Right now the Thermal Mass and Buoyancy Ventilation team is all about concrete and cypress. They’ve been busy creating and installing the shiplap jointed, 1-1/8″ thick concrete internal thermal mass panels. These panels line the walls of one of the Test Buildings and create the designed cooling and ventilation effects. With Jeff at the helm of formwork building, they’ve completed three out of four panel pouring phases. The panel-making process is separated into phases, so most of the formwork can be used more than once, eliminating waste. Formwork, or molds, are fabricated with precision in the woodshop. The team installed phase 1 before Cory began his journey to Nova Scotia to participate in a residency with McKay-Lions Sweetapple Architects Ltd. Congratulations Cory, we miss you already!
Also on the agenda as of late; exterior finishes! With weather-proofing complete, the team has taken to installing the cladding part of the ventilated cladding system. This system is completed with 8″ and 6″ cypress boards which are protected with Cabot® Bleaching Stain. The stain also helps the wood age consistently in the sun. With Livia cutting and Jeff and Rowe installing, the cypress siding is flying up!
Unseen are the myriad of other little things the team is finishing up such as electrical and grading. The team is keeping the momentum up so stay tuned to see the buildings fully wrapped!
Live from behind multiple stacks of full-scale detail drawings, it’s the Thermal Mass and Buoyancy Ventilation Research Project Team! The team has continued their pursuit to draw every detail of the Test Buildings. These drawings have cemented aspects of the building such as cladding, roofing materials, and entryway design. Certainly, there is still much more to decide and conquer. Let’s check out what the team’s got so far.
Concrete Barrier Bargains
First up, a much-needed win for the TMBVRP team; they got concrete barriers! The Cooling Porch, a space for literal chilling underneath the Test Buildings, uses recycled concrete barriers as a retaining wall and seating. Road work being done on Highway 61 in Newbern revealed many of these stackable, concrete barriers just asking to be reused. The construction team doing the roadwork donated and delivered all of the extra concrete barriers straight to Morrisette Campus. However, this generous gift was not the only score for the team. Next, the team found more concrete barriers at the Greensboro Highway Department Office just 10 miles down the road. The Greensboro Highway Department has 40 more barriers and the team can have them if they can move them. Time to start the powerlifting team!
Meanwhile, as the team solidified the material of the Cooling Porch seating, they also came to exterior cladding conclusions. The last post touched on how the team committed to using timber for their open-joint cladding system. Now they have decided on wood species and size. The team chose Cypress in both 6″ and 8″ boards to clad the Test Buildings.Cypress is a locally available and weather-resistant cladding option.
The variation in board sizes allows for more flexibility around complex details. For example underneath the walkway, attached underneath the door, 6″ inch boards come up too short. On the other hand, 8″ boards overhang too much and interfere with the cladding on the Cooling Porch ceiling and Chimney. The mix of boards also allows for board spacing to differ slightly without drawing attention. Uniform board sizes make it easier to spot mistakes and the team is keen on hiding those from you.
A Smattering of Details
Because it would be entirely boring to describe each of these details; the TMBV team will just hit the highlights for you. First, the roofing material will be 1/4″ corrugated metal. While Rural Studio is no stranger to corrugated metal, this is a less common type. Being just 1/4″ in depth, this material has the advantages of durability and low price of normal corrugated metal, but with a more subtle profile. Below, you can see just how that ventilated roof and corrugated metal interact with the cypress clad chimneys and drip edge flashing. These were definitely some of the most complicated details due to the aerodynamic shapes of the chimneys and roof.
Next up is the door. Although the Test Buildings will be used as quasi-dorm rooms for 3rd-year students, the team does not want them appearing too residential. Just in case the polygonal shape and hovering nature of the Test Buildings don’t shout, “Experiment!” loud enough the door has got to be different too. The door acts as a punch through the SIPs wall and Internal Thermal Mass to emphasize that one is entering into an active system. This is done by highlighting the depth of the wall with a thin 13″ aluminum frame, slightly thicker than the wall. This detail was unabashedly stolen from the beloved Newbern Library project, the smart detail treasure trove.
