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3. The advantages of thermal insulation of log homes - the scientific study

          In view of the frequently recurring questions about the advantages of our clients thermal insulation of log homes have included below an article that detailed explanation of this matter on the basis of empirical research conducted in the USA.

 Thermal insulation of log walls

          It is believed that the walls of houses of wooden construction are not cumulative or only have minimal thermal capacity (heat accumulation), which is the reason that these houses quickly getting cold, but also heat up quickly. This type of belief is correct, but what should be strongly emphasized, only partially, because that does not apply to total timber construction.

Discussing the theme of a detached timber construction, you must specify what is meant by this term.

Wood construction is one in which building components are made of solid wood such as wood refined. This includes the following:

 Frameworks

The so-called Canadian homes and houses ready made, solid wood or of wood-based materials. The space between elements of the skeleton is filled with thermal insulation. The wooden structure of the building is only a frame for the appropriate layers of insulation. It is the number of layers and thickness, rather than building a wooden structure, determines the heat passing walls or roof, and thus the efficiency of the building.

Solid Log Wall

       Slightly different look at the houses made of solid wood - logs, it means an appropriate thickness, allowing for ensuring adequate insulation of walls with no insulation. So far, the walls of these houses, both as the timber-framed, were treated as not accumulate heat (not so. Heat capacity). Slowly, however, this myth is overturned as demonstrated in a study described below.

Are houses of the above structures can be energy-efficient homes?

In autumn 1980, the United States, for the Department of Housing and Urban Development and the Department of Energy's research was conducted to determine the impact of accumulation of heat (heat capacity) the construction of walls on the size of energy use in individual buildings.

It has been six identical buildings, only differing in the construction of external walls. The facilities were maintained the same level of temperature throughout the 28-week test period between 1981 and 1982. Technicians recorded the exact center energy consumption for each building.

To study were used following buildings:

Building # 1 - insulated timber frame with external wooden upholstery, glass wool insulation, vapor barrier and the plasterboard, with a total thickness of the wall - 11.8 cm.

Building # 2 - not insulated wood frame building with wooden external padding, without the fiberglass insulation, with a total wall thickness of 8.9 cm.

Building # 3 - insulated brick house with concrete blocks, with a facing of brick, polystyrene insulation, vapor barrier, grate and plate plasterboard, with a total thickness of the wall - 29.8 cm.

Building # 4 - not insulated brick house with concrete blocks, grate, vapor barrier and the plate, no styrofoam, with a total thickness of the wall - 24.6 cm.

Building # 5 - log house with solid rectangular cross-section, with tongue and groove, without any additional insulation, no vapor barrier and inner panels plasterboard - with a total thickness of the wall - 17.8 cm.

Building # 6 - insulated masonry home, with brick, loose fill insulation perlito, concrete blocks and plaster interior, with a total thickness of the wall - 40.7 cm.

After 28 weeks of study were:

 - During the three-week spring heating period, the log house (# 5) consumed 46% less heating energy than the insulated wood frame building (# 1).

 - During the 11-week period of summer cooling, log house (# 5) consumed 24% less energy to cool than the insulated wood frame building (# 1).

 - During the 14-week winter heating period, log house (# 5), insulated wood frame building (# 1) and insulated brick house (# 6) consumed a similar amount of heating energy.

Why house with walls made of thick logs 18 cm consumed less energy to heat and cool a building than a typical building of frame wooden construction, which is considered so far for the construction of energy-efficient, why in winter, a similar amount of energy consumed at home with layered brick external walls? These questions meant to be answered in the testing. 

The answer to the question posed above is, inter alia, in the index of thermal inertia – that is the factor that says: The higher the value, the building maintains a more constant temperature, because the heat stored during the day gives them out after sunset, when outside air is cooled. Buildings with low thermal inertia rapidly become warm from the sun and quickly became cold.

The following sections indicators for the thermal inertia of wooden solid logs in comparison to rates of other materials commonly used for external walls of buildings; 

- Solid wood wall thickness. 15.2 cm - 4.17 

- A wall of concrete, approx. 15.2 cm - 3.92

- Solid brick wall with thickness 15.2 cm - 3.37

- Mineral wool thickness 15.2 cm - 0.05 

- Solid wood wall thickness. 20.0 cm - 5.28

- A wall of concrete, approx. 20.0 cm - 4.34

- Solid brick wall with thickness 20.0 cm - 4.02

- Mineral wool thickness 20.0 cm - 0.07 

The above table shows that the solid wood walls have a much greater "heat buffer" from the walls of brick or concrete. Best from above to prevent too rapid changes in temperature inside in summer and also in winter. 

In conclusion it should be noted that the houses with solid wooden logs, can be defined as buildings with low energy consumption. The above statement does not apply to buildings of wood frame construction, which reaches its thermal properties only through the appropriate thicknesses of insulation, 

They used wooden structure creates only heat losses (so-called thermal bridges). 

At this point it is worth to mention how to connect logs (3 examples and their features) that may have a significant impact on the integrity and stability of the structure:

Round logs - overlaps

If the log diameter is 25 cm in place of the same joints of one with the second log surface is reduced by up to half of what negatively affects mainly the already mentioned "heat buffer" and stability. Furthermore, "rotunda" no way to plane, is exposed to a greater extent on the settlement of dirt, and the inner wall surfaces are much more burdensome for finishing.

                                                                                         Source: SIELANKA Group

Rectangular logs - combining overlay 

Like the above, this type of bonding is less stable and prone to numerous bridges, thermal (heat loss).

                                                                                         Source: SIELANKA Group

Rectangular logs - connect to 2 Splines

This technique is much more stable, tight joints provide foreign pen and felt between them. Studies repeatedly show infrared camera greater tightness of such technology.

                                                                                         Source: SIELANKA Group

An extremely important factor for maintaining the heat of the log house is also the implementation of the relevant joints (castles in the corners of the building). Leaky locks expose users of log homes to large heat loss. In addition to the specialized corner cut-outs must also use appropriate seals (eg felt). Corner of this house is a critical his place, which need special attention (picture page 15).