Papercrete over cob?

Ok so I have been planning/researching/clearing my property for a year now and have around 5k saved to build my home with. I plan to start on it this spring and hope to be finished before our first freeze next year. There is just one problem, I still haven't decided on what material to use. After I attended my first workshop I came away inspired and dead set on using adobe mainly because I was a brick mason for awhile and laying adobe is essentially the same process and therefore felt the most comfortable to me, BUT as I tend to do I am second guessing myself.

My main concern is insulation. Its gets miserably hot here in summer and below freezing in the winter and I just don't see how a huge thermal mass home would be comfortable. I have considered wrapping the home in foam board but don't really want to, so finally my question --- Does anyone have any information regarding applying papercrete over adobe/cob as a insulation wrap? Or thoughts on how it might perform? Or should I just use straw bales instead?

Jeremy Nodine wrote:Ok so I have been planning/researching/clearing my property for a year now and have around 5k saved to build my home with. I plan to start on it this spring and hope to be finished before our first freeze next year. There is just one problem, I still haven't decided on what material to use. After I attended my first workshop I came away inspired and dead set on using adobe mainly because I was a brick mason for awhile and laying adobe is essentially the same process and therefore felt the most comfortable to me, BUT as I tend to do I am second guessing myself.

My main concern is insulation. Its gets miserably hot here in summer and below freezing in the winter and I just don't see how a huge thermal mass home would be comfortable. I have considered wrapping the home in foam board but don't really want to, so finally my question --- Does anyone have any information regarding applying papercrete over adobe/cob as a insulation wrap? Or thoughts on how it might perform? Or should I just use straw bales instead?

I wouldn't use ANYTHING with portland cement in it with cob.. Too many moisture/temperature compatibility issues. Anyhow, portland cement is full of industrial flue waste, it's toxic crap. People might want to think about that.
Cob goes well with straw-bale building. The colder your climate, the more you will need to insulate around the thermal mass and bales play well..
Get your thermal mass on the sunward side and slightly east, your insulation on the shade and generally west.

It is my understanding that papercrete transpires moisture quite well, and with clay added and only 10% cement. I imagine it would bond well to cob/adobe to form a cheap insulative "skin" that would be much easier to then plaster over with earth than polystyrene foam board would be.

I just haven't been able to find any information about what I am proposing so I turned here...and yes concrete is bad but is sometimes a necessary evil.

I would want to see some extensive testing of the combination before I decide to trust it.
The straw-bale/cob/earthen plaster combination(s) are known to work.

Hello Jeremy,

Thanks for posting this, as I know many are asking similar questions. In general I have to agree with kirk on this one. Even though you are only using a 10% portland additive to the paper slury, it is the general condition, and characteristics of portland that are so objectionable. Without even considering the carbon footprint of portland manufacture, the other reasons not to use it, (even in small amounts) is mechanical-physical characteristics.

I am sure you have read that papercrete is hydrophilic by nature, as is lime and clay as well, however unlike lime and clay, portland tends to hold and transport moisture to location you don't want it. This is why when the dubbing in log cabins started getting replace with cement instead of lime or cob dubbing, the logs started to rot. The cement (OPC) held moisture for much longer periods of time and directly against the wood. Cob dubbing actually draws moisture away from the wood surface and dries it out rapidly. This has also become an issue in the UK where old lime mortars got replace with portland based mortars and the issues of "rising damp." became rampant, as well as, rotting timber frames where the "nogging bricks" started getting mortared with portland mortars. Another quick way of thinking of it is this: which would you rather wear on a cold fall day during a walk and a rain storm rolls in: A cotton sweater (portland)? A wool sweater or fleece (lime and cob)?

Without knowing your build location, I can't really give much more advice on the proposed architecture you may want. I can say look to the traditional vernacular for you region and see what architecture lasts the longest. Performance of traditional architecture can always be improve with more insulation. I would also point our that the "thin wall" (1 meter or less) masonry (cobb, rammed earth, stone, etc) does not have the correct proportions, in most cases, to achieve effective thermal inertia in climates that present extreme cold temps and humidity. The humidity part seems to play a large role in this.

Another perspective on papercreters is to add clay or lime in small proportions instead of portland, similar to what is being done with "slip formed" walls of wood chip and/or straw.

Regards,

jay

Thanks Jay! This is the kind of answer I was looking for. I live in zone 7b in the piedmont of South Carolina the specific location is Landrum S.C here are some numbers on the climate. Annual Average Temperature is 55.6°F Avg Percipitation per year is 54.22 inches with a Annual Average Humidity 71.04%. I feel like this limits my options to earthen construction such as adobe or cob but I feel I will no doubt need some sort of insulative layer on the outside of the house. Do you feel foam board is a viable option to wrap the house? I have heard of others doing it over adobe but wondered if this caused any issues with water not being able to transpire. I have even been pondering if imbedding foam board into cob as I built the walls up would work. While neither of these options may be ideal I have a limited budget, a crap load of clay, and already know how to build with cob/adobe so I'm trying to figure out some way to make it work.

