Rustic Precision Blog

The search for the Ideal Wall system is the Holy Grail of the sustainable building movement. The Ideal Wall is cheap and easy to build with, needs little in the way of heating or cooling, has little or no embodied energy, and lasts for a really, really long time.

Increasingly, the concensus is that the systems we’ve been using for the last sixty-plus years don’t meet these criteria. Not only do they waste energy, but they’re only designed to last sixty years! What’s happened is that we’ve optimized residential construction to take advantage of cheap, abundant energy. Thanks to advances in the last sixty years, houses can be made cheap enough that they can be treated as disposable: they need serve only for the duration of their occupant’s attention span. Historically, houses cost enough that they had to serve many generations to justify their expense. Now many houses are built and torn down in 1-3 generations. Until sustainability recently entered the public consciousness, no one cared about making them last longer.

Combined forced air heat, ventilation and air conditioning (HVAC) systems make disposable houses possible. Aside from the considerations of where to route forced air ducting, HVAC systems don’t constrain how houses can be built. Now that cheap energy is almost gone, conventional wisdom says to adapt the same HVAC technology to a more energy efficient building shell.

This approach ignores thousands of years of research on sustainability, building materials, and human comfort. For the last few thousand years (the recent half-century largely excepted), humans have been discovering building materials that are sustainable, long-lasting, and comfortable. Given that we hadn’t yet discovered cheap energy, most anything that was comfortable was also very energy efficient.

Even some of the oldest buildings built from these materials are amazingly comfortable and use little or no energy. The field of “natural building” wants to reacquaint architects, builders and consumers with these materials. Despite some of the advantages of the advantages, professionals seem to reject attempts to reintroduce them. Why is that?

First, so-called “natural building” systems are very challenging to work with: with few exceptions, they require huge amounts of labor, don’t mesh well with currently available construction elements (like windows and doors), and frighten off most skilled tradespeople. Tradespeople fear them for a variety of reasons, not the least of which is the difficulty in producing a standardized, high-quality building on-time and on-budget with these materials. Currently, they’re not cost-competitive with stick framing.

Second, each natural building technology – rammed earth, adobe, strawbale, cob, cordwood, light straw-clay, etc – is well suited to particular climates, but not others. Many proponets of these systems make light of materials’ limitations.

Thermal Mass
Residential architecture seems to cycle between extremes of comfort and convenience, and splendor. Yet it seems we’ve forgotten how to achieve the sort of homey comfort that everyone talks about. Window seats and yard-size bedrooms photograph well, but rarely provide the experience suggested by the accompanying text; articles don’t mention that sitting with your backside to glass is uncomfortable for all but a few days of the year, or that sleeping in a cavernous room is downright agoraphobic.

The human psyche thrives on stability more than contrast. More than anything, thermal (temperature) stability equals comfort. Thermal mass provides that stability. At some level, a home is supposed to be a castle. In addition to permanence, what castles share is mass.

Humans (and animals) may or may not be able to sense mass through the forces of gravity, but they sure respond to a massive warm or cool body. That’s because mammals, reptiles and plants all appreciate radiant heat more than the convective variety. Given a choice, a cat will nap in a sunny window sill, but not in front of a hot air register. Why? Because thermal mass is the storage and re-transmission medium for radiant heat. It’s a heat buffer, a heat battery: heat goes in slowly, and comes out slowly. And what works for heat works for cooling as well; a cool mass stays cool for a long time in hot surroundings.

We’ve figured this out over thousands of years, but somehow, we seem to have forgotten. Again, it probably comes back to cheap energy: creating and installing equipment to blow cheap energy all over the place is faster and cheaper than designing a building to perform well.

The ideal wall should combine the best of old and new. It has to make everyone in the building industry happy: builders, architects, mortgage lenders and insurance agents. It also has to serve the clients’ and the community’s long term interests: great value, great performance, longevity and sustainability. Last but not least, it has to be exceptionally comfortable and esthetically pleasing.

I believe that all the pieces for this optimal wall system exist, unassembled and therefore unrecognized for what they could be. I also believe that the main barrier to its widespread adoption is that no one’s seen it on the hoof.

