Log homes and energy efficiency

On a recent road trip around the State of Washington, we stayed at a motel constructed of older style Pan Abode buildings built sometime in the late 50’s. 

The structures seemed in remarkably good condition for their age, but the stresses on these structures are perhaps not what they would be in a wetter area of the state–like west of the mountains–in the Seattle area.  The structures seemed well suited to their hot and dry climate.

What I found interesting was the insulating ability of the 4″ thick walls–or their lack of ability would perhaps be more accurate.

This first picture is of the exterior wall.  The red rectangle corresponds to an area at the interior that will be discussed below.

Pan-abode type building

This next picture is what the wall structure looks like.  You can see the double tongue and group shape with the wall being approximately 4″ thick.

Pan-abode type wall structure

On the interior, with thermal camera, the wall and pillow temperatures show in the next two pictures.

Thermal image Thermal image

In this next picture we see the wall with the pillows moved away from the wall to reveal how the wall was “insulated” by the pillows.  The wall, heated up by the direct sun shining on it at the exterior, could not give up its heat to the interior as readily as the other areas of the wall. Thermal imageThermal image

My understanding is that modern Pan Abode structures are a double-wall type of construction that allows for the installation of insulation inside the walls.  This would certainly be required by modern energy codes for both heating and cooling. 

Regardless, these pictures demonstrate very well how poor 4″ of wood is as insulation (about R-4).  By themselves, it would take exceptionally large logs to meet modern energy efficiency standards.

By Charles Buell, Real Estate Inspections in Seattle

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