Jim Reiland

Hi there Joshua!  Sounds like what you're proposing is something called a "straw bale wrap."  It's do-able, but not often done for the following reasons.  

First, the bales themselves are quite heavy compared with more conventional insulations--upwards of 7 lbs. per cubic foot. Each 2-string bale will weigh around 65 lbs., and each 3-string bale could be closer to 80 lbs. You'll need to stack the bales to whatever wall height you have...which is a lot of weight!  While a Larsen truss system might work, those trusses will need to be really well attached to the farmhouse framing, and I'll wager that the existing framing isn't up to the task of cantilevering 100s of pounds of straw bale additional framing, plaster, and new siding weight per linear foot.

Most bale-wraps have a completely new concrete foundation poured around the existing building's foundation (and also attached to it if in a seismic region) to support the additional bale weight (plus the weight of any framing, plaster, and siding)..and that alone gives lots of people pause.

Then, if you get beyond that hurdle there's the roof overhang to consider. If the exterior walls of a building are suddenly 15" or 18" or 23" thicker, the existing roof may not provide adequate coverage for the new wall surface. As Christo and John mentioned, a good roof overhang is important, and you need to be guided by your typical rainfall in this regard. If you have very little wind-driven rain you might get away with 12" or so of roof overhang, but I prefer at least 24" and usually built homes with 30" - 36" of overhang, especially for taller walls. So your retrofit may require extending the rafters, and adding new roof decking and roofing (and a new gutter). On sloped roofs this will lower the roof line enough to drop it below the top of some windows, which impacts sightlines from the inside, and also reduces how much sun light enters through those windows. This has proven to be another challenge that dissuades people from pursuing a bale-wrap.

The final major impediment I have run into is the question about what to do with the windows. If the exterior walls are now much thicker, should the windows remain in the plane of the original exterior wall (which makes for very deeply inset windows as viewed from the exterior?  If so, the exterior window reveals need to be detailed against moisture intrusion--think really deep window sills and really good flashing!  Or could the windows be moved to the exterior of the new wall surface? Yes, but then you'll also need the framing from sill-plate to top plate to support the windows so they don't rack....unless you want to go with "floating" window bucks....

Here in the arid west I have seen quite a few straw bale walls that have metal siding, but the metal isn't up against the bale surface. When the bales are stacked we make sure there's framing in the exterior wall surface to support whatever siding will be installed, then we plaster the bales--a thick, leveling scratch coat--to give them some protection against insect intrusion, fire, etc.  After attaching 3/4" or 1" furring strips through the plaster to the now-embedded framing to create a "rainscreen gap" we attached either cement board or metal siding. The top and bottom of the air gap has insect screen. This rain-gap air space addresses the concern for moisture moving through the wall from inside and condensing in the bale wall, or moisture from humidity or wind-driven rain penetrating beyond the siding.

If you were willing to go through all of this I think it's possible to do a bale-wrap, even in your area.  I'd strip the existing siding off the walls to expose whatever insulation and framing you have there, do any needed electrical, plumbing, air sealing around electrical and plumbing perforations, and rodent-intrusion work, then pour a new foundation, extend the roof, add whatever framing needed to support the new roof extension and windows (if moving them to the exterior wall plane), stack the bales right up against the now-exposed original framing, and proceed with whichever siding system you like.

If your farm house was built pre-plywood (circa 1950s) it probably has let-in diagonal bracing to provide shear. You might want to check that this is still OK--now would be a good time to upgrade if necessary!

I'll also note that the original bale wraps were done on CMU (concrete masonry units) walled homes in the American Southwest, where the combination of interior thermal mass (8" of concrete) and exterior plastered straw bale insulation made for really comfortable and stable interior temperatures.  

If your farmhouse has lath-and-plaster interior walls it has quite similar thermal storage capacity to the 1"+ of plaster used on the interior of a typical straw bale wall assembly. The original plaster may have been gypsum or lime (which are vapor permeable), but it has also probably been painted and repainted many times over the decades?  The many layers of paint will function as an air barrier. You may want to remove it (be sure to check for lead paint and do it safely--paint applied prior to the early 1970s in America probably had lead in it...) so that any moisture in the form of water vapor moving towards the cool dry interior (assuming you run air conditioning) during hot, humid summer days doesn't get trapped against the inside surface of the interior original lath-and-plaster walls).

Complicated, right?  You're building an entirely new wall assembly--including a new foundation and extended roof--around your house and using the original exterior walls as an insulated chase for electrical and plumbing.