Problem: the Empty Fridge
Somehow, the relationship between thermal mass and comfort is underappreciated. At the moment, the significance the building community accords to thermal mass is pretty low. While thermal mass is vital to passive solar design (solar heating and passive cooling), passive solar is seen as too extreme for the masses. The paradigm of the day is to construct a house that performs like a Styrofoam picnic cooler.

I like to call a super-insulated house, heated with forced air, and otherwise lacking thermal mass, an empty refrigerator. As the fine print will tell you, refrigerators only achieve their rated efficiency when they are kept full. An empty refrigerator cycles on and off more frequently, chilling the air inside, only to lose a portion of the cooled air each time the door opens. Without the mass of all that already cold food, the system wastes energy.

Heat recovery ventilation (HRV) and energy recovery ventilation (ERV) are systems that recapture the energy used to heat or cool a home and add it to fresh air intentionally introduced into a home. Even in homes so equipped, regular events — like entry doors being opened and closed, and exhaust fans for bathrooms and ranges running – flush energy from a home. Forced air then must kick on to warm (or cool) the air in the building.

Unfortunately, since there’s no massive warm (or cool) wall or floor in the vicinity, the occupants rely on the air surrounding them to keep warm or cool. As a result, everyone wants the thermastat set ten degrees higher (or lower) in order to average things out. At an intuitive level, they are missing the promise of temperature stability characteristic of thermal mass.

The Well-Stocked Fridge
The equivalent of a full refrigerator is a home with sufficient thermal mass. In coastal California and Oregon, and other climates with mild winters and/or significant temperature swings between day and night, the benefits of insulation, even the super insulation provided by straw-bale and SIP construction, are modest compared to the combination of thermal mass and passive solar heating. I’ve seen a number of otherwise uninsulated and unheated structures that never fell below 50 degrees Fahrenheit, or above 75, in temperatures ranging from 10 degree lows to 115 degree highs.

My point isn’t to dismiss the importance of insulation. I have also been in old, thick-walled, uninsulated stone homes in Switzerland that managed to serve as infinite heat sinks for countless cords of firewood and never really became warm. Without a doubt, most climates require insulation. And there is definitely such a thing as too much thermal mass: if your house takes a week to heat up, you could very well end up burning fires day and night to combat the chill of winter’s last storm, only to have to swelter through the first few days of an early spring in an overheated house.

Arguments For Mass Walls
The Ideal Wall for most climates should have both mass and insulation. In other words, the Ideal Wall should resist air infiltration, provide a path of low thermal conductivity to the outdoors, and provide thermal mass to stabilize indoor temperatures.

I’ve found few architects or building scientists who dispute this, at least in principal. The point of contention seems to be that the combination of mass and insulation is difficult to implement. Therefore, they argue, various technologies favoring one over the other are most appropriate.

For example, Bill Chaleff, a SIP proponent who has penned a number of great whitepapers, defines thermal performance purely in terms of insulation and air infiltration. In his paper SIPs 101 – for Martians!, he compares different wall systems against 13 criteria. Against “thermal performance”, SIPs score highest, and masonry next to lowest. Yet, clearly, he’s aware of the role of thermal mass in building, as he has a good paper on passive solar and plenum-heated mass floors. It’s unclear whether he believes thermal mass is only advantageous in passive solar design, or whether it should be implemented in floors.

Under most circumstances, if you have to choose between putting mass in a wall or a floor, the floor is a better choice: the floor presents a better target for sunlight for passive solar gain. My point is that mass in the floor and walls provide superior comfort and temperature stability. Also, with mass in the walls, it’s possible to do without the mass in the floor, or impair it to a greater extent with a wider range of floor finish options.

An argument I often hear against mass walls is that they are too thick: they waste real estate. I don’t buy it. If interior space is so precious, why do we have so many unconditioned attics? An enduring, high-performance wall system is as legitimate a use of a building’s footprint as any that I can think of.

Another argument I hear against mass floors is that concrete slabs are too hard underfoot. I’d like to point out that slabs don’t have to be concrete: soil-cement and adobe both make for warmer, softer, medium-wearing floors. Needless to say, many other options exist. Once again, if you have mass in your walls, you don’t need it in your floor.

