thermal mass

Panel Making

This week the Thermal Mass and Buoyancy Ventilation Research Team got to use the largest skill saw they’ve ever seen and we’ll tell you why!

In the technical workshop Sal last week, the team decided to narrow the number of materials they will test throughout the experimental cycle from four to two. The lucky two will be concrete and softwood! Concrete is often used as a thermal mass material while softwood is not which will make comparing the data collected from the separate experiments all the more interesting. The Optimal Tuning Theory calls for the thermal mass to be externally insulated which allows the thermal mass material to be much thinner than a typical thermal mass. Therefore, the concrete and wood need to be panelized.

The thermal properties of wood act most efficiently as a thermal mass when the cross grain is exposed to the air. This means that panelizing the softwood is more like creating giant cutting boards. To practice this process the team used 8″ x 8″ Cypress timbers and their matching 16″ diameter skill saw leftover from the Newbern Town Hall project. The team learned that 6″ x 6″ timbers would be ideal for their project, that way they can cut the cross-grain pieces in one cut with their 16″ skill saw without having to rip down the timber.

The concrete panels are far more straightforward, build a mold, pour the concrete, let it cure. However, the team has to think about how the panels would be attached to a larger structure. To solve this they cast PVC into the panel which will allow it to be screwed into a structure.

Voila! We have much refining to do of the panel making process, but the first two turned out well. We also have here a rendering of the habitable structural with the separate concrete and wood panel rooms. Our next step is to apply what we learned working with these materials to designing and building our first experiment. Thermal Mass and Buoyancy Ventilation Research Team out.

The Experimental Cycle

The team with the longest name possible is back this week diving deep into the science behind the Optimal Tuning Theory with its author, engineer, Sal Craig. Sal, along with his colleague, architect Kiel Moe at Mcgill University in Montreal, Canada, are our partners in the Thermal Mass and Buoyancy Ventilation Research Project. The team has weekly meetings via Skype with Sal and Kiel to discuss the project, but this week they had an in-depth technical workshop.

Behind our simple understanding of the Optimal Tuning Theory, there are very intricate scientific equations that Sal has written, solved, and published in his peer-reviewed paper, The optimal tuning, within carbon limits, of thermal mass in naturally ventilated buildings. Although the student team does not need to obtain an engineering degree to work on the project, it is important they grasp the basics so the project is truly a collaboration. They need to be able to have a conversation with Sal about the possibilities of the project instead of asking his permission. 

The team studied up for their technical session with Sal


Thankfully, Sal is a wonderful teacher and the students were able to reach a deeper understanding of the theory with him during their day-long technical workshop. Afterward, they were able to make a couple of important decisions about the project together one of which was defining the undergraduate phase of the project as an experimental cycle.

The experimental cycle will be comprised of testing the Optimal Tuning Theory at three different scales they are calling Desktop, Human, and Habitable. These scales are important because the theory is meant to be proportional. The Desktop experiment will resemble a small chimney made of thermal mass material, the Human scale experiment a full-sized thermal mass wall, and the Habitable experiment will be a full structure i.e. the pod where the interior walls will be entirely thermal mass. 

Livia with her beloved schedule

Defining the experimental cycle has allowed the team to start scheduling and setting deadlines, something Livia has been dying to do. Completing this cycle in the undergraduate phase of the project will allow freedom for the graduate phase. Thanks for tuning in!

How do we build that?

Now that the pods have been given forms, it’s important to figure out how we can make them stand up. To accomplish this, we are comparing three different structural systems to find the best method. We are considering Cross Laminated Timber (CLT), Structural Insulated Panels (SIPs), and more conventional stick framing systems.

All of these systems require slightly different assemblies, and we drew many wall sections to begin to understand them.

These forms also require unconventional joints at odd angles, so we did studies of how to join corners, whether with panelized systems such as CLT and SIPs, or stick framing.

By the end of these studies, and with the help of a review from Hank and Julie of KoningEizenberg Architecture, we began to realize that these forms were too complex, and could be simplified without forgetting our experimental requirements. This led us to a form we’re calling the “Rowhouse”. 

