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freakboy
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Posts:32
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| 06/28/2008 7:41 AM |
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I am sure this topic has been covered in the past but after searching thru 16 pages of topics i could not find any. could someone direct me to a thread covering this topic. I am more interested in energy saving comparisons vs. cost. I am currently working on an ICF project and want to learn more about sip
Thanks for the time |
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Dont run thru the forest with your face on fire
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The Panel Guy
Registered Users
Posts:57
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| 06/28/2008 11:36 PM |
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| An 8 inch ICF has the same R-Value as that of a 6 inch SIP - Approximately R-25. Increasing the thickness of the ICF will provide you with minor increases in R-Value as concrete only has an R-factor of .8 per inch thickness of concrete. Increasing the thickness of a SIP panel give you large increases in R-Value as as EPS has an R-Factor of 4 per inch. Both systems are solid wall construction and perform relatively the same. |
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rnortman
Registered Users
Posts:97
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| 06/29/2008 9:07 AM |
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Posted By The Panel Guy on 06/28/2008 11:36 PM
An 8 inch ICF has the same R-Value as that of a 6 inch SIP - Approximately R-25. Increasing the thickness of the ICF will provide you with minor increases in R-Value as concrete only has an R-factor of .8 per inch thickness of concrete. Increasing the thickness of a SIP panel give you large increases in R-Value as as EPS has an R-Factor of 4 per inch. Both systems are solid wall construction and perform relatively the same. A straight R-value comparison doesn't tell the whole story, because of the thermal mass of the concrete. The effect of that thermal mass depends on the climate where the building is located -- in cold climates, the thermal mass doesn't help a whole lot. In warmer climates -- especially climates where the night temperature is low and the day temperature is high, like Phoenix during most of the year for example -- the thermal mass is extremely beneficial. It will absorb heat during the day, preventing the heat from reaching the interior, and then release the heat overnight, keeping the structure warm. (Personally, though, I think would prefer AAC over ICF for such a climate.)
The original poster didn't say where the building will be located, or really any details at all, which makes a relevant comparison of different building technologies impossible.
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The Panel Guy
Registered Users
Posts:57
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| 06/29/2008 1:06 PM |
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I've often heard it stated, particularly on this forum site, about colder climates and ICFs. We primarily use ICFs for full or walkout basements (California). Every great once in a while we get a client whose looking for the Katrina safe, hurricane proof, bomb shelter above ground home. What I've never understood about the conversation is that it would be my hope that the foam on the outside of the concrete doesn't allow the concrete to function as thermal mass. Who wants the concrete to heat up to the point where it moves through the inner foam and adds heat to the living environment during the summer period. I've always thought the point of an ICF was the same as a SIP, which is to block heat and cold from transferring through the wall structure from inside or out.
Since we use them primarily for basements and the ground temperature stays around 58 degrees in most of our climates, we've never used an ICF for the thermal mass aspect. We use it cause it's way cheaper to build with than having to but the forms and the immense amount of labor to install them, then strip them off and haul them off. It's an added benefit to have a wall system in place that we simply have to attach finishes to that has an R-Value that exceeds our Title 24 requirements.
I would like to hear more about this thermal mass concept and how we are suppose to expect ICFs to actually function or how they scientifically do function. |
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rnortman
Registered Users
Posts:97
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| 06/29/2008 3:13 PM |
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I'm just an amateur, so I'm probably way out of line spouting my mouth off about this... but I have read a fair amount about it, so I'm going to spout off anyway. Take what I say with a grain of salt.
In real life, there's no such thing as a perfect insulator. Heat will move through any material, it just moves through insulators slowly. Imagine it's hotter outside the house than inside. With an ICF, the heat will move through the foam slowly, and reach the concrete. The concrete transmits heat within itself quickly, but it also has a lot of thermal mass, so a lot of heat has to transfer into it in order to heat it up. So when the heat slowly trickles through the foam, that slow trickle gets absorbed by the concrete with hardly any change in temperature of the concrete -- the concrete sucks up the heat before it gets into the interior of the building. By the end of the day, the concrete will have increased in temperature by maybe a few degrees as a result of sucking up that trickle of heat. Now the sun sets and it gets cold -- now the concrete will release the heat it absorbed into the foam in both directions. The insulation of course will also limit this heat transfer to a slow trickle. Some of the heat will go into the house, and some will go to the outside wall. But the time the sun rises, the concrete will have cooled down again, ready to absorb the day's trickle of heat.
By way of analogy, imagine there's a 20-gallon drum of water elevated on a platform several feet up. That's heat from the sun. There's a very narrow tube coming through the bottom of the drum -- that's your insulation, allowing the heat to trickle through slowly. If that's all you have, the trickle spills right onto the ground (your home's interior). But now put a 10-gallon bucket at the bottom of the tube -- that's the concrete. Before the water spills onto the ground, that bucket has to fill up and overflow. That's thermal mass (sort of).
