Condensation, and other moisture related challenges in natural building...

(Note to Readers: This is a conversation split from "Raised Earth Foundations" thread...)

Bill, if vapors of moisture make it through the packed clay and into the house, why is that a problem? Vapors condensing is a problem but that would not happen in this scenario because there is air on either side (the gravel below and the home above. We obviously don't want a completely moisture free home so where will it come from? In the case of a straw bale home; moisture in the air will pass in and out of the bales (as long as a breathable plaster was used). This in my opinion is a very desirable because it exchanges the buildings air constantly and that without a expensive and complicated electric dependant air exchange unit. I personally think sealed boxes for houses are completely unnecessary. If we allow moisture to move through the walls and that's fine why can't it move through the floor as well?

If there was a vapor barrier under the floor wouldn't that actually creat condensation instead of eliminate it?

Phil

An excellent question my man. Interior moisture is a problem during the winter because of this:



See the mold/mildew and failing paint? This is the result of high interior humidity and cold outdoor temperatures. The same thing is probably going on to some degree inside of the walls. Strawbale walls face the exact same issues ESPECIALLY if you are not paying attention to building airtight and allowing air movement through walls. Most strawbale is infill so the wood, timber, or posts that hold it up could be exposed to conditions below the dew point. You absolutely do not want your interior humidity too high and you dont want it coming into contact with structural members below the dew point. Dont confuse a walls ability to dry (permeability) with humid air movement. There is no science to indicate that permeable walls increase indoor air quality. Most folks familiar with the prevailing research are focusing on how much outdoor air to provide/indoor air to exhaust with a "complicated electric dependent air exhange unit" otherwise known as a "fan".

Introducing humidity in the summer makes it less comfortable and if you have any type of AC, its increasing the energy costs. If you dont think sealing a house is important, then I hope you are off-grid and not upwind of me or my family and friends during cold weather.

As for under the floor, piers pretty much eliminate the concern but of course must be balanced with other stuff. In most other situations, as I see it, the higher vapor load is in the ground. The vapor barrier can cause condensation but thats a good thing because its on the ground side and redirected into the gravel layer and drained to daylight.

Another huge point I should be harping on more is Radon and other soil gases. A gravel layer, vapor barrier and plumbing vent stack has the effect of depressurizing below the floor/slab to help control this concern and reduce the pressure of vapor below the home. This is one of the risks Ive been referring to. According to the American Lung Association, radon is the second leading cause of lung cancer. There are many other soil gases of concern that we do not measure and test for. Dont know how well packed clay blocks this radioactive gas but my guess would be not as well as a vapor barrier.

We are getting off topic with the window photo, but...oh well...

See the mold/mildew and failing paint? This is the result of high interior humidity and cold outdoor temperatures. The same thing is probably going on to some degree inside of the walls. Straw Bale walls face the exact same issues ESPECIALLY if you are not paying attention to building airtight and allowing air movement through walls.

Often claimed, still not prove to be true, and definitely not in the real world builds over the last 20 years of SB architecture I have seen, accept where they wrapped the SB in...you guessed it...house wrapped, plastic, and/or concrete parging. Every case that I have seen or noted that presented the above issue had an "air tight" treatment of some fashion and those with a simple draft proof plastering of clay and/or lime...no issues thus far...

Most strawbale is infill so the wood, timber, or posts that hold it up could be exposed to conditions below the dew point. You absolutely do not want your interior humidity too high and you don't want it coming into contact with structural members below the dew point. Dont confuse a walls ability to dry (permeability) with humid air movement. There is no science to indicate that permeable walls increase indoor air quality. Most folks familiar with the prevailing research are focusing on how much outdoor air to provide/indoor air to exhaust with a "complicated electric dependent air exchange unit" otherwise known as a "fan".

Lets try to stop (I know I have) with this constant "no science" claim...

In regards to air quality (and other points) this ongoing comment of "...there is "no science..." is rather weak... There is "no science" for many things...this neither validates nor disproves what may (or may not) be going on. Lets try to stick with historical empirical evidence, observation, and track records we may have access to and experience with...

There is evidence of good indoor air quality...the now thousands of residents of these SB and other natural builds. Lime render is an "air sweetener" and has been understood as such for millenia and only now is being looked at "by science."

Free moisture intake capacity of building materials, like timber frames, clay and lime plasters as well as other natural materials is another area there is "no science" looking at closely...yet...there is millennia of evidence that it takes on a great deal, and releases more efficiently, naturally and holistically than the man made materials do. So yes we can used fans and other technology...but...if we don't have to...why do it? And, if we do need venting can we do it in a way that employs little or no technology? What are the states of homeostasis in natural builds? So many questions, so little science looking at it...Why...no money form industry as there is little money to be achieved from these modalities as they are grass roots in orgin...This does not change the history of them, nor the empirical evidence of the many natural systems successes and applicability even today in our building practices...

As for under the floor, piers pretty much eliminate the concern but of course must be balanced with other stuff. In most other situations, as I see it, the higher vapor load is in the ground. The vapor barrier can cause condensation but thats a good thing because its on the ground side and redirected into the gravel layer and drained to daylight.

This is not my experience when a "raised earth foundation" is facilitated properly nor are there issue at all with a properly build "post and lintel" foundation either... The plastic is simple not needed or warranted if this system is fully understood and has been facilitated by a some that thoroughly understands traditional building modalities. I have never seen, experienced or heard tell of "moisture issues" in these builds...

Brian did you know you can stop and/or mitigate Radon with clay and gravel layering...I have, as have others that practice these methods...I really think, and I mean this in a very positive way, one should use or work with a method for a while before trying to find faults and issues with it. Radon mitigation is a "very new" field, and again...there is a lot of science pending on the subject...natural building has about 10,000 years, all toll, behind it...most with very positive outcomes......

If the air outside is cold and the air inside is warm and moist, the windows will have ice/condensation on them. This we know. Is there any possible way to mitigate this besides keeping the relative humidity of the home below??... Is there a %? Is there a scientific number for this Brian? Are you saying a vapor barrier would prevent condensation on the windows? I would also be shocked if the inside of a straw bale wall condensed moisture, unless of course the walls were parged with cement, etc. do you have any experience with condensation inside of SB walls?

