dmaceld - If I remember your earlier posts correctly, your heat pump pushed the heat through a crawlspace without ducts and then through openings in the floor to heat the living space. Can't remember if you also used the attic as the return plenum.
That being the case, would it not be more correct to say you are heating 4000 square feet and maybe 6000 if you are using the attic as a return?

Posted By FBBP on 30 Dec 2014 12:26 AM
dmaceld - If I remember your earlier posts correctly, your heat pump pushed the heat through a crawlspace without ducts and then through openings in the floor to heat the living space. Can't remember if you also used the attic as the return plenum.
That being the case, would it not be more correct to say you are heating 4000 square feet and maybe 6000 if you are using the attic as a return?

Not really. If you want to look at it that way then we would need to talk in terms of building volume, not square feet. What actually matters is not the floor area or building volume but the cumulative area of all the exterior surfaces of the building envelope. In a multi story house the heat load for two floors will not be double for that of one floor, but will be increased in proportion to the additional outside wall area. A basement, when compared to a vented crawl space probably results in a wash if not even a heat load savings. Using floor area is a actually an inaccurate, but handy shorthand, reference when discussing HVAC loads. In fact, the HVAC programs require you to input wall lengths, heights, and orientations along with all the doors and windows and their locations. You also have to input roof dimensions and pitch, or ceiling if vented attic.

Interestingly, when I ran the calculations in HVAC Calc, and I think also in HEED, heat loss through the roof was virtually the same for an insulated ceiling with ventilated attic as it was for the insulated roof with conditioned attic. In other words, using the attic for a return plenum added zero to the heat load. As far as loss through the crawl space the area exposed to outside air and soil with insulation has less heat loss than for an insulated floor with ventilated crawl space. That's mostly because the exposed surface area of the "foundation" wall is a lot less than the floor area. That's one big reason builders of all types of homes should use sealed and insulated crawl spaces with some forced ventilation.

Dmaceld, I agree we need to be careful about mixing commercial and residential when discussing HVAC calculation methods. However, there is nothing inherently inappropriate about using commercial HVAC methods for residential buildings if your goal is maximum analysis accuracy and you are licensed and well-versed in using these methods. For most residential construction, I would certainly agree that Manual J is more than adequate. My point to Lbear was more about Manual J inaccuracies not being solely associated with ICF construction.

Yes, over the years we have used DOE2, HEED, eQuest, Energy10 and several others whose names allude my memory. While these tools are very useful for gaining a fundamental understanding of the basic driving elements that influence heat gain/loss in a building, none of them really do a very good job of accurately breaking out and book keeping the hourly BTU contributions of all the driving elements when designing buildings that have highly interactive and integrated heating/cooling mechanisms (e.g., hydronic radiant, passive solar, passive cooling and ICF). Being able to successfully forecast, utilize and/or control all the hourly BTU contributions from all of these highly interactive and integrated heating/cooling mechanisms significantly influences our ability to maximize both building energy efficiency and comfort level.

No, this ICF software is something that I developed independently on my own to try to better understand and quantify the real R-value performance and the hourly heat flow characteristics of ICF. Of course I used all the well-established principals of thermodynamics and heat transfer while developing it. I figured this would be a good forum to share this software and perhaps get some constructive feedback. Our longer term building goals are to evolve past just using standard ICF in our building designs and to more aggressively explore the use of actively engaging the concrete like we do for our hydronic radiant floor heating designs and use ICF having most (if not all) of the insulation on the exterior which several ICF companies now produce. By actively engaging the ICF concrete, I mean using embedded PEX to circulate either cool or warm hydronic fluid that would be geothermally cooled or solar heated. We have done this successfully for a garage/shop (i.e., without the added complexity of hydronic radiant and passive solar) and are looking to do this for commercial/residential buildings.

dmaceld I agree that square footage is only a shorthand reference but it serves its purpose in this case.

My house is a 2 storey with attached garage with a full suite over the garage. The basement is a walkout with just over half the walls fully exposed to the exterior. A total of 5200 square feet of heated space plus the 1000 square feet of garage is heated. All walls with the exception of two over the garage are ICF from footing to trusses. Basement and main floor have 9 foot high ceilings.

We are not as cold blooded as you, we only keep the house at 74º ;-)) Our design temperature is -32ºC or -26 ºF.