Help me wise permies!

The foam is likely to act like a moisture barrier. Water vapor will not be allowed to move through the walls, but be stopped by the barrier, turn into liquid water (especially when it's cold outside) and do damage.
Placing foam inside of a cob wall will do the same as above AND insulate out half of your thermal mass. The outer mass will tend to stabilize at VERY COLD, drawing heat out of the building MUCH faster. Yes, even through the insulation.

I'm afraid that foam board and cob are incompatible materials. The kinds of measures that you will have to take to force them to work together will be greater than the benefits..
A good friend of mine, living in Minnesota insulated his cob building with wool/lime. So far, it appears to work well with no troubles.

Hi Jeremy, et al.,

By addressing points in Kirk's entry, we can carry this conversation a little further...

The foam is likely to act like a moisture barrier.

Foam is not like a moisture barrier...foam IS A MOISTURE BARRIER. This can be a bad thing in many applications, while in others not applicable.

Water vapor will not be allowed to move through the walls, but be stopped by the barrier, turn into liquid water (especially when it's cold outside) and do damage.

I agree with everything in that statement with the modification of "may cause damage if not planed and mitigated for."

Placing foam inside of a cob wall will do the same as above AND insulate out half of your thermal mass. The outer mass will tend to stabilize at VERY COLD, drawing heat out of the building MUCH faster. Yes, even through the insulation

This one is not fully accurate, as foam by it's nature creates a true "thermal break" because of the concentrated R factors over such a short distance. This would also be the time to bring up "dew point" and where it occurs inside the thermal matrix of a wall. If the "dew point" takes place within the foam layer, you do not get condensation, as the dew point is within the sealed structure of the foam where there is no moisture. So you can design a cobb wall with foam as part of the system and have it function...but as Kirk has pointed out, is it worth it, probably not compared to other systems.

The kinds of measures that you will have to take to force them to work together will be greater than the benefits.

Here is the real question for not only the use of foam, but the use of cob itself in many applications. Compared to other mediums of construction, are you really saving any money or effort by trying to use cob? In cases yes, while in many others you are not.

The trick to "thermal inertia," and higher R factors working in concert with one another in these "mass wall" systems is "air breaks." So, as an extreme example, say you went through the effort of using cob with a foam core thermal break. You would have to create and "air break" of at least 20 mm (~3/4) between the cob and the foam. These types of spaces can also be enhanced by the application of a "radiant barrier," but the air space in those applications must be "dead air space." With the foam to the outside of the cob mass wall, you will have to vent the air space back into the living space, which is fine to do, as the cob has little R factor to it in the first place, l and the foam would then take the brunt of the thermal resistance work for the wall diaphragm. Then the exterior could be clad in wood board, shingle, stone, or a myriad of other systems.

I would close by addressing that whatever system you employ, try to do some comparative wall cross sectional drawings, and thinking about cost both monetary and time for each. If you would post pictures of them, we could discuss the pros and cons of each.

Regards,

jay

Hi Jeremy, et al.,

By addressing points in Kirk's entry, we can carry this conversation a little further...

The foam is likely to act like a moisture barrier.

Foam is not like a moisture barrier...foam IS A MOISTURE BARRIER. This can be a bad thing in many applications, while in others not applicable.

Water vapor will not be allowed to move through the walls, but be stopped by the barrier, turn into liquid water (especially when it's cold outside) and do damage.

I agree with everything in that statement with the modification of "may cause damage if not planed and mitigated for."

Placing foam inside of a cob wall will do the same as above AND insulate out half of your thermal mass. The outer mass will tend to stabilize at VERY COLD, drawing heat out of the building MUCH faster. Yes, even through the insulation

This one is not fully accurate, as foam by it's nature creates a true "thermal break" because of the concentrated R factors over such a short distance. This would also be the time to bring up "dew point" and where it occurs inside the thermal matrix of a wall. If the "dew point" takes place within the foam layer, you do not get condensation, as the dew point is within the sealed structure of the foam where there is no moisture. So you can design a cobb wall with foam as part of the system and have it function...but as Kirk has pointed out, is it worth it, probably not compared to other systems.

The kinds of measures that you will have to take to force them to work together will be greater than the benefits.

Here is the real question for not only the use of foam, but the use of cob itself in many applications. Compared to other mediums of construction, are you really saving any money or effort by trying to use cob? In cases yes, while in many others you are not.