Hi Philip,

I can share a bit...some if not all we understand, (some we still don't and only speculate about.) Just like condensation on a glass of ice water, or on a window in a steamy bath, the thermal differential creates a dew point...

So, what do we do...?

Well some may suggest making a space "air tight" and relying on well tuned mechanical ventilation systems, super insulated windows made of plastics or impervious paints and claddings, as well as, perhaps additional internal barriers on the heated side to stop moisture from also moving into the walls.

What I can share from my 40 years of study, observation and building...no system works well forever, and the more complex the system (or dependant) the time duration of compromise (failure) is accelerated.

So, what do we do...?

What I have done is observe the ancients and what they have left behind, studied as much as I could of who is left with pieces of this knowledge, and try to make logical comparative analysis of this information. It has been a long path...it is still stretched out in front of me...yet...there does seem to be more light with each passing year...

What I have learned from these studies, and listening directly (and indirectly from these ancient builders) is to make every system as absolutely as simple as possible, if some element of the design is apt to be compromised...facilitate easy replacement if at all possible, if this can't happen make it from materials of and enduring nature...design in modularity...use materials that has a full range of environmental capacity (i.e. being able to take on free water, and then efficiently release it naturally as one example)...understand that certain interstitial and interior living conditions will at time fluctuate in a way that is not optimal, yet through the concert of natural elements of the chosen building materials, will be mitigated these events naturally...like in a window, where the natural wood window can do much more with "free water" than can a plastic window, where a thermal curtain can mitigate the dew point, where milk and lime paints also absorb free water safely and effectively later releasing it with little damage to the materials...Where understanding that in a natural house there is also a natural climate swing that at time takes place and that this and the building elements need to work freely and naturally as possible within that full range of changes and with as few complexities as possible in the give system...No system is ever perfect...all the time...yet I have discovered, in my observation...little has really improved much over what has come before...only perhaps some certain level of understanding...which, seems to only lead to more questions and an even deeper appreciation for the wisdom that came before us...

Jay, thanks for the reassurance and the endorsement, it means the world to me. I hope it goes without saying that Jay would be my first point of contact for any style of build in his region.

Excellent questions Phillip. I hope Jay and others dont mind a quick reply to your question/comments that might go better in the strawbale thread but this is relevant here I think because an improperly built foundation, natural or not can introduce unwanted moisture. I think the good boots needed with strawbale needs to be anally detailed, especially in rainy, humid climates.

I have no hands on experience with strawbale walls, other than my hillside garden's retaining walls which I replace every 2 years. Ive used strawbales for gardening for a a long time and even when completely dry out of the covered trailer, they can be extremely irritating to my respiratory system. About 15 years ago, I almost went to the hospital after a severe coughing fit lasted for days after handling some bails with mold in them. Even if I had been involved with any, one to a couple examples may not be representative of the big picture.

I love the idea of strawbale as a natural alternative to walls because of the R value. In our humid Southeast climate, my research indicates strawbale is still unproven. While many proponents brush off moisture concerns, the ones with experience, take interior strawbale moisture very seriously. The uh oh pictures in that link are probably the result of bulk water intrusion through the windows but its possible they are from window or window framing condensation (high interior humidity + cold structural condensing surface). Another nugget of wisdom from Andrew Morrison of Strawbales.com "if the humidity is high, so too is the moisture content of ...your bales!"

Here is a catastrophic anecdote where they used a dirt floor which implies no vapor barriers or concrete. Was the lack of a vapor barrier at the floor the reason for the failure? Who knows but I bet it was not built to Jay's standards and a contributing factor.

I agree with the author of this good strawbale overview that "Moisture intrusion is the #1 concern with straw bale homes, just as it is with conventional homes." Iam sure you would agree with that but there are two big forms of moisture intrusion you seem to be discounting the importance of. The ground and air leaks. Both could contribute to pushing the bales interior humidity to the danger zone and I dont care how permeable the coatings are, when bales get to a certain moisture level they will grow nasty stuff.

Prefer to hear it from a source with more experience? How about Chris Magwood, well known natural builder and author of several books on natural building. I strongly encourage folks interested in this subject to read up on this forum thread. Disclaimer: Its taken from a .com website so probably shouldnt be trusted

Chris says "However, higher than average humidity in the building can mean seeing condensation on windows in cold weather and a sense of "dampness" if levels rise too high (above 70-75% RH). Wall permeability may not be able to keep indoor RH at or below these levels, even though the walls themselves are not experiencing any issues that would cause failure." His whole post there is pretty awesome and wish he was a regular contributor here. In our climate, summertime exterior humidity is what causes most worry but I think people need to be aware of these wintertime concerns in all cold and mixed climates. Interior humidity can come from many sources. Along with the ground, uncontrolled air infiltration and exfiltration people should be doing their best to keep interior humidity below condensation levels. This means using a fan or window to vent showering, bathing, cooking humidity and being careful with houseplants. For thermally efficient homes (airtight and well insulated) it probably means adding mechanical ventilation as Chris advises in that post.

Jay, thanks for calling me out on overplaying the science card. What I should have said was no "studies" have looked into improving IAQ with permeable walls. Even that might be overstepping but I would love for someone to link to such a thing because we all would be interested in reading it I think. Iam one of many here who are interested in forming their decisions with numbers, measurements and repeatable results.

Speaking of which, whats with the U-factor vs R-value thing? You do know they are the same measurement expressed as the inverse of each other right?

Youve been using that MI professor anecdotal quote for years now. Youre correct that science changes overtime and at one point there were some, certainly not all, scientists and other experts recommending vapor barriers in above grade walls for cold climates. This is an excellent example of thought reversal. However, many are still getting good results with vapor barriers in exterior above grade walls. As far as I know, prevailing thought has always recommended vapor barriers for separating home and ground and Iam not aware of any major players that recommend omitting them.

Thanks for your comments on balancing site development resources. Congratulations on building or sourcing a compactor to run on biodiesel or alcohol. Sounds pretty cool and would be interested in knowing more. If only I could get my grading contractors to use B20 or B100.

Iam also very interested in learning more about these natural radon systems. Chris Magwood seems to agree with me that plastic is easiest but we both agree piers without crawlspace walls work and its possible with an exposed gravel layer. In our area the granite gravel is known to have high levels of radon so I still recommend further depressurizing that layer with a vent stack and using plastic on top of the gravel layer. This plastic layer can mitigate radon at .4 mils. How thick and compacted do you have to go to get similar results with clay?

