This has maybe been tried/done before. What would be the pros/cons of putting pex lines into the IFC walls to act sort of like vertical radiant heat?  I'm sure the BTU loads for heating would be huge, and not make sense, but say in a hot climate to use a ground loop to cool to earths temp. then circulate throught the south / hottest walls.  this is just a thought i have had. i have no idea if code would allow this or if it is possible, just want to get some opinions. so please lets hear it thanks
Darren

Hayduke,

I don't know about specific code in your area, but the answer to your question (IMHO) is yes, it could be done, but the cost of it would never be realized.  Depending on the thickeness of the walls, you are working with a product that has a thermal value around a R50, so the cooling benefit would be minimal.  As I say this we also have folks that wish to build their home above grade with 10" thick ICFs, which we don't think makes a lot of sense either, but in the end its what the owner wants.  I would hate to think the costs associated with doing radient in the walls though.

Anyway those are my thoughts.

Renangle

It might be worth trying if there wasn't foam on the inside face of the wall. With a standard ICF, don't waste your time.



Do Pigs Fly? I didn't think so.

Not in an ICF wall, but think about a steel-skinned SIP wall.  Run the PEX between the hat channels used to hang the drywall and use it for heating and cooling.  In cooling mode you'd have to make sure your controls never let the glycol get below the dew point of the cavity, but other than that it sounds like it has great potential.  Lots of surface area, galvanized steel is a good reflector and drywall is a poor insulator. 

Shortly,

I'll bite. There are no crazy ideas. Just ideas that have/have not been prooven/disprooved. I saw on another board where someone did radant in a shower wall. Though they did conplain about not having enough output

Many concepts can work but your location is key. As you mentioned keeping in mind the dew point, where are you located? In many cases, where it's hot it's also humid

In the future when energy costs are much much higher, all methods will be explored more closely. My current concept is varriable insulation via vacuum  insulation. You go from R-250, Perfect vacuum, to R-0 at no vacuum, depending on the outside temp. Simple concept of absorb it or release heat depending where you are on the thermal flywheel. The ground has no control so to speak at it holds 52 deg F. year round. Add insulation at the wrong time and it called "perafrost".

Patrick T.

You said it. Ground temps do vary: Low in the North, High in the South.

JC, if ICF's don't have a thermal performance of 50, what do you believe them to have? And are you saying with a ICF with 5" of foam over 6" of concrete has the same thermal performance of a 5" foam sips wall with no thermal mass?

As an experienced ICF installer with no thermal mass knowledge, it would appear that ICF's would retain and give of heat in the winter with a heated interior long after the furnace shut down. Our customers have claimed in areas where power sources quit often, that there ICF houses have only dropped a few degrees over 12 hours compared to others that have dropped 20-30 degrees.

Your thoughts?

Dave

R-Value(as well as U, or any other measurement) is static. Therefore, the R-Value of an ICF(or SIP) wall is the sum of it's components. EPS around R-4 per inch, concrete(it's a thermal conductor) R-0. So, it's, depending on the block, around R-20.


Yes. Actually a bit worse(no OSB).


As far as temperature drop, it will vary depending on the insulative properties of the structure, and the air infiltration rate. Both ICF's and SIPS excel at reducing air infiltration. It's probably not the mass, but the tightness of the structure.

The real problem is that people are trying to assign a value to thermal mass. That depends on many factors, and it's impossible to assign a single value that covers all environments. Furthermore, it seems that some people(manufacturers mostly) are trying to add to the R-Value due to the reduced air infiltration rate. They are calling it: Effective R-Value. Sorry, that's Apples and Oranges. Two different things. You can't boost an R-Value just because the assembly reduces the air infiltration. Any one who is knowledgeable concerning Heat Loss/Gain knows this. Then there is the issue that since the mass is insulated to the interior, what value is it? ORNL recommends that for thermal mass applications, the mass be uninsulated to the interior of the structure.

The bottom line is that trying to assign a fixed value of R-50 to an ICF wall has no basis of fact.