The trick to "thermal inertia," and higher R factors working in concert with one another in these "mass wall" systems is "air breaks." So, as an extreme example, say you went through the effort of using cob with a foam core thermal break. You would have to create and "air break" of at least 20 mm (~3/4) between the cob and the foam. These types of spaces can also be enhanced by the application of a "radiant barrier," but the air space in those applications must be "dead air space." With the foam to the outside of the cob mass wall, you will have to vent the air space back into the living space, which is fine to do, as the cob has little R factor to it in the first place, and the foam would then take the brunt of the thermal resistance work for the wall diaphragm. Then the exterior could be clad in wood board, shingle, stone, or a myriad of other systems.

I would close by addressing that whatever system you employ, try to do some comparative wall cross sectional drawings, and thinking about cost both monetary and time for each. If you would post pictures of them, we could discuss the pros and cons of each.

Regards,

jay

Great info guys thanks, love this forum.

The trick to "thermal inertia," and higher R factors working in concert with one another in these "mass wall" systems is "air breaks." So, as an extreme example, say you went through the effort of using cob with a foam core thermal break. You would have to create and "air break" of at least 20 mm (~3/4) between the cob and the foam. These types of spaces can also be enhanced by the application of a "radiant barrier," but the air space in those applications must be "dead air space." With the foam to the outside of the cob mass wall, you will have to vent the air space back into the living space, which is fine to do, as the cob has little R factor to it in the first place, and the foam would then take the brunt of the thermal resistance work for the wall diaphragm. Then the exterior could be clad in wood board, shingle, stone, or a myriad of other systems.

Hmmm you got me thinking....so let me see if I follow you here, are you saying I could for example build a pallet frame to hold the foam then cob around that leaving air space and then vent at top and bottom of the walls and it would work? If so could I vent it to the outside? Would I even need a vent if it is fully encapsulated? I had already considered a pallet wall system with some form of insulation infill as it would likely save me time/labor overall.

A good friend of mine, living in Minnesota insulated his cob building with wool/lime. So far, it appears to work well with no troubles

That's pretty incredible to attempt cob in that climate. How exactly did he incorporate the insulation? How long has he lived in it? Any more info is much appreciated!

Hmmm you got me thinking....so let me see if I follow you here, are you saying I could for example build a pallet frame to hold the foam then cob around that leaving air space and then vent at top and bottom of the walls and it would work?

Yes, if all the other components are working in concert with the system.

If so could I vent it to the outside?

That would be no...Kinda defeats the purpose of going high tech with a continuous foam thermal layer if you vented to the outside as it would take you heat with it.

Would I even need a vent if it is fully encapsulated?

So we don't go too far down the rabbit hole, this is a complex system we are discussing, with many potential pitfalls, which is what Kirk was warning about. It's not possible to "fully encapsulate the foam, as the foam is what is doing the encapsulation with this type of thermal envelope. the cob just becomes an internal structure to create a thermal heat sink by way of mass.

I had already considered a pallet wall system with some form of insulation infill as it would likely save me time/labor overall.

Easy to write and think about, very difficult to make work well in concert with all the other components. We are getting into some pretty detail wall system designs.

This thread has me thinking..wondering...
Jeremy,if you're using pallet frame work,could it be filled with loose-pack clay/straw to obtain the insulative portion you seek?
I'm unsure how c/s compares to foam board.
Would the cob/adobe then go on the inside of this framework or outside? How thick would you make it?
I,too, am interested in the performance/comfort of the Minnesota cob home insulated with wool.
All the best
Kate

Hi Jeremy, there is a builder Kelly Hart who used papercrete over earthbags. Not exactly cob, but it is a type of rammed earth. Here is the link http://www.earthbagbuilding.com/projects/hart.htm He does report good insulation with it. The only concern I would have in your climate is the moisture. Most papercrete is done in dry desert like environments, I always thought of SC as humid. Since you live in the South, you should investigate doing rice hulls in earth bags. It is insulated, faster to build then cob and cheap. You live closer to the major rice states ie Missouri, Mississippi, Alabama. Often times you can get the rice hulls for free. It contains high silica like strawbales, so it insulates, resists mold, fire etc, but that probably belongs to another thread. Good Luck

Jay C. White Cloud wrote:

Placing foam inside of a cob wall will do the same as above AND insulate out half of your thermal mass. The outer mass will tend to stabilize at VERY COLD, drawing heat out of the building MUCH faster. Yes, even through the insulation

This one is not fully accurate, as foam by it's nature creates a true "thermal break" because of the concentrated R factors over such a short distance.

Ahh. Here we may need to agree to disagree.
NO insulation is 100%, heat WILL move through no matter HOW good it is. There is no such thing as a "true thermal break".
One of the BEST ways to reduce the insulative value is to put it in the situation discussed above. Heat ALWAYS "rolls down hill", always from hot to cold and the larger the difference in temperature, the faster heat will jump, in larger quantities.

