Evaluating the performance of installed equipment can be intrusive and time consuming. The WCEC has two projects focused on developing tools and techniques aimed at simplifying these measurements.
In the first project, the WCEC is developing a simplified screening tool for duct and envelope leakage. The process involves placing temporary temperature, relative humidity, and pressure sensors in strategic locations in a building and monitoring these parameters over several days to diagnose air leakage issues.
- The duct leakage measurement detects mixing of air streams based on tracking the absolute humidity of air in various locations. For example, the cold supply air in a building’s HVAC system has lower absolute humidity than the occupied zones; in an open ceiling plenum return one would expect similar humidity conditions at the return shaft as in the occupied zones.
- Air leakage from the supply ducts is detected by evaluating the absolute humidity in each of these locations.
- For the envelope leakage measurement, small changes in building pressurization due to outdoor flows for ventilation of the building are measured. A one-time estimate of ventilation flow into the building along with the building pressure signal enables envelope leakage to be evaluated.
For the second project, the WCEC is developing a low-cost, high-accuracy, and easy-to-use ventilation screening tool. The goal for this tool is to provide building owners or managers with a new, low-cost data source for identifying and troubleshooting ventilation related issues. The ventilation air screening tool consists of wirelessly connected carbon dioxide (CO2) sensors that are temporarily distributed in each zone and a web-based user interface to record, visualize, and analyze the data. The basic concept is to operate the ventilation system as designed, elevate CO2 levels in the zone and observe the decay of interior zone CO2 levels as they approach outdoor levels. Using this method with distributed CO2 sensors allows us to directly measure the ventilation rate for each zone simultaneously.
Work on the simplified screening tool for duct and envelope leakage is funded by the Department of Defense ESTCP program. The simplified screening tool is being applied at 10-15 buildings to validate its use across buildings of different sizes and different types of HVAC equipment. This project is also testing alternative hardware setups, such as battery powered sensors and the use of absolute pressure sensors for detecting building pressure relative to outside. Out of the 10-15 buildings, one will be chosen to perform an envelope and/or duct sealing retrofit to evaluate the impact on site energy use when sealing air leakage.
Work on the low-cost, high-accuracy, and easy-to-use ventilation screening tool is funded by the Office of Naval Research and sponsored by Naval Facilities Engineer Command – Northwest. A minimum viable product of the wireless CO2 sensor and web-based user interface are being developed and improved based on stakeholder input. By the end of the project, the ventilation screening tool will be tested in the laboratory, in UC Davis campus buildings, and finally in Naval Facilities buildings.
The WCEC completed a project led by XCSpec for the National Institute of Standards and Technology that validated the simple envelope and duct leakage screening tool. That work was also the focus of a UC Davis Energy Systems graduate student Master’s Thesis. The project found that the screening tool was able to measure envelope leakage to within 5% of the standardized test result and duct leakage to within 17% of the standardized test result.
Sponsors: NIST, DoD ESTCP, Office of Naval Research