Hey Brian, et al,

I agree, the foundation of any structure has to really be scrutinized. Those of SB and Cobb "way more" than any others, as these types of structures have "zero" tolerance for "wet feet."

I have heard of others also have some severe reactions to "bale botanicals" including straw. Often this is a "fungus" in the bale as much as the botanical elements themselves. I have also noted that what is often called straw, is often not...It is "hay" or a mix of "hay" and straw. Good for the garden and animal bedding...not for architecture.

Hmmm...for the concept of unproven, this view tends to come from the uninitiated and/or those that don't want to compete with this as a building modality, or could really do with understanding the systems history and modalities much better. The link doesn't really have all the fact quite accurate and even suggesting fiber glass insulation made me stop reading as this is not a web site to read about "experiences" with SB architecture, and/or other Baled or pack natural cellulose materials...like sawdust.

The oldest known straw bale house in Europe is the ''Maison Feuillette'' built in 1921 by an engineer. Mr. Feuillette was seeking a solutions to construction problems that addressed greater thermal mass and quality. The house still inhabited and perfectly preserved today is unique, innovative and exemplary building type demonstrating, even in a humid environment that a timber frame structure with straw bale infill and modular construction modalities can be facilitated in a broad range of environs. Even with only single pane fenestration it meets even todays French standards for thermal efficiencies. The RFCP (French straw bale building network) launched an international campaign to save the house a while back as, ''This building proves the durability of straw bale construction and it is a precious tool to give weight to recent straw bale construction building code'," the network says.

Maison Feuillette straw bale circa 1921 and still going strong, plastered in lime...and please note...covered in Ivy? also proven that plant coverage is not the issue so many claim!!


Straw bricks (clay slip and straw have been dated back over 3000 years) so this concept is anything but a "new one" at all. The oldest standing straw-bale building in the world (that we know of currently?) is the 108-year-old Burke house in Alliance, Nebraska. The Burritt Mansion, circa 1938, in Huntsville Alabama kind of puts to rest that SB architecture does not work in the humid south if the designers and facilitator know what the heck they are doing...

Burke House in Bayard, Nebraska, circa 1896 SB building is possibly the oldest in the United States, but there may be others hidden behind walls...we just don't know?


Same structure today even after much neglect over some years...


Yes the ones with experience do take interstial moisture in SB architecture serioulsly, the also state very clearly, "....Moisture is not often a problem in straw bale homes as long as the house was built well..." So lets be really clear...moisture is not an issue in SB architecture when facilitated by someone that knows what they are doing and just follows some fairly simple (and logical) steps. This is (especially if not structural) an excellent modality of building a super insulated structure whether just bales or some other straw or sawdust based modality. The photos refernced was not a window issue at all. If memory serves me, it is a structure that had a concrete foundation and then plastering; a said practice I might add as "general contractors" tried jumping onto the "natural building" bandwagon, and brought their very bad practices of concrete and vapor barriers with them. When done properly, even in humid climates...it just isn't an issue.

Folks do please...thoroughly read...all of Brian's links, and do not extrapolate to much of "I think" without actually "knowing," before you proceed with SB or any architectural form. Even among the so called experts on this subject (like so many fields with sociology and agendas) there is not agreement nor consensus on all points. Morison's wife boots became covered in mold from more than just the "humid climate," as leather will mold even in the desert depending on the oils and tanning methods used...again...have a complete knowledge of many areas can render understanding well beyond the limited view we have today. Even experts can be mislead (I have plenty of times...) by what we "thought" was going on... Morison (the last time we corresponded, still did not see a reason for possibly employing wood cladding and a "rain screen" system on SB architecture...just one point two experts still debate...I don't know about today?

In the "catastrophic antidote" I have more questions than I can address here. I have had this very issue brought to my attention more than once in 40 years of doing this work. More than half...it was not mold or a moisture issue at all...but a lack of activity in the structure and the "white mold" was mineral deposits raising to the top of the mineral soils...often (being crystiline) looking just like mold...Again...one must have a "broad view" to really "see broadly." So even if it is a mold issue...o.k. address it...This isn't a reason not build a certain way...and I would never have put plastic down in the basement...I would have done a very thorough "forensic examination" of the entire structure, then draw the best conclusions I could have before rendering a diagnostics.

...when bales get to a certain moisture level they will grow nasty stuff...

Agreed...absolutely...and it should never get to this if you have a "draft proof" well designed and facilitated build, and anyone trying to facilitate one of these in good order really does need to, "...care how permeable the coatings are..." as this is a cornerstone of "good practice" in natural building in general and SB particularly. Don't ever make the mistake to think it isn't!! Or, the building will never last a decades to centuries as the examples above...that are in humid locations!

As for Chris M. please do read his work...he is an expert...we don't all agree, of that there is no doubt...we are on the same path, and typically we land in the same locations, yet I stand by my experiences and knowledge base...as It is broader than some and I work on it all the time...

You know and I know that U factor is the reciprocal of R factor...or I assumed so. Nevertheless, U factor is used to illustrate "thermal storage capacity" more than R factor...that is why the U.K. has it written into their building codes. They still build "mass walls" out of just brick and/or stone...no thermal (R factor if you will) insulation or very little. That was my point... its not always...all about...thermal resistance...but thermal storage as well. This is why a timber frame with cobb and stone inside and a straw bale (or related) natural insulation is the very best of both worlds. Also the reason that "cold climate" designs for "log and stack wood" architecture works so well also...out performing many "modern builds" well beyond what many "building scientists" ever expected and are still trying to figure out how...

I have watch the CCBT video several times...I have seen similar 30 years ago...I can tell you from experience...they do not last and perform as expected for very long...

I am still not sure why this method is still being "pushed" as a functional building system? Maybe with the "tech" of modern venting and heat recovery systems they can be "made to work"...for a while at least? Natural building systems in general is an "all in bet" in most cases and not something to just "half do" or "half understand." I leave it to the readers if they want to wrap themselves in plastic and rely on "tech" to always work to make the new "air tight" homes a viable living space. Can this be done? Yes, I think it probably can. For how long? We just don't really know, and for me...I just don't care for modern materials, and all the "unknowns" about how they can effect us. They simply are not my first choice...or...recommendation to folks whenever possible.