JC,

Thermal mass can be a tough factor to gage. Location, location, location, or better described, temp swings, dictate more than anything. The extreams would be 1) a structure of 2' adbe walls, no insulation or heat in a climate where the daily temp swing was exactly 30 deg above comfort level in day and 30 below at night. In this case, the lack of insulation is allowing the mass to dampen temp cycle swing. Case 2) is a very cold climate where the temp is nearly constant -5 with massive insulation. Even with high thermal mass the main benifit would be to retain heat after either the heat source stops or say the door was left open for an extended time. The ORNL site does have graph based on 10+ regions effective R. I think they define it as "how much traditional insulation is it equal to"? Also thermal mass benifits vary greatly based on time of year. A region may have good temp cycles in the Winter but constant heat in the Summer.

As far as insulation being inside the mass, two points come to mind. What is practical and condesation issues. The 2"-2 1/2" of insulation on the inside will not stop the mass benifit but will buffer it. In our design we will have 4 5/8" on the outside and 2 5/8" on the inside. With this arrangment, we have the majority of the insulation on the outside of the thermal mass but have both buffering and easy ele/drywall install. We will have 4" thick concrete floors adding to our thermal mass.

Patrick T.

Go to LINK to see the stance taken by the ICFA regarding R-value and the performance of ICF walls.

First of all the publisher is not a neutral party, and they state this:

There ya go, they are trying to increase the R-Value due to lower Air Infiltration. As I stated it's Apples & Oranges. I will give them some amount of credit for not stating R-50!

I'm not bashing ICF's, and I like the product. I would just like to see some truth regarding their R-Value.

Hopefully the attached will be of some interest regarding insulation and thermal mass of ICF walls. The PDFs show output from a program called HEED from the energy folks at UCLA. It's at LINK. The program calculates heating/cooling load of a house hour by hour using 30 years of hourly temperature data.

The program's default R value for an ICF wall is about 26 and the time lag, i.e. time for a temperature wave to pass through the wall, is 11 hours.

I input very high and low set points for the thermostat values so as to minimize, or eliminate, a/c cooling. This helps to better illustrate how outdoor temperature affects indoor temp for an ICF house. The output is for Aug 1 to 12, which about the hottest part of the summer in SW Idaho.

There are two 3D graphs, one for outdoor temp and the other for indoor temp. The graphs clearly show how the indoor temp swings much less than outdoor temp, and how that swing lags the outdoor temp.

The graphs are not be taken as absolute but only illustrative, although the results should be reasonably realistic.

Been done.....Christopher Faust built a zero energy house on the research park campus of Texas A&M University years ago.  He used Blue Maxx with ground loops.....House is still there, using no energy.  It is a small model, but the concept works.

I don't see how anyone could build with concrete and not consider that there are thermal mass benefits. Certainly it is insulated, but that EPS insulation only gives you R-10 +/- between either the inside or the outside to get into the concrete mass. Does anyone realistically think that the concrete temperature will not change throughout the day with only R-10 insulation? And then when that temperature swings the other way, yes your concrete is going to release this heat, and given an equal amount of insulation on the inside and outside about half of it will release each way, and isn't this what thermal mass is about - tempering? Is this an ideal place for thermal mass - clearly no. But to say the thermal mass contributes nothing is also clearly wrong. Infiltration is clearly a factor, but with SIPs you can address this (with proper stick-built construction you can address this, but it takes attention to detail). However with ICF you do get thermal mass benefits, and that gives you icing on your cake.

Now would I want to heat my house by heating my concrete ICF walls, I can't see how that would be efficient.  You have the thermal mass, but immediately half that heat goes outside the envelop, and that doesn't seem like a very efficient use of energy.  I would think that an interesting application would be to use the walls as your heat sink for an evacuated tube solar collector, which might work even better on below grade walls.  Combined with hydronic heating in the floors, you could store several days of heat (especially some of you in cloudy climates) without kicking in your backup heat source.  

There is an interesting older discussion from a guy in Colorado that built ICF, and actually put temperature sensors in his walls at various places (inside concrete, outside concrete, center of concrete mass) and on the various walls (south, west, east, north). LINK.