In our last post we shared a few ways our living homes improve the foundation of a home while adding to the larger integrated system. This time we will take a similar look at the above ground structure of our homes.
We build every home super insulated and super air tight. The basic concept is to separate the inside climate from the outside while exchanging fresh, filtered air at the perfect rate. Think of it similar to building underground for perfect comfort except you have access to abundant natural light, fresh air and the outdoors.
All this starts with the wood framing. Unfortunately wood construction often gets a bad rap since it’s so often used poorly and cheaply. In our desert climate there’s a romantic push towards using concrete (like concrete blocks) for the thermal mass and inability to deteriorate from weather or bugs. Unfortunately this construction nearly ensures bad indoor air quality while living inside a giant oven all summer, not to mention the huge sucker punch to the global environment.
Fortunately wood construction has fully matured for buildings 3 stories and under (and is coming of age in really big ones with mass timber construction). We now have over 40 years of experience and testing with “new” technology into what works well and what doesn’t in a modern, wood home. Below are 8 things we feel are critical in building world class, durable, comfortable and efficient homes.
1 | advanced framing
It’s almost embarrassing to include this one. It’s so common sense and really should be basic code by now. Unfortunately it’s not in the code and many homes are still built sans common sense.
Advanced framing is a collection of a few concepts. Basically wall studs are 24″ apart instead of the typical 16″, the roof trusses sit right on top of each stud which cuts out wasted wood and adds strength. From there corners are framed without wasted wood, ladder blocking is used where interior and exterior walls meet, headers are sized appropriately and without wasted wood studs. Typically wall studs go from 2×4 to 2×6 to accommodate the increased spacing but in our case we have a really slick double 2×4 wall that is our own hybrid of some existing concepts (see #2 below).
Advanced framing decreases unnecessary waste which adds insulation, saves wood, makes stronger buildings and theoretically should save cost since there’s less material and labor involved (but more design and foresight). Framing factor is the term for how much of the wall space is “wasted” by wood, basically what can’t be insulated. A typical wall has a framing factor around 25%, an advanced framed wall improves that to 15%! That’s a lot more insulation and in reality helps more than it sounds due to reduced thermal bridging.
A well designed (but still very standard) advanced framed wall dense packed with cellulose will get you to a “true” (not accounting for thermal bridging) R-17 wall. Compare that to a typical “energy efficient” wall of R-13. After accounting for thermal bridging a simple and cost saving advanced frame wall gains around 50% over a typical “energy efficient” wall (what you would see in most Energy Start certified homes)!
2 | double stud exterior
Once you’ve accepted advanced framing as the only logical way to build a basic wall what’s the next step? Well advanced framing still has one major and one more minor drawback.
The major one is thermal bridging. This is the phenomenon that no matter how much insulation a wall has energy will still take the path of least resistance (sound familiar from high school physics?). A typical 2×6 stud is plenty big enough to act as a local highway, bypassing energy you want to keep outside right past your fancy insulation to the inside of your home.
Think of it like this; You have a 5 lane highway and for some crazy reason you want to close the whole thing. You’ve got 4 lanes blocked off but the middle one is still open. How are all these cars getting through? This is thermal bridging. No matter how much insulation is added if a path of least resistance is left energy will take it every time. You may slow it down but the plan still has a fatal flaw.
Eradicating thermal bridging is one of the core concepts of the quickly growing Passive House movement. There are many ways to get rid of thermal bridging but many of them (such as ICF, exterior foam, SIP panels) add increased complication, added risks to homeowners, huge environmental impact and poor integration as a larger system. We set out for a more elegant and complete solution.
Our solution also gets rid of thermal bridging in a way that uses the fastest growing, most sustainable trees (2×4’s instead of 2×6’s), is structurally amazing, easy to build and super durable. This system has 2 2×4 walls “tied” together (not with string) on top and bottom with a gap between that gets packed with insulation and stops thermal bridging. No energy highways, no uncomfortable hot spots in your home.