People, in cold climates, ALWAYS put the thermal mass inside and insulate around it (to the outside). If you are going to vent between the thermal mass and the insulation (perhaps a good idea), vent it to the INSIDE of the building! Keep the heat in!
My friend dipped the wool in lime putty and just stuck it onto the cob.. A bit like a plaster, I suppose but NOT troweled down tight and put on rather thick (3 or 4 inches). He may have plastered over it, but I'm not sure of it.

Hi Kirk,

I don't think we are at a point of having to "agree to disagree," yet as we may have to clarify a few points first, that one of us is not seeing certain principles of "thermal dynamics," clearly. I have asked John Elliott for advice on this, as his background in science would be very germane to this conversation. I also don't mean to be so "detail picky" but not understanding these principles is leading too many wall systems being built that are not functioning in application as the builder thought they would. This is part of the reason I write on Permies, so we can have the accurate information being applied to wall matrix, not the assumed, or misunderstood.

1. I don't believe I said any insulative material is 100%, but what I will state as a fact of science is that some materials have higher resistance levels (R value being the most common measure here in North America I do believe) than others.


2.

NO insulation is 100%, heat WILL move through no matter HOW good it is. There is no such thing as a "true thermal break".

I do believe Kirk, you may need to go back and read your basic principles of "thermodynamics." You are correct "heat will move through no matter how good it is," but the time coefficient at which it does has a direct correlation to how effective the "thermal beak" will function. I am not sure where you got the idea that there isn't such a thing as a "thermal break," because if there wasn't the Shuttle would have had a real hard time at reentry into Earth's atmosphere, and there are several chemistry experiments that would not function well without there being sound principles behind the concept of a "thermal break."

3.

Heat ALWAYS "rolls down hill", always from hot to cold and the larger the difference in temperature, the faster heat will jump, in larger quantities.

Hmmm, I don't believe heat ever rolls or moves down hill without some convective or other physical motivation. Heat only moves up by principle. Cold can in theory, and principle roll down hill (or mountains) and does, which often creates "cold waves." I have a notion that you may be thinking about portion of the anomaly that is the "Mpemba effect," which is not a constant by the way. Your second premise would seem to suggest that if its cold outside, you will lose heat faster from a 90°F room than from a room that is 65°F, on that we would agree, just as when it gets hotter outside the harder "cooling devices" have to work. Nether of these counter the reality of a "thermal break," only that some material are more efficient than others as retarding these events.

4.

People, in cold climates, ALWAYS put the thermal mass inside and insulate around it (to the outside). If you are going to vent between the thermal mass and the insulation (perhaps a good idea), vent it to the INSIDE of the building! Keep the heat in!

Yes I agree, but that is exactly what I recommended in the first place; please reread the second to last paragraph of my entry on : 11/10/2013 5:11:03 PM I would further point out that this system is well understood and in good practice with several "mass wall" construction modalities. For example, several Rammed Earth wall companies have a percentage of the wall matrix's thermal mass on the outside as a "buffer" to "thermal inertia" further augmented by a "thermal break," of 100 mm foam insulation to increase wall efficiency to temperature coefficiency flux and then the majority of the thermal mass to the inside of the living space, which creates a "thermal heat sink," in winter and a cooling dampener in summer.

5.

My friend dipped the wool in lime putty and just stuck it onto the cob.. A bit like a plaster, I suppose but NOT troweled down tight and put on rather thick (3 or 4 inches). He may have plastered over it, but I'm not sure of it.

I would have to evaluate the schematics and design specs for an application like this, however on the face of it, I would never recommend "dipping" a "wool" or "fiber mass" that was intended for insulative value in a lime render, as this is only going to decrease its thermal efficiency, and facilitate other very possible denigration events.

Jay C. White Cloud wrote:Hi Kirk,

I don't think we are at a point of having to "agree to disagree," yet as we may have to clarify a few points first, that one of us is not seeing certain principles of "thermal dynamics," clearly. I have asked John Elliott for advice on this, as his background in science would be very germane to this conversation. I also don't mean to be so "detail picky" but not understanding these principles is leading too many wall systems being built that are not functioning in application as the builder thought they would. This is part of the reason I write on Permies, so we can have the accurate information being applied to wall matrix, not the assumed, or misunderstood.

I quite appreciate your writings and so far have agreed with every point but the one. Your mission is a good one, one that I myself share to the best of my own understanding(s).

1. I don't believe I said any insulative material is 100%, but what I will state as a fact of science is that some materials have higher resistance levels (R value being the most common measure here in North America I do believe) than others.


2.

NO insulation is 100%, heat WILL move through no matter HOW good it is. There is no such thing as a "true thermal break".

I do believe Kirk, you may need to go back and read your basic principles of "thermodynamics." You are correct "heat will move through no matter how good it is," but the time coefficient at which it does has a direct correlation to how effective the "thermal beak" will function. I am not sure where you got the idea that there isn't such a thing as a "thermal break," because if there wasn't the Shuttle would have had a real hard time at reentry into Earth's atmosphere, and there are several chemistry experiments that would not function well without there being sound principles behind the concept of a "thermal break."

