On all the projects we have seen I think the primary flaw was in foundation prep. All the projects -100% - are failing because of moisture problems. Not a good advertisement for natural building, but we still want to try it at some point in our lives.
The old buildings around here are bone dry inside and the foundations are all the same on the ones that last, the structure itself is usually "post and pier" with the pier being drylaid stone and the timber framing or post and beam framing of oak just sitting on top of the piers with no tie down.
We have ruled out strawbale building. No confidence that it suits us or our climate. I'm sure it can be done, but the high potential for failure is too much risk for us. It is appalling how fast they can fail. I wouldn't be able to sleep for wondering if there was moisture getting in somewhere. And moisture is the consistent theme if our climate.
Cob and stone have mass and that can work against you here it seems. Condensation from top to bottom of the wall can be a problem even on a dry foundation (not sure yet why in the places I've seen it but have thought on the exterior it could be from the rapid temperature swings. Interior not sure why.) and for more than half the year it seems the mass is either accumulated too much heat to offer relief to indoor temps or so cold it sucks off more heating btus than necessary. I suppose with enough thickness to the mass and an effort to properly charge the mass at the beginning of winter and maintain the charge properly and shaded in summer this could be overcome, but we think we'd do better off just starting with something more insulative.
Many old local buildings have sawdust insulation. We'd like something more fire resistant and rodent and bug proof.
So that brought us to clay-straw. But we've not experienced this modality at all in a build. Only saw a test 8" "wall".
Our ideal design at this point would be timber framing versus post and beam to avoid thermal bridging of metal parts and resultant condensation points. Timbers set to the inside and left exposed on the interior because we love the look. Clay straw infill, transitioning to a thick cob plaster as the outside cladding supported by a wide foundation sill. Entire wall to be 18-24 inches thick at least 12inches of clay straw.
Occasionally we still consider encapsulating the framing in clay -straw and earthen plaster (would have to be timber framing with wood joinery only, we think, because of the risk of internal condensation points of metal joinery) Encapsulating makes it more fireproof as far as we can tell, but more risk of missing termite damage in the case we didn't get the foundation built well enough to discourage them.
Question 1 how can we ensure no thermal bridging at the timbers? (We have observed thermal bridging on a post and beam strawbale infill design. Moisture means softening which means cracking, which means drafts and more moisture. No good.)
Would encapsulating help reduce thermal bridging? And facilitate drawing moisture away from the wood to the exposed wall surfaces? How much mass would need to be on the outside to insulate the timbers?
Question 2. Does clay straw need wattle or trussing for structural integrity? The test spot we saw was very hard, built up incrementally to dry between runs rather than poured all at once. Not sure what is traditional.
Question 3. We know we want standing seam metal roofing, but are unsure what our insulating material should be. Ideally we want the attic floor and ceiling to be the insulating point and the roof left alone.
Question 4. How to overcome thermal bridging at corners, top of wall to eave and from eave to attic floor?
We have lots of time to understand the potential flaws and redesign any areas as needed. Plus our first build will be a small shed, then a two room cottage and, then the house we hope will stand 100s of years.
Thermal sink, "flywheel effect"... concepts I've run across but don't have a good grasp of.Is there one particular book or source that does a good job of explaining concepts such as this?
Interstitial moisture as you called it on another thread is the area that we wish to understand better right now. We understand, I think, the "hat and boot" concept of keeping things dry but want to understand how to prevent condensation points in the wall better. Any resources for that?
We do understand the concept of keeping the wall breathing. No vapor barriers in a natural built wall for us. but even with a breathing wall, certain spots can create condensation.
Obviously metal is the worst at doing so. Some stone types do so more than others. Why?
Is it all in the "thermal conductivity" or is there something else to consider?
Then there are the "dead air" corners of a poorly designed room perhaps exacerbated by thermal bridging in that area and so on which isn't necessarily interstitial moisture at first but can lead to it. And surface condensation is as unwelcome as interstitial as far as I am concerned. Mold can be a big problem here inside or outside a wall.
We don't want to rely on air conditioning and dehumidifying machines. Our design needs to address these things.
Sawdust....would love to hear more of the how's. Maybe a whole new topic?
The only person I ever found that knew anything of the how simply remembers topping off the sawdust insulation with his grandfather after it settled enough to cause a drafty cold area. Remove wood paneling enough to scoop it in, fill, close the wall. Sounds too simple.
Termites.... why do some buildings escape for a century and others get infested in 5 years?
So far on the old buildings we know are not being maintained with chemicals we've theorized that the foundation is designed to be so dry it discourages termites because they'd have to go so far for water.
The crawlspace was usually left open to chickens. We have wondered if that is important?
What other vernacular design concepts might we be missing that kept these buildings termite free?
...the kitchen and bath areas- a summer kitchen and an outdoor shower, pool, and steam hut area are high on our priority list...
The summer kitchen we first thought would be attached to the main house by a dogtrot breezeway, but we are now leaning towards making it a standalone structure with a pergola or covered patio area in between it and the house.
I had not heard the term "stackingfunctions" before permies. I'm just motivated by efficiency in survival technique.
...the summer kitchen might actually just be designed as a porch area rather than a walled structure...
For the indoor bath areas, we are not sure whether the big house has an indoor shower at all. The cottage probably does. At any rate the bath area I would like to see designed right behind the wood cookstove with a sliding panel wall on the stove side of the room to be opened making it easy to really warm up the bath room air before bathing and dry it out after bathing. Summer use would be minimal due to a pleasant and practical outdoor shower design.
We are too modernized to leave indoor kitchen, toilet, and bath rooms entirely off, but do want to find efficient, easily maintained therefore enduring designs for these areas. Hopefully we can glean enough insight to do so even if our final design is not quite traditional.
Judi Anne wrote:
Are there potential problems with installing closed cabinetry against natural material, breathing walls? Exterior walls. I think it might work better against interior walls that are not wet areas on the either side. Closed cabinetry installed on an exterior wall seems it might create temperature differences creating condensation and just reduce air flow along the wall too much. Is there a definitive answer to this?
Most old-fashioned furniture and cabinetry I've seen examples of are either open shelving or built with legs and set a few inches front from the wall. I prefer furniture built and placed that way in my current modern spaces because of occasional mildew on exterior walls in cold weather and just ease of cleaning in general. I like knowing air and light and my broom get behind the furniture without wrestling it around.
Judi Anne wrote:
Second questions is about windows in natural building. I looked through permies a bit and didn't see much on the topic. We do want to have many windows. I like bright, naturally lit spaces, so while I know it's not traditional to have so many windows it is a luxury we want to include and design out as many of the problems as we can foresee. being able to open for ventilation is also a big deal for us. When it's nice we like the breeze to pass through the house.
Is there any reason vinyl frame, gas filled Windows should not be used in a natural materials build other than objections to purity of material choice?
We have made double pane in wood frames with old glazing technique. Some got condensation and needed to be reworked, but overall we could build and maintain them. That is our second option. However, at least in the short term gas filled do seem to be more energy efficient letting less heat pass through. Observations? What would you choose?
The second part of window design is where in the thick wall to install them. I would prefer installed to be flush with the exterior (minus the finish plaster depth.) The house will be designed with a deep overhang so Windows and plaster will be well protected from precipitation. The wide interior sill can be useful space, and gives a buffer zone with heavy drapery for insulating at night or during extreme weather.
However, I've been thinking of the stone house I lived in briefly in Europe and there the Windows were installed to the middle or even flush with the interior. What is preferred in a thick wall?and why?