Rural Studio Blog

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!

An Efficient, Resilient, and Healthy Home

The Front Porch Initiative is dedicated to addressing housing quality and affordability in persistently impoverished rural communities. We believe that everyone, rich and poor, deserves a “shelter for the soul.” Rural Studio has spent decades designing and building homes for our rural neighbors that are efficient, resilient, and healthy, and now, we want to expand rural homeownership outside of our service area in West Alabama.

Rural homeowners, especially those in persistently impoverished communities, often struggle to qualify for a mortgage. We can meet this challenge by re-thinking housing affordability, so we’ve asked the question: what can an efficient, resilient, and healthy home afford the owner, lender, and insurer?

Traditionally, housing affordability is addressed primarily by reductions in the cost of building a home, through using less expensive materials or other means of value engineering. Our approach makes housing more affordable not by simply reducing initial construction costs, but instead by also increasing overall building performance. Energy performance, durability, and resilience, and a focus on wellness can better enable a homeowner to pay their mortgage month after month, and year after year—and at no increase in monthly cost to the homeowner.

Simply put, for every $1 a homeowner can afford to increase their monthly mortgage payment, they can finance an additional $200 of building construction costs. So, if by increasing energy efficiency we are able to reduce a homeowner’s monthly energy bill by just $25 per month, we can shift that same $25 to their monthly mortgage payment. Due to the long-term financing of this investment, the homeowner can now afford to finance an additional $5000 in energy-efficient construction with no increase in their total monthly home-related bills.

With the understanding that homeownership is the foundation of financial wealth building, we connect the “first costs” of home procurement (the overall cost of the mortgage) to the “second costs” of homeownership (monthly mortgage, utility, and insurance bills), creating a new paradigm of how a lender might consider the mortgage eligibility of a homeowner. By changing this mortgage paradigm, homes can afford rural homeowners the opportunity for safe, reliable, and efficient shelter. Moreover, higher-quality, higher-performance homes reduce risk to both the lender and the insurer.

Freear Awarded 2020 President’s Medal Tonight!

Join us tonight at 6 pm CST for a special online program as The Architectural League of New York presents the 2020 President’s Medal to Rural Studio Director Andrew Freear! The event will include remarks by Marlon Blackwell, Rosalie Genevro, Paul Lewis, and Billie Tsien, tributes by many friends of Rural Studio from around the country, and Andrew in conversation with Billie and Marlon. ⠀

FREE and open to all – please register in advance via Zoom here.

Raising Chimney

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.

a graph showing two days of temperature signals, where the air temperature falls below the panel temperature
Black = Exterior Air
Dashed Gray = Interior Air
Orange = Thermal Mass Surface,
Dashed Orange = Thermal Mass Interior

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.

a graph showing two days of airflow data, where the downdraft is larger than the udraft
Blue = Bulk Air Flow

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. 

two small white dogs in a car

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!