I might need to go back and look again, though it is my understanding that temperature gradient MUST ALWAYS be a consideration in these types of calculations, regardless of the material.
In the case of the shuttle, appropriate materials were chosen to handle the gradient over time.. The same gradient over more time may not have worked quite so well, or a higher gradient over the same duration. Design tolerance and all that.

3.

Heat ALWAYS "rolls down hill", always from hot to cold and the larger the difference in temperature, the faster heat will jump, in larger quantities.

Hmmm, I don't believe heat ever rolls or moves down hill without some convective or other physical motivation. Heat only moves up by principle. Cold can in theory, and principle roll down hill (or mountains) and does, which often creates "cold waves." I have a notion that you may be thinking about portion of the anomaly that is the "Mpemba effect," which is not a constant by the way. Your second premise would seem to suggest that if its cold outside, you will lose heat faster from a 90°F room than from a room that is 65°F, on that we would agree, just as when it gets hotter outside the harder "cooling devices" have to work. Nether of these counter the reality of a "thermal break," only that some material are more efficient than others as retarding these events.

As to "rolling downhill" I was being metaphorical.. The meaning I intended was in the sense that heat will be conducted better across greater differences in temperature.
I've found that it is often not enough to be scientifically correct. It is important to (ALSO) be able to paint useful mental images, otherwise the target audience either won't understand or won't retain the information. In the past, I have found a useful mental image in comparing thermal transfer to a ball rolling downhill; slope representing difference in temperature, etc.
I think this time I did a poor job of "setting up" the analogy. I tend to think in a kind of audio/visual shorthand that will often not come across well if I don't take proper time with it.

4.

People.. (when)In cold climates, ALWAYS put the thermal mass inside and insulate around it (to the outside). If you are going to vent between the thermal mass and the insulation (perhaps a good idea), vent it to the INSIDE of the building! Keep the heat in!

Yes I agree, but that is exactly what I recommended in the first place; please reread the second to last paragraph of my entry on : 11/10/2013 5:11:03 PM I would further point out that this system is well understood and in good practice with several "mass wall" construction modalities. For example, several Rammed Earth wall companies have a percentage of the wall matrix's thermal mass on the outside as a "buffer" to "thermal inertia" further augmented by a "thermal break," of 100 mm foam insulation to increase wall efficiency to temperature coefficiency flux and then the majority of the thermal mass to the inside of the living space, which creates a "thermal heat sink," in winter and a cooling dampener in summer.

My intent was to agree with you and underline the sentiment. I am quite aware of what you are describing and completely agree 100%
Again, I didn't signal that I was moving to a different topic and speaking to different question. My bad... I must have been tired and getting sloppy.

5.

My friend dipped the wool in lime putty and just stuck it onto the cob.. A bit like a plaster, I suppose but NOT troweled down tight and put on rather thick (3 or 4 inches). He may have plastered over it, but I'm not sure of it.

I would have to evaluate the schematics and design specs for an application like this, however on the face of it, I would never recommend "dipping" a "wool" or "fiber mass" that was intended for insulative value in a lime render, as this is only going to decrease its thermal efficiency, and facilitate other very possible denigration events.

It was an experiment that appears to have worked (so far) in the case of my friend. Certainly, dipping the material reduced it's insulation values by quite a lot; he apparently had enough wool to make up for reduced efficiency of the material. As to the longevity of it, time will tell.

Jay C. White Cloud wrote:Hi Kirk,

I don't think we are at a point of having to "agree to disagree," yet as we may have to clarify a few points first, that one of us is not seeing certain principles of "thermal dynamics," clearly. I have asked John Elliott for advice on this, as his background in science would be very germane to this conversation.

Thanks for drawing me into this conversation, Jay. I was staying away from it because I didn't want to pencil out any heat transfer calculations.

But since Jeremy is practically a neighbor, I should point out that the climate of the southeast is very amenable to a high thermal mass home -- and without any added insulation on the outside of it. We don't have the heating loads that they have in the North and the Midwest, and even though the summers seem "miserably hot", the energy needed for cooling in the summer is less than the energy needed to heat in the winter. One of the advantages of the climate here is that we don't have that many days when the HVAC system needs to be running non-stop. Winter days are usually warm enough that if it is sunny, you get enough heat gain that the furnace won't come on until after sundown. Conversely, in the summer, nights cool down so that the AC doesn't have to run all night. With that kind of climate, you want more thermal mass because the more you have, the more the swings are evened out.

So my two cents is to re-evaluate the high thermal mass without any other insulation.