I have no doubt that you'll achieve all of the thermal efficiency you had hoped for, but if that's your primary goal there are other ways to achieve it. For example, Larsen truss walls that are only 4" or 6" thick and filled with a lighter weight insulation, and whatever siding you want. Or you could use wood-fiber exterior insulation panels (a lot more environmentally friendly, though not as "efficient-per-inch" as rigid foam) attached to existing sheathing, then add new siding. You still need to deal with detailing the windows to the new wall plane, but that's a lot less involved that adding a new foundation and extending the roof.

That's why so many people who consider a straw bale wrap end up not doing one--there's a lot to it!

Jim

Many Hands Builders

Back in 2001 the California Straw Building Association was only five years old.  

Founding members--builders, architects, engineers and owner-builders--were excited by the new (to them) building system presented by stacking and plastering straw bales to form walls for buildings. Energy efficient, non-toxic, simple, and beautiful--lots to love!  The straw bale "revival" had begun just a decade earlier--in the late 1980s when a handful of builders from the American Southwest learned of a building system that originated on the plains of Nebraska soon after baling equipment arrived there, circa 1890s.  There was so much to learn--and much to share.

CASBA held a Pro-Course--a one day event where builders, engineers, and architects shared what they knew. That was in 2001.

How things have changed!  After a twenty-five year hiatus CASBA is holding another Pro-Course, this time over several days in Cottage Grove, OR, from August 21st - 23rd (we hope participants can arrive early, the afternoon of Thursday, August 20th, but actual teaching time will be Friday - Saturday the 21st - 22, with wrap-up and departures on Sunday the 23rd.

Visit the California Straw Building Association's website for more details https://strawbuilding.org/event-6704105 and to register!

The course has lots to offer. In 2001 pretty much everyone building with straw bales was laying them flat, sometimes load bearing (roof loads supported by the bale walls), but in the seismically active west, more often bales laid-flat within a wood frame of some kind (non-load bearing, or post-and-beam). Cement stucco was a common plaster finish. Building codes pertaining to straw bale buildings were rudimentary, and the building science around thermal and moisture management of bale wall assemblies wasn't well understood. There were just a couple of commonly used shear wall systems.

Today, straw bales go into building walls laid-flat, on-edge, and on-end, and there are a dozen lateral force resisting systems (shear walls) available to structural designers. There's a well-developed model code in the U.S. available for adoption. Clay and lime plasters have largely replaced cement plasters as finishes, and we know a good deal more about how these wall systems manage temperature and moisture fluctuations.

Finally, a lot of thought has gone into how to build more efficiently, and better.

And all of this will be part of the course, which features a pre-course on-line video component as well as on-site classroom and hands-on.  

We have experienced instructors on-site--Miles Taylor, Lydia Doleman, Chris Foraker, Catherine Odell, Kita Glass, Jenna Bader, and me.  The web instructors include straw-bale and straw-clay code authors Martin Hammer and David Eisenberg, architect Bob Theis, structural engineer Anthony Dente, CASBA's executive director Massey Burke, and natural builders Amanda Fischer and Myles Danforth.

I'll hazard a guess that between us we have worked on hundreds, if not thousands of straw bale buildings--plenty of insights to share!

Class size is limited to 30 participants; there's an early-bird special that ends on June 30th, so if you want to learn all about current best practice in North America for straw bale construction, check out this course!

I hope to see you there!

Jim

Many Hands Builders

I couldn't agree more with the premise of this program, that "building is a birthright." At the very least, it can be an important expression of what it means to be human.

My wife and I experienced great joy and satisfaction from having a hand in building our straw bale home. We didn't just save a small fortune by taking on parts of the construction that we had the time and skill to complete; we also developed an emotional connection to our building that's difficult to describe, but palpable.

When I became a building contractor I wanted that opportunity for others, and encouraged clients to participate in any way they felt comfortable.  A few kept their involvement to writing checks as work progressed, but most also joined the crew during some construction phases--placing straw bales and applying clay or lime plasters being among the most memorable.

If I weren't already retired from a career in "mostly natural" building I'd apply for one of the Arc11 apprenticeships!  There's so much still to learn, AND I know the instructors and the founders of Arc11 to be passionate about natural building materials, extraordinary craftspeople, and truly gifted teachers.

An exceptional program!

Jim
Many Hands Builders

Hi Maggie,

If I understand your question, you want to replace two non-load bearing, second-story partition walls--presumably 2x4 stud with sheetrock on both sides and no insulation?--with hempcrete walls?  

