Thermal Mass & Buoyancy Ventilation Research Project

Getting Down to the Details

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.

Cladding Material

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 Patio 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 patio 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 Patio. 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 Patio. They can also use the old sidewalk pieces as a mosaic, ground material for the Cooling Patio. 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!

Concrete Content

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!

A Moment in Time

The Thermal Mass and Buoyancy Ventilation Research Project Team have a new design approach which is moving the design along swiftly and with confidence. The team struggled to create cohesive or decisive designs, each member picking small bits of the project such as the cladding or the siting without looking at the total package. While this felt like progress, it was more of going through the motions than collaborative design. Then Andrew Freear threw them a lifeline; draw the whole building(s) in ‘a moment in time’.

sketches of cooling patio seating arrangements
Cooling Patio seating arrangement sketches are everywhere

The team was to design and choose the best options at that moment for cooling patio arrangement, structural system, site, cladding material, etc. Next, they were to draw and model the whole thing out, details, and all, as a team assuming the chosen parameters. After the team could really evaluate, decide what works and what doesn’t, and design again. Well, Andrew must have had something in his tea that day because the TMBVRP is now on the fast track. In the past two weeks, the developed four design iterations, built two models, and two mock-ups on Morrisette Campus. Let’s take a look at the process and where the design is now!

Iteration 1

iteration 1 model photo showing full length of super shed
iteration 2 1/4"=1' model birds eye view

For the first full design, the team chose the site at the east end of the Supershed. This is a much dryer location than the previous “Two Trees” site. The Test Pods, in this arrangement, act as an extension of the Supershed by mimicking the slope of the roof. By mirroring and offsetting the pods, both rooms have a view from the doorway looking out over Morrisette campus. This offset allows for the access stair to tuck down the side. The walkway between the pods holds them apart and gives a view of the sky from underneath in the Cooling Patio.

Next, the team explored a vertical, ventilated timber siding. This open-joint cladding system shades the SIPs (Structural Insulated Panel) structure from solar heat gain and wraps both chimneys. The structure supporting the Test Pods, while elevating them 10′ off the ground, was a steel frame attached to columns. This steel frame was able to slide underneath both pods between the Downdraft Chimneys. The relatively light steel columns highlight the cantilevered pods. The 1′ thick SIPs’ floors on each pod act as one large beam able to span across the steel structure while distributing the building’s load. All of this allows for an uninterrupted space for the Cooling Patio while making the two pods appear to float.

Reviewing this iteration, the team decided the Cooling Patio head height was entirely too tall for a small gathering space. There is also little interaction with the Downdraft Chimneys in this first scheme. The project collaborators suggested the doors not be above the Downdraft Chimneys to mitigate airflow disturbance. They also pointed out that vertical cladding is less successful for shading than horizontal. With internal and external feedback the team got to work on a new design.

Iteration 2

Iteration 2 plane

Iteration 2 started with moving the doors from in front of the Downdraft Chimney opening in the pods. This drove the rest of the design because the roof angle is always tied to the chimney locations. The Updraft Chimney, the one on attached to the roof, needs to be on the high side of the sloped roof. This way rain and debris cannot pool around the Updraft Chimney. Also, to distrubute airflow as evenly as possible, the chimneys need to be as far apart as possible. Therefore the Downdraft Chimneys must always correspond to the low side of the roof slope. Switching the roof angle to an “anti-Supershed” slope, allowed for the Downdraft Chimneys to move out from underneath the doors, while keeping the same mirrored, offset pod arrangement.

Whew, the team got the pod arrangement and door to chimney relationship fixed, but they created another problem: structure. The structural steel frame would no longer be able to fit in between the Downdraft Chimneys. So, the team thought to take full advantage of the structural possibilities of the very thick SIPs and attach the columns directly to the underside of the floor. While at first, they thought this would be impossible, their contact at a SIPs manufacturer told them it is done quite often on hunting blinds. “The hunting blind” will go on the long list of nicknames referring to the strange yet recognizable form of the Test Pods. The Tree House, The Periscope, The Wind Catcher….

