natural ventilation

Back in Business

The Mass Timber Breathing Wall Research team has been in quarantine for the past several months, but they’ve kept themselves busy. The summer was spent finishing up experiments, carefully documenting data, and finally writing and submitting a paper on their research to a scientific journal for peer review. The team is currently waiting to hear back from the journal, but keep an eye out for a future post with details!

Now that a new semester has begun, the team is back on site (following COVID-safe protocols!) and finishing up the two mass timber test buildings on Morrisette campus. After sitting under a tarp for a few months, the pods needed a little TLC. But one of the benefits of stacked timber construction using threaded rods is the ability to take the building apart again – which is great for test buildings that may need to be altered in the future. The team (plus our volunteer, honorary teammate, and Rural Studio graduate student, Charlie Firestone) unstacked, re-braced, and re-stacked the walls and ceilings for both pods over the course of two weeks.

Once all of the wood was up, steel plates and angles were threaded on along the ceiling and floor to evenly distribute force from the threaded rods. The walls were tightened down, and lag screws driven through the thinner North and South walls to pull the corners tight. A layer of sill seal (a compressible gasket) in all of the joints ensures that any gaps or irregularities are sealed. Finally, a couple coats of spar urethane sealant protects the pine from moisture and mildew.

Switching material palettes for the roof, a steel space-frame spans over and between the two timber ‘boxes’ to support the corrugated metal roof. The team fabricated all of their trusses last year in Birmingham (thanks again to Turnipseed International and the guys at the shop!), so they were ready to go up as soon as the wood was sealed. It was a long morning in the Hale County heat, but with the help of Prof. Steve Long and the Bobcat everything went up smoothly. Purlins were welded in place, and corrugated sheet metal will be going up soon!

Since the days get so hot here in the summer, afternoons have been spent doing prep work for the next day and finishing interior details. The lofts (which are centered over the space to prevent asymmetric airflow) were installed, resting on ledgers which run along the east and west structural walls. Railings and ladders – fabricated from 1” steel tubes – were screwed in place.

The last few tasks are installing the roof metal, doors, a metal grate walkway that runs along the front of the two buildings for access, and lighting and electrical. Stay tuned for updates on the paper, and finishing details on the two test buildings!

Constantly sweating,

The Master Builders

Soundtrack: We’re Still Here | For Giants

New Cat, New Data, New Designs

Live from HomeLab it’s the newest member of the Thermal Mass and Buoyancy Ventilation Research Project team, Sonic! More on our scrappy, little intern later, we’ve got fresh Wood Chimney Experiment results.

Longhaired black kitten shining in the sun

TMBV Research Project’s last post discussed equalizing the environment of HomeLab to improve the accuracy of the Concrete and Wood Chimney Experiments. While the screen on the eastern side is blocking direct solar radiation, the team discovered a new heat source. The roof of the carport is significantly hotter, even on the underside, than the team thought. This was discovered while trying to understand the Chimney’s airflow data. To show how trapped heat can affect the experiments we will take a look at the long-awaited Wood Chimney Experiment Data.

The above airflow data was taken from the first week the Wood Chimney was up and running and shows both updraft and downdraft. Automatically, the Optimal Tuning Strategy is validated for wood, as well as concrete, by the existence of both airflow directions within the experiment. Go, Wood Chimney, Go! However, the updraft is nearly twice as strong as the downdraft which did not quite make sense. The team looked back to their thermal imaging photos for an answer as to why there is such a large difference between the updraft and downdraft.

The thermal imaging photos show that the top of the Wood Chimney Experiment is much, much hotter than the side of the chimney. This can cause a build-up of hot air at the top of the chimney which explains why downdraft is so much lower. While in downdraft, the air is brought in from the top and expelled out of the bottom of the chimney. It works the opposite in updraft, bringing air in from the bottom and expelling out of the top of the chimney. If there is much more hot air at the top of the chimney, that causes turbulence, making it harder to bring in air during downdraft and too easy in updraft. So what is causing this heat at the top? The HomeLab ceiling!