Regards,

j

I just came across this page destroying the hopes I had to build a straw bale house in atlantic canada.
The link: http://www.longbrancheec.org/pubs/strawbale.html
Since humidity/rot/longevity/health is a regular subject in straw bale house building, I wondered whether there is any truth in the facts claimed on this page?

I read about 3/4 or the article until it mention that the bales were being stuccoed. Whoever wrote the article was not in a position to be writing about SB architecture in my opinion. Andrew Morrison who is a very strong authority on SB lives in and builds SB Houses in the Pacific Northwest. I attended one of his workshops and he has sound ideas backed up with LOTS of experience. If moisture is in fact a problem for SB, it will be eliminated if the house is heated with wood. The cold dry months combined with wood heat will nutralize any moisture that was gathered over the warm moist months. Don't let the ignorance of this article shoot down your dreams.

Hello Zinneken,

All I could share or add that might address the link above, which has been referenced twice in this post already, is that locations are indeed different. IF someone is thinking of building a SB home, they must weigh all the variables. As to specifics in the referenced post, I can say that it is but "one view" and also a "disclaimer of liability," as well for the writer.

It is simple mistake to "read into" any position, whether reflecting a positive or negative view point, and the realities with very between the two perspectives, as they do in most things in life. Clearly, from the photos I shared above, SB architecture can be done in many different locations, wet and dry, if facilitated correctly for those specific biome localities.

I also have to share when someone speaks with "authority" about SB architecture, I find it disturbing to me when they also make reference to "stucco" and "fiber glass insulation" as well as, other elements of modernity. This devalues the validity and depth of their complete understanding of other architectural systems and dynamics, especially as a comparative or suggest alternative to SB.

Regards,

j

So just to be clear, the last two posters dismissed the link without reading the entire thing which means they probably didnt read the conclusions. If you did read the conclusions, what is it that you disagree with there?

Philip seems to be dismissing that "...we would offer a note of extreme caution and concern for building with the breathable straw bale..." based on the fact that you can in Philip's words, eliminate moisture concerns heating with wood. This strategy would not eliminate all moisture concerns. Roof leaks, window leaks, flashing leaks, air leaks, could all rot the inside of strawbale walls even heating with wood. This blasting of wood BTU strategy is also unlikely to tame the poor attention to details surrounding "good boots".

The authors main concerns was humidity during the warm months, times you would not burn with wood. So the burning with wood strategy would be assuming no problems would develop during those warmer months. Depending on the design, different areas of the house may see less drying than others.

While burning with wood will certainly contribute to drying, many of us are striving to create homes that are comfortable without burning stuff indoors. Combustion brings fire risks and many IAQ concerns and wood in particular is not known for healthy indoor air quality. Of course many projects will still include it but I think most would agree, the more wood we can leave to build soil and not have to chop up and burn to stay comfortable the better. Better thermal envelopes means we dont have to blast so many BTUs through our dwellings to dry them out and stay comfortable.

As for the stucco, I dont think the author makes any distinctions between Portland, more traditional lime or gypsum. While it would be great if they had, the numbers to draw from are still very small and think most strawbale projects arent the type to employ "unbreathable" renderings anyway. The negative viewpoints of the posts on the link seem to be grasping for any opportunity to discredit the information.

Take the fiberglass comments for example. The author compares the Rvalue of strawbale to the Rvalue of the most common insulation material in the country. Weve discussed the R-values of insulation before and while most installations dont achieve it (because of air leaks), 3.5 is the accepted Rvalue of fiberglass and the author makes no comments on using it, they just offer it as a basis of comparison. I think thats the best material they could use for comparisons, considering its the most commonly used one.

The author of that link is merely presenting information. The stucco and fiberglass comments posted here shouldnt lead people to believe that climates with high humidity and rainfall shouldnt take strawbale construction lightly. The lack of successful examples seem to be the main concern so early adopters need to be very careful with their detailing and spread the word on the results. Also keep in mind one of the main conclusions that most examples in these climates are less than 10-15 years old.

Rather than scare people away from this construction practice, my posts and that excellent link are trying to make people aware of the concerns. I dont think there are any conclusions in it that experienced strawbale builders would disagree with.

Hi Brian,

So just to be clear, the last two posters dismissed the link without reading the entire thing which means they probably didn't read the conclusions. If you did read the conclusions, what is it that you disagree with there?

Actually Brian, I had Read Paul Gillmore's views quite some time ago, and way before this post thread. First, I don't think anyone is necessary"just dismissing Paul's views" but questioning them and perhaps whether he has as strong a voice on this subject matter as some would suggest in this post thread. I agree he makes some good points, yet also seems to vacillate on others and it also seems he is not making very good comparisons at all or bringing up the very long and positive history of SB in many different biome types. That is the way I read much of his writing on the subject. It reads to me as vacillating, ambivalent and as a "disclaimer," that's just my view.

Wood heat is an optimal format for SB architecture, as it is a very much a "drying heat." As per the list of other possible challenges (i.e. Roof leaks, window leaks, flashing leaks, air leaks) I would have to suggest that these are not really valid points for or against SB, as any of those referenced challenges are a big problem in any architecture, and have nothing to do with whether one uses a "dry heat" or some other source of heat. I agree, a good foundation is very important, as are many other detailings, yet again, this has no bearing on HVAC. Either a structure, SB or some other form, modern or traditional, is detailed well in design or it isn't.

Nobody is suggesting "blasting BTUs" through a building with wood or any other heat source. I would also challenge your perspective of wood heat as being very subjective. There are those that are proponents of it and other that are opponents, with arguments (often very subjective themselves) on both sides. Masonry heater (of which RMH are part of) are probably some of the most efficient heat sources there are, and when working in concert with good design, can create a wonderful, and high quality living space.

Stucco, and Paul's reference to its use is in the "contemporary vernacular," if one chose to actually dig deep into his comments and back research. This means OPC which is a big "no-no." Each of the 7 times he writes the term he is referencing a case (a very poor example I might add unless you are trying to detract from SB) of an OPC based contemporary applications on a SB structure in the far North...a very bad example and poor application of choice for a finishing modality on any SB build.

Take the fiberglass comments for example. The author compares the Rvalue of strawbale to the Rvalue of the most common insulation material in the country.

