[Cob] Insulative Values of Cob & Strawclay

[Frank Hanlan]

Hi All,

@ Sky

"Cob can be either, but if you make a tight cob house, it'll outperform a batt-insulated house any day."  Sorry Sky, I don't agree at all and I strongly doubt that any energy efficient builder would either.  Energy efficient builders are building tight would frame houses with .5 to .9 air changes per hour (ach) at 50 pascals which is key together with mass to hold heat and moderate temperature swings.  In these houses they are including whole wall insulation values from R38 to R60, attics from R50 to R100, basement walls from R20 to R40 and under slab from R10 to R20.  Without insulation cob house simply cannot match the performance of these houses.

I certainly agree with and support Christopher's & Shannon's concerns about R values.  I live in Edmonton, AB and in the winter we often get high temperatures of 0 degrees F and less with wind chills from -20F to -40F for days and even 1 or more weeks at a time.  The result is that any exposed wall or wall without thermal breaks would get cold and take a large amount of heat to warm up and keep warm regardless of the amount of sunshine we were getting.  Since we are further north we get fewer hours of sunshine even on sunny days.

If you are looking to super insulate exterior walls and or roofs for both new builds and retrofits I highly recommend Larsen trusses.  Martin Halladay, the Energy Nerd of www.greenbuildingadvisor.com, recently did a great blog post on them.  see http://www.greenbuildingadvisor.com/blogs/dept/musings/all-about-larsen-trusses

Sincerely yours,
Frank Hanlan

Edmonton, AB

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