The cladding, stair, and roof material all took a turn. While the stair and cladding changed direction, the roof material changed from membrane to metal. The roof metal also became the underside material and wrapped corresponding sides of the chimneys. The exterior cladding now acted as a fence around the outer edges of the pods while the metal appeared to wrap underneath. The Cooling Patio height dropped to nine feet, which still seemed a bit high. The team had a good feeling about iteration 2. Mostly, it directed them to give more attention to the Cooling Patio. How does it feel to be in that space? It was also time to see how these Test Pods really looked on Morrisette Campus, not just in model.

Iteration 3

Students level with eachother

First, photomontages, collages of model photos and site photos, were created to get an estimate of just how big these pods look on site. The results are in: the pods are pretty dang big. There was also a slight column movement from the last iteration, but that’s a very boring drawing. These images really got the team thinking they needed more visualization. So it was time to build a mock-up.

This one-day mock-up tested the height of the Cooling Patio space, seating arrangements, and pod siting. The columns are accurately placed and support a frame that represents the underside of the pods. This gives the relative ceiling height of the Cooling Patio. The team first built the columns and frames to give a head height of 8′ 6″. They pretty immediately lowered it to 7′ 6″ as it still felt too generous for an intimate space of gathering.

The mock-up helped to establish an undercroft ceiling height but revealed some disfunction between all of the elements in the space. The team needed a more robust mock-up to understand how the retaining walls, seating arrangements, columns, and Downdraft Chimneys interacted. Plus, the team had a really good time building. It was off to Lowe’s for Iteration 4 and Mock-up 2.

Iteration 4

Before getting to Mock-Up 2, let’s address lateral load. While the columns can be specified to support the weight of the buildings, what will keep the Test Pods from tipping over in the next high wind storm? For iteration 4, the idea was to tie all the columns together underground in the foundation. That foundation than extruded upward to become the retaining wall and the support for the seating. Seating as a way to gather around the cool-air chimneys, which act as spacial barriers, drove the placement of the walls and columns. The resulting design was translated to Mock-Up 2.

The biggest worry about iteration 4 was the distance between and size of the chimneys. However, sitting in the complete Mock-Up 2 space, the chimneys did not feel too crowded or large. Instead, they felt like the integral feature they are. They divided the space into three but still allowed for continuity, through access, and visibility. The space between the chimneys is more compact and private while the larger spaces at the Cooling Patio entries allow for gathering.

The ground to sky connections really began to stand out in the photomontages of iteration 4. This brought to mind both material pallet and column placement. While the team originally thought the benches in the Cooling Patio might be light, thin material, it became quite clear it should be something heavier. This way the Cooling Patio is clearly an element of the ground, while the pods are an element of the sky. This idea also brings into question whether the columns always hitting the foundation/retaining wall perfect actually makes them stand out more. A regular, orthogonal placement, while still keeping clear of the gathering space, may make the columns somewhat disappear.

The Thermal Mass and Buoyancy Ventilation Team is moving on to iteration 5, 6, 7, on and on. They are enjoying their new design process as the idea of building these two floating experiments becomes more real every day. Next up, the team is taking a deep dive into the interior of the pods. Thanks for reading and don’t forget to take it one moment at a time and STAY TUNED!

Citing, Siting, and Siding; All exciting!

Exciting news, the Thermal Mass and Buoyancy Ventilation Research Project Team have published their Chimney Experiment data onto an online data repository! The team has uploaded data to the Craig Research Group Dataverse through Salmaan Craig at McGill University. Great thanks to the team’s collaborators at McGill, without which this would not be possible.

online data repository interface

The team will continually update and upload data as new data is gathered and past data is analyzed. From there, anyone can download and review the raw and analyzed data for both the concrete and pine experiments. This data is a citable source for any publication investigating the passive cooling strategy. There is also an experiment guide available to download which details the design of the experiments. Using this guide others can replicate or improve upon the experimental setup. This process is great practice for the team as they start writing a scientific paper about their experiments for a peer-reviewed journal. Now for some good ole design talk!

The TMBVRP team decided the experiment is best served as a free-standing structure although they loved utilizing the SuperShed as a super roof and a superstructure. The experiment needs a little extra room to breathe and ventilate than the Supershed can provide. The question remains, where do you place a giant occupiable cooling chimney so it sticks out just enough? Not quite a sore thumb, but definitely not a wallflower.

