A Dynamic Thermal Network Model Applied to Ventilated Attics

Syracuse, NY

The need for tools to analyze heat and moisture behavior in wooden constructions is increasing with the increasing awareness of the moisture problems. An example of a construction with a history of mould problems is cold attics. Most heat models of attics use a lumped node technique for energy balance and ignore the variation in heat transfer coefficients. A model based on so called dynamic thermal networks has been developed that takes into account radiation between the interior surfaces and the different boundary conditions at the outside and inside surfaces. The first step is to develop analytical solutions for the step responses for the whole attic including a composite roof. The second step is to create a dynamic thermal network based on these solutions. With the thermal network it is possible to do hourly (or any given time step) calculations for several years in a very short computer time which makes it possible to easily test different parameters: ventilation rate, insulation thickness, solar insolation etc. The analytical response solutions also provide good insight into the physics of the thermal problem. A simple parameter study of exterior roofing insulation is presented as an example. The work is part of a large project in Sweden investigating wooden constructions.

https://surface.syr.edu/ibpc/2018/MS8/1