Given the extra expense, a super-insulated mass wall is a hard sell on technical merit alone. It’s the comfort they offer that most strongly differentiates them; but people need to experience it firsthand. I am confident that if examples of super-insulated mass walls were more common, this paper would be unnecessary.

Perhaps you are one of the many people who’ve never had the opportunity to visit an occupied adobe building in the winter. So, if you will humor me for a moment, swap the seasons. Imagine and compare walking around in a large commercial building, say a Costco, in the heat of summer. Now imagine that, on the same day, you’ve just entered a winery. Think about Costco’s large, shaded slab — nice and cool underfoot, right? But think of the winery: that sense of cool is three-dimensional. (If you’re also thinking about all that chilled wine, so much the better.)

If you haven’t had any of these experiences, then even this thought experiment was a failure. In that case, I’d ask you to take my word for it: the trouble of putting mass and insulation in walls is worth it.

Uninsulated mass walls abound. Unfortunately, attempts to replicate them in climates without adaptation and insulation have led to the erroneous belief that mass walls are unsuited to most climates, when quite the opposite is true. I would argue that the only reason not to consider them would be for buildings that are of such a temporary nature that the copious use of energy seems like an acceptable remedy for their deficiencies. (Does this sound like the rationale for our current housing stock?)

Current Wall Systems with Thermal Mass
I’d like to mention a couple of wall systems that combine mass and insulation, and how they do vis-à-vis thermal performance — that is, the version that considers the importance of thermal mass.

Insulated concrete form (ICF) systems sandwich concrete between split layers of insulation, usually closed-cell foam. This is less than optimal for both insulation and thermal mass, because the half of the insulation is between you and your thermal mass, working against you. Some specific products merit being mentioned by name. Durisol™, made from mineralized wood pulp/cement, is a filled cavity masonry unit that biases the concrete mass in the block towards the living space, and adds a thin blanket of mineral wool between the mass and the outside of the block. In my opinion, that’s a sensible layout. Rastra™ (foam/cement) is a hybrid ICF/masonry unit that splits the slightly insulative block material with the concrete fill (the structural/thermal mass.)

Rastra literature would have you believe that ICFs and high-tech masonry are a low embodied energy building system. While the grid structure of the resulting cores makes efficient use of the concrete, it’s still a high-embodied energy wall system that’s not easily recycled or reused. Apparently the embodied energy in the concrete fill lands on someone else’s tab. Neither of these two systems gives you an R-value better than about 12. Based on R-values for closed cell foam, regular ICFs fall in the range of 15-25.

SIPs. Their superior conductive and air infiltration resistance, not to mention their efficient use of materials, makes for an ever-growing school of converts. Combined with slab floors or other mass, they produce a space that performs pretty well. My only beef is that, in common use, there’s no mass: they produce the perfect empty refrigerator. That said, and at the risk of getting ahead of myself, I feel that they are a critical component of an Ideal Wall.

Straw Bale. I consider straw bale to incorporate thermal mass because it requires interior plaster anyway; that plaster can be built-up to any depth. Arguably, it’s the greenest super-insulator of all time. It’s challenges include the fact that it’s not really structural, it’s highly vulnerable to water damage during construction and throughout it’s life, (necessitating first-time-perfect water detailing) and it eats up the most real estate of any wall system. Nevertheless, from a sustainability standpoint, an Ideal Wall based on straw bale and earth is topic worthy of a future paper.

Natural Stone. Due to the lack of uniformity of natural stone, it will remain forever labor intensive. Proposals I’ve seen for insulating natural stone, like stacking it against an interior SIP wall, give up the benefits of its thermal mass. Of course, stacking it against two faces of a SIP wall yields a very durable, attractive, and expensive wall of modest embodied energy (if locally sourced) with at least average moisture performance. (Stone walls can wick water, and thus offer minimal protection to the OSB SIP faces.)

Faux stone. “Cultered stone” is a veneer made from concrete, and as such, is a high-embodied energy product. As it offers minimal mass, its function is largely decorative.

Cast Concrete, and Concrete Masonry Units. Readily available and easy to work with, composite concrete walls systems that incorporate rigid foam are available. In my opinion, despite their longevity, the energy required to manufacture cement and transport the materials rule out these systems as sustainable building materials in single-family and low-density housing.