As you explore this make sure to consider the proposed wall's weight.  The original 2x wall with sheetrock is probably much lighter and easily supported by the floor joists without sagging.  Hempcrete, while having more fire barrier, acoustic, thermal, and hygric (moisture control) benefits than typical 2x partition walls is also probably much heavier, even if installed at a similar 4" thickness.

Jim

Hi Sam,

Thanks for the referral to Straw Bale Building Details: An Illustrated Guide for Design and Construction by the California Straw Building Association. As detailed as this book is, it’s not quite granular enough to answer your question.

It’s not uncommon to pair timber framed structures with straw bale wall wraps, with the timber frames either interior or exterior of the straw bales, but this coupling complicates the structural design.

Modern timber framed structures tend to use lighter-weight insulated wall assemblies like either foam-filled structural insulated panels (SIPS) or framed, plywood skinned walls with blown-in cellulose insulation.  

You’ll want a structural engineer to have a look at your plans because a plastered straw bale wall is considerably heavier than either SIPS or blown-in-cellulose wall assemblies. There’s an in-depth discussion on pages 69 – 74 in the CASBA book’s chapter on structural design. In a nutshell, the weight per square foot of wall area (PSF) for a plastered straw bale wall can be several times heavier than more conventional modern wall systems, i.e. 40 – 60 PSF vs only 11 – 15 PSF!

The wall weight needs to be factored into the calculations on loads and forces the timber frame resists, which will depend on where you’re building (high snow loads? high winds?  seismic activity?).

If I were building in Nebraska high winds would be the governing factor.  Where I live and worked in S. Oregon high seismic activity is a bigger concern.  A few years ago I worked on a timber framed (not a timber portal, which is a little different) straw bale wrap project.  The timber frame came from a one hundred-fifty-year-old barn that had been dismantled in Wisconsin and transported to the Oregon building site.  

The frame itself was in outstanding condition—clearly able to resist the snow loads and wind forces it experienced for over a century on the Wisconsin prairie.  However, when wrapped with straw bales on a building site where earthquakes are common, supplemental bracing was needed. In this case the engineer specified steel strap tension only “X” bracing at several places around the building perimeter, carefully anchored at the sill and top plates, to handle in-plane forces (like wind or earthquakes applied parallel to the walls).  There are at least nine other ways to address in-plane forces with straw bale walls, all detailed in the book.

To handle out-of-plane forces (wind or earthquakes applied perpendicular to the walls) the engineer specified 17-gauge galvanized stucco mesh tied-through to the same mesh on the opposite side at 2’ horizontal centers at every bale course. This effectively creates a “basket” so the bales work together--the wall can wiggle, but it won't buckle.

Other ways to address the out-of-plane forces (all of which are specified in the IRC (International Residential Code) Appendix AS Strawbale Construction, Section AS 106 Strawbale Walls—Structural, include the 2x2 14 gauge welded wire mesh you mentioned, polypropylene mesh (deer fencing, and often used with clay plasters), and also paired battens (bamboo or 1 x 1 fir poles, etc.) extending from sill to top plates and similarly tied through on 2’ centers at every bale course (think splinting a broken leg).  Although it has fallen out of use in the United States, interior pinning of bale courses with rebar, bamboo or wood poles can effectively resist out-of-plane forces, too.

Because straw bales have a rough surface that supplies plenty of tooth (lath) for plaster, mesh isn’t strictly necessary unless it performs a structural role. Many builders prefer to work without mesh if they can because it reduces both material and labor costs.

RE compressing the bales. If you purchase dense bales they won’t compress much, at least not in single story wall heights. Both CASBA's book and the building code IRC Appendix AS describe a method for determining a straw bale's dry density, which needs to be over 6.5 lbs. per cubic foot. I was able to find bales that averaged between 7 and 9 lbs. per cubic foot.

Bales placed on-edge compress less than bales laid flat, and bales filling the top several feet of the wall can be oriented upright (on end) and over-tightened (using compression straps) then released once in place. This functions like a “spring” to take up any space caused by settling.

The only other method I'm familiar with requires more planning and can be cumbersome; placing strapping (heavy-duty fiberglass pallet strapping) placed under the sill plates at 2' centers when the sill plates are first installed). If the strapping is long enough to run over the top plate on both sides-it needs to be coiled and tucked out-of-the way during most of the bale stack, or cut with just enough strapping exposed to attach buckles that secure longer pieces that run over the top bales before being cinched tight. When the second to last bale course is complete the straps go up and over that course and are sinched down, compressing the bales in the wall. With any luck, the top bale will snugly fit into the remaining space. I didn't favor this method for a couple of reasons: if we weren't doing the framing we needed to coordinate with another crew for which this was an unfamiliar step, we needed to keep the straps from getting tangled in pre-bale-stack construction tasks like running electrical wires and plumbing.

