Question

Can I improve the energy efficiency of my log cabin by adding foam insulation and drywall to the inside of exterior walls?

Asked by John
Sainte Genevieve, MO

I have purchased an 800 sq ft log cabin in Missouri as a weekend home. The old paneling has been torn down and currently the furring strips remain over the exposed timbers. I asked my contractor to have these removed, but he suggests that for energy efficiency--especially for use in the winter-- I should install insulation and drywall over the furring strips. The walls are about 4 inch thick 6 inch tall timbers. But I was concerned that this would prevent the log walls from having their thermal effect, and compromise their natural energy efficiency. Who is right? Thank you for your help! 

Answer

Polly Osborne, FAIA, LEED AP

Answered by Polly Osborne, FAIA, LEED AP

Los Angeles, CA

Polly Osborne Architects

May 2, 2012

Dear John,

While you may wish to leave the logs exposed for aesthetic reasons, there is no reason to leave them exposed to save energy. Log cabins are not particularly energy efficient.

  • Though manufacturers claim they are energy efficient because of the thermal mass, this mass is made of wood, and wood isn't a very good thermal mass.
  • Thermal mass stores the temperature gathered in the day and releases it at night, and vice versa, resulting in a more even temperature.
  • Good thermal mass materials are concrete, stone and water.

Ideally add exterior insulation

Ideally, a layer of insulation on the outside of the building would help hold this temperature and south facing glass would help gain it.

But since you have a nice log cabin, you probably don't want to cover the outside walls with insulation.

Adding insulation inside

Insulation and drywall on the inside is a very good suggestion.

An open cell foam would continue to allow the wall to breath, and that could help to avoid any condensation occurring from the difference between inside and outside temperatures. A building paper between the logs and the insulation might also be a good idea. 

Since the logs themselves will create many voids because of their shape, another solution would be to allow an airspace between the logs and an insulated panel, such as EPS rigid insulation sandwiched on drywall on the interior, with some ventilation between, so there is no moisture build up.

These solutions do not rely on the wood's thermal qualities, but on the quality of the insulation you use.

In the long run, that's a better bet.

 

 

For more information:

Read "I have a log home. Will insulating my interior walls lower my electric bill?" a Q&A answered by Harold Remlinger.

Also, read "What is the value of log construction to meet energy efficiency or other green standards? The logs would be locally sourced." a Q&A answered by Polly Osborne.

Do you have a question about greening your home? GreenHomeGuide invites you to Ask A Pro. Let our network of experienced green building professionals – architects, designers, contractors, electricians, energy experts, landscapers, tile & stone specialists, and more – help you find the right solution.