The more minor (remember from above, it’s been awhile) drawback of typical advanced framing is the limited insulation. Each climate has it’s point of diminishing returns on insulation levels, set primarily by the maximum difference of interior and exterior temperatures. Now, in Arizona we like to consider ourselves super tough with how effortlessly we handle the extreme summers but this difference never gets close to a really cold climate such as Maine or Wisconsin. Because of this our wall insulation hits diminishing returns around R35-40 rather than R50-60. The great thing about a double wall is you can tune the gap between the two walls for the desired insulation level.
We tuned total wall thickness to 10 inches giving us R-38 of insulation. With a framing factor (remember from above) of 10% (!) we have a true wall R value of 34 with zero thermal bridging. Remember the example above; typical “energy efficient” home true R value of R-13 (with bridging), a “should be code” advanced framed wall with cellulose at R-17 (with bridging). After accounting for the energy transfer of bridging our walls are about 4 times more efficient than most homes claiming to be energy efficient. We would love to see more Arizona builders adapt these concepts.
3 | floating walls
We love the desert and we love connecting with the outdoors. We want every VALI home to foster a strong connection to the outdoors, blurring the lines of inside and out. A big part of this is simple, “floating” surfaces. All our perimeter walls and ceiling carry a smooth white surface from inside to out, separated only by full height glass. This is all possible because of carefully designed framing details and hidden support that allows interior planes to match perfectly with exterior and structural support to be built into wall sections surrounded by glass on both sides.
4 | proper overhangs
That floating ceiling plane isn’t just for good looks. It’s also sized perfectly for a more mutually beneficial connection with the fireball in the sky. Our homes have no windows on the East or West side to protect against harsh desert sun where shading isn’t possible. We size the North side for protection from early morning and evening sun but also for maximum collection of that lovely Northern light.
The South side is where the real magic happens; perfectly sized overhangs keep the sun off windows and interiors during the hottest months when the sun is high in the sky. During winter when the sun is lower the overhangs allow extra light into the home and radiation to hit the exposed concrete floor, absorbing energy to release later. As a matter of fact unless you like your toes overly toasty in the winter you would likely never turn on the heat in any of our homes!
5 | ultimate shell
All our homes will be fully plywood sheathed. I know what you’re saying “I don’t see any plywood in those photos.” And yes, you are correct. The age old plywood OSB debate was one we went back and forth on. The only thing that really matters is what value we add to an end buyer and most buyers don’t value the premium for plywood, even once they fully understand the benefits.
In the progress to an elegant solution we realized that our new (and amazing!) liquid applied air and water sealing system called R-Guard (more on this in a future post) takes much less material to cover plywood than OSB. R-Guard is also a premium (expensive) material. We did the math and it’s about cost neutral to switch to plywood within our complete system. All future houses will have the added piece of mind of full plywood sheathing protected by the best sealing system in the industry!
6 | continuous shell
The modern rectangular shape of a VALI isn’t only for style points. It’s the elegant combination of what; native cultures built in our region (the best solution without modern products), can be properly air sealed at the exterior and most durable location, can properly tie into and protect all windows and doors. All this comes together to easily and durably create a house tight enough to hold water. Or if you prefer tight enough to keep your interior air clean, comfortable and healthy while keeping dust and mold out of your walls.
More about the air and water sealing system in the next post.
7 | pest treatment without the toxins
Boracare uses nature (borate) rather than harsh chemicals to protect a home and humans from pests. In our last post we talked about our Stego physical barrier system for pests. If any persistent buggers somehow make their way to the wood they are looking for they will find it treated with Boracare (and filled with borate treated cellulose) and terribly inedible. The bottom 4 feel of all wood is treated with Boracare. It is a totally non toxic to humans with no chemicals to off-gas while preventing insects and mold growth.
8 | flexible interiors
While we are fond of the layout of our homes and think you will love their comforting feel we are also aware that lifestyles change and the future may look very different. We only have to look at the roots of modernist design from the 60’s to see that change. To accommodate future changes none of our interior walls support any weight of the roof. They are all connected with floating clips and could easily be stripped out for a totally new configuration.
If you have questions about anything above or want to know even more feel free to get in touch with us. Our next topic will be on our air sealing and insulation. In that post we will show how we seal up these super thick walls and fill them with the building equivalent to a perfect, snugly down comforter.