RE a box beam.  When I have wrapped a timber frame with bales we affixed a box beam to the timber frame and used door and window posts set in the exterior bale surface to support the box beam’s outside edge to prevent sagging.  

Finally, if your building performance goals include energy efficiency I wouldn’t attach mesh  to the outside of the timber frame (inside surface of the bale walls) and stack bales against the mesh for two reasons.  

First, it’s impossible to stuff gaps through the mesh from the inside, which will probably result in wall insulation that is uneven, with convective loops forming between the plaster skins that readily move heat between the wall surfaces, lowering overall R-value.  

Second, gaps will emerge where the plaster and timber frames meet—the plaster may shrink, and the timbers will swell and contract with seasonal humidity changes.  I have seen and attempted repairs on many such gaps in timber framed straw bale construction.

A better solution, assuming the structural design doesn’t call for mesh attachment to the timbers, is to secure (glue, screw, nail) thin (1/2’) plywood “fins” to the outside edges of the timber frame (inside surface of the bale wall), extending around 1” – 2” onto what will be the bale surface once the bales are stacked.  Interior mesh, if used, can be stapled to these fins which are then plastered over. As the gap between the plaster and timber frame opens and closes the fins block air movement.  I take an additional precaution and place a folded layer of building paper here, stapled to both the fin and the timber, not so much to separate the timber frame from plaster (code requires a separation between exterior lime plaster and wood framing due to lime’s tendency to wick moisture inwards), but to further air-seal that joint.

Lots of good advice here Patrick.

I agree that simple designs cost much less to build than anything else, i.e., single story, gable or hipped roof, rectangular footprint. Designers impart their "insights" to the process in that they usually have experience with code requirements, how more recent developments in building materials and methods can make the construction process more efficient, how to maximize interior space, etc.

Usually, but not always. If you study successful building plans you'll often see common cost-saving measures--kitchens, laundry and bathrooms sharing a wall to simplify plumbing and electrical runs, bedroom closets between adjacent living spaces to dampen noise, closets or pantries under loft staircases, few-if-any hallways, etc.

Another way to estimate your likely building cost is to ask local contractors or home builders associations what it costs to build a "custom" home per-square-foot. I was a contractor in S. Oregon where the cost for a permitted, beyond-code-level, entirely contractor-built custom-straw bale home cost ranges between $250 and $450 per-square-foot today (2025). This may seem high, but it's the about the same as what any custom "green" (energy efficient) home costs in my area.  

For reference, here the code-level conventional tract home cost is still over $200 per-square-foot, the lower cost having mostly to do with material and labor economies of scale achieved by building the same structure over-and-over (and sharing the same soft costs: architectural, engineering, etc.).

Paying extra for a building that is more energy efficient, probably-longer-lasting, and healthier for both occupants and the planet is worth it to many people--if they can afford it.

Between 50% and 70% of a building's cost is labor--much to be saved if an owner-builder takes on as many steps in the building process as they can. I have worked with clients who, for example, handled all of the ceiling insulation, interior finishes, kitchen cabinets, counters, and appliances, landscaping, and more--whatever they felt comfortable doing. Some plugged into the crew doing the bale stacking, plastering, or placing earth floors. Some contractors may not appreciate the "help," but I felt that having a hand in fashioning one's home is a rewarding experience that our highly specialized society has largely forgotten.

Also, note that the walls of a building usually account for less than 10% of the overall construction cost--whether conventional, straw bale, straw-clay, hempcrete, etc. Work parties and workshops can trim construction costs, but not as much as many expect.

Jim
Many Hands Builders

Not sure I can add anything but an observation. Here in the U.S. there's an established market for straw bales so farmers who want to do something with this "by-product" need to keep it dry. After the grain is harvested and the straw cut and baled it's often stacked under tarps in the field, or moved to a nearby barn. It's likely that there's a similar demand for straw in other places. If you can locate farmers who sell into that market there's some chance they have dry straw bales available. Here it's used for animal bedding, mulch, and erosion control, increasingly it's becoming feedstock for straw panel board, and much of it is shipped overseas for manufacturing.

