New Spin On 159yearold Tech Could Easily Visualize Air Leaks In Homes
No one wants to live in a drafty home, but finding a serious air leak in your home can be a daunting task. Now scientists have found a much easier way to do this, using a technique dating back to 1864.
Today, the modern "impact test" is one of the most popular methods of assessing the tightness of a house.
This involves placing a fan on the outside door of the house and then using that fan to draw air out of the building. This reduces the air pressure inside the house, allowing the high-pressure air outside to circulate as quickly as possible. This large flow of air is captured by an infrared camera or a non-toxic smoke called a smoke stick.
Looking for a simpler, less invasive alternative, scientists at the US Department of Energy's Oak Ridge National Laboratory (ORNL) turned to a 159-year-old technique called Schlieren photography. Although the exact working principle is quite complicated, it is a process that makes it possible to take pictures of liquid flow that is invisible to the human eye.
A special type of Schlieren photograph used in the ORNL system uses small shifts in the background of some images to show an air leak that is not at the same temperature as the surrounding air. With normal camera output, these changes can be perceived as flickering patterns, similar to mirages on hot, asphalt roads.
The setup has been successfully tested in sunny and overcast conditions on brick, concrete and vinyl siding blocks, with a ceramic heater blowing warm air through a small crack in the material. So far, the system requires a temperature difference of 12 to 15°C (22 to 27°F), but lead scientist Philippe Boudreau hopes to reduce that difference to 5°C (9°F).
"We know that the context-driven Schlier approach is robust to leak imaging at specific temperatures and now shows promise for quantification as well," he said. "We will continue to measure airflow, but so far the results have been generally positive."
You can see the airflow in the video below.
Overview of Schlieren's optical technique with focus on the background.
Source: Oak Ridge National Laboratory.
