Welcome to our 5 part series on the Smart Enclosure System. This is part 4: The Assemblies of the Smart Enclosure System.
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In previous parts we’ve been equipped with the principles and the three tiers framework. Now we look to apply them to the various assemblies we see professionals working with every day.
We start with retrofits and then move to new build. We cover higher performance wood construction and finally we’ll cover how to make the most of metal and concrete construction types. For each assembly type we’re producing a hardcopy book and free ebook that has comprehensive details, illustrations and text - with links to photo libraries and videos to help you take action and implement the Smart Enclosure System today.
Let’s begin with retrofits.
If possible, choose renovation before new build, because it’s the smartest form of construction. Renovating and reoccupying old buildings is rightly considered an act of sustainability in itself. Using the existing structure can mean 50 to 75% less embodied carbon, on day one of occupancy, than a new building would generate.
Yet too often high performance and historic building preservation are seen in opposition. This is a false dichotomy — our historic buildings can be very energy efficient while retaining their essential historic fabric. And historic buildings can be made better and longer lasting in the process. The two goals can and should support each other.
Today we have books addressing masonry retrofits and wood frame retrofits.
The approach to a retrofit project varies depending on whether or not the historic character of the building can be changed. The building may be in a historic district or be specifically designated as historic landmark, leaving little choice in exterior design alterations. Does the exterior need to be preserved? Do we want it to be preserved? Or can the building be wrapped from the outside? What’s the condition of the exterior and, or, interior details?
Wrapping the exterior can significantly change the look of the building, but when designed well, the new shell can provide a beautiful and well detailed appearance. Yet in many cases the historic exterior cannot be substantially altered or the team doesn’t want to alter the exterior and the priority is on an interior renovation. In this case the retrofit can be successfully completed with more attention given to details, to ensure continuity of the control layers.
While every existing building has its unique aspects and the building science must be carefully considered, we can still make these old building enclosures very robust and energy efficient. We can make them Smart Enclosures that will continue to last for generations to come.
But obviously we can’t always retrofit - there's going to be a lot of new construction.
New construction, while bringing with it more embodied energy than a retrofit does, provides ample opportunities to implement a low embodied carbon solution with large amounts of carbon sequestration, at the highest level of performance. And while new construction covers a vast variety of building types, we’ve started by looking at the common wood framed assemblies that we see in the high-performance and passive house community: 2x stick framing, I joist outrigger, and double stud and we currently have a book dedicated to each assembly type.
Working with the three tiers structure each assembly type is detailed toward higher and higher levels of performance - less toxic, better carbon balance, and more durable.
Then, going beyond typical assembly types, it’s exciting to see high-impact bio-based assemblies like mass timber and straw bale, making headway in the marketplace.
Mass timber has many performance benefits, including fire resistance, acoustic performance, material stability, and construction efficiency. The mass timber Smart Enclosure compliments the mass timber structure with wood fiber insulation, maximizing carbon sequestration and its negative carbon potential.
Mass timber can now deliver tall buildings of every sort, and with the improvement of fire codes underway, in a sane world, we should expect metal and concrete structures to be abandoned as the materials of choice. If we really care, mass timber should be the future of big buildings, starting now.
And while straw bale and related approaches like hemp, would seem to be an anachronistic choice at first glance - we should look closer. While uncommon approaches at the moment, they may be the most effective carbon sink available to construction professionals today. Because straw and hemp are rapidly renewable resources full of carbon drawn from the atmosphere. It can be even more effective than wood in our climate mitigation efforts.
As mass timber is emerging quickly today, let’s not be surprised if straw and hemp follow.
Of course metal and concrete structures are not going away - and so they cannot be ignored.
Metal is problematic because it typically has high embodied energy and it doesn’t sequester carbon. However, metal can, and should, have high levels of recycled content. We want to make these assemblies as smart as possible by limiting other materials with large embodied energy like foam plastic insulation; making the enclosure more durable and operationally efficient for 100+ years; and we want to maximize the use of wood and other natural materials in the overall design strategy.
Regarding concrete, while there are many variables at play, concrete is often worse than metal because the embodied carbon of concrete, and particularly of Portland cement, is just so damn high. Like metal, it’s not going away, and there are a number of things we can do to make it a smarter option such as using recycled fly ash and slag binders, and recycled aggregate, while wrapping the concrete in wood insulation. Just remember, with concrete, the least amount is the best amount.
While these nine assemblies cover a wide variety of buildings being built today, this list is admittedly far from comprehensive - so, we hope that you find these approaches adaptable to the particulars of your needs.