take a 6” concrete Icf wall (not accounting for rebar or foam right now) it is 0.1524 m thick x 1m x1m for a total of 0.1524 cubic meters. The mass of concrete is about 2400 kg/m3 so it’s 365.75 kg. So it takes 321,364 J to increase the temp of this concrete by 1 degree Celsius. To put this into better perspective we can turn it into celsius heat units. So if our outside air temperature was 169.22 degrees Celsius, it would contain the energy to raise the concrete 1 degree. This is crazy, because we have foam on the outside and that energy transfer could never happen that quickly and we don’t see those kind of temps. The same would be true of negative temp differences. To get the whole engineering view of this, we would need to take into account the k-value of the foam, the k value of the concrete, and then use this same thermal mass calculation to really get an idea of how much time you would have before you ever felt a difference on the inside.
12.51 is r value of 3” eps R-value is calculated from k value, and is basically the heat conductivity over the entire square meter. Expressed in W/m2K watts per meter squared kelvin. Watts is joules/ second. After all of this we can calculate how much energy will be allowed across the foam, and will in turn raise or lower the temperature of our concrete core. (Note this is just accounting for conduction, there can be convection and radiation if the sun is shining on the outside of our wall, I’m not accounting for that) 12.51 joules/ S for every degree C difference. Let’s say our outside air temp is 30C and the temp of the concrete starts at 10C That is a delta T of 20C so we are transferring heat through our foam at a rate of 250 J/second. If you look in the comment above we need 321,000 J to raise our concrete 1C. So it will take 1285 seconds to raise the concretes temp by 1 degree. Or 21.42 minutes. This equation will change continually based on the temp difference and that will change how fast the energy will transfer. For the sake of my sanity and time, and to put out the worst case scenario, if the rate stayed the same at 250 J/second. It would still take 7.21 hours for that concrete to reach 30C. This is the absolute worst case scenario living in Death Valley, with no shade and no temp changes, and no taking of energy from any HVAC systems inside. Then that energy still has to go through another 3” of EPS on the other side of the concrete. Needless to say ICF is awesome.
I’ve always wondered why the exterior foam isn’t twice as thick as the interior. It would protect that thermal mass of the concrete better I think. Some builders have used 2x8 framing to get R40 walls but wood is very expensive here too. This winter we had -40C for a whole damn month in central Saskatchewan. Frost went down over 4’ in the ground. Good video and I like your logic and thought process.
Vendors also offer 2 inch thick inserts which go between the plastic supports and can then be fastened to the inside of the icf form. IE you can get a form for 10 inches of concrete, then add 2 inches of foam to the inside and outside walls with the foam inserts, and still have a 6 inch concrete wall.
Concrete has an R value, it is low. You're describing thermal lag due to mass, and it is only more energy efficient in climates that go above and below the indoor temp within the lag period. Think about it, if it takes two days to cool down how long will it take to warm back up? During steady temp weeks a framed wall will perform the same as an ICF, you just delay the bill. You are correct with respect to the temp swings, high thermal mass structures don't change fast, that could be good or bad. If the building is designed for temp setbacks and local temp control more thermal mass delays getting the room to comfort levels. If you turn the heat down in winter before leaving for a holiday how long does it take once you turn the heat back up? Climates where it oscillates above and below like the high deserts or shoulder seasons are where you realize efficiencies. Look at adobe or pueblo buildings. If someone is trying to sell you ICF with this R-equivalent, they don't understand their product or how thermal systems work, they most likely won't be more efficient in your climate costing you more money than promised in HVAC operating costs. Please find some introduction to thermodynamic courses, you've got the basic concepts just need to put them all together.
This is why I believe the interior foam should use max two inches and the exterior panel should be at least 5 inches. This is how I built my home and the energy bills are about 1/2 of what a well done 2X6 wall would accomplish. I live in minnesota
But you forget, this has concrete sandwichwd between a few inches of foam, which does have a high r-value. This is a hybrid system, and we're seeing it work well.