And from the Details, a Mock-up is Born
After drawing and redrawing all those tricky details, Steve Long and Andrew Freear suggested the team practice building them before attempting them on the real deal. This is a time-old tradition at Rural Studio known as the mock-up. A mock-up is a condescended version of a building, or a small part of it, that allows students to practice and visualize construction. For example and as seen above, 20k Ann’s Home Project team built a wonderful mock-up where they tested all their cladding and roofing details to scale. The Thermal Mass and Buoyancy Ventilation Research Project team used this mock-up as inspiration when designing their own. You can take a look at the TMBVRP Test Building mock-up construction document set (CD set) below!
Every detail the team solved can be seen in the mock-up. The entire structure will end up being approximately 6′ x 6′ x 10′. The height is a bit substantial for a mock-up but practicing detailing the chimneys at full scale is very important. The team is making framed walls to the same thickness as the SIPs (Structural Insulated Panels) instead of building with SIPs for the mock-up. This will save a lot of time and money. The team finds the mock-up rather cute on paper though it won’t seem so miniature in person. They plan to start building the mock-up soon, but first, need to gather all the real materials they would use on the Test Buildings. It’s important they practice on something as close to the Test Building design as possible.
The Thermal Mass and Buoyancy Ventilation Research team is happy to be down in the weeds of detailing as their research becomes real. Thanks for Tuning in!
Live from behind a stack of full-scale detail drawings, it’s the Thermal Mass and Buoyancy Ventilation Research Project Team! Lately, the team has been investigating all details inside and out. Starting out with material pallet and ending up at chimney flashing, the team is kicking it into high gear.
Unsurprisingly for a project so focused on the interior systems, it was difficult to make decisions regarding cladding. Initially, as seen in previous models shown above, the team experimented with separate cladding systems for the chimneys, Cooling Porch ceiling, and exterior walls. For iteration 1 of the test building design included a timber open-joint cladding system wrapping every surface. Next, for iteration 2, the cladding system wrapped only on the exterior wall faces of the buildings and the adjoining chimney faces. However, thin sheet metal covered the roof, cooling porch ceiling, and the chimney faces which touch those surfaces.
The consistent cladding of iteration 1 appealed better to the monolithic nature of the SIPs structure. It also reinforced the importance of the chimneys to the buildings as a whole from the exterior. From there the team began to test if the timber was the correct mono-material for the test buildings. Seen above are renderings testing different materials for the cladding, columns, retaining walls, and benches. It is important to view these materials as they interact in the Cooling Porch. While sheet metal and polycarbonate cladding options may look more monolithic, timber is a low carbon material that better represents the heart of the project. In some cases, timber as a building material acts as a carbon-sink meaning it stores and processes more carbon than it produces. This of course relates strongly to the passive goals of the Thermal Mass and Buoyancy Ventilation Research.
Recycled Retaining Wall
Now the team is settled on the timber cladding, but they are not convinced of the retaining wall and bench materials. These aspects want to be a more earthen material as they rise from the ground towards the test buildings. After investigating rammed earth and concrete, the team wanted to find something more stackable. Concrete and rammed earth are beautiful, but they require formwork which requires more time. Something stackable will give the team more flexibility as well as members are movable.
Thankfully, down here on Highway 61 road work is being done to remove a load of 8″ x 8″ x 8′ stackable concrete barriers. The TMBVRP team is getting their hands on some of these reusable members and are calling around to local highway departments to find more similar materials. If they find enough, they will have a durable, stackable, and reusable material for their Cooling Porch. They can also use the old sidewalk pieces as a mosaic, ground material for the Cooling Porch. Above are drawings showing the use of these recycled materials.
Structure and Detailing
For the past three weeks, the team has been meeting consistently with Structural engineer Joe Farrugia. He is guiding the team through lots of math to size their columns. While the gravity load on the columns is extremely manageable, the wind load is more difficult. The test buildings height means they will face more wind load than a structure this size typically experiences. However, Joe is confident that the structural system the team has chosen is doable with the correct column sizing.