Simply put, there is no comparison. SB is going to be superior to fiberglass insulation (FG) every time, as FG insulation is undoubtedly one of the largest "con games" in the manufacturing industry being subjected on architecture. Cellulose or Log Architecture wood have both been germane and a much more applicable comparative, and the examples used by other SB authorities. This is being brought to bear more each year, and anyone continuing to suggest that FG insulation is a viable choice compared to all the others, natural or manufactured is a travesty in my opinion. I have been reading, studying and examining FG insulation for over 40 years, and find it to be so inferior, that I can only imagine that having the clout of a company like Owens Corning Corporation is the reason it is even still on the shelves...which I personally suggest is just one more indication of the issues we have in the normative culture (not good practice) in so much of contemporary architecture.

Also keep in mind one of the main conclusions that most examples in these climates are less than 10-15 years old.

Brian, I know it can be difficult to completely read all the posts in a thread, and all too often linked information that I sometimes get carried away with. Nevertheless, just in this post thread I have offered 3 examples in the full range of hot, humid and wet climates that Paul warns against and these are all the chronological record holders of the SB world as we know it today. So lets not suggest to readers that 10 to 15 years is anywhere near accurate. SB has been around for a very long time and each year it, and other straw and botanically based examples are only expanding and in good measure I might add.

I feel that many (perhaps not you but that is not the way I often nor do others, read your comments) are indeed, "nay saying" many of the natural building choices for insulation, including SB. I agree that any choice needs to be vetted well, employed logically and designed into the architecture by someone with extensive experience.

Regards,

j

Thanks for the views! I don't understand all the acronyms, but I get the general feel of balance. In general I would say it could be great for john doe like me to have a reference/index of recognized straw bale builders on may rely on to contract them for building a SB house, wherever they are. There are a couple that pop up on Google, I'm sure there are many more, and a yellow pages like index would help john doe's like me.

I just came to think, have these original/old/long standing SB houses been "examined", I mean, like the compactness of the bales, their size, whether they were treated with some old time chemical or whether the straw had some kind of chemical on it from just before harvest, chemical that would prevent or slow down rot?

Here is a photo of a natural build. You can see that there is almost no detailing and the clay render is failing, yet there was absolutely no damage to the adobe bricks that the structure is made of. This home has been in constant use for 150 years. There is obviously no vapor barrier, not even good hat and boots. The detailing is poor, yet after a good coat of clay inside and out, the home/bed and breakfast was in nearly perfect condition.
Since the entire wall and coverings is created from clay, moisture can migrate right through without issue. The clay is coming off on the outside because of so much water damage, yet there was no damage inside the home.

I just built a test rammed earth wall in a moist climate not far from NE. I changed the mix often to see what would happen. Some parts did well, others did not. I played with adding lime, portland cement, fly ash at 10-20% by volume. I had too high rock content as my first wall...I ended up stuccoing it with a cement stucco with fiberglass small fibers in it and added earth mix to make sure it last as learning experience wall since I am selling it.....I tried using iron oxides as pigment, it did not do well in rain and did not look like Rammed Earth. I learned later to drop the rock out, and change to a mix of just sand and soil. I changed to ratio in these pony walls shown to get the striations. I added high levels of portland cement to these walls since the walls are only 3 " and 5" thick and to add white to get some color due to lack of other sand-soils....Everything looked good until I hit the bottom of the wall with a vacum, some parts broke apart. So I decided to add baseboards. I should have added a bonded in 2x if I thought this were going to happen. I had tried impact test with a hammer on wall after I sealed it with an acrylic sealer and it looked good but I guess the test was not that good. I tried to use some plastic anchors, the earth did not like, broke out, so I ended up fastening the baseboards with glue and reduced head screws. It turned out ok just not as natural as I wanted. Just goes to show how many variables in natural building and homes can end up in trouble if you do not get the design right. I tried everything, no way around a sealer if you want a durable concrete like surface. I'm not convinced the portland cement did any good....I'd need a lab test, but my soil was not that great as a binder.

More pics of pony wall..I have a write up and more comments but I am getting an acronym error?

I think Jay and Brian have both brought some excellent points to the discussion. I’m familiar with both natural and unnatural (or main-stream) construction that these moisture retarders (class 1-3) and barriers (.6 < perm rating). A perm rating this industry gives to manufactured products in factories is its ability to permeate moisture (or pass it through the material) as we know which is one parameter for design purposes. There is also (moisture content) or an ability to hold water (clay, some not all, having a high ability to store it).

All we need to do is wet some soil, form into a ball, and see how well it manages water (no scientific proof needed, field test acceptable). These factory products struggle to manage water, so they stack other products on them, or furring strips for air passages under roof and wall cladding’s with different perm rating’s to protect them from fungi’s (a complicated science due to the number of spores and how they are generated, usually a food, heat, and moisture is needed). The moist air in wall cavities reduces r-value or u-value in wall assemblies made up of foam, and loose batting conductance. Some say dense packed cellulose is not affected. U-value is not a materials ability to store heat-coolth-or moisture. That is a dynamic mass concept “Orlando National Research Lab” and others tried to quantify for concrete by assigning a “Dynamic Benefit Mass System” to manufactured or built on site products. In summary, they found that average commercial grade concrete “stores” heat in the first 4-6” inches and it takes a week on average to load in depth from the surface. I validated this with rammed earth recently with my own little test of a delta temperature of 50 F (see attached). When you put any of these products in a home, it changes the detailed performance of detail components. Mass, or storage, interacts with the “whole house” “dynamic system”……WUFI-software that is based on empirical evidence to make sense of moisture in these systems, but it struggles, in part due to a lack of definition of materials properties, but, there are programs that do a very good job at it for much more money. You two are trying to make sense of a very complex interactions of thermo-fluid dynamics without the pro tools most engineers use, replaced by your experience and history but, it can change from the climate zone alone as Brian points out in the SE, to the design and specific materials used.

I mention all this since I think it is important to understand factory products and what has derived out of them to understand the differences to natural designs, and they are different. A “wall insulated” with high r-value home that has little “moisture or thermal content” or storage in loose or dense pack insulation's that needs all these protective layers more than a “dynamic mass” home. How well it’s r-value, breathability, or fungi resistance is very differently from mass natural materials like clay, straw, etc... Having experience with both, they can both be built to last or fail depending on the knowledge of the designer and builder.
Jay, what ratio of render –clay-to-sand-to whatever is proven in what climate zone? A natural builder can change the ratio’s that determine performance at will with no prescriptive code, so what is it that will work in Brian's and any climate zone or an “all and one solution” or how do I design the proper ratio’s in a whole house system in any climate zone? A design guide would be nice? BTW: I know the history of NE straw bales many of them failed, the two you quoted I know too that need a lot of maintenance throughout the years.