Along with possible sites for the pods, the team is investigating the use of berms. Why berms? The cooling patio will likely be an excavated area so cool air from the chimneys will sink and collect. This space needs some sort of semi-enclosure to help trap the cool air. Therefore the excavated dirt can create berms, trapping the cool air while providing shade and seating. The berms can also divert water so the cool air pool does not become a catfish pond. The team is analyzing sites in proximity to other pods and Supershed while giving each location a fitting suburb names. Right now they are considering two design schemes: Two Trees and East End.

Two Trees would address the “other side of the street” created by the Supershed and the row of original pods. This site is most appealing due to the natural shade provided by the, you guessed it, two trees. Thanks to team collaborator and Auburn professor, David Kennedy, for introducing the team to shading and solar radiation software. This software, through Rhino, will show exactly how much solar blocking the trees provide. While the trees are a bonus, the water is not. Water from all of Morrisette Campus drains right through Two Trees. This is also why the team has steered away from a site at the west end, the lowest point on campus. At this location, the team also thinks the pods compete with the Supershed in a strange manner. For these reasons, the team decided to take a look at the East End. East End could serve as a continuation or cap to the Supershed. However, there is no hiding from the sun in this location. Thankfully it is more beneficial to the experiment that the pods receive equal solar exposure rather than partial but inconsistent exposure. The team will continue to evaluate both sites.

The team is currently exploring high albedo, ventilated cladding systems. Albedo refers to the amount of energy that is reflected by a surface. A high albedo means the surface reflects most of the solar radiation that hits it and absorbs the rest. A shading or reflective cladding system, when coupled with the use of SIPs, will allow for the interior system to work unaffected by exterior solar heat gain. Metal cladding is an easy way to reflect radiation. A light-colored timber rainscreen can also reflect heat and shade the structure behind it. The team is exploring both options.

The Thermal Mass and Buoyancy Ventilation Research Project Team is also getting into the structure needed to support the pods, 8′ above ground. To start the team looked at a local precedent: silos. In Hale county, silos for holding catfish and cattle feed are aplenty. They can support up to 30 tons with a light-weight steel structure. Steel manual in hand, the team has been investigating how they could apply a similar structure to lift the pods. This allows for an open space beneath for the cooling patio. Next, the team will investigate the possible benefits of using a wood structure.

The team will keep pushing their citing, siting, and siding ventures forward while living it up in Hale County. They’ve been utilizing the great outdoors for grilling and being grilled in reviews. Livia sometimes misses out on the fun as she is dedicated to the landscaping at Morrisette. For more research graduate student shenanigans make sure you stay tuned!

Lab to Barn, Science to Design

Live from Rural Studio Red Barn, it’s the Thermal Mass & Buoyancy Ventilation Research Project Team! The team, though they might come to miss the cat interns and the AC, is so excited to be back on campus. For health safety measures, the team has an entire studio room to themselves which also acts as a convenient hiding place from Andrew Freear. The TMVRP Team is being as safe as possible as they sorely missed Newbern and the Rural Studio staff and faculty. This week the team will cover their pod design process while bombarding you with design iteration images. Enjoy!

As the Wood and Concrete Chimneys chug along, quite literally, the TMBVRP team have been designing their test buildings. Like the Mass Timber Breathing Wall team’s nearly completed test buildings, the TMBV test buildings apply their research at a small building scale. After some initial testing, the TMBV test buildings can be used as 3rd-year accommodations. The Studio calls the funky dorm rooms for 3rd-years on Morrisette campus “pods.” In true Rural Studio fashion, the design of these pods is an iterative process, but must always be grounded in what is necessary for the experiment. Now, science experiments are not only driven by the hard data we might get out of them. Many experiments are experience-based, especially when trying to describe a phenomenon to the public. Think about going to a science museum, touching the electrified ball and your hair shooting up from your head. Static electricity makes a lot more sense to you when you experience it rather than if you had read data and looked over graphs explaining it. The design of the Thermal Mass & Buoyancy Ventilation pods revolves around both data and experience production. A main objective of the Thermal Mass & Buoyancy Ventilation Research Project, while being rigorously tested for data currently, is for inhabitants to experience the comfort of the cooling and ventilation effects. Let’s journey through TMBV Pod design as the team tries to focus on both experiment and experience!