Our heatloss was also worked out with Wrightsoft but our designer use the proper R50 for our ICF walls. The heat loss without infiltration came to 52000 btus. We now heat with a 50000 btu boiler and even when we have had a week of weather hovering around design temperature, it has not run more then 80% of the time. Please note that Alberta does not have strong diurnals during the winter. Also any lag time that might be ascribe to mass is taken out after a week at design temps.

So our heat loss works out to 10 btus per square foot or 8.25 if we include the heated garage. The delta is 100ºF

Yours works out to 13.5 btus per square for with a delta of 67ºF.

All the info you have given us over the past years indicate that your house is very well detailed (at least as well as mined) so I would say the increased heatloss is not a result of poor building practices.

As you say, your heat input matches your house so I wonder about two things
1) is what the engineers say the out put of the hp is a the given temps correct and or is it correct for that application?
2) would your heating input cost be half of what it is if you piped the warm air properly through the crawlspace and sealed and insulated the attic?

My point in this discussion is that I cannot agree with your statement and would have to strongly agree with LBear that a "PROPER" man "J' would result is a super large heating system when using R23 for heat replacement purposes.

Sailor - if there is an increase of .7 r value per inch (5.0-4.3) with a drop of 45ºf or .016 per degree then with a drop of 70ºf less -26ºf (my design temp) or 96fº the increase would be 96x.016 for 1.536 per inch if the increase is linear (I thought it was a curve but I can't find the data sheet right now)
So the outer layer of eps on my house at design temp would be just over R15 rather then R10.75 or an increase of about 30%. Would that not be worth calculating when designing lag time?

If as you say the core of an ICF building will be the difference of inside and outside temperatures, then at design temp my core would be 25ºf. I have never yet seen frost in my walls or any other ICF building I have built or worked in in the Calgary region.

From Nudura
(d)
Studies using WUFFI software and thermal coupling show that the concrete core of ICFs never drops below 33 degrees F even in winter temperatures as a result of the room temperature modifying the core temperature of the concrete – thus exhibit no risk due to freezing.

FBBP,

“So the outer layer of eps on my house at design temp would be just over R15 rather than R10.75 or an increase of about 30%. Would that not be worth calculating when designing lag time?”

Yes, that is why there are separate input parameters for both the interior and exterior insulation R-values. If you enter your nonsymmetrical R6/Inch for the exterior insulation and R4.3/Inch for the interior insulation, the thermal mass temp is a constant 29.7F for a constant indoor temp of 70F and constant outdoor temp of -26F. Of course, we account for the heat transfer from BOTH the indoor temp and the outdoor temp…so that Nudura statement is pure nonsense and violates fundamental heat transfer principals! If your actual measured thermal temp is different for these conditions, please let me know as you have proven our fundamental heat transfer principals to be untrue and this would indeed be very noteworthy!

Seriously though, I could certainly see how ground temp wicking effect could cause your thermal mass to stay warmer than this fundamental heat transfer principal predicted 29.7F. Ground wicking temp effect likely becomes more significant the more the outdoor temp differs from the local ground temp…either lower or higher…but would likely only be more significant for first-level construction than higher multi-level construction. -26F is likely something like 60F lower than your ground temp…which seems significant to me. As I indicated previously, I didn’t include ground temp wicking effect when I developed this ICF performance software, however, it could certainly be added in the future. My initial goal was to understand and quantify the basic ICF thermal mass performance characteristics before delving too far into these extreme areas.

With regard to the lag time, as you well know, there isn’t any lag time associated with the aforementioned constant temp conditions. However, you could certainly enter your nonsymmetrical R-values and your desired non-constant indoor/outdoor temp profiles to observe how the thermal mass temp changes and what the effective R-value becomes.

BTW, exercising your nonsymmetrical R-values resulted in me finding a bug in the software where I essentially reversed the interior/exterior insulation input parameter R-values when doing the initial thermal mass temp estimate calculation. This bug caused the thermal mass to oscillate unexplainably and required some head scratching to find it and understand it. Anyhow, I found and fixed it…and I will upload the corrected version to our website later this week when I get a chance…such is software development…thanks!

Sailor - when you reload the software. Could you do one that leaves your own local data in place? It would be interesting to compare.


