Characterization of the Kit Cook Ductwork System

The Covid-19 pandemic triggered a massive transition to remote work, leaving cities with millions of square feet of unused office space. Simultaneously, housing prices soared. These unused office spaces have the potential to become low-cost homes. Kit Switch is a start-up that brings prefabricated modules into vacant spaces, transforming them into livable homes. Kit Switch has not outfitted their kitchen module product, Kit Cook, with a ductwork system to guide contaminated air to a building’s exhaust outlets. Since each building has unique room layouts, it is not feasible to design a one-size-fits-all ductwork configuration.
We characterized Kit Cook’s range hood (IN-R100 Hauslane Recessed Range) to derive a relationship between back pressure (psi), the resistance to flow, and airflow (cubic feet per minute or CFM). During experimentation, we tested a galvanized steel ductwork system to failure, or below 100 CFM, by adding bends and duct lengths to increase back pressure. We measured airflow at the duct end. To characterize until failure, with airflow under 100 CFM, we had to supply extra resistance via mesh gauzes in between duct lengths. In a configuration with Kit Switch’s specified maximum ductwork length of 20 feet, 7 90-degree bends, and 3 gauze layers, we reached failure at 87 CFM. With data from our zero-bend control configuration to the failure scenario, we plotted a performance curve of back pressure versus CFM, which predicts that failure occurs when back pressure is 0.0213 psi. To mitigate leakage, we assessed the efficacy of the caulking method, an industry standard. After comparing airflow in configurations with and without the caulking method, we found that the method does reduce leakage. Finally, we performed deflection tests on 10 feet of 18-gauge duct, the industry standard thickness. We suspended this duct with supports at 4-feet intervals and determined if the ductwork sagged more than 0.5 inch—maximum values permissible by code. Qualitatively, there was no deflection, suggesting that the 4-feet standard is acceptable.
To deliver the configuration limitations in a user-friendly manner, we developed Kit Check, a spreadsheets tool for installers. A user can input the bend number of a predicted ductwork configuration and compute values indicating back pressure and airflow. Lastly, we prepared Kit Guide, a simplified installation handbook that includes methods and codes we learned during background research.