While the team is attempting to draw every detail of the test buildings, they’ve found the trickiest spots to be around the chimneys. Making sure water moves off the roof consistently and air moves behind the ventilated screen is crucial. The TMBVRP will spare you the pain of walking through each flashing bend and board cut. Struggles emerge when the chimneys converge with the angled roof, but it’s very doable with lots of thinking, drawing, and redrawing. Then Andrew Freear and Steve Long, come in to save the day because how you’ve redrawn it five times is still wrong. Lots of covered wall reviews later and the TMBVRP team is on their way to compiling all the details in a digital model and drawing set.
Looking forward to keeping this momentum going, the TMBVRP can be found in Red Barn from dawn to dusk. Feel free to bring by some late-night snacks but for now thanks for TUNING in!
Live from—wait, is that a 3′ x 4′ concrete panel? Lately, Thermal Mass and Buoyancy Ventilation Research Project Team has been delving into the interior of the test buildings. Inside, Wood and concrete thermal mass line the walls of the test buildings. The thermal masses thickness and surface area are optimally proportioned based on the thermal properties of the materials, size of the room, and ventilation required. This proportioning makes the whole passive temperature and ventilation control strategy tick. Therefore, the TMBVRP team must figure out an elegant solution for hanging the thermal mass to create a beautiful interior which also operates optimally. Let’s take a look at how they are tackling this task. Hint: it involves very big concrete panels …
Typically, designers think of concrete as the go-to material used in passive thermal mass strategies. This is why the TMBVRP team is testing it in the Testing Buildings alongside the more surprising material; Southern Yellow Pine. If you remember from previous posts when the materials are proportioned properly using the Optimal Tuning Strategy they can be equally effective at cooling and creating buoyancy ventilation cycles.
However, when it comes to hanging the two materials on the SIPs walls, Pine is obviously much more straight forward. The pine boards attach to the SIPs panel walls with a simple screw. Well, multiple simple screws. On the other hand, the team will have to get much more creative to secure the concrete panels.
To start, the team tested two strategies hanging concrete panels; masonry anchors and cone form ties. First, they cast the masonry anchors and cone form ties into two 12″ x 12″ concrete panels. Similar to the panels in the Concrete Test Box in size, but different in the attachment system as the security of the panels in the test box is far less crucial as no one will be sleeping in it. Both test panels are attached at all four corners to shear walls in the Red Barn.
Masonry anchors are fluted plastic chambers that adhere to the concrete and are screwed through tp attach concrete to wall. They allow for a connection point that looks as if the screw passes directly through the concrete. However, for the sake of durability, the team would include a washer in this scheme to keep the screw from bearing into the concrete.
Likewise, the cone form ties act the same as the masonry anchor, but are larger in diameter and thickness. Also, they are able to set into the concrete to create a nice reveal. While the team liked the effect of this reveal, team collaborator Professor Salmaan Craig revealed a possible hurdle for the experiment. Revealing edges at the attachment points could slightly disturb the direction of heat transfer. The direction of heat transfer is integral to the strategy which is why the panels are insulated on the back. And, while this is a very small area that could be affected it is multiplied enormously by the number of panels and screws. We call this problem, fastener effect loss. Fastener effect loss assumes, very conservatively, that the small area around the reveal is ineffective to the system.
Next, the team ran the numbers and if all the panels were 12″ x 12″ with four form ties each, 6% of the thermal mass would be lost to faster effect. Now, that’s not bad at all for a real building, and again that’s an extremely conservative estimate. However, for an experiment establishing the most ideal situation for a small building, 6% is not negligible enough. Going forward, if the team prefers the cone form ties, they will need to lessen the amount of panels therefore lessening the number of form ties. Fewer form ties means less fastener effect loss. Fewer form ties also means bigger panels. The team sketched out many different possible panel arrangements but decided they needed to test just how large they could cast a concrete panel. Above on the far right, you will see their biggest panel possible design. This design consists of 3′ x 4′ panels in a running bond pattern.
