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Using "Best Practices" with cordwood construction prevents problems.

We would like to thank Doug Kalmer for raising a very important point about cordwood construction (Country Conversation and Feedback, March/April 2006), namely, the problem of air infiltration caused by log shrinkage. Doug is also correct in noting that the bond between mortar and wood is not ideal. Because of this, all necessary precautions need to be taken to minimize this anomaly. Some cordwood builders have underestimated the necessity to generate extremely dry softwood before construction. The current "Best Practice" literature on cordwood encourages (de)barking, cutting to length, splitting some of the wood and then drying it to its lowest possible air-dried moisture content (12% in Wisconsin).

The Eastern Red Cedar (Juniper), while technically a "softwood" (insofar that it is an evergreen), is a dense tight-grained wood and really performs in the wall like a typical hardwood. We prefer to think in terms of "light and airy" woods or "dense tight-grained" woods, instead of "softwood" and "hardwood," because many softwoods can be dense and hard and many hardwoods (such as quaking aspen) can be light and airy. The light and airy woods are preferred because they are more stable (less expansion and contraction) and have a higher R-value.

One of the major focal points of the Cordwood Conference held in Merrill, Wisconsin on July 30-31, 2005, was to catalog a set of "Best Practices" for cordwood builders to follow and a "Cordwood Code Guide Booklet." Both of these were successfully accomplished (Cordwood and the Code: A Building Permit Guide and Continental Cordwood Conference Papers 2005).

Those builders who have had logs loosen have the opportunity to remedy any air infiltration by using one of the various horizontal log cabin chinking products such as Perma Chink or Log Jam. These products are normally used for chinking the spaces between logs in a horizontal log home. They adhere to the wood and move with the wood as it expands and contracts during the year. As good fortune would have it, it also sticks (like glue) to mortar. By putting Perma Chink on any areas where logs have loosened the air infiltration problem is readily solved.

Doug used fiberglass and Styrofoam[TM] as insulation between the inner and outer mortar joints. These materials could have contributed to the infiltration problem. If fiberglass takes on moisture from any source, it may mat down and might not fluff back up again, creating voids. Styrofoam[TM] is virtually impossible to install in the irregular space without creating large voids. It is easy to fill voids with sawdust insulation. Doug says, "I can't imagine how a sawdust-filled cordwood wall would ever dry out if moisture got into the sawdust." The answer is to treat the sawdust with hydrated lime: one part lime to 12 parts sawdust, well mixed in with a hoe. If the sawdust stays dry, fine. If it gets damp, it sets with the lime and creates a light-weight rigid foam type of insulation. We have seen both scenarios when we have had occasion to install new doorways after 25 years at Earthwood. No deterioration of the wood or the insulation.

To address the infiltration problem from a scientific standpoint, a "Blower Door" test was performed on a "Best Practices" cordwood home in the Merrill area as part of writing the Cordwood and the Code document. The blower door tester and Director of the Energy Star Program in Wisconsin (Joe Nagan) gave the following statement in his report: "Cordwood construction itself, did not appear to contribute much to the leakage rate... The infrared scan showed there was not a significant change in the appearance of the cordwood wall due to air leakage while conducting the blower door test. The appearance of the cordwood wall during this winter time blower door testing did not change significantly from light (warm) to dark (cold) while viewed through the lens of the black and white infrared camera ..."

This test, in a cordwood home that was built with Best Practice techniques (which are: post and beam frame; roof applied before cordwood infill; softwood is barked, split and dried to lowest moisture content; slow curing/setting mortar mix used; good tuck pointing of mortar and--after a heating season--any gaps, checks or leakage points attended to with Perma Chink or Log Jam) demonstrates that, if proper planning and preparation techniques are executed, cordwood will meet and exceed the building codes and can provide an attractive, energy efficient, inexpensive alternative home building method. Incidentally, the cordwood in this home was white cedar, much more stable than red Cedar.

Potential cordwood builders need to know that cordwood is a labor-intensive, sweat-equity type of construction. If you have more time than money, this may be the building technique for you. Or not. Investigate any alternative building technique thoroughly, read all available literature, take a workshop, visit a cordwood home, talk to the owners and--if you are still leaning that way--build a practice building to see if cordwood fits your style and pocketbook.

Richard Flatau is the author of Cordwood Construction: A Log End View (2006) amd Cordwood Pole Shed Plans. Cordwood Construction, Merrill, WI; 715-536-3195; www.daycreek. com/flatau

Rob Roy, Director of Earthwood Building School. Author of Cordwood Building: State of the Art, among other titles. West Chazy, NY; 518-493-7744;
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Title Annotation:Alternative housing
Author:Flatau, Richard; Roy, Rob
Publication:Countryside & Small Stock Journal
Date:May 1, 2006
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