On the other hand, if you're in a climate that's either always hot or always cold 24 hours a day, the thermal mass doesn't do much, because that water just keeps pouring down -- it's a limitless trickle, and the bucket will fill up and then just stay full. You need the hot/cold day/night cycle for the thermal mass to do much good. This applies to using them in a foundation wall -- the ground is a steady 58 degrees all the time. There's no hot/cold cycle to take advantage of the thermal mass, so in that case ICF is just what you said -- a quick way to build a well-insulated basement wall.
The end of the story is that thermal mass lets you design your HVAC to handle something like the average temperature over a 24-hour period, rather than the peak afternoon temperature. (Or, in the winter, the overnight low.) Averages are usually much easier to deal with than the peaks and valleys, and you get more efficient usage of your HVAC. Of course, thermal mass doesn't have to be in the walls -- if you have concrete floors inside the building envelope, those will also suck up whatever heat makes it through the walls and keep the temperatures down. But it's a bit better if the mass is in the walls, because that prevents some of the heat from making it inside in the first place (because some of the heat will be transmitted back to the outside overnight.)
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freakboy
Registered Users
Posts:32
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| 06/30/2008 6:32 PM |
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Mortman that is one of the best explanations I have read yet. Thank You!!!
The ICF project underway is in Massachussetts
The rep from the ICF company has been extremely helpful with great customer service but... when he told me that ICF performs very well in exteme temps (constant cold or hot) I really lost faith in his credibility. I have read a lot from unhappy Canadians who built with ICF. Also I have read the recent report (forget the organization, referred to by this web site) and the conclusion of the report was that thermal mass works best when it is closer to the living space NOT with equal amouts of insulation on both sides.
From what little experience I have so far I think that SIP must be easier and quicker by far.
Most heat is lost thru the ceiling of a home and SIP addresses that in one neat package rather than dealing with another process to learn or sub out.
I really want to believe in the thermal mass thing but find it hard to believe that it is that much better than SIP.
Back to my original question, are there any threads in this forum comparing the 2 arguments.
The pump truck for our first pour alone was $800.00. One more pour to go. |
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Dont run thru the forest with your face on fire
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PanelCrafters
Registered Users
Posts:1330
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| 06/30/2008 6:55 PM |
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Posted By freakboy on 06/30/2008 6:32 PM
I really want to believe in the thermal mass thing but find it hard to believe that it is that much better than SIP.
Back to my original question, are there any threads in this forum comparing the 2 arguments.
Mortman is not lying to you. Please check out This Article. |
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....jc
If you're not building with OSB SIPS(or ICF's), why are you building? |
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newhome
Registered Users
Posts:16
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| 06/30/2008 7:58 PM |
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Based on my reading and research, where your mass should be really depends on your climate.
Northern climates with more of a heating need than a cooling need are better off with the mass on the interior with no insulation delaying the flywheel effect. Insulation should be on the outside. This keeps any heat gained from solar during the day inside the structure and radiating back into the livable space. This maximizes your gain. Interior insulation just slows it down. It will also temper day time temp swings during the cooling season as well.
Mass in a colder climate should be an addition to the insulation not a substitute for it. For me that would mean that a SIP would be more cost effective for R-value than ICF’s in cold climates.
This all takes into account that you design a home with systems that work together. In other words there is no point incorporating mass for the sake of mass. It needs to work together with solar gain, insulation and the appropriate windows. |
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rnortman
Registered Users
Posts:97
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| 06/30/2008 10:05 PM |
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Posted By freakboy on 06/30/2008 6:32 PM
Mortman that is one of the best explanations I have read yet. Thank You!!!
The ICF project underway is in Massachussetts
The rep from the ICF company has been extremely helpful with great customer service but... when he told me that ICF performs very well in exteme temps (constant cold or hot) I really lost faith in his credibility.
Well, he is an ICF rep... you have to expect a certain amount of bias. When the temperature is more or less constant, thermal mass hardly matters at all, and in that case R-value and air infiltration is really all that matters. SIPs will give you more R per dollar in most cases, as far as I understand it. Now, ICF walls do have very good whole-wall R-values compared to stick-built walls, and they're also much tighter. (Air infiltration is really what it's all about. You could have R-200 walls, but if you leave your windows open, it doesn't really matter.) And even in Massachussetts, there are temperature cycles to deal with, so thermal mass does a little bit for you. Just not nearly as much as it would in Phoenix. The only walls that truly see nearly steady-state temperatures are foundation or bermed earth walls. (Makes you want to seriously consider building foundation walls with fiber-cement SIPs, doesn't it? Hmm....)
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freakboy
Registered Users
Posts:32
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| 07/01/2008 10:18 PM |
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panelcrafters, thank you for the link. It confirms how I interpreted the Oak Ridge Labs study. It seems ICF depends on climate conditions, some climates make the system achive a high effective R-value and some climates do not. It just needs to be sorted out which climates are best for thermal mass to work best. I am in agreement with newhome on sip probably being better for cold climates.
Our ICF salesman says effective R-value for his system is R-40. That may be true for AZ and mabey in MA during the summer, but I doubt it for the winter months here in MA. No doubt that the ICF home will be WAY better than stick built with fiberglass insul (usually installed carelessly) but, much of that improvement is probably gained from air sealing which occurs from the solid wall. |
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