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Log Home Basics
Log homes may be
site-built or pre-cut in
a factory for delivery
to the site. Some log
home manufacturers can
also customize their
designs. Before
designing or purchasing
a manufactured log
home, you need to
consider the following
for energy efficiency:
The R-Value of Wood In a log home, the wood helps provide some insulation. Wood's thermal resistance or resistance to heat flow is measured by its R-value. The higher the R-value, the more thermal resistance. The R-value for wood ranges between 1.41 per inch (2.54 cm) for most softwoods and 0.71 for most hardwoods. Ignoring the benefits of the thermal mass, a 6-inch (15.24 cm) thick log wall would have a clear-wall (a wall without windows or doors) R-value of just over 8.
Compared to a
conventional wood stud
wall [31 D2 inches (8.89
cm) insulation,
sheathing, wallboard, a
total of about R-14] the
log wall is apparently a
far inferior insulation
system. Based only on
this, log walls do not
satisfy most building
code energy standards.
However, to what extent
a log building interacts
with its surroundings
depends greatly on the
climate. Because of the
log's heat storage
capability, its large
mass may cause the walls
to behave considerably
better in some climates
than in others. Logs act
like "thermal batteries"
and can, under the right
circumstances, store
heat during the day and
gradually release it at
night. This generally
increases the apparent
R-value of a log by 0.1
per inch of thickness in
mild, sunny climates
that have a substantial
temperature swing from
day to night. Such
climates generally exist
in the Earth's temperate
zones between the 15th
and 40th parallels.
Minimizing Air Leakage in Log Homes Log homes are susceptible to developing air leaks. Air-dried logs are still about 15–20% water when the house is assembled or constructed. As the logs dry over the next few years, the logs shrink. The contraction and expansion of the logs open gaps between the logs, creating air leaks, which cause drafts and high heating requirements. To minimize air leakage, logs should be seasoned (dried in a protected space) for at least six months before construction begins. These are the best woods to use to avoid this problem, in order of effectiveness:
Controlling Moisture in Log Homes Since trees absorb large amounts of water as they grow, the tree cells are also able to absorb water very readily after the wood has dried. For this reason, a log home is very hydroscopic—it can absorb water quickly. This promotes wood rot and insect infestation. It is strongly recommended that you protect the logs from any contact with any water or moisture. One moisture control method is to use only waterproofed and insecticide-treated logs. Reapply these treatments every few years for the life of the house. Generous roof overhangs, properly sized gutters and downspouts, and drainage plains around the house are also critical for moisture control.
Building Energy
Code Compliance for Log
Homes
Because log homes don't have conventional wood-stud walls and insulation, they often don't satisfy most building code energy standards—usually those involving required insulation R-values. However, several states—including Pennsylvania, Maine, and South Carolina—have exempted log-walled homes from normal energy compliance regulations. Others, such as Washington, have approved "prescriptive packages" for various sizes of logs, but these may or may not make sense in terms of energy efficiency. The American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE) 90.2 standard contains a thermal mass provision that may make it easier to get approval in those states that base their codes on this standard. To find out the log building code standards for your state, contact your city or county building code officials. Your state energy office may be able to provide information on energy codes recommended or enforced in your state.
Building &
Restoration of Log
Cabins
Foundation
 The foundation of a log cabin is made of stone pillars. The stones provide a sturdy base to support the cabin and act as a barrier between the cabin and the earth. The stones may settle over time and the foundation is carefully examined for damage or wear and subsequently repaired during restoration.
Wall
Construction
The walls are made
of logs, placed
either vertically or
horizontally,
depending on the
style and size of
the cabin. The logs
are notched at the
corners to allow
them to fit
together. Corner
notching is a
notable
characteristic of
log cabin
construction because
it provides
stability by locking
the log ends in
place, enabling the
logs to fit together
in a secure manner.
Many different
methods of corner
notching exist,
ranging from simple
"saddle" notching to
the common "V"
notching or
"steeple" notching,
which get their name
from the shape of
the notch cut into
the wood. These
notching methods are
marked by a cut into
the wood that allows
another cut piece of
wood to fit together
like a puzzle piece.
Another commonly
used technique,
"square" notching,
differs in that the
logs are secured
with the addition of
pegs or spikes.
Roof
Log cabin roofs are often gabled and are comprised of hand-split, wood shingles. The roofs often develop damage and leaks over the years and are commonly included in restoration.
Doors
Many log cabins
have both a
front and rear
door. Due to the
many times the
doors are opened
and closed over
the years, the
doors are often
not in good
working order
and require
repair during
restoration.
Both doors on
the cabin can be
comprised of
boards that are
hand-dressed,
open inward and
are fastened to
the log
structure with
pegs.
Windows
The cabin features two windows, located on either side of the chimney. The windows hold glass panes, which most likely need to be replaced during the restoration of the cabin.
Chimney
The cabin has a
chimney that
sank and
deteriorated
into many
different pieces
over the years.
The chimney was
rebuilt during
cabin
restoration.
Definitions:
Handcrafted log home
A home that is
constructed of logs that
are individually fit
together.
Milled log home
Constructed of
machine-lathed logs, and
is also used to describe
a log home built from a
kit.
Insulated log
home
Constructed with
half-logs attached to a
standard 2x6 frame
structure.
Chinking
The mixture used to fill
the gaps between logs -
can be natural materials
or synthetic.
Shrinking
The normal loss of
diameter in logs as they
lose moisture.
Settlement
The downward movement of
log courses as the logs
shrink.
Checking
The natural cracking of
logs as they shrink.
Butt joints
Occur when two logs are
placed end-to-end.
Log course
One layer of logs placed
atop the entire
foundation of the home.
Log wall
exterior
The inspector shall inspect exterior surfaces of log walls, when such surfaces are visible, looking for:
The inspector shall inspect interior surfaces of log walls, when such surfaces are visible, looking for:
In addition to the items specified in NACHI Standards of Practice 2.1 and 2.2, the inspector shall inspect:
In addition to the items specified in NACHI Standards of Practice 2.4 and 2.6, the inspector shall inspect:
The inspector is not required to:
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George Timmerman CHI - CMIA* 280 Kemp RD * Suwanee GA 30024 * (770) 495-4870 |