Strawbales (approximately 2.5/inch) has high insulation compared to strawcrete in general they say. The Crete will perform more as a mass storage system, assigning an r-value to it can be misleading. The bale will have a higher r-value and depending on the density, specific heat, and thickness or the render (stucco, plaster) will determine how much mass storage or thermal resistance or passage (u-value) is added. Some heat may never thermally bridge in u-value of conductance in some climates, so it or resistance can mislead. If it has more clay it will manage water better, if it has more binder, sand, straw, less….some structural bales need dense renders that take down its ability to breath. Bales need more protection than cretes from moisture infiltration and air. I create strawcrete with water, it absorbs, holds, evaporates it. This winter I did not notice a free in -20 F with cretes made of straw (hay) or hemp I casted around wood frame work that protects it from rot. Bales won’t do that as well, as easy.

As far as vapor barriers…usually polyethylene, I’m with jay please provide a link to a manufacture that has at least a lab test showing a chemical life when in contact with at least a few or many soil types, building materials, acids, ground chemicals, etc., that define an expected life. I’m not aware of many that have dug out foundations at specific time intervals to draw conclusions. I have no scientific data, only my own experience, but I think a Crete or perlite, hemp, straw or an “aerated concrete” caste around a wood floor would not need it, provide better insulation and moisture management, compression strength. I think some of these people using poly, foam, and setting their houses on it are nuts! And building codes allow it. A sub-slab foam with fungi food fire retardants and formaldehyde, again, mainstream trying to protect concrete slabs with high levels of Portland cement that are strong, granted, but do not manage water and moisture well, so the so called experts think the foam moves the winter dew point condensation to it, and the poly stops and condensation from infiltrating into the home through the concrete slab….no prove just guessing and hoping the dew point actually moves to foam, which will more than likely deteriorate along with the poly (4-6 mil) in time..

Sorry about the multiple post only way past an abbreviation error.

This is my test pic of the exterior wall that stored heat in the first 4"...it stayed very hot to touch at the surface, cooled down at was gone at 4" depth. If I went a week it may of got deeper, however, it did not thermally bridge 12" (300 mm) nor do my inner pony walls. I have no idea why I need to know a u-value or r-value this is mass effect.

Hello Terry,

I had to give you an apple just for the effort you have put into thinking about this and trying to test the different concepts...big "A" for effort!

If I missed any of your questions, or other things perhaps to discuss, please let me know...

As for adding OPC to rammed earth formulas, that has become a more common practice here in North America than in other regions from what I can tell. I neither recommend it to folks, nor find any great value in these contemporary add mixes. The "Great Wall" has stood a long time without them and I see no reason to mess with vintage formulations if they can endure for over 1000 years without them.

There is more information on this subject than I have time to add, nor is it applicable to this thread topic. I will suggest one place to start reading and the many places it can take a reader is at:

One of the great inventions in ancient China...sticky rice traditional mortar additives.

Sticky rice and other natural additives have been added to RE and Mortars for a very long time...

U-value is not a materials ability to store heat-coolth-or moisture.

As Brian pointed out, and I am sure you know U is a reciprocal of R factor...

As such (and this is why the U.K. and the European Union uses it as much or more than R factor) U factor does give a "number" to reference when considering the thermal storage capacity of stone, cobb and brick vintage structures which are way more prevalent in Europe than they are here.

I agree U Factor is not a materials ability to store heat, yet as indicated in 1000's of documents over the decades in Europe, U Factor does give an indication of a material's ability to potentially store heat. I also agree there is much more to this than just a simple number...yet...it is a guide, and better than none at all.

If we get "technical" we have to examine the actual physical properties of sensible heat storage of a specific material (water having one of the highest.) Yet going through all the mathematics of applying:

q = V ρ cp dt

q = sensible heat stored in the material (J, Btu)

V = volume of substance (m3, ft3)

ρ = density of substance (kg/m3, lb/ft3)

cp = specific heat capacity of the substance (J/kgoC, Btu/lboF)

dt = temperature change (oC, oF)

to each material is not as prudent as using the rough guide of U factors...

You two are trying to make sense of a very complex interactions of thermo-fluid dynamics without the pro tools most engineers use, replaced by your experience and history but, it can change from the climate zone alone as Brian points out in the SE, to the design and specific materials used.

Actually Terry, as indicated in the math above, I work with PE all the time and the "pro tools" that goes with it...In most cases it just is not germane or necessary to used these when dealing with vintage materials and natural modalities in architecture. If we need them for a specific examination or "defense" with officials, they I (or the PE) use them. Until that time U factor...like R factor is an acceptable rough guide...

Jay, what ratio of render –clay-to-sand-to whatever is proven in what climate zone?

Each location is going to have such different material types (sand, clay, lime, straw, etc) available, it is difficult (if not impossible) to quantify "ratio." This is a reason manufactures, and most Contractors can't make money with them, and therefore often undermine ever trying to use these materials in the first place. For most Cobb its a range of...50%-85% sand...50%-15% clay...straw (or wood chip, or hemp, or reed, or...) to taste and then add water to a dampness of a wrung out rag...

A natural builder can change the ratio’s that determine performance at will with no prescriptive code, so what is it that will work in Brian's and any climate zone or an “all and one solution” or how do I design the proper ratio’s in a whole house system in any climate zone?

This is one I get often, and the response one of my favorite teachers put to a contractor back in the 70's that asked this was...."if you have to ask...then I guess you don't know and will have to figure it out..."

He wasn't being rude or flippant, yet as an Amish fellow could be very blunt. He often said that if someone can't go into a forest or quarry to get and/or make there own materials they don't have the skill sets to be trying to do this work for others and charging money...He was very "old school." Each location is going to present with such different challenges that there will never be a "set ratio" or even "set guideline" for each step...in very specific ways for many things, while others there can be.

BTW: I know the history of NE straw bales many of them failed, the two you quoted I know too that need a lot of maintenance throughout the years.