Other Properties of an Ideal Wall
Listed below are an aggregation of desirable attributes for a wall. They’re drawn from walls made from many different materials.
The exterior portion of an Ideal Wall should

• last a really, really long time — 300 years, at a minimum
• block entry of liquid water as much as possible
• allow any liquid water that does enter to drain and/or escape as vapor
• be easy to repair
• not feed, shelter, or provide passage for insects and microbes (fungus and mildew)
• self-heal cracks and other minor thermal/moisture trauma

The interior portion of an Ideal Wall should

• provide for a range of finish options
• buffer and release water vapor, without condensing it
• facilitate installation and modification of utilities: electrical, water, sanitary, and gas
• facilitate the mounting of cabinets

The wall system as a whole should

• be easy to build and require nominal trade skills
• provide great tensile, compressive, and shear strength, and stability in seismic events
• fail gracefully, rather than catastrophically, when stressed by loads and moisture
• facilitate easy installation of doors and windows
• provide anchorage for interior walls and suspended floor systems
• use minimal energy in production and transportation
• reuse or recycle easily, or decompose gracefully under specific conditions not encountered in normal use

Properties of Earth as a Building Material
When people think of building materials, earth doesn’t usually come to mind. In fact, most people confuse earth and garden soil. Earthen building materials, which include cob, adobe, and rammed earth, are actually similar to concrete. (For simplicity, I’ll sometimes refer to all of them generically as “adobe”.) In each case, a binder coats and binds particles of aggregate. Sometimes reinforcing fiber is added for tensile and shear strength. “High-strength” sack concrete achieves its strength through the addition of glass fiber. Adobe uses straw or manure.

Although clay, the binder in adobe, is weaker than cement because it cures through dehydration, it also has no inherent energy associated with its manufacture. Through careful formulation, compressive strengths of up to 2000 psi are possible without additional binders [http://en.wikipedia.org/wiki/Compressed_earth_block]. This far exceeds the design strength of ordinary mortar (1500 psi), and is close to standard 5 sack concrete.

Common misperceptions about adobe are that seeds sprout in it, microbes thrive in it, and that it composts any wood and other cellulose in close proximity. The opposite is true: earthen building materials tend to “mummify” anything buried in it, whether it’s organic material, or other building materials. By blocking air and liquid water, embedded material desiccates and stabilizes. Seeds quickly abort; wood is protected from large humidity swings and insects; straw remains bright for hundreds of years. By contrast, concrete, with its water-wicking tendencies, tends to rot anything it touches.

Another common misperception is that building with earth is like using ice blocks for igloos: that it’s a material with a very narrow range of application. The truth is, worldwide, there are more homes built of earth than any other material. Earth is used extensively, and often exclusively, in cultures where labor is less expensive than other natural resources. And while it’s true that it’s most common in desert climates, you can find examples worldwide, including in very wet and very cold climates.

Ironically, it’s used extensively in the areas of the world with the cheapest oil. Factors other than climate appear to influence the use of other building materials over earth.

I suspect the real reason earth doesn’t get the respect it deserves is that it’s “common as dirt.” As they say, familiarity breeds contempt. I’m asking you to forget what you might know about the material for a moment, and pretend that it’s high-tech, new, exotic, and expensive – whatever sexy quality that piques your curiosity. Below, case by case, we’ll consider how earth-based building materials fair against the wall criteria listed above.

Useful life.When protected from wind-driven rain by appropriately maintained lime-based stucco, a roof with overhangs, and a foundation that prevents the base of the wall from being saturated, earth walls last practically forever. In Devon, England, a place with a maritime climate (plenty of wind-driven rain) and a history of earth building, there are many 300-year-old, multi-storey houses. In Yemen and other dry regions where neglect has less of an effect, there are 900 year-old, 9 storey buildings. Earth buildings last as long as people want them to.

Blocks entry of liquid water. As I said earlier, clay is the binder in earth-based building materials. Clays are expansive to varying degrees. The expansive nature of clay causes it to become increasingly water repellent as it gets wetter. Consider that the most expansive of clays, bentonite, is the active ingredient in kitty litter! Due to the generally capillary nature of aggregates, the overall performance of an earthen wall is not quite as good as that of a pure clay wall. (Note: a pure clay wall would be undesirable for a host of other reasons.)