We will continue investigating structural systems using the Rowhouse form. We are currently investigating using the SIPs systems, as they offer a high insulating value while integrating structure. Our next steps will be designing the thermal mass panels that will live in these structures.

Grain Silos to Air Silos

Welcome back to another round of Thermal Mass and Buoyancy Ventilation! Now that you’ve seen what we looked like in our presentation, here’s some of what we were actually talking about.

Our project relies on the testing of materials to observe how they work as thermal masses according to the Optimal Tuning Theory. To be able to do this scientifically, we need spaces in which we can test our four materials. These four spaces need to be identical so that they can be directly compared to each other. In each of the four spaces, one material will be tested, either timber, concrete, brick, or earth. These four spaces will be arranged into a “foursquare” configuration, housed under one roof.

Once we decided on a layout for the four spaces, pod forms could begin to be generated. For this, inspiration was drawn from the silos that surround us. In order to gather our airflow into a measurable point, the pods will take on a funnel shape, both on the top and bottom. This is because the ventilation cycles will function both in updraft and downdraft. After creating this funnel shape, we iterated on the basic shape to create options for the pod forms.

From here, we’ll be evaluating these forms, and researching structural systems to support them. Eventually, we will select one form to house our experiments.

Ready to Transform

From costume contests to coding classes, the Thermal Mass and Buoyancy Ventilation Research Project takes on a new form everyday.

In the past weeks, the team has been designing a Pod which is a small dwelling or dorm that 3rd-years use for sleep and storage. The Pod will be used to test the Optimal Tuning Theory. The team presented the Optimal Tuning Theory and their current pod design at the annual Rural Studio Halloween Review. Unfortunately, all of you lovely readers were not able to make the review, so this post will be dedicated to explaining the Optimal Tuning Theory and showing off the teams Halloween Review Costumes.

What is the Optimal Tuning Theory?

First, let’s get a couple of definitions out of the way, what are Thermal Mass and Buoyancy Ventilation? Thermal Mass is a property of the mass of a building which enables it to store and release heat. A typical example would be an adobe home or pueblo where the thick, earthen walls absorb the hot, desert sun during the day keeping the interior space cool. Later during the cold, desert night the thick, earthen walls release that heat into the interior thus warming the space. Buoyancy Ventilation, often refereed to as the “stack” or “chimney” effect, utilizes the natural ventilation cycle of hot air rising and cool air falling to supply air to a space without mechanical systems.

The Optimal Tuning Theory theorizes that a space can be comfortably and passively ventilated, heated, and cooled by coupling an internal Thermal Mass with Buoyancy Ventilation. If these systems are synchronized or “optimally tuned” it would allow architects and builders to use the ancient practice of Thermal Mass building in a more predictive manner. The typical issue with Thermal Mass buildings is that the Thermal Mass is never able to release all the heat it absorbed in the day, therefore the cycle does not start over the next day and the passive system does not work efficiently. By keeping the Thermal Mass on the interior, shaded from the sun and insulated, and using Buoyancy Ventilation to draw out access heat or supply heat from the air, the system is able to reset for the next day. The Optimal Tuning Theory is the crux of the Thermal Mass and Buoyancy Ventilation Research Project.

The Thermal Mass and Buoyancy Ventilation Research Project Team will build a Pod as a scientific instrument to test the Optimal Tuning Theory. A Pod is an appropriate, human scale that they can test the temperature and air flows of easily and can be inhabited by 3rd-years later on.

Now for the real magic, Rural Studio’s own Transformers! Each TMBVRP team member transformed into a classic Rural Studio vehicle. From left to right starred: Livia Barrett as Andrew Freear’s Honda Fit including his front license plate that reads “British Nut;” Rowe Price as the crisp, new Student Truck; Cory Subasic as Hale County Classic Tractor fit with hand wheels; and Jeff Jeong as our beloved Johnny Parker’s beloved BobCat. The team came second in the local costume contest, but Jeff won Best Pumpkin! Thanks for TUNING in, we hope to see you at Soup Roast!