•••so that Nudura statement is pure nonsense and violates fundamental heat transfer principals!•••• Have you ever had the pleasure of coring ICF walls in the dead of winter (and I mean real winter ;-))? I have never had my cutting water freeze during a core or have water freeze to the core when it comes out despite cutting at very low temps. Basement developments are usually done in the winter when I don't feel like working outside.
Being ICF will never violate fundamental science principals but it has been my experience that many times the scientist does not apply them properly or the picture is not clearly understood. As you know from this forum those that have worked in the ICF field from the beginning often disagree with the "scientists" At sometime the scientists will realize what they missed in their calculations and realize what they claimed to be nonsense or old wife's tale was in fact, fact. Hundreds of installers can't be wrong ;-))

"Could you do one that leaves your own local data in place? It would be interesting to compare."

Yes, it has actually been there from the very beginning as I explained to Arkie on the page 2 of this thread. Just enter 97537.1 for Spring, 97537.2 for Summer, 97537.3 for Fall, or 97537.4 for Winter into the first Outdoor Temp Profile input parameter to use our local Rogue River, OR profiles. You can also now do the same thing for the first Indoor Temp Profile input parameter if you want to duplicate what I accomplished for Lbear as explained on page 2 of this thread.

With the exception of an ongoing concrete curing exothermic reaction or some significant ground temp wicking effect, the ICF concrete core temp will be exactly as calculated by the software...or by a simple hand calculation too. I have personally measured the temps of more ICF concrete cores and more slab-on-grade concrete floors than I care to remember... Not once did the concrete temp disagree with what would be expected and predicted. When is comes to claims about ICF performance, most everything you read is from the companies associated with it...and most everything they claim has little basis in fact. As they say, follow the money and the truth will become crystal clear...

Posted By FBBP on 30 Dec 2014 03:36 PM

Being ICF will never violate fundamental science principals but it has been my experience that many times the scientist does not apply them properly or the picture is not clearly understood. As you know from this forum those that have worked in the ICF field from the beginning often disagree with the "scientists" At sometime the scientists will realize what they missed in their calculations and realize what they claimed to be nonsense or old wife's tale was in fact, fact. Hundreds of installers can't be wrong ;-))

This is NOT directed at Sailaway or anyone here. I of course believe in science but at the same time scientists are bias and even their studies have been proven flawed and bias. Just watched a documentary on the Missoula Floods and the PhD scientists admitted that they are bias and scientific research/studies are sometimes bias and even politically driven. Long story short, some scientists ignored and ridiculed other scientists and their research because they were being bias. Fifty years later, they admitted they were wrong and the entire scientific data was turned on its head and the position about the flood was reversed and changed.

I am not saying that the ICF studies are all wrong but I do believe there will be changes and updates as time proceeds and more data is collected from ICF buildings and how they perform over the years and even decades.

Very true Lbear, but conductive heat transfer through materials is a very well-understood and long-accepted "science" as opposed to much more complicated Missoula Floods or Global Warming "science". And scientists scrutinize scientific work and when errors are found the scientific theories are revised. When was the last time you heard a politician admit that their BS propaganda and demonizing of their opponent was wrong?

sailawayrb, You appear to be serious about improving your program. I believe I read above somewhere that you have empirically tested ICF walls with thermocouples or similar and found that the center of the wall temperature is typically the average of inside and outside temperatures. If I didn't read that then I apologize. Nevertheless, there are definitely a few here that believe this to be the case.

We have conducted thermocouples studies on numerous jobs here in Texas including the Academy at Nola Dunn school in Burleson, Texas. In every case, we've found that the core temperature of the wall never vary by more than a few degrees (like plus or minus 5 degrees C) from the inside set point -- regardless of outside temperature -- winter or summer. Similar analysis has been conducted in Canada and Northern US climates with the same result. Furthermore, the temperature gradient between the inside surface and outside surface of the concrete is always very flat as I would expect.

These results make sense to me since heat only moves one way. In the winter heat is absorbed by the mass which is insulated on both sides ultimately (or slowly) escaping to ambient. How could the insulated mass temperature be anything but close to set point? In the Texas heat, matters are reversed but again heat is mechanically removed from the mass one degree at a time by the HVAC.

The fact that the concrete is never below freezing in and ICF structure doesn't surprise me at all since the core is absorbing heat from the source and over time releasing it to the outside.

I wish you the best with your program. Regards.

Texas ICF,

“I believe I read above somewhere that you have empirically tested ICF walls with thermocouples or similar and found that the center of the wall temperature is typically the average of inside and outside temperatures.”