Allows any liquid water that does enter to drain and/or escape as vapor.As much as clay is water repellent, it is vapor permeable. Provided it is protected from complete saturation, clay responds to vapor pressure and equalizes with its surroundings relatively rapidly.

Is easy to repair. By thoroughly rewetting a clay surface, new material can be added to achieve a chemical bond, not just a mechanical bond. Repairs achieve the strength of the original material. This is not the case with concrete.

Does not feed, shelter, or provide passage to insects or microbes. As mentioned earlier, earthen building materials contains aggregate and a binder. As is the case with concrete, insects derive no nutritive value from either, and have great difficulty tunneling through the matrix. Similarly, with its relatively high vapor permeability, earth desiccates microbes, plants and sprouting seeds.

Self-heals. When earth is rewetted, the clay mobilizes and bridges small cracks and fissures. This is not a common attribute in other building materials.

Provides for finish options.Against this criterion, earth has strengths and weaknesses. The evenness of the surface is a function of the construction method (for example, rammed into full-height forms, versus stacked in irregular masonry units, versus wet-hacked roughly plumb with a machete.) In general, the surface does not compare well with drywall. It does accept screws, so drywall can be fixed to it. Since it doesn’t exhibit water expansivity to the extent that wood does, natural (vapor permeable) paints and plasters bind well. Non-vapor-permeable finishes can cause serious problems if the entry of liquid water is a possibility.

Buffers and releases water vapor, without condensing it. Earth can store a considerable amount of water vapor without adverse effects. When the vapor pressure reverses, vapor is re-released from whence it came. The net effect is relative humidity stabilization, a very positive contribution to indoor air quality.

Facilitates installation and modification of utilities: electrical, water, sanitary, and gas. Earth can encapsulate utilities, but it’s generally a bad idea. Retrofitting earth walls to accept utilities is difficult in the best of cases. SIPs are electrical-friendly, with their pre-fabricated channels, but my understanding is that you can’t (or shouldn’t) put plumbing in them. Masonry and straw bale suffer from the same problem. Stick framed walls are the friendliest in this regard; pretty much anything goes.

Facilitates the mounting of cabinets.Earthen walls have some screw-holding capability, but screws cannot be driven repeatedly into the same holes or the holes tend to crumble and widen.

Degrades or decomposes minimally in normal use.Earth degrades through only one mechanism: erosion. If protected with breathable plaster, earth will not erode. Earth can tolerate wetting up until the point of near saturation. If allowed to dry slowly, it will suffer no damage.

Is easy to build, and requires nominal trade skills. Compressed earth blocks (CEBs), like those produced by the Cinva Ram Adobe Block Press, are highly uniform in length and width, and within ¼” or better in height. Using ½” earth mortar joints, they’re both a precise and forgiving system. Cast blocks have greater variation. Headers can be wood, reinforced concrete, or channel iron. Rammed earth requires specialized form building skills, similar to poured concrete walls. Headers and the requisite bond beam are reinforced concrete. Cob is perhaps the hardest of all to work with, given that it is free-sculpted, but it is also the most flexible. In all these systems, window and door installation, addressed below, is complicated.

Provides great tensile, compressive, and shear strength; stability in seismic events. Pure adobe earth, and rammed earth, are very similar to low-sack concrete. It ranges from about 300-2000 psi, depending on the shape and composition of the aggregate. Additional strength and stability can be achieved by adding additional binders like fly ash or cement. Without reinforcing fiber, compressive strength is good, shear strength and tensile strength are not. Cob, which has added long straw fibers, has significantly improved shear and tensile strength. Given the weight of the material, its strength-to-weight is low to medium.

Fails gracefully, rather than catastrophically, when stressed by loads or moisture.Dry failure of unfibered adobe is similar to that of unreinforced masonry. Rammed earth usually has rebar in it, making it behave more like low-sack reinforced concrete. Cob, with embedded straw fibers, fails gracefully under extreme loading of all sorts. Without stabilization, when subjected to moisture, earth-based building materials fail catastrophically when they reach saturation. Again, up until that point, they suffer little or no damage. Saturation can occur when (a) the wall sits in standing water, (b) when a watertight plaster is applied, or (c) a horizontal surface is exposed to weather, facilitating ponding. For all but the very wettest of climates and flood plains, these conditions are easily avoided through good design. Stabilized earth (stabilized through the addition of cement, motor oil, or proprietary, biodegradable formulas) is even less prone to weathering and failure.