Excellent John E., and knowing that about the build location is most important. (folks need to put their full details with their names!) Thanks also for joining the conversation, good advise you have given. I think, should I ever get a chance to build again in the South East I would use a combination of timber framing, mass cob wall and one of the clay chip/straw slip systems working in concert with one another.

_______________________________________________________________________________________________________________________________

Hi Kirk M.,

to pick up where we left off...

I might need to go back and look again, though it is my understanding that temperature gradient MUST ALWAYS be a consideration in these types of calculations, regardless of the material.
In the case of the shuttle, appropriate materials were chosen to handle the gradient over time.. The same gradient over more time may not have worked quite so well, or a higher gradient over the same duration. Design tolerance and all that.

It is good that you have brought up "gradient," into the conversation. That gradient, though often a statistical measurement in some respects which can have a rather "squishing" interpretation, can also be very poignant to creating a mental picture. I would also state that the "steep slope," of the gradient is the "thermal break," I have been speaking of. It is that section of a wall system matrix that causes a long reduction of time for a temperature (hot or cold) to move through a material.

It was an experiment that appears to have worked (so far) in the case of my friend. Certainly, dipping the material reduced it's insulation values by quite a lot; he apparently had enough wool to make up for reduced efficiency of the material. As to the longevity of it, time will tell.

These types of home grown "experiments" can have great benefit to an individuals understanding especially if shared as you have. It is when lay folk will extrapolate information from these "little empirical tests," that are more based on assumption or subjective conjecture that I become wary. If I may use this case as an example, (please not it is not a criticism just observation base on experience) here was an attempt to increase "thermal efficiency" in a system, that in theory has merit, yet in practical application probably was not well thought out from the "far view."

Wool as an insulator is wonderful, but you have to ask first, what is its "real life-real time" durability to perform its thermal function? Will the lime rendering decrease the thermal resistance enough to not make the labor and cost worth the effort. Was the wool treated for infestation of pest that eat, and utilize wool as a nesting material? Is there a way to periodically check and/or service the inner function of the wall system matrix including the wool. Did the augmentation drastically or only marginally increase system performance? These are just some examples of questions I would have asked before even considering such an experiment, or having another conduct same.

When a concept is examined, take not just a few steps back but many, before considering "real time," application.

Regards,

j

Kirk Mobert
Jay C. White Cloud
And the "pClould'' : (If apple can have its own 'iCloud' then we can have a ''pClould''), This is actually a serious question, espoecially in light of further reading At >

Cold Climate Housing Research Center> cchrc.org > A branch of the University of Alaska, Fairbanks ! If we can agree that we know Cold, these people Know COLD !

So- the question, though it is a far step away from Traditional Building, what is your opinion on Anti-Bridging Building concepts generally, and the use of Thermoblok aerogel insulation
as a real world tool, rather than a theoretical means of Allegedly greatly increasing the R-Value of 'Most Forms' of traditional building.

I think we all agree that venting water vapor to the inside is a best use practice almost always ! I look forward to your opinions ! Big AL !

Hi Allen,

Good stuff you brought up, and forgive me for jumping around, but first I have to tell you that I have been crazy excited about "Aerogel" since the late 80's when I first read about it. I say, and you know I am an extreme traditionalist, if you are going to go "high-tech," do it with caution, but go all out. This is one of the most exciting insulative materials around not only for the high R ratings, but also for the light transmission properties. In reality now more than theory I could build a traditional double wall timber frame system, with 100 mill bridge system and fill with Aerogel and do infill panels of light of opaque glass/plastic between frame members on the outside and inside (or stained glass) and have very high light transmission with a wall that is more thermally efficient than current super insulated solid wall systems. This product could really shake things up. If we can safely start manufacturing at a sustainable and environmentally safe way the Aerogel insulative beads, these combined with natural materials could change the way we build, and the efficiency. Question I don't have yet:

What is the product durability, and sustained R over time?

Will it actually hold up under real world application?

Can we bring the cost down to realistic values that all can afford?

Complete environmental impact of this manufacturing process?

Carbon foot print for manufacture?

http://cchrc.org/

These folks know "COLD" and are a great resource to study. The only issue I have with most of these systems:

1. Too technology dependent to have long term applicability. If something is mechanical and crucial to a system, then you have a very weak link. It is not a matter of if the power goes out, but when, and not if it will break, but when.

2. Super high tech insulative wall systems that look good to the thermal Engineer, but what will these systems look like under real world use (neglect?) in 30 years?


Your point about,

I think we all agree that venting water vapor to the inside is a best use practice almost always

I am a bit lost by this comment? I know I will have lots of water vapor if I keep a home at a healthy humidity level, and that I don't want the water vapor trapped in the interstitial wall system assembly or condensing on surfaces, but I am not sure about venting to the inside? Could you expand what you meant Al?

