A guest post from our friend Lucas Johnson of Vali Homes
How I Met the Havelock Flock
In the before times, when we met in person over drinks at busy bars to share ideas, our conversation got started.
Andrew Legge, the founder of Havelock Wool, and I traveled like maniacs around the Pacific Northwest trying to convince people that it was time to stop using bad building products and to invest in solutions that provide health, comfort, sustainability, low carbon, durability, and social justice. It is stressful to fight against the power structure so we certainly enjoyed a cocktail or two together.
A core theme of our conversations was always science. That is the central passion of my life and building science is the focus of my career. And after years of collecting data, it became clear that Andrew, and the rest of his Havelock team, deeply care about doing the right thing for the future of our society and our planet.
So when Andrew asked me to write a guest piece, I was stoked to share my scientific expertise in as fun and unbiased a way as possible.
A little about me
It has been a joy and honor to work with hundreds of deep green professionals on thousands of buildings throughout my career.
I love science and I hate bad building products. That may seem oversimplified, but sometimes simplicity on the other side of complexity is the most valuable outcome. An example of this thought process is that I’ve come to realize building science must be decoupled from sales and sponsorship; otherwise, it is not science. This is because bias is the backstabber of objectivity.
I’ve delivered building science through managing utility programs, developing certification systems, starting divisions for general contractors, running regions for suppliers, and consulting for architects and engineers. Upon analysis of my experience, the most common bias I experienced was assuming all buildings need to be high performance.
However, high performance is expensive, and it isn’t worth delivering if we have to use toxic high carbon impact insulation materials and airtightness systems to make it happen. As I say, “the ingredients create the results”. Just like a good meal we need to use healthy ingredients. There is no magical property of design that can turn bad building products into a good building.
And sometimes, when you live on a tight budget, like my family, you can’t afford high performance. The exciting conclusion though is that we’ve figured out an approach to deliver truly good, low-performance building that achieves climate mitigation, health, comfort, social justice, and durability goals.
My primary frustration during my career to date was that my positions often made it difficult to deliver true science since the structure of our industry didn’t allow me to follow the scientific method in the large majority of cases.
So, the next step in my journey has been becoming a co-owner of Vali Homes. We are making science the “4th leg of the table” along with architecture, engineering, and construction (classically called AEC) as the other three legs. We believe independent science is the critical missing ingredient in the market. Building science should not be delivered as a side hustle; it must be paid for directly to minimize bias.
That’s all for now, very nice to meet you, now let’s get into the crucial stuff to know as you get started on your own project.
5 nerdy things you need to know as you begin building
#1 What are the basic components of a wall assembly?
The basic components of a wall assembly include the framing system, which is typically light wood construction (aka 2x4s and 2x6s).
The studs, the vertical support elements, are attached to a “bottom plate” and a “top plate” to create a full structure. The studs are typically 2×4 in older construction and 2×6 in modern construction. Typical studs are spaced at 16” OC (16 inches on center) but many builders choose to save wood and reduce costs by using “advanced framing”, which typically has studs spaced at 24” OC.
The bottom plate is attached to the foundation system with “ties” that hold it in place for structural stability and to limit movement during events like earthquakes. The bottom plate to foundation system interface is often one of the largest air leaks in buildings and this can be easily fixed with proper materials and proper sequencing. A typical approach is to place an EPDM gasket on top of the foundation and then lay the baseplate on top of the gasket. This creates a mediocre air seal, so we recommend also using your exterior and/or interior air barrier products to overlap the base plate and connect to the foundation for a complete seal. In addition, the EPDM gasket can be upgraded to a quality sill tape solution like Pro Clima’s Extoseal Finoc. This gasket or tape also should serve as a capillary break so that water doesn’t move from the concrete foundation into the wood framing system.
Most top plates are “double top plates” meaning there are two pieces of 2x lumber laid on top of each other. This allows greater weight to be added to the roof and more structural stability overall. A best practice here would be a similar approach to air barrier products for the bottom plate that contemplates your particular transition to the roof.
Walls also need to contain plumbing, electrical, and other infrastructure. I’ll spare the details for now, but figuring out how to make sure these elements don’t ruin your air and water control layers is mission-critical.
Then walls need to have insulation. The best practice is to have both continuous exterior rigid board insulation and interior “cavity” insulation between the studs. All insulation should be vapor permeable, non-toxic, low carbon or net carbon-storing, and durable. Insulation products that use natural fibers like wood, wool, straw, hemp, cellulose, etc. are typically the best options overall.
After insulation, we need to control air and water movement, which is an exceedingly complex subject I’ll summarize with two key rules. First, you want both interior and exterior airtightness delivered with durable non-toxic membrane and/or tape-based systems. Second, the airtightness membranes need to help minimize wetting and maximize drying, which means being waterproof yet vapor permeable (or vapor variable). A key thing to remember is to eliminate as many vapor-closed materials as possible. There are a lot of options in the market, but a simple way to divide “good” from “lower quality” is to select monolithic, or non-microporous, membrane systems that are Red List Free and meet Passive House standards.