Facilitates installation of doors and windows. Installing doors and windows in earth walls is similar to installing them in thick masonry walls. Anchorage requires installation of additional materials, like a wood frame. Sill pan flashing must be carried through to the outer surface of the wall. Most window installers become confused.

Provides anchorage for interior walls and suspended floors. Interior walls can be lagged into earth walls, but as mentioned under “cabinets”, screw holding capability is mediocre. Anchoring suspended floors, particularly in a remodel situation, can be a real challenge. In new construction, the wall usually steps in at each floor, and a wooden ledger is leveled in mortar to support rafters. Posting up is an easier solution. In a retrofit situation, if posting up is not acceptable, this can be a real challenge.

Does not wick water.Earth walls don’t move liquid water.

Uses minimal energy in production and transportation. All forms of earth walls can be made with 100% hand labor and zero embodied energy. Realistically, assuming mechanization and locally sourced materials, energy use is low. Suitable soils are very common. Where the sand/clay ratios are inappropriate, usually both sand and clay can be locally sourced and formulated. Without a doubt, it is the greenest of all building materials by weight, area, or volume.

Reuses or recycles easily, or decomposes gracefully under the right conditions.If stripped of a protective roof, in time, earth walls will erode and disappear. Adobe blocks are easily reused.

What can we conclude from all this? Earth as a building material has a number of strengths that make it the greenest of all building materials. It also has glaring deficiencies that must be at least partly responsible for its lack of widespread adoption in the western world. Simple earth walls score poorly for finish options, ease of anchoring cabinets, installation and alteration of utilities, installation of windows and doors, shear strength and stability in seismic events, and familiarity among western tradespeople. They also do not provide sufficient insulation in hot-humid or continuously cold climates.

Composite Walls
What if we create a composite wall system by sandwiching something else between two layers of earth? That something else should be an excellent insulator, and contribute the missing shear and tensile strength. It should have excellent screw/nail holding capabilities. It should accept windows and doors in a straight-forward manner, and provide regular carpenters and other tradespeople with a familiar point of reference. Finally, it should have integrated conduit for wiring, at least. Sound familiar? We’re talking about SIPs, of course.

A hybrid system and candidate for an Ideal Wall is a SIP wall sandwiched by adobe CEBs. The CEBs on the outside of the wall are there to protect the SIP for all of eternity. On the inside, they provide thermal mass and regulate humidity. The SIP wall provides ultra-fast installation, easy door and window installation, wiring, and last but not least, insulation. Though they’re high-tech and require energy in their manufacture, SIPs offer a lot of value for that embodied energy.

Presciption for a CEB/SIP Sandwich Wall
Assemble the building like this: pour an extra-wide stem wall foundation. Then pour a slab; this could be a grade-level or suspended slab. Alternatively, for a low-mass floor, build a suspended floor over a gravel-lined, sealed, conditioned crawlspace. Build the SIP wall (for extra longevity, using fiber-cement faced panels) at the center of the stem wall. Frame an unvented roof, apply roof surface, and seal it to the SIP walls. Note that wind uplift isn’t a concern if the roof is securely attached to the SIP wall; the huge weight of the CEBs hold the SIP wall down for all of eternity.

Install special tack-welded window sill pans with self-furring plaster lath so that you can later field-cut them at the edge of the CEB wall. Install the windows and doors.Stack the interior and exterior CEBs to within a block modulo of the roof, anchoring courses on each side with masonry ties at horizontal mortar joints. The spacing of these ties should be specified by an engineer.

Use wooden trim to close the visual gap where the CEBs stop short of the roofline. Stucco the CEBs with lime plaster, or, with sufficient overhangs and for a purist look, leave them plain.

Note: since it requires a long, damp cure, lime plaster is more tempermental to apply. But unlike cement stucco, lime never needs replacement – just maintenance and repair. This is because lime, like earth, continues to mobilize calcium, making it self-healing. This same deposition mechanism forms stalagtites in caves.