Yes, this is precisely so PROVIDED that BOTH the indoor and outdoor temp remain constant for several days…which will likely never precisely happen except perhaps in a laboratory. However, we can precisely prove this to be TRUE with the software program because we can make the indoor/outdoor temps constant.

“ In every case, we've found that the core temperature of the wall never vary by more than a few degrees (like plus or minus 5 degrees C) from the inside set point -- regardless of outside temperature -- winter or summer… These results make sense to me since heat only moves one way.”

Heat moves from warmer temps to colder temps. However, this does not mean that heat only moves one way through ICF walls. Let’s do a simple thought experiment…

If the indoor temp is 70F, the concrete temp is 50F (because it was cooled from previous cold outdoor temp exposure), and the outdoor temp is now 70F, how does the heat move with regard to the concrete at this time? The warmer 70F indoor heat moves OUTWARD into the colder 50F concrete. The warmer 70F heat moves INWARD into the colder 50F concrete. In this case heat is moving from BOTH the inside and outside into the concrete and causing the concrete to warm up. So heat DOES NOT ALWAYS move one way through an ICF wall.

If the indoor temp is still 70F, the concrete temp is still 50F, and the outdoor temp is now 30F, how does the heat move with regard to the concrete at this time? The warmer 70F indoor heat moves OUTWARD into the colder 50F concrete, just as it did in previous example. However, now the warmer 50F concrete heat moves OUTWARD to the colder 30F outdoor temp. In this case heat is indeed moving in one direction, from inside the building to outside the building. Yes, if one only considers this unique situation, one could mistakenly believe that heat only moves one way through ICF walls.

Bottom line, heat moves into and out of the concrete depending on the indoor/outdoor temps as governed by fundamental heat transfer principals. If you book keep the amount of net heat moving into and out of the concrete, you can accurately determine the concrete delta temp change over time because we know the density and specific heat capacity of concrete...which again is governed by fundamental heat transfer principals. ICF concrete temp does NOT magically just stay “like plus or minus 5 degrees C) from the inside set point -- regardless of outside temperature -- winter or summer”. The only way this could be true is if the outdoor temp also only varied plus or minus some nearly same value from the inside set point. Yes, if one only measures the concrete temp during this unique situation, one could mistakenly believe that the concrete temp is always plus or minus 5 degrees C) from the inside set point.

Yes, if one exercises the software program and studies the hour-by-hour temps, hour-by-hour heat flows, and resulting total heat flows, one can only conclude that ICF does NOT have an effective R-value that is significantly better than the conventional R-value.

sailawayrb,

I never said heat only moves one way through an ICF wall. I said heat only moves one way - hot to cold. This is true within the concrete as well - hot to cold only. The problem with your analysis may reside in the temperature gradient you've assigned to the wall. Your comments require that I dig out some old heat transfer data and spend a few hours on this. Will get back to you. Regards.

Yes, we are in agreement and please do TexasICF. I would sincerely greatly welcome some specific constructive feedback. I think the ground temp wicking effect has some merit and increased significance in some areas. I have not found any significant problem with the software program. However, I am somewhat disappointed and really don't like the conclusions...I have two ICF homes.

Well sailor, I built my own ICF house (and as an engineer, who spends most of his time at a desk, it was an interesting experience), and I'm not disappointed. You just need to go in with your eyes open and don't expect magic. I have a very quiet, comfortable house that doesn't rack in the wind (of which there is much), is very hard to burn (being rural that was important), and requires very little maintenance (I'm getting old, sometime I will have to slow down). I also designed the HVAC with an eye toward the low pass filter characteristics of the structure, and it is very cheap to heat and cool. If I had built it purely on a cost basis the ICF would have been a silly thing to do, but for me the intangibles make it worthwhile.

I also suspect there is some value to the wicking argument, but once you include heat soak of the soil under the footer (it is really not that much area) I think it will be a small second order effect.

Dave,

Oh no, I didn’t mean to imply I was disappointed with our ICF homes (in a very rural location in southern OR and in Maui, HI). We love our ICF homes for all the reasons you indicated…plus all the reasons I originally indicated…increased fire resistance, increased structural life, increased structural strength, reduced inherent infiltration, reduced outdoor noise transmission, and thermal mass characteristics that can be successfully designed and better integrated with passive solar heated buildings…

No, my disappointment was not being able to quantify and prove that ICF has an effective R-value higher than the conventional R-value. So I am more disappointed in myself for believing that this was the case for so long...sort of like believing that a wind turbine can power your car! However, I keep hoping that I or someone will find an error in the methodology I used for this software program, LOL!