I am starting to build ICF in North Carolina, since I will do the walls myself is hard to compare cost, but with the lumber prices and the added cost of outside panels, insulation (close cell), and other expenses I am a firm believer that there is no comparison, not only with the R factor but also with noise, mold, rot, bugs and more. I wish I have the money to also do the roof in ICF
Spring of 2023 I hope to start construction in Mitchell county North Carolina will be doing ICF walls for sure my hope is to be able to do an ICF roof that's the big question for me right now, Mitchell County is in climate zone 5
You’re absolutely right about what you said! I don’t have any experience with an ICF roof. Pretty easy if you go flat or ultra low slope. What system would you look at for the ICF roof?
@@uptokode right now looking at quad lock. I like their wall system do you have any ideas or thoughts about that system. What I was wanting is what they show as R-30, 2 inches on the inside and 4 inches on the outside for the wall and then as for the deck system quad lock as well. Planning on a fairly low slope shed roof. Probably 4/12
I don’t know much about quad lock. What I do know is that they have a good roof system. I think 4” exterior foam and 2” interior would be a good combination.
Like all your Icf videos and it is very effective. Can you make a video on mechanicals (HVAC) sizing due to the effectiveness of icf house? Getting ready to build 3 miles from ocean for the hurricanes
Thanks for exlanatory and educational video. I turned the sound to the upper limit - 100% both in Windows and RU-vid. But the sound was not loud enough for me. This is strange because I saw you had a mike on your shirt.
Thanks for all the good videos. It was better if you had emphssized, if the tempreture doesn't fluctuate, then the thermal mass wouldn't help at all. Also, for below grade because of the thermal mass of the groud, the thermal mass of ICF has no good extra benefit.
It can still be beneficial to both of those scenarios. Unless the place you live in has either 24hr sunlight or 24hr constant darkness it can still be beneficial to you depending where the thermal mass is located within the wall assembly. In my climate, having a basement made with ICF, the ground temperature can help stabilize the core of the entire house. Keeping it cooler in the summer, therefore requiring no A/C. It also helps keep it warmer in the winter. Adding lopped sided insulation and moving the thermal mass to the inside of the wall assembly further improves its capability.
@@aaronolsen8787 first of all, there is no doubt that ICF is better than stick frame and regular concrete. Priod. I am just being sheldon cooper and maybe splitting the hair, but in theoey: if you have regular concrete (outside) and add the same amount of insulation as ICF inside, it will be slightly better insulation because of thermal mass. If you have doubt please do the heat transfer formula. The reason ICF is better than that plan is that it will be actually cheaper to do ICF than doing concrete and then adding two extra layer of insulation. Peace!
@@hameedtalebi2351 ideally you wan the thermal mass on the inside of the wall, that will make the condition space temperature stable. if I can chose I will build a concret/brick wall inside with continues eps on the outside
I see the advantage of a thermal mass when the temperature fluctuates, but what about a thermal mass in say Florida in the summer? Does it get hot and just keep baking your house?
Very valid point. You are correct from my understanding. Typically in those hot climates A/C is a requirement no matter what. Since ICF is far more efficient and air tight, your cooling requirements are far less than traditional homes. ICF is always an advantage.
Your analogy is partially correct. If temperatures are cyclic then thermal mass helps. I am thinking of spring and fall where during the day I want to air-condition and at night I want to heat. But if it is always significantly colder outside than inside then total energy to heat the house over a month is totally dependent upon the insulative properties. ICF does have a major advantage in that its a true air flow barrier where most 2x6 wall have air leaks. Also, most ICF walls easily achieve the advertised R-value and 2x6 wall often don't . However, WRT the testing method for R-value, I conclude it is wrong. What should be done is to put a constant temperature on one side of the wall and an energy flow measuring device on the other side of the wall. Then allow it to run for a few days until it reaches steady state. This will tell how much energy is going through the wall. A perfectly made 2x6 wall with r-20 should have the same energy flow as an icf with r-20. In reality, the 2x6 usually has more imperfections and thus it doesn't.