The team learned, from the thermal images above, that the ceiling of the carport was nearly 120 degrees Fahrenheit, which clearly was the reason for the heat build-up at the top of the Wood Chimney Experiment. To combat this the team stapled a radiant barrier to the rafter of the carport to insulate and reflect heat away from the tops of the chimney, trapping it at the ceiling. The radiant barrier is made of Reflectix insulation which looks like shiny bubble wrap. In the thermal images, you can see the radiant barrier lowers the temperature above the chimney by nearly 10 degrees.

The radiant barrier works! Both the thermal images and data show that the excess heat at the top of the chimney was increasing the updraft and making the downdraft more turbulent. The top surface of the chimney also dropped 8 degrees. The amount of air per second is now mirrored in updraft and downdraft at about 0.05 l/s.

in the last post, the team left y’all with thoughts on a “Human Scale” experiment, to test the Optimal Tuning Strategy and App at a larger scale that can be experienced. After a discussion with the entire Thermal Mass and Buoyancy Ventilation Research Project team, including partners at McGill University and Rural Studio faculty, everyone found the Human Scale experiment is not necessary to validate the Optimal Tuning Strategy. The data from the Chimney Experiments is primo and the team can move on to designing a permanent, Inhabitable Structure. The Inhabitable Structure will be a usable example of the effects of coupling thermal and buoyancy ventilation in a building as well as being a mechanism for producing data. Rural Studio will be able to use the spaces on the day-to-day, but it will also show people the system works and can be applied in the community. While the team has thoroughly enjoyed learning about design through crafting an experiment, they are excited to get back to architecture! There is still plenty of science to come, don’t be fooled.

Balancing science and design seemed like too big a job for 4 students, 2 cats, and a Copper so the team hired a new pet intern. Meet Sonic! He was found at just 4-weeks old out on a county road with only his thoughts and half a tail. As you can see, he is getting along great with the other interns and doing some great sketching. Stay Tuned for updates on Inhabitable Structure design and the teams myriad of four-legged friends.

Thermal Imagination

Live from HomeLab, it’s time to evaluate our experimental environment! While the Wood Chimney Experiment racks up data, the team is trying to better understand the thermodynamics of their Lab. Of course by “Lab” the Thermal Mass and Bouyancy Ventilation Research Project Team means their carport. Let’s get into it!

Quickly after building the Wood Chimney the team noticed sunlight hitting it’s lower half in the early morning. Although a small amount of morning sunlight will not stop the Optimal Tuning Strategy from cooling and ventilating the Wood Chimney chamber, it creates unequal conditions between experiments. One of the objectives of this research project is to understand if southern yellow pine is comparable to concrete as an internal thermal mass material. Due to concrete’s thermal properties, it is consistently used as a thermal mass material. If the team can prove that wood can also be a consistent thermal mass material when sized correctly the rural south can utilize their natural resources to provide not only structure in builds, but temperature and ventilation control. Therefore, these experiments need to have equal conditions.

The first step in creating a more equal environment was building a shade structure for the low, eastern light. Made of dimensional lumber and an extra blue tarp, the shade screen blocks any direct sunlight from hitting the chimney while allowing air to enter the bottom of the chimney. This will equalize the amount of heat from direct sunlight, also known as radiant heat, the Concrete and Wood Chimney’s experience. However, the radiant heat on the eastern side of the Lab, shown on the left above, experiences may lead to higher ambient air temperature around the Wood Chimney.