When massing the general size of the pods, the team can use the Optimal Tuning Strategy app. From the app the team knows the amount of surface area needed for the thermal mass, the thermal mass thickness, and the size of the ventilation openings based on the information they input which is how much ventilation, temperature change, and height the pods need. General massing schemes are quickly generated from these design parameters. The team is creating massing schemes for two to three pods, one with concrete thermal mass walls and one or two with wood ones. These massing schemes also explore whether to share walls in a multi-unit pod or separate the pods to highlight the material difference within. As long as these massings can fit the app outputs, a 3rd-year, a bed, and the sensors we need for testing that’s all of the design work to be done, right? Nah. While these are sleeping quarters for students, they are also examples to the public of how spaces that utilize thermal mass and buoyancy ventilation can feel.

To create a peak TMBV experience, the team is elevating the pods! This will allow for a gathering space underneath the pods where anyone can sit and enjoy the cool air being naturally pumped out of the spaces above. The TMBVRP team calls it, the “Cooling Patio.” Here, students, faculty, or clients interested in the system can experience the effects of TMBV without lingering too long in a 3rd-years dwelling. It also highlights one eventual goal of the work; naturally cooled public spaces enjoyed in the Black Belt. The Cooling Patio is located underneath the buildings because the TMBV system operates in downdraft during the day. This means during the day the air is pushed out of the lowest opening as opposed to at night when the air is pushed out of the highest opening. Therefore in a typical building, you would not need to elevate the structure above the ground, you simply need a low and a high ventilation opening. The TMBV Pods’ ventilation “top and bottom” openings are so literal for both the quality of the experiment and the Cooling Patio.

Why the pod is elevated may now be clear, but why do some of these drawings have such tall chimneys? The exaggerated Chimneys are an experiential detail like the elevation of the spaces. They are not necessary for the experiment or the TMBV strategy to work. A typical building would not need tall Chimneys to utilize Thermal Mass and Buoyancy Ventilation, just as they would not need to be elevated. The tall chimneys are specific to the Thermal Mass and Buoyancy Ventilation Research Project Pod as they highlight the ventilation created by the passive strategy. This is another detail, like the cooling patio, that will work as an experiential demonstration of the research. Increasing the overall height of the structure, beyond what surface area is needed, highlights the ventilation aspect of the system. The elongated chimneys do not increase the amount of air ventilated through the spaces, it does increase the speed of the air as it exits the spaces. The faster the air exits the interior space into the cooling patio, the cooler the patio space will feel. Think of it as the difference between being hot with a fan and without. Moving air always increases the cooling effect and therefore the cooling experience. This increased airspeed will help with explaining how Thermal Mass and Buoyancy Ventilation works as visitors and users will be able to clearly feel the cool air rushing out. Now, the design is focused on three main outcomes: replicating the experiment so TMBV works effectively at building scale; providing a comfortable and useful space for sleeping and demonstrating; and creating a space below the buildings in which people can gather and experience the strategy working for long periods of time. What comes next is siting and about 1,000 other details.

Siting began by looking at various locations around the Super Shed and the existing pods. The Team began exploring the pods as stand-alone buildings. Next, the team explored how they could utilize the roof and structure of the Super Shed. While investigating stand-alone sites, the team also did some surveying of the Super Shed. Both options have benefits. A stand-alone structure would allow for greater height, not being capped by an existing roof, so a more generous cooling patio space and higher airspeed into that space. The existing roof of the Super Shed, however, would provide constant shade and rain protection making it a very similar environment to the Chimney Experiments in the carport at HomeLab. Both have experiential and experimental benefits that the team is still exploring.

The Thermal Mass and Buoyancy Ventilation Team has a lot of hard work ahead, but nothing makes it better than being back in the Red Barn. Seeing the old and new faces of Newbern, even from a social distance, is exciting and motivating. Thanks for Tuning in!