Next, Jeff and Rowe got to work creating the panels for biggest panel possible design. The estimated weight for these panels is 200 lbs. While this is fairly difficultl for construction, the size of panel cuts down on the number of panels needed from 128 to 39. So while it may be hard to lift, the team would have to make far fewer panels. And the fastener effect loss shrinks exponentially as the design goes from using over 500 screws and form ties to under 200. The question still remains, however, will the panels crack at this size?
To address the issue of cracking concrete panels, the team tested two different mixes for their large panels. If you remember from their blog post on concrete thermal property testing, the team obtained the thermal property data from three different standard concrete mixes. They ended up using the Quikrete Pro-Finsh for the Concrete Test Box, but thought for the large panels they should also try the Quikrete Fiber-reinforced mix. The fiber-reinforced mix is increased in structural integrity which will be beneficial for larger panels by reducing possible cracking. Jeff and Rowe built two form works to test both mixes at the 3′ x 4′ panel size.
Look at that! Both the fiber-reinforced and smooth finish concrete mixes came out great! Very smooth with zero cracks, but very heavy. Above you see the fiber-reinforced panel which turned out just as good as the professional finish and would be much stronger. This does not mean that the team will be using the enormous panels, most likely they will cut them in half. However, the team now knows their largest limit on size is possible. The team will continue to weigh their options between attachment method, panel size, and panel arrangements as they solidify their design. Keep tuning in to see where these crazy kids and their crazy concrete end up!
Live from HomeLab, it’s the Graduate Program! The Thermal Mass and Buoyancy Ventilation Research Project team members are officially Rural Studio master’s students. The team’s summer semester has started off hot with ventilation opening calibration.
Even with the latest ventilation opening adjustment, described in our airflow post, the data from the Concrete Chimney Experiment reveals the airflow is still choked. As you can see in the temperature signal graph below, the thermal mass surface temperature never rises above the interior air temperature as it should in an optimally tuned space. If we then look at the airflow graph below, we see that the updraft, bulk airflow during the night, is nearly double the downdraft, bulk airflow during the day. When the blue line is above zero, the system is in updraft and when below zero it is in downdraft. Both of these graphs allude that the thermal storage cycle and the buoyancy ventilation cycle are out of sync. This is due to a lack of air. Air drives the cycles as it brings warm air into the chimney to be absorbed and offloaded by the thermal mass.
The team examined their previous math for calculating the total area for the ventilation opening. They’ll spare you the gory details, but the predicted bulk air flow rate they were using to calculate the size was too small resulting in a ventilation opening that was too small. Thanks to the airflow sensors they no longer needed to use a predicted air flow rate and instead used the actual average airflow rate coming from the Concrete Chimney Experiment. After this recalculation the ventilation opening nearly doubled from 3/4” to 1 1/8”. The team then let the chimney do her thing for a week.
The data is in and it is as hot as the Alabama asphalt. The team, along with their colleagues were correct in their assumption that the flow was being choked AND the new ventilation opening size is allowing the chimney to operate optimally! In the temperature signal graphs, the thermal mass surface temperature and the interior air temperature properly oscillate. Therefore, the thermal mass is absorbing the heat properly allowing it to be warmer than the interior air at times.
As you can see from the airflow graphs, the bulk airflow of the updraft and the down draft has equalized and is becoming more symmetrical. Both outcomes, in temperature and airflow, reveal there is now a proper amount of air moving through the chimney. The downdraft is still a bit more turbulent than the updraft however and the team wondered if this was due to the concrete pad underneath the chimney releasing heat it absorbed throughout the day. To combat this heat, the team jacked up their Concrete Chimney Experiment… literally!
To raise the chimney, in order to give it some more height via cinder blocks, the Thermal Mass and Buoyancy Ventilation Research Project used car jacks. The team will see if this helps with the heat interference and its possible effects on the air flow.
As you can see Wolfie is still in town on his summer vacation! He and Copper like to observe the team work. To insure their safety as the chimney was being raised they watched from inside the car. They really love the car. For more science, design, and cute pets, stay tuned!