Yes many did fail, agreed. Yet few folks I know of that comment about these have really examined why they did (mostly neglect and poor foundations as many just sat on the bare ground and really where only meant for temporary use.) and even fewer have spoken with folks that built and lived in these and related structures. (My grandmother and here relatives built and lived in several.) I would love to read more of your knowledge on the maintenance needs of these "two structures," as my knowledge and experience with them and others is they need no more general maintenance than any home and often much less. Especially considering the age of them. SB architecture (and other natural modalities) are going to need the same level of care as any home, yet the materials are often right at hand...if one has the skill sets. This is a wonderful thing about natural building...

Strawcrete (the original lime based formula not the modern OPC type) is something that presents as very interesting and of potential great value, if you have lime skills and straw or other plant fiber. Lime/cobb with straw and some just lime and straw have been used in the UK for probably over 1000 years as a mortar and other "mass material." I would suggest folks read about it if interested, but that deserves its own post thread...

...some structural bales need dense renders that take down its ability to breath. Bales need more protection than cretes from moisture infiltration and air. I create strawcrete with water, it absorbs, holds, evaporates it. This winter I did not notice a free in -20 F with cretes made of straw (hay) or hemp I casted around wood frame work that protects it from rot. Bales won’t do that as well, as easy.

I tried to follow along with the above... yet I feel I perhaps was lost at times...

Structural bales...neither need nor rely... on their renders for any structural support of the wall or roof. If one is designed this way, it is far outside normal design modalities and parameters for such architecture. I would also point out again that I do not condone nor recommend "structural SB," and would only use it as an infill method. Bales do need more protection than would perhaps a "strawcrete" structure. That is possibly very accurate. Yet I am not sure an entire structure made of traditional SC would be fiscally, ergonomically or logistically applicable in most areas compared to other building material choices. I feel it would be a very solid structure and have many benefits similar to rammed earth. OPC based materials do not in my experience work well at all with natural materials and in short order facilitate rot, and other issues. I have seen log cabins that are over two hundred years old with their original cobb and/or lime mortar chinking turned to rotting heaps in a matter of a year or so when some "Modern Contractor" thought it would be better to replace these original (and natural materials) with OPC base mortars. Especially if it is "wetted" on a regular basis by weather and poor roof overhangs.

I think some of these people using poly, foam, and setting their houses on it are nuts!

Well......that is about the best description I myself could have stated. If is really questionable how many of the "modern materials" will last over the centuries. I know how the natural materials last, as I see that all the time...

I just came to think, have these original/old/long standing SB houses been "examined", I mean, like the compactness of the bales, their size, whether they were treated with some old time chemical or whether the straw had some kind of chemical on it from just before harvest, chemical that would prevent or slow down rot?

Hi Zinneken,

Yes some of us have looked at them, and there are more young folks in the building arts taking a closer look each year at these more natural and sustainable building practices. As for "chemical" treatments...No...they were not employed nor really necessary. Borates could be used I suppose if one was really concerned yet I am not really sure of the gain, nor would I general recommend them.

Bill, I just loved what you wrote about the cob and adobe...so true! Thanks for posting that...

Jay, thanks for the replies, good ones! and thanks for the apples, I did all that with a shovel and hand rammer just to get feel what it was like back in history.

I think it is important to understand that today's effort in "air-sealing" is to dis-allow air-moisture passage "through" the wall as validated by a blower door test that pressurizes and depressurizes the envelope of the home including the walls, floor, and roof, to an air change per hour at 50 pascals worth of pressure. The building is pressurized then allowed to leak down to determine a value. Since we know that moist air inside wall cavities trumps r-value of some insulation types, especially loose filled batts, it is important in these types of insulation's. Other densely pack not as severe since air is not allowed to circulate or create "convective loops" in stud wall cavities, including floors, roof. Also, if a home is exhaust vented only the fans can depressurize the building causing pressures outside the home to infiltrate since pressure moves from high to low. Infiltrating atmospheric air (wet, dry, etc) to interior air is not desired, it can create higher hvac loads, hot and cold spots, condensation, rot, fungi, etc, especially in cold climates. That is why many are incorporating a heat ex-changer that more efficient does not cause the delta pressures; takes in fresh outside air, heats, cools, or regulates it's relative humidly, then exhaust it. There are clever ways to accomplish this naturally with perhaps a mass heater by crossing vent paths. The inside and outside air cross paths in the ex-changer so there is little loss of conditioned air. So, we do not isolate any component of the envelope, wall, roof, floor, and find an efficient way to air seal by a continuous barrier. There are many locations and ways one can accomplish this. Polyethylene is one, a continuous layer on the inside so the wall dry's to the outside if it does get moisture, on the outside so the wall dries to inside. Some say to "trap" air in an envelope or seal it is not a good idea, or put the barrier both in and out since the envelope or cavity can not breath. I say that depends on the insulation, natural products like mineral wool or dense pack cellulose can be sealed in if there is no heat or fungi food, other schools of thought are sealing a cavity does not allow convective loops.

As far as bales, we now have 2015 IRC building code in appendix r and s. It regulates moisture content at time of construction, plasters, stucco's, bale density, etc. It's an international standard. The core of the bales should not see air especially moist nor should it pass "through" the walls. Once the core gets wet it is very difficult to dry it, next to impossible unless heated air can reach it. Many straw builders have passed 1-5 air change per hour blower door test by using 'air fins' or sealing all the fenestration's and penetrations...Not easy, lots of time detailing. Not as bad for the surface since as we know the geometry of "straw" and the reason we call it that is it allows for capillary action or wicking. Take a straw and put some water in it, watch the water evaporate in the straw by capillary action. Code does not require a vapor barrier because the dual clay renders regulate it at the surface and provide an air barrier usually.

Thermal bridging or passing hot or cold air through wood, dirt, membranes, is another concern. Many are insulating the finish floor to prevent this, soils can thermally bridge if ground temperature set up at temperature differential to the interior.