In the arid western U.S. where the dry season months of June - September coincide with the grain harvest we take advantage of the "dry weather window" to get straw bale walls stacked. There's a joke shared among straw bale builders here: "if you want it to rain, build straw bale walls without first having a roof overhead."

I mostly worked on non-load bearing (post and beam) buildings and tried to have a completed roof over the walls before stacking bales. The handful of times I departed from that precaution--usually because of scheduling issues with roofers or roofing material delays--it never failed to rain!

In S. Oregon it has been a sure fire way to end a drought!

Jim
Many Hands Builders

Hi Tom,

Sounds like a fun project! It sounds like you’re running into a closing weather window for lime plaster (you don't say which plaster you're using but lime is the most common exterior plaster on straw bale buildings in N. America).  As your post notes, freezing temperatures could cause a still-fresh lime plaster to delaminate, so best to apply it when temperatures are above freezing, and for proper curing, between 45 and 80 degrees Fahrenheit during most of the day.

Wall trusses.  You're probably not using Larsen trusses, which are cantilevered away from a foundation and are not load bearing. Larsen trusses were developed as a way to "wrap" an existing building with insulation by affixing a wall truss to an existing wall in order to create an insulation cavity around a building.  Wall trusses (also called ladder trusses because they look like a ladder) resemble Larsen trusses except they are load bearing--they rest on the foundation's sill plate(s), and a top plate or box beam bears on them.  Lots of people—even architects and builders confuse the two—but the distinction matters.  Both create a cavity for insulation that overcomes the issue of thermal bridging, but wall trusses are also structural.  They resist loads (roof weight) and probably perform some lateral force resistance function (shear walls), while a Larsen truss’ primary purpose is to create an insulation cavity—it doesn’t have a structural role.

Ideally you'll get a scratch and a brown coat on those walls before freezing temperatures arrive, but if you just get a good scratch and cover it with something to keep the rain and snow off you should be OK for the winter. I have used tarps to surround a building with base coat plasters during winter.  If you can attach them to furring strips intended for the siding with staples or cap nails, great!  You may need to cut or fold the tarps so the windows aren't covered (so much nicer to work in a building when there's sunlight coming through windows!), but at least you can use the tarps again.  I have seen builders use building wrap for this purpose, though it's likely sacrificial.  If well attached it should last the winter season, but removing and repurposing it is unlikely.

A note of caution about applying lime plaster late into the fall (the closing weather window mentioned above). You want to keep your straw bales as dry as possible.  Applying plaster introduces moisture to the bale surface. Normally this will move out of the wall well before there's a chance for microbes to wake up and start eating the straw.  During warm, dry weather this drying takes place in just a few weeks or a month because the moisture inside the wall--higher pressure--wants to disperse to an area with lower pressure (warm and dry).

Imagine you have taken a hot shower in a closed bathroom.  You step out of the shower and there’s moisture clinging to everything--especially the mirror.  High pressure. Open a door or turn on the bathroom vent fan and voila—moisture dissipates to areas of lower pressure (the rest of your house or outside).
If you introduce moisture to the straw bale wall just as you're entering a cool, wet season, the vapor pressure conditions outside will be very similar to vapor pressure conditions inside the wall--and the moisture will linger. Fortunately, microbes are inactive during freezing conditions, and the outer few inches of the walls where introduced moisture is lingering are likely to be pretty cold, too.  

Clay plasters are more vapor permeable than lime plasters, and also hydrophilic so they seem to wick moisture away from straw bale walls more quickly.  Unfortunately, clay plasters don't stand up to weather so well as lime plasters.  

An air gap between ¼” and ¾” should suffice for your rainscreen under the siding.  I have used ¾” primarily because I could purchase furring strip stock of that thickness.

Jim

Many Hands Builders

I'll add that blown-in cellulose is also an excellent nearly-natural choice for wall cavity insulation.  Like the other mostly-natural insulations--cotton, wool, hemp wool and blown-in chopped straw (which is currently available only in Europe), cellulose is treated to resist decomposition and flame spread.  It has a very low embodied energy (which means that not much energy was used to create it) and makes use of a waste product (newsprint and other waste paper).  It also offers outstanding insulation comparable to the batt insulations listed here, and also helps to resist air movement between interior and exterior wall surfaces.  

I have applied an interior wood lath and clay plaster over blown-in cellulose on several projects--the combination offers outstanding insulation and distributed thermal mass.

