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.
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.
Wood Chimne Airflow Graph
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.
Top of Wood Chimney 
Side of Wood Chimney
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!
HomeLab ceiling 
HomeLab ceiling w/ radiant barrier 
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.
top of chimney before radiant barrier 
top of chimney after radiant barrier Airflow data without radiant barrier 
Airflow data with radiant barrier
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.