I mention all the above since to me strawcrete or hempcrete, lime binder, when casted around lumber accomplishes these without alot of the headaches and detailing strawbale. See attached...We can use wet straw bales for strawcrete, round ones which are abundant, compared to small that need to have a moisture content level less than 15% by weight per code. The strawcrete provides a thermal break to the rock and soil below and an insulation or some storage, protects encapsulated wood from rot and termites, etc. If moisture infiltrates it wicks and evaporates through the pores or air cavities. Perlite due to it's ability to drain might be better. If we put this in a vented crawl space, wall, or roof with air flow it stays dry to the outside. The rock provides drainage and prevents freezing, the soil more water storage and management. If we are in a wet climate or close to a water table, we could run drain tiles. No vapor barrier required.

Corrections, thoughts, anyone?

Hi Terry,

First let me give compliments on really getting into this and thinking about it. As all that do learn, this is a complex and rather convoluted topic, with many layers and considerations. Many of the "modern elements" are theoretical and/or "wishful thinking" at best. I see all to often manufacturers and those testing the materials running along "assumptions" based on principles of physics that individually are of course somewhat understood, yet when forced to work in concert often yield other results...results we have yet to fully understand (or accept.)

Today's effort in "air-sealing" does attempt at inhibiting air-moisture passage into the interstitial areas of walls, and the blower door test I find can be rather misleading and not compelling argument for some of the suggested practices of making a structures "air tight" or attempting to as it is virtually impossible unless one is using the materials we design space craft or submarines with. Having been in the later I can say with some authority...these to "leak" and have a plethora of mechanicals that are often triple backed up just to get the entire system to work." Maintenance is an every happening and ongoing burden.

Even if a test reveals that a structure is "well sealed" it is not going to stop moisture from getting into wall voids no matter what system is employed. This seems to be a "big elephant in the room" that is either ignored or devalued. Using plastics on either side, in my experience creates a condensing surface for moisture accumulation...that will in time accumulated more, no matter what great efforts are made to try and stop it. For me, I am not sure why such herculean efforts to reinvent systems of architecture are made (other than manufacture and contractor profit) when more holistic systems already exist, such as the ones being examined by you... Whether we utilized dense pack cellulose or mineral wools, or some other natural material; the moisture "that will" get into interstitial zones should not have any condensing surface to inhibit its passage nor other plastic or related barriers to impede easy egress. The use of "mechanicals" to do this is flawed solution in my view because if a system relies on these to "always" work, what happens (like in a submarine) when they don't, and what backups are going to be created? Then, we move into more maintenance and relying on "moving parts" to make a system work. Complexity seldom leads to simplicity...and the simpler a system is...in the long run...the more enduring..

The new regulations in SB architecture are just that..."new"...and it will be some time before all the "bugs" are worked out of that. It is also a way for many to try to understand, and standardize a method that is difficult at best to standardize. The inside of the bales, like any wall system in the "real world" are going to see vaporized water pass through them and anything that impedes this from a simple passage through will indeed compromise the wall system. "Believing," in my view, that any type of "air tight seal" is going to stop this from happening, even albeit slowly perhaps, is not really taking into account what goes on inside walls in real world applications over time. I also agree, detailing a straw bale house is tedious when done well, yet I do not find it much different than any other building system. It must be done and it must be done in ways to stop all drafts from taking place and/or methods of impeding those drafts that does not funnel the moisture laden atmosphere into wall voids.

Thermal bridging is a concern, yet it to is dependent on the system employed and other thermal dynamic characteristics. I have lived in several log type structures in my time. These are a direct thermal bridge to the cold outside, yet by their mass and other dynamic principles, when "draft proofed" serve very well in cold climates. Double wall systems, that create a thermal break, and log architecture can even serve in severely cold climates and have for centuries. I can't stress enough those attempting a natural build in understanding a system completely is more important than just looking at a single component and its characteristics.

I mention all the above since to me strawcrete or hempcrete, lime binder, when casted around lumber accomplishes these without a lot of the headaches and detailing strawbale.

Having done both, and/or seen both facilitated well (and poorly) I can suggest with some resolve that SB is much easier to do for the average builder than any of the limecrete based systems. I like the limecretes, and if sources of appropriate lime is not a challenge (I have made if from scratch and it ain't easy work by a long shot) then it is a viable choice, yet I have seldom seen it as either easy or inexpensive. Some areas, like the U.K. has a jump on us, and in time I think the cost here will (I hope and pray) come down. Yet again, as a "building system" it ergonomically and logistically is not going to facilitate an "easier" system of building compared to others. Yet I would also say that "easy" should not always be at the top of a least for reasons to do or not do something...

We can use wet straw bales for strawcrete, round ones which are abundant, compared to small that need to have a moisture content level less than 15% by weight per code.

Hmmm...well that may not be quite accurate.

We mustn't confuse "hay bales" (which most round ones are) with straw. I would further suggest that there is much more to "strawcrete" than just adding lime and water. It is very labor intensive.

I am not sure I would ever suggest to a client incapsulating wood inside a wall system of limecrete base materials and espeically a floor. Termites and other wood loving insects can get into these systems and I am very reluctant (especially in floors) to ever fully encapsulated in either cob or limecretes. Chinking in a log structure, infill systems of timber framing or layered systems (like a limecrete slab) and then wood frame work, I suggest would be less complex, easier to facilitated, and service in the future should something need to be altered, repaired or upgraded.

If we put this in a vented crawl space, wall, or roof with air flow it stays dry to the outside. The rock provides drainage and prevents freezing, the soil more water storage and management. If we are in a wet climate or close to a water table, we could run drain tiles. No vapor barrier required.

In the "big picture" of a natural designed system, I agree with the above description with only some suggested alteration. The above describes "raised earth foundations" (which I am sure has been read by now) and allowing moisture to dry from either inside or outside depending on the current weather systems barometric push. I don't use vapor barriers, nor are they a "must have" in good design if other systems are employed well. Water tables are to be known and understood, yet even these can be addressed as the Dutch and Venetians have done for centuries.

I like the photo and schematic. I would move the wall frame work to the outside of the "mass material" be it cobb, limecrete or some other, depending on the vernacular design system chosen. If the wood floor frame work is resting on top of the limecrete mass I find that excellent.

Regards,

j

Related to this challenge and perhaps something that deserves its own post...

Natural Ventilation...

EcoMENA is just one of the many up and coming facilitators of natural building design that understands the value of relying on "natural systems" for ventilation instead of mechanical.

At the moment, the current issues I can think of with vapors entering a building are perhaps the development of mold and maybe making clays and plasters more moist (which might affect structural integrity???)