Exterior Foundation Insulation Options: To Parge or not to Parge.

With all the hype about rising energy costs, r-value, energy 2000, energuide 80 and so on, R24 is quickly becoming the new code standard for exterior walls.  A stick built home with 2 x 6 studs is now faced with another 2" of exterior, closed cell Styrofoam to meet this code, while log homes in northern areas are now pretty much required to have an 8" minimum thickness.  Energy 2000 and energuide 80 guidelines are currently the way to go when you're looking for ways to prevent heat loss and reduce energy dollar expenditures.  Wall thickness of course is only one part of the energy efficiency equation and not a very significant part at that, when you consider the potential for leaks and drafts around windows, sill plates, roofs and basements.  Doesn't make a lot of sense to increase your wall thickness without addressing the other, more significant, heat lose areas.  One of these areas is the foundation.  There is not a lot of code requirement, that I'm aware of, for foundations, which is a little strange to say the least.  Most new home owners and builders however are quick to realize the value of a well insulated basement and are mainly opting for an R-20 (2 x 4 insulated framing and vapour barrier) on the interior walls and 2" of Styrofoam on the exterior, below grade, walls.  That still leaves two or three feet, or more with walk out basements, of uninsulated exterior foundation walls.  Currently, there is not a lot of information or guidance out there on the web on the best approach to insulate this exposed exterior space.  New, insulated R-10 products are available that imitate everything from stone to timber, however the cost is often 14.00 to 18.00/ sq. ft., and with most walk outs averaging over 200 sq ft + costs can quickly exceed 5 or 6k installed.  At this cost, installing 2" Styrofoam, from footer to sill, and parging is one option that should be explored. 

Our home has a 9 ft basement with exterior Styrofoam insulation from the footer to the sill.  I added another foot of Styrofoam to the top of the standard 8 x2 sheet.  The problem with parging Styrofoam is not necessarily a product issue (will it stick and not crack in sub zero temperatures) but rather the lack of success stories and buyer confidence.  During my Internet research I could not find one single example of someone who used 'styrofoam parge'.  Nevertheless, the cost difference was too great to ignore, not to mention the artifical look of insulated imitations on a log home. Professional masons tell me that with all the bonding agents available today it should not be a problem to find the right parge mix.  In fact, masons often develop their own blend of mixing agents to match the requirement of any finished surface.  While this may not be an option for the DIY crowd, there are a couple of manufacturers who produce a pre mix product specifically for use on Styrofoam.  We opted for a product called Parge Plus by True Foam.  http://www.truefoam.com/.

Here's a few snaps of before and after the application.