To understand if this is having a significant effect on the Wood Chimney in comparison to the Concrete Chimney the team got out the FLIR thermal imaging camera. Thermal imaging is simply the process of converting infrared radiation into visible images that depict the spatial distribution of temperature differences in a scene viewed by a thermal camera. This will help us understand the distribution of heat in the lab. From the thermal imaging photos, we can see the difference in temperature in the Lab. The eastern side, on the upper left, because of the radiant heat from the sunlight stays consistently warmer. The western side, on the lower right, is cooler than the rest of the space because it is mostly shaded from any sunlight. Also, due to the size of the Lab, there is clear heat stratification. As heat rises, it gets stuck under the ceiling. While this environment is not detrimental to the experiments, the team is hoping to be able to move the experiments to the Fabrication Pavilion on Morrisette Campus. There, the experiments will have more consistent shade in a much larger space. The larger space will make a more consistent environment as heat will stratify farther away from the top of the Chimneys.

The team has also begun thinking about their next scale of experiment. They want to test the Optimal Tuning Strategy at human scale. This means the space needs to be large enough for someone to experience the cooling effects as well as see what an internal thermal mass looks like in a space. Scaling up, besides being experiential, will also seek to prove that the Optimal Tuning Strategy is truly proportional and applicable for public buildings. The team has to consider what proportions of space will make the Human Scale Experiment data comparable to the Test Chimney data. This is not so straight forward as they need to make sure the experiments do not become too tall or tight as to impede quick, safe construction as the Human Scale Experiment will be a temporary structure for testing. The Thermal Mass and Buoyancy Ventilation Team is using the Optimal Tuning Application to design the Human Scale Experiment at this schematic phase. The application was recently published by Wolfram Demonstrations Project! The team will soon do a post on understanding and using the app.

Thermal image of Dijon the cat

Last, but not least, here is a thermal image of HomeLab mascot Dijon. No conclusions were made about Dijon based on his environment. Keep Tuning in as the TMVRP team works from HomeLab!

Wood you believe we did it?

Timber pun prepared and deployed? Scientific apparatus built? Yes to both! Live from HomeLab, the Thermal Mass and Buoyancy Ventilation Research Project team is proud to present to you, the Wood Chimney Experiment! No science lessons today folks, just photos.

Students posing with their test chimneys.

SPOILER ALERT! On the left, you see our tried and true, the one who taught us so much, the Concrete Chimney Experiment. On the right, the Thermal Mass and Buoyancy Ventilation family welcomes their newest member, the Wood Chimney Experiment. Now let’s look at the building process.

The top and bottom insulation blocks are created by adhering two 6″ x 3′ 7″ x 3′ 7″ to make them 1″ thick. If you would like a reminder on why this insulation is necessary for the experiment phase and not necessarily for an actualized building you can read this post. The airflow cones are carved out so that they align with the airflow opening of the chimney interior chamber.

Here we’ve got the chimney walls coming together! Four sandwiches of ZIP sheathing, GeoFoam, and Wood Thermal Mass Panels all attached to create an interior chamber.

Three walls up, the fourth needs its sensors! The TMBVRP team thinks it would be absolutely wonderful to be in a space surrounded by edge grain wood that is also naturally ventilated.

The Sensirion airflow sensors will also be in this experiment. Incorporating how sensors can be attached within the chimney and their cords can make it out of the chimney without being squished is a crucial part of the design.

Before the Wood Chimney Experiment interior chamber is sealed, the fourth wall containing the temperature signal sensors must be attached. The temperature signals, read about temperature signals here, will be sensed with thermocouples and heatflux sensors. Next step in the process will be building up the insulation surrounding the interior chamber.

The Thermal Mass and Buoyancy Ventilation team is aware they used to refer to these scientific apparatus as “Desktop Experiment’s”. Technically the inner chamber could stand on a desk, but a more appropriate name might be Carport Experiments or Taller than the Team Experiments. Let’s just call them the Chimney Experiments for clarity. These experiments are still the first and smallest experiments for the scalable Optimal Tuning Strategy. And look, the Wood Chimney Experiment is done! Batt insulation and 2″ GeoFoam walls encase the interior chamber and ZIP tape is used to seal the entire experiment.

Students posing with their test chimneys.

Thank you to all who have encouraged and supported the Thermal Mass and Buoyancy Ventilation team! The team is very excited to have reached this point, but the work is no where near over. It will take time to learn a new data retrieval and analysis workflow for the new sensors. The team is excited to get to it, but first we are going to celebrate our Wood Chimney Experiment! Cheers y’all and STAY TUNED!

