What is a convective loop, and why does it affect walls?
We specify R-vlaues for our wall systems, and if we try hard, we also apply a level of airtightness to our wall system. This strategy is good but it’s not the whole story of heat transfer. If the insulation is installed poorly, (batt doesn’t touch a surface on all 6 faces) or is the batt lacks density, convective looping can occur.
Convective looping happens when a difference in pressure is caused by a temperature change across a wall, with air constantly moving in a loop from hot to cold. If the outdoor temperature is cold and the indoor temperature is warm, as seen with a winter condition, then the convection loop will occur in a clockwise direction. When the temperature conditions are reversed so will be the direction of the convective loop.
The lesson is to install insulation with a resonable density, and to make sure all 6 faces touch a surface. Splitting the batt around pipes and wires helps.
My friends at Construction Instruiction have a couple of simple videos iluustrating the convective looping effect. Click on the links below.
https://constructioninstruction.com/video/convection-wall-loop-winter/
https://constructioninstruction.com/video/convection-wall-loop-summer/