Didn't see the link to the test, so I cannot be too sure what I'm saying is accurate. But, there are things to consider anyway. I believe Kody's interpretation of the test is based on just one iteration of the test, because that's how R-Value is evaluated. Keep in mind that the thermal mass had to start at some temperature and for it to have taken so many hours for the outside 0° temperature to effect the inside 70° temperature, the thermal mass (concrete) likely started at 70°. What we do know is that the insulation is the same on both sides of the concrete, so I believe that after that first 48hrs, the concrete would have been the average of the two temperatures, 35°F. From that point, you would be dealing with 70° vs 35° and only through the inside layer of insulation. So after the initial 48hrs, the change in interior temperature would happen at a shorter intervals. Inanimate objects simply average all the temperatures they are exposed to, based on the length of time they are exposed (talking purely conductive heat transfer and taking radiant and emissivity out of the equation, that is) So with something as heavy (massive) as concrete, it takes time for that mass to change temperature. However, the test has controlled temperatures on each side, so if you were to maintain the 0° and the 70° for let's say a week, then turn off the power, the concrete would be about 35°F and the only thing keeping that 35° from influencing the warm side is the thickness of insulation between the concrete and the warm side. It's going to take a few hours to bring that warm side down, not 48hrs. In my humble opinion.
@@uptokode I appreciate you not taking offense to my comment because I meant none. In fact, I really appreciate what you do! I'm not a scientist or a degreed engineer, although I work as a Mechanical Design Engineer and I used to perform research at a materials research think-tank. Most of the research I was involved with included heat transfer measurements, so I have a better than average understanding of how that works. That being said, my characterization of what's happening in the ICF, was an educated guess, however I believe I'm not far off. In my opinion, thermal mass throws off the R-Value (or U-Value) testing due to the delay is causes. The default R-Value testing is not set up to deal with that delay. If I were doing a test to evaluate any building assembly against another, apples to apples, I would do what I previously said: hold the internal and external temperatures steady for a week, then kill the power. Measure the rate of change on the 70° side. Now you've got equivalent R-Value, regardless of wall, window, door assembly type. Thermal mass is tough to nail down because it can work for you or against you, depending on the situation. Keep up the good work! You've got me sold on Nudura Plus. If the wife wouldn't be opposed to it, I'd use Nudura One and leave all the interior walls concrete. Now that fully maximizes the benefits of thermal mass!
It’s a superb idea! I’ve never done one but I have lots of ideas. I would probably stick with a low slope system for ease and speed. And yes quad lock (I heard) has one of the best roof systems. Use Fortruss for flat work or low slope.
I believe such a comparison needs to take into consideration 3 factors. There is the rate at which thermal energy can flow through a material. There is the amount of thermal energy that makes it through the material. And there is the amount of thermal energy absorbed by the material. I have heard that the space shuttle will turn away 90% of the heat generated during re-entry. 10% makes it to the cockpit. And the astronauts have a fixed amount of time to get out before that 10% (still lethal) reaches them.
R20 wood wall vs R20 icf. Doesnt matter how long it takes for the thermostat to turn on. If u have ur house set at 70 degrees and the outside is -30 for a week straight. You are still heating. The better system is spider tie. Where the concrete will use the thermal mass to hold the inside temperature
The thermal mass core does make a difference. Yes you still have to heat it. Most climates fluctuate in temperatures throughout the day and night and an ICF wall is far more stable. I do want to see in real life the performance of a 1 sided ICF with the concrete exposed for maximum thermal mass usage.
@@JohnSmith-xx9se I agree I mean the warmth of the house will always keep the thermal mass warm to a certain extent from the inside but where does that push pull from different thermal pushing go
@@JohnSmith-xx9se I've been told that one of the drawbacks of ICF is that the walls/foundation works like a heat sink and can actually pull heat from the inside out and down to the foundation. And in cold temps the opposite works as the foundation (which is cold) weeps the cold up the walls and into the house...
It’s sad that R-value is still used at all for code, it’s gotta be the worst measure used since 2” spray foaming is miles ahead of any amount of bat. Then again it seems that most houses are built strictly for cost anyway so the general masses are really to blame for that lol
Couple of really good points! I’m not a fan of spray foam for multiple reasons. Mostly because people assume it seals everything and it surely doesn’t. Especially where lumber joins to each other. Walls to floors, etc
@@uptokode yeah, if you watch Spray Jones channel, he uses a spray caulking after the spray foam install is complete. I figure even if someone didn’t seal up the seams, spray foam is still 100x more sealed than bat. At this point I see bat’s only use is to reach the r-value for code. Good part of ICF is you only need to spray foam the roof & seal the seams & openings. I actually want to icf used to build roofs so hurricanes don’t rip them off lol