Jim
Many Hands Builders

Good on you Matt for thinking about making an older building better!  Most of us who use more natural building materials to make energy efficient buildings have focused on new construction, but there's a much larger opportunity in renovation and remodel work in the U.S.  Housing stock in our country is "replaced" at the glacially slow pace of between 1% and 2% each year.  If we're to make all of our buildings more energy efficient as quickly as possible we can't wait 100 years for all of the existing stock to be replaced--we need to make older buildings better, and we could do it with more natural building materials.

I think using light-straw-clay for insulation in your exterior walls isn't a great idea.  At 12" thick LSC has a resistance to heat flow of only R-21, which may not be adequate for your location.  Apart from being quite heavy (15 lbs. to 20 lbs. per cubic foot), a 12" wall thickness would require a second sill plate interior of the existing one, which places much of that weight over flooring that may not be supported by either a thickened slab or floor joist.  If you're working over a basement or crawl space you may be able to remedy that.  In any case, assuming the existing building's walls are made with 2x4 or 2x6 studs, you'd be losing some interior floor space to thicker walls.  Just filling the existing 2x stud bays with LSC gets you to less than 1/3 or 1/2 of R-21.  

Although not completely "natural," you might consider hemp wool, sheep's wool, or cotton batt insulation. They are all comparable to fiberglass and rockwool (R-3 to R-4 per inch of thickness) but made with much more natural and lower embodied energy fibers treated to resist burning.  All are available in batt form as cavity insulation like rockwool or fiberglass.
 
To bump your wall insulation consider these three options:  

(1) a Larsen wall truss attached (cantilevered) to the exterior walls that functions like a sweater, wrapping the building's body in an additional layer of insulation. This gives you two separate but attached insulated stud walls. Use the hemp wool, cotton, or sheep wool insulation in the stud bays and sheath with siding appropriate to your area. You may need to remount windows and doors into the new exterior wall plane or fuss with exterior sills, reveals, and soffits so the windows and doors are inset into the exterior wall surface--it's a cool look and reduces wind washing (heat loss from air movement against the window surface).

(2) a wood fiber board wrap of the entire building. Many building codes in cold climates now require an R-21 + 5 wall insulation achieved by standard 2x6 wall cavities filled with fiberglass or similar, sheathed with plywood or OSB, then covered with 1" of rigid foam board (R-5 per inch).  A more natural alternative to the foam is wood fiber board like Gutex.  Though it's considerably thicker at 2 1/2", wood fiber panels are still vapor open so moisture can move out of the wall assembly towards the exterior.  Insulating wood fiber panels are very common in Europe and have been available in the U.S. for the last decade or so, but can be hard to find locally.  Similar challenges and benefits as mentioned above when it comes to remounting the windows/doors or dealing with exterior window reveals, sills, soffits, etc.

(3) an offset stud wall to the interior of the existing wall.  Leave the windows and doors as they are mounted on the exterior sheathing (assuming you're not going to replace them) and add an interior sill plate and top plate to the inside of the existing one, place 2x studs offset from existing.  Move electrical boxes to the new interior walls (may need to change box locations and heights as you'll be limited by how the slack in the original cables running to the boxes, and as mentioned above, adjust the box depth for whatever interior finish you're planning to use.  Note that there are adjustable depth electric boxes, but they cost more than regular boxes.  Fill both stud wall bays with whatever mostly-natural batt insulation you like. The offset eliminates thermal bridging, and the extra insulation thickness can double the wall's R-value. But the cost is reduced interior space and some fussing with the new, deeper interior sills, soffits and reveals for windows and doors. Assuming your exterior sheathing (plywood or OSB) is in good shape, use whatever exterior siding is appropriate to your area.  

I like the interior lath and plaster option because it gives you a distributed interior thermal mass--more material to absorb and release heat so you have a more stable interior temperature.  Clay plasters are probably the easiest to work with, and with baseboards installed through the house (and chair rails in the dining area) can be very durable.  In any case, clay plasters are very easy to repair.  Note that the weight of a 1" thick plastered wall is around 15 lbs. per square foot (1/2" sheetrock weighs  a lot less at 1.6 lbs. per square foot!).  If you have a crawlspace or basement you may need to reinforce the floor under the new interior wall so it can support the extra weight.

Eves. Some years ago Fine Homebuilding magazine published an article that described construction features that helped ensure building longevity--sufficient roof overhangs was at or near the top of the list.  The roof overhangs on all of the strawbale or LSC projects I worked on here in S. Oregon and N. California had roof overhangs of at least 2'.  I think you can afford to go with less if the exterior siding system you use has a proper rainscreen (air gap between the sheathing and the siding).

Jim
Many Hands Builders