Regards,

j

Jay C. White Cloud wrote:
Hi Kirk M.,

It is good that you have brought up "gradient," into the conversation. That gradient, though often a statistical measurement in some respects which can have a rather "squishing" interpretation, can also be very poignant to creating a mental picture. I would also state that the "steep slope," of the gradient is the "thermal break," I have been speaking of. It is that section of a wall system matrix that causes a long reduction of time for a temperature (hot or cold) to move through a material.

For me, (as visualization tool) a higher slope would represent a higher temperature gradient, allowing the "ball" (heat) to move faster; a lower slope (flat land) would represent materials with lower conductivity (insulation) . It turns out that this is a better analogy than first meets the eye. Heat itself appears to have mass, inertia, etc.. You might find this interesting: Thermomass theory.

My original point was that sandwiching foam insulation between two cob layers could GREATLY reduce the effectiveness of the insulation. If the cob mass on the inside is a comfortable room temperature and the cob mass on the outside were below (or at) freezing, I imagine that the effectiveness of the insulation between would be HORRIBLY reduced. Direct conduction, being the most efficient way to transfer heat, with no possibility of boundary layer effects to reduce heat escape, etc, etc, etc..
No matter how good your insulation is, the above scenario is just about the WORST condition to place it under.. Furthermore, chances are quite good that the insulation would, over time, become saturated with water. Insulation materials tend to be good sponges, cold/hot transition areas tend to collect condensation; much evidence of this condition can be found ANYWHERE that a vapor barrier has been placed on the wrong side of an insulation layer. Far too many of the buildings built in the 80's that were wrapped in Tyvec are now having the lower 3 feet of joists replaced along with ALL of the insulation. The stuff is coming out of the walls dripping with condensate in some cases.

These types of home grown "experiments" can have great benefit to an individuals understanding especially if shared as you have. It is when lay folk will extrapolate information from these "little empirical tests," that are more based on assumption or subjective conjecture that I become wary. If I may use this case as an example, (please not it is not a criticism just observation base on experience) here was an attempt to increase "thermal efficiency" in a system, that in theory has merit, yet in practical application probably was not well thought out from the "far view."

Wool as an insulator is wonderful, but you have to ask first, what is its "real life-real time" durability to perform its thermal function? Will the lime rendering decrease the thermal resistance enough to not make the labor and cost worth the effort. Was the wool treated for infestation of pest that eat, and utilize wool as a nesting material? Is there a way to periodically check and/or service the inner function of the wall system matrix including the wool. Did the augmentation drastically or only marginally increase system performance? These are just some examples of questions I would have asked before even considering such an experiment, or having another conduct same.

When a concept is examined, take not just a few steps back but many, before considering "real time," application.

Regards,

j

I tend to agree.. However!
Most often in my experience, theory and reality simply fail to line up. Sooner or later, someone has to be the first to try a thing, even if the idea being tried has only a marginal chance of success (maybe ESPECIALLY if).
In this case, his chances of success were deemed to be (by him) a little better than half. His personal risk/reward analysis gave the concept double-thumbs-up: He was a bachelor, living alone, building a one-room hovel on the land of a friend. The wool was given to him, so the (potentially) most expensive element was free of charge. His job was such that he had the free time to do it for himself. He was used to living in a canvas yurt through the winters of Minnesota. He built a rocket stove heated bed to sleep on, etc, etc..

So, although it's NOT an experiment that I would recommend for a family home, in HIS case it was entirely worthwhile.
It was good for us (the greater community) as well; his experiment worked to some degree and points to further possibilities, perhaps it could be improved and carried forward.

_______________________________________________________________________________________________________________________________


Aerogel is VERY interesting stuff. I remember in the 80s when it was first announced. Very cool.

My opinion pretty much echoes Jay C White Clouds.. The only thing that comes to mind to add to his list is end-of-life consideration. When the building has finally out-lived its useful lifespan, what must be done with the left-overs?? Can they be recycled/re-purposed, will they rot gently or should they be taken to a toxic waste facility?

Kirk, you still are not getting it?

My original point was that sandwiching foam insulation between two cob layers could GREATLY reduce the effectiveness of the insulation.

No it couldn't Kirk if it is the correct type of foam, (or even a properly vented void with something like "clay straw,") could be designed to work. I am not theorizing here, I have seen it done, and the inner wall probes are providing the data that when these systems are well designed and utilized in the correct environment, they work.

If the cob mass on the inside is a comfortable room temperature and the cob mass on the outside were below (or at) freezing, I imagine that the effectiveness of the insulation between would be HORRIBLY reduced.

Well as I have already stated, you would be "imagining" incorrectly.

Direct conduction, being the most efficient way to transfer heat, with no possibility of boundary layer effects to reduce heat escape, etc, etc, etc..

Yes, that is true, and why you need that gradient which is your "thermal break."

No matter how good your insulation is, the above scenario is just about the WORST condition to place it under..

