I am often asked questions about log homes vs. timber frames using SIPs for the building envelope.
"Are the panels more energy efficient than logs?"
"Can you use any kind of siding with panels?"
My "tongue in cheek" response to comparison questions between log homes and timber frames is that "we're very similar except timber frame homes come without the drafts and flies!" In reality log home construction has come a long way and many manufacturers have come up with various techniques to battle the challenges facing anyone trying to make a tight envelop out of a stack of logs. There are different ways to spline the logs together, bolt, screw, and chinking to help keep them tight and prevent air infiltration or nice little warm insect nests.
In addition log home manufacturers have to deal with wood shrinkage and expansion. Since wood expands and contracts across the grain, then shrinkage is cumulative over many logs in a stacked wall, creating a need to create some sort of air and insect barrier at the top of the log wall as the log wall gets shorter and taller over the seasons since its outside is exposed to the elements and the interior to a more consistent temperature but potentially alternating moisture content.
In a timber frame home the shrinkage is limited since the wood is not exposed to the elements, joinery techniques are employed to avoid shrinkage impact on the exterior skin, and the tightness and stability of the panels help keep insects and draughts at bay. As in any type of home construction (except perhaps adobe and concrete) there is always the danger of termites or ants, so an annual insect treatment is recommended in any timber frame, conventional or log home. See our Owner's Manual for more recommendations on the avoidance of insect infestation in our homes.
So, the answers are:
Yes, panel enclosure systems on timber frame homes are much more energy efficient than a log home due to the increased tightness to air infiltration and the much higher R-Value in walls and roofs. Air infiltration is severely reduced in panel enclosure systems since all the seams, window & door openings and roof penetrations are sealed with spray in foam. In addition there are no repetitive solid wood members like logs or 2x6's in conventional homes conducting heat through the walls. After all wood is a conductor of heat.
Yes, pretty much any siding can be installed in much the same way that it is on a conventionally framed home. Any time you build an energy efficient building it is important to allow the siding to "breath" since we are making the walls so tight there is no inside air to help dry out wind driven rain and moisture that can collect behind the siding. Therefore we recommend to conventional builders as well as panelized home owners that a "rain-screen" be installed behind your siding. Whether that is clapboard, shingles, log siding, or boards the best way to prevent long term moisture presence behind the siding is to install a building wrap such as 15-30# felt covered in material that creates an air space such as "cedar breather", this woven mesh of plastic holds the siding off of the felt and allows air to pass behind the siding drying out any moisture or wind driven rain that might make its way into your wall.
For more information see our Owner's Manual or the Foard Panel website at: www.foardpanel.com and be sure to stop by our booth at the New England Log & Timber Frame Show at the Expo Center at the Radisson in Manchester, NH February 12-14, 2010. Email me for a free pass to the show - limited supply.