Rough Electrical, Plumbing, and Finish: the Harder Part
Adobe’s harshest critics complain about these areas in particular. I expect it’s because their point of reference is stud walls. Actually, the rest of the sequence for new construction isn’t that challenging.

Cabinetry, fixtures, wiring – in new construction
Attach wooden frames of the same dimension as the CEBs (“gringo blocks”) to the SIP faces and build them into the CEB course work. These anchor interior walls, cabinets, additional floors, and so forth. Alternatively, the wall system won’t suffer if you stop the CEBs for appropriate wall sections, like kitchen, bath and other areas requiring built-ins. This allows you to recess cabinetry into the wall by a full block width (6-8”), making it less obtrusive. Run wiring through the SIP panel walls normally, and bring it to the wall surface through gringo blocks (which also serve for mounting switches, outlets, and other fixtures.)

Floor support
Posts are the simplest support for suspended floors. Attach posts directly to the SIP wall and integrate with the inner CEB wall, or leave them flush to the block surface and through-screw them into the SIP panels in a retrofit situation. Alternatively, you can suspend floors from the top of the sip wall/roof system – with wood, cable, or chain – and through-lag through the interior block and both SIP panel faces.

Another interesting possibility is the use of custom, adjustable height brackets with a top-hanger flange that could be tapped into a notched mortar joint, and through bolted with a long panel screw through both faces of the SIP. The slot for the bracket could be plunge-cut into the wall using a circular saw with a diamond blade (the circular saw would work like a giant biscuit joiner.)

Let me stress that all but the post-recessed-into-the-wall are just ideas; they need input from an engineer.

Plumbing
It’s my belief that plumbing shouldn’t be run in the exterior wall system. As in SIP buildings, run plumbing up through the floor directly, or inside interior wet walls.

Remodeling
Since I am strongly influenced by Stewart Brand’s book How Buildings Learn, I prefer to think of new construction as a special case of remodeling. This keeps new construction greener — both by extending the building’s useful life, and minimizing waste during subsequent remodels.

For electrical outlets, switches and small fixtures, cut enough adobe from the wall to fit a min-gringo block. Anchor it to the SIP wall with screws, then drill through the SIP panel into the wiring channel. Fill around the area around the gringo block with a suitable filler, and patch the plaster.

If the interior is bare block, the situation calls for more delicate work. On layout for the SIP prefabricated channels, hammer-drill a hole large enough to fit ¾” conduit through the CEB and to the first SIP face. Continue the hole with a spade bit until it reaches the channel inside the SIP. Cut an area slightly larger than the fixture and centered on the hole with a grinder. Run wiring through the SIP and bring it to the surface. Slide a length of conduit over the wire and tap it through the CEB and into the SIP. Attach the fixture to the conduit and fill around it with a suitable filler.

The “suitable filler” may require some experimentation. It should be roughly as hard as the CEB, easily packed, and non-shrinking as it dries or cures. Mixing polyurethane glue (which expands as it cures) with sand might be a place to start. White glue and sawdust is another possiblity.

Mount cabinets by grinding out a horizontal, shallow area and filling it with a screw-friendly filler. This serves in lieu of blocking. For further tear-out strength, drive and leave protruding screws before applying the filler. Alternatively, leave out a section of CEBs, so you can recess the cabinetry and affix it directly to the SIP. To stabilize a long run of wall compromised by such a break, add king studs as needed, screwing them to the block ends.

Add additional floors as before: by posting, suspension, or possible tapped-in-place top hanger brackets plus through-bolting.

Conclusion
Combining two earth-friendly wall systems – one of the oldest in existence, and one of the newest – yields a hybrid system with superior insulation, superior thermal mass, superior moisture management, superior durability, and – most important to the consumer – superior comfort.

I hope that the solutions to the challenges posed by this system prove it feasible and worthwhile. If several houses can be built and demonstrated, new clients can be attracted, educated and served. Most importantly, with input from a larger community of architects and builders, barriers to greater adoption – the costly and unconventional aspects – will go away.

By lasting at least five times longer than the houses currently being built, by consuming less energy and fewer natural resources during its construction, and using far less energy during its lifetime, each such house can make a leveraged contribution to a better quality of life for us and future generations.