by Michael Schettine
Posted on Aug 14, 2018
In this short video, water is used to visualize air leakage sites that are present in the majority of framed walls in the US. New regulations require better sealing of houses to reduce air flow in new homes. The main reason 40-50% of builders fail to comply with new air sealing mandates are the air gaps we reveal in this video.
The concept is simple, use water flow to show possible air flow gaps in standard construction. This test site is a typical 24” inch on-center constructed frame wall. As the water is poured into the cavity the leakage is immediately visible outside the building all along the test area. Considering that air is 800 times less dense than water, it is clear that large amounts of air flow will occur in this type assembly. The video does a great job showing that the water flows through nearly as quickly as it is poured. In a wind event air is trapped by the siding overhang that acts like a small soffit trap where the gaps are located. The small soffit directs air intrusion directly into the insulation cavity from below and it travels upward to exit out the top, creating a dynamic air flow (stack-effect) within the wall.
The end result of this air flow is excess energy loss that is largely preventable by reducing or blocking the air flow.
In the video, a small model of a standard frame wall is used to allow the “wall” to be turned upside, showing that the same water (air) flow occurs at the top plate (double plate) as at the bottom plate (single plate). These openings provide a source of dynamic air flow between sheathing back-side and insulation and formation of a stack effect in a completely enclosed building.
This short video uses simple methods to show clearly (times 800% air to water ratio) that with current construction practices large amounts of air flow are possible and likely, even with insulation present. New methods are needed in order to meet the more stringent air flow requirements for new housing.
We encourage you to try this test on your own job site! If you do, and don't mind, please share your results using the form below!