R Value vs. Thermal Mass

One of the first questions we are asked by customers when they visit a model home is “What is the ‘R’ value of your logs?” However, the method by which the energy of logs is measured is ‘Thermal Mass’ and not ‘R’ Value. 

Here are a few references to help you  understand the differences:

  • R–value measures how well a building’s insulation can prevent the flow of heat into and out of the home. Having a higher R-value means you achieve a greater insulation performance, which means more savings on your next heating and cooling bill.
  • Thermal Mass is a material’s capacity to absorb, store, and slowly release heat over time.

Back in the early 1990s, the Log Home Council (LHC) set out to prove two things:

  1. Logs have a thermal mass because of their cellular structure, bulk, and thickness.
  2. This thermal mass provides significant energy saving benefits because it releases heat back into the house when temperatures drop.

The LHC’s first study compared heat loss through alog wall to a conventional framed wall. They found leakage occurred in the same places as a framed house, at the peak of cathedral ceilings, around window and door frames and at tops of walls. As a result, the conclusion was leakage was not due to the log walls.

The second study concluded that the thermal mass of log walls does significantly reduce energy use for heating in cold climates.

This means that after 13 years, the Nations Model Energy Code finally recognized the energy conservation benefits of thermal mass. This recognition was the goal of the LHC a part of the Building Systems Council of the National Association of Home Builders (NAHB).

Have questions? Contact us. We’re here to help.

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