That is probably more than enough for now. Forgive me, I love this stuff.
#2 What are the major problem areas of common building practices?
As mentioned above, the problems in the construction industry are mostly driven by a lack of transparency and a lack of scientific process. These failures of our market lead to a lot of confusion about what products are the optimized options to achieve a given set of goals for a project. We must demand better information with more accuracy and precision.
I’ll also add that there is a tremendous amount of structural violence built into the culture of the construction industry. Borrowing from my wife’s field of cultural anthropology, we’ve been calling this “embodied injustice”. In short, it is the poor wages, exposure to toxic materials, and other negativity that workers with less privilege are forced to experience because we want to save some money on our projects.
These two major flaws lead to an industry where it is considered normal to use toxic materials that lead to high failure risks. In regards to how this influences your living space directly, it is critical that you review the lifecycle impacts and health implications of:
- Airtightness and waterproofing materials
- Insulation materials
- Interior finishes, such as drywall, cabinets, or paint
- Furniture you bring into the space
Ideally, you can find “Red List” free materials with a Declare Label from the International Living Future Institute. At a minimum, you should review the Material Safety Data Sheets (MSDS) and/or Environmental Product Declarations (EPDs) provided for a given product. Every product is required to have an MSDS, whereas EPDs are a relatively rare yet more in-depth lifecycle-focused review.
#3 Why the obsession with airtightness and do houses really need to breathe?
One of my favorite questions! Because it is so silly from a scientific standpoint. Of course, they don’t need to breathe; buildings are not organic life (although they certainly are living in a sense). This is an issue of poor vocabulary and a good way to emphasize accuracy versus precision.
While it is generally accurate to assume buildings need to allow air and water vapor movement, calling both those types of movement “breathing” is not precise. Air movement can be called “breathing” somewhat accurately although it is technically “convection” that drives it. However, water vapor movement is entirely different and should be called “diffusion”.
So, the precise way to state the goal is: buildings should generally minimize convective air movement yet maximize vapor diffusion in assembly systems.
#4 What building materials pose the most health risk?
The data indicates that spray foam insulation tends to create the highest toxicity, highest carbon, and highest moisture failure risks. A close second is XPS rigid board insulation when looking at the overall environmental impact summarized in documents called Environmental Products Declarations (EPDs). There have also been a lot of stories and speculation around mineral wool insulation having serious issues as well.
You also need to be extremely careful about interior finishes and the glues often used to attach them. This includes flooring, drywall, cabinets, paint, and many other items.
And if you care about the planet as much as your home, then you also need to consider the impact that products create off your site as they are made and delivered. Those impacts cannot be removed from the use of that product.
#5 What are the most crucial building science concepts?
Understanding the scientific method and how to review scientific research is the critical first step that is often missed. Too often we jump straight into the technical concepts, which are secondary to the scientific process.
Effectively the main thing you need to know is that a lot moves towards less. That is physics in a sentence.
For example, you’ve probably heard “hot moves to cold”. This is because hot means a lot of energy and cold means a lot less energy. So the heat energy transfers to the cold to balance the energy states. This happens in three primary ways: convective, conductive, and radiant.
Convective means heat energy moving through air, conductive means heat energy moving through a material through direct contact, and radiant is way harder to explain.
Convective is like a hairdryer in slow motion, conductive is like burning yourself on a pan or putting your hand on ice, and for radiant, I’ll say just think about how the sun feels warmer on your face than the air temperature or how cold windows steal your heat. Interestingly, radiant heat determines comfort far more than actual air temperature, but that is a subject for another day!
So there is also “wet moves to dry”, which is why you need to assume everything will get wet at some point somehow. As we’ve increased airtightness and insulation, we’ve limited heat flow through assembly systems (aka floors, walls, roofs, etc.) which means they are getting wetter and are experiencing less drying. This means we are now walking a moisture tightrope whereas conventional buildings had lots of air leakage and oversized heating systems to bake themselves dry. It is well worth delivering high-performance assembly systems, but it is only worth doing if those systems will be durable (aka manage moisture properly) and if those systems are made of truly good ingredients that improve our health and don’t cause damage to the planet or our fellow people.
In closing, I’d say there is a lot to consider when building in today’s environment. The industry conversation is improving every day and therefore making lots of decisions easier to make. Nevertheless, we are in the business of trying to help so please reach out to me @valihomes or your friends at Havelock who are trying to be more than just an insulator provider as it relates to this very important subject that we all need to learn more about.
Senior Principal at Vali Homes
If you’d like to learn more or schedule a time to chat, please visit: www.valihomes.com/contact-us