Preparing a Timber Pun for a Post Title

Live from HomeLab, it’s Wood Chimney Experiment preparation. The Thermal Mass and Buoyancy Ventilation Research Project team members are continuing their efforts to refine a passive cooling and ventilation system which can be deployed to public buildings in the rural South. Due to the fantastic results from the Concrete Chimney Experiment, the team is starting the Wood Chimney Experiment. They have developed an experimental method for designing and building chimneys which test the Optimal Tuning Strategy. They also have honed their data collection workflow and analysis. Now they can move on to testing how timber can work as a thermal mass. You can read about why we are using mass timber as a thermal mass here.

The first step in Wood Chimney Experiment preparation is gathering materials. The team collected sensors that the Mass Timber Breathing Wall team is no longer using. Rural Studio has been growing its scientific equipment stock which allows for reuse between research projects.  The TMBVRP team is inheriting data loggers, heat flux sensors, thermocouples, power supply, and airflow sensors. They will be using different temperature sensors, thermocouples and heat flux sensors, then are used in the Concrete Chimney Experiment. These sensors, like the GreenTeg Go Measurement System, will still deliver the proper temperature readings. This equipment is flexible and adaptable making it easily reusable between projects.

Sensors and power source for wood chimney experiment.
Reduce, Reuse, Re-sense!

Next, you might remember the team’s good friend, GeoFoam. GeoFoam is a type of dense expanded polystyrene foam usually used for earthwork under roadways. Both research teams have been able to use it as insulation for their experiments after the geofoam was donated to the Studio from a construction site. Remember, the team must cut smaller sections of GeoFoam from a huge 8’ x 4’ x 4’ block using a hot wire. The team was able to do so underneath the Morrisette Campus Fabrication Pavilion for a designated time and with faculty approval to ensure safety during the pandemic. They collected the rest of the batt insulation from storage in Brick Barn as well as materials for the structure of the experiment. Everything was hauled back to HomeLab for construction.

Next, the Thermal Mass and Buoyancy Ventilation team continued cutting down and shaping openings in the Geofoam. The top and bottom pieces of the chimney are made of two 6” thick pieces of GeoFoam that are adhered together as 1’ of insulation is needed for the proper U-Value for testing. The top and bottom pieces have cones carved out to ensure proper airflow. Resident King of Precision, Jeff Jeong, double and triple checks each piece of foam. This way the Chimney comes together like an airtight puzzle.

The base for the chimney is constructed out of 2” x 4” lumber and plywood. The legs of this base are taller than the Concrete Chimney Experiment to match its height after being raised. Another difference in the design of the experiments is the walls of the interior chimney which the wood panels will be attached to. The walls for the Concrete Chimney Experiment are, from the chimney chamber outward, concrete panels, insulation, plywood, and then more insulation. The walls of the Wood Chimney Experiment will be pine panels, insulation, ZIP sheathing, and then more insulation. Notice Dijon doing his best to help in the photos below.

Last, but not least, is pre-drilling holes for the concrete panels. The concrete panels will be screwed to the insulation, ZIP sheathing wall. There will be four walls to complete the chimney. Notice the grain direction of the panels. This edge grain allows for parallel heat transfer between the air within the chimney chamber and the pine panels. Not only is the Thermal Mass and Buoyancy Ventilation Research Project testing if timber works as a thermal mass but how the grain direction affects its efficiency as a thermal mass.

The Thermal Mass and Buoyancy Ventilation Team is excited for the Wood Chimney Experiment to come together. So are the kittens! The team would not leave you without a HomeLab mascot update. While Dijon mostly naps, Rosemary is trying to get some construction experience to build her resume. They’ve had to tell her she is not OSHA certified, but she is fine napping a safe distance from construction now. It was not a hard sell. Stay Tuned to see the completed Wood Chimney Experiment!