If you don't know what you are doing, and have not designed advance insulative wall systems before, I would tend to agree. This is not work for the novice builder, but that does not render the modality ineffective, if you understand all the systems and how they work in concert with one another.

Furthermore, chances are quite good that the insulation would, over time, become saturated with water. Insulation materials tend to be good sponges, cold/hot transition areas tend to collect condensation; much evidence of this condition can be found ANYWHERE that a vapor barrier has been placed on the wrong side of an insulation layer. Far too many of the buildings built in the 80's that were wrapped in Tyvec are now having the lower 3 feet of joists replaced along with ALL of the insulation. The stuff is coming out of the walls dripping with condensate in some cases.

If your insulation is saturated your system is not well designed and/or applicable for the biome you have built it in. House warps and "vapor barriers" (like many modern insulative materials) are great in concept, and in lab testing, but not "real world" application. I do not condone most of these methods, as they are not necessary, and should not be used. Those that think they should typically have not been designing and building for more than 15 years, and few have gone back for any in depth forensic examination of modern architecture that employ them. Make your house "draft proof" nor "air tight", use natural venting, and understand the insulative system you chose very well before using it, and the architecture should have little issue with effective thermal resistance.

OK then, JCWC..
Under what conditions would you sandwich insulation (rigid foam or otherwise) directly between two layers of cob?? I will remind you that the original post did NOT include venting, it talked about a direct sandwich, which is what we've been discussing. Changing the parameters changes the conversation.

As far as I can tell, the advice that you and I would give (have here given) on this subject is practically identical.

It seems that we agree on everything but how one particular material type will perform. Are we just quibbling over technical details or is there an actual difference of approach here?

Whichever it is, I'm certain that an antagonistic tone is unnecessary.

Hey KirK,

My apologies if I sounded antagonistic, bad headache, hellish couple weeks fighting with construction bank loans and a myriad of other things going on that leaves me in a "blunt mood," yet I still feel obligated to respond to all the different folks that dialog with me, and the different websites I write on. I was going to seed you a pm last night but got on to other things. I would have been miffed too if someone responded to me with out some "front loading" (or a back-loading with a pm.) So sorry about that, I make this public so you know I am sincere.

Now as a warning, when I come across sounding antagonistic (I'm not that type of person) I am actually just press for time and I go into my "blunt professor - Daiku 大工 mode, not that you need to be given a lesson on anything, that's just how I get, please forgive.

Now lets get into it...(Jeremy, if you are still with us, please ask anything you would like.)

Under what conditions would you sandwich insulation (rigid foam or otherwise) directly between two layers of cob?? I will remind you that the original post did NOT include venting, it talked about a direct sandwich, which is what we've been discussing. Changing the parameters changes the conversation.

Kirk, I love you man...but I'm in a blunt mood, so go back and read the full post because I'm having to repeat myself, and that is why I am getting blunt. The OP (Jeremy's original post) did not talk about a "sandwich" it talked about, what is called in the construction trades a "warp" (Jeremy's term, but also sometimes called a "render" or "frosting") method for the insulation, which is a completely different methodolgy than a "sandwich" and typically does not need a venting system, if don correctly, because the "dew point" lands within the foam. If an insulative "render" is used (like straw clay) it needs to be permeable (breathable) just to avoid the interstitial moisture buildup you showed concern about. What came next was in the fifth post (my post) I set up some of the issues with OPC (backing up what you said- and on that we do agree fully.) I also set up the parameters for considering vernacular architecture for a region and alternative systems to what he was considering. On the eighth post (mine again) I introduced the "sandwich" method with proper venting, so lets start over by you re-reading the entire conversation, (I have twice just to make sure my advice and topic points didn't have flaws in them.)

Now I think, if you have re-read things, we can get on with the subtle differences in our methods, and boil this all down into some really useful info.

Regards,

j

p.s. I am sending you a pm Kirk.

I re-read the thread.
It IS as I suspected.. I see no real disagreement besides over the properties of the foam. Other than that one thing, the advice is the same.

I understand that he did at one point say "wrap", I do understand the difference.
What I responded to was the following:

I have even been pondering if imbedding foam board into cob as I built the walls up would work.

Which has a COMPLETELY different sense.

Anyhow, whatever.. We've already hijacked the thread enough with this nonsense and we really don't disagree on how to go about it.
Thanks for explaining, thanks for doing what you are doing here.
I gotta go out and build this week, so I'll be out of touch 'till the weekend.
Out

I agree...

Jeremy, if you have any more thoughts/questions please let us know. I hope you found some value in our more than detailed cross examination of insulation and mass walls. Check out Kirk's site and look at the work he is doing, if he is near you, maybe contact him about a course. Just remember that cob, as wonderful as it is, is but one of many vernacular forms for building.

Regards,

jay