Yes, I tend to agree with you about the ground temp wicking effect likely being less than very significant, but I plan to explore that more before completely dismissing it. I think you are also correct that the footer area (or perhaps the extended vertical rebar posts) would limit this secondary effect. I am not sure about the building heat loss soaking into the ground...as I could see how that could raise the ground temp and improve the associated wicking effect...at least in Winter.

For the primary thermal mass effect, I believe you had it right all along...namely that you do NOT get a free lunch! For any constant daily repeating outdoor temp profile, what the ICF gives in benefit during one period of the day, the ICF takes away and more during another period of the day... Yes, if you dissect this 24 hour day you can find this beneficial period and even work out a higher effective R-value for this period. However, when you consider the entire 24 hour period, the net benefit approaches zero. In fact, I will be bold and flatly state that there is zero effective R-value benefit. I believe that any deviation from the conventional R-value is more likely the result of computational round off error from summing all the thousands of finite element samples that needs to be done to properly calculate the effective R-value for the entire 24 hour period.

Bottom line, the usefulness of this software program (other than proving the aforementioned effective R-value conclusion) is the valuable hour-by-hour thermal mass heat rate information that can be put to good use for passive solar design.

Gary from Build It Solar just made me aware of this study:

Monitored Thermal Performance of ICF Walls in MURBs

So perhaps more substantiation...

I've seen this report. Looks to me like the average temperature inside to outside is about 10.5°C and The average temperature of the concrete is about 14.5°C. How do you explain that?

Wouldn't your program as it stands now say the concrete average temperature would be the same as the average of the inside and the outside temperature?

The study is critically flawed in that it only measured during the Winter months. There is of course a benefit to thermal mass when the outdoor temperature varies above and below acceptable levels.

TexasICF,

No, my program uses the entered concrete properties and the entered indoor/out temp profiles to determine the concrete temp every 36 seconds after accounting for the associated concrete time lag effect. Again, the only time my program would have the concrete temp be identically the same as the average of the inside/outside temps would be if BOTH the indoor/inside temps remained perfectly constant for the 24 hour period. Yes, you can certainly use the program to run this situation (say 70F and -26F for the indoor/outdoor temps for standard ICF) and get the uninteresting but correct result that the concrete temp will be 22F.

How do I explain the results of that study? Frankly, I don’t and I really can’t…that’s really the job of the authors who have all the data and wrote that study, LOL! It would have been nice if the authors of that study clearly showed all three real time temps (i.e., indoor temp, concrete temp, and outdoor temp) like my program clearly shows. Then we could enter their indoor/outdoor temps into my program and see if the program provides the same concrete temp profile.

I will say that my program does show this thermal mass temp buffering effect as one would fully expect. For a constant indoor temp, if the outside temp varies by a larger plus/minus X amount about the inside temp, the concrete varies by a smaller Y amount about the inside temp. Is it this thermal mass temp buffering effect that appears magical to you? I suppose in a way I could see how this could be perceived that way. As I indicated previously, I have measured our actual concrete temp profile in relationship with our measured indoor/outdoor temp profiles. To the ability I was able to measure these temps, the program shows the same concrete temp profile as was measured. So I am very confident that the program is calculating the concrete temp correctly.

In any event, this buffer effect does NOT result in the program calculating a higher effective R-value than the conventional R-value. Just because the concrete temp is warmer than the colder Winter outdoor temp doesn't mean that the building Winter heat loss will be any less. Similarly, the same would be true for Summer heat gain or anything in between. You have to keep in mind that you only have 2.5” of insulation between the indoor temp and the concrete temp (i.e., thermal mass effective heat flow) as compared to 5” of insulation between the indoor temp and the outdoor temp (i.e., conventional heat flow). So you are essentially trading less insulation and a smaller delta T against more insulation and a greater delta T…resulting in the total 24 hour thermal mass heat flow and conventional heat flow being identical and therefore resulting in the effective R-value and conventional R-value being identical.

The program also gives reasonable results when say you run it with 0.1” of exterior insulation and 4.9” of interior insulation. In this case the concrete temp hovers closer to the outdoor temp as would be expected. Or if you run it with 0.1” of interior insulation and 4.9” of exterior insulation. In this case the concrete temp hovers closer to the indoor temp as would be expected. In both cases the program indicates that the effective R-value is the same as the conventional R-value.