It is known even to a novice builder that log houses have two main drawbacks - thin walls and shrinkage of crowns. The latter occurs in connection with the shrinkage of wood. Therefore, methods are used that prevent deformation of the walls and contribute to their effective insulation. According to existing standards, the walls of the house should be no thinner than 20 cm.
This problem can be solved by the technology of a double beam, which was first used by builders in Finland. There are few trees in the country that are thick enough to be used to build houses, while protecting them from the severe frosts that are typical for the region.
What is the essence of the new technology?
Finnish engineers have managed to develop a technology that allows building warm wooden houses at a relatively low financial cost. She received the name "double beam". In fact, this technology has little in common with a bar in the usual sense. Its essencelies in the fact that in order to achieve the proper thickness of the walls, two tongue-and-groove boards are used, between which there is a layer of insulation.
Houses based on double timber technology have improved thermal insulation characteristics compared to houses made of solid timber of the same section. Compared to insulated glued beams, this technology does not use adhesives. Insulation is often ecowool or mineral wool.
Double beam: production
The production of material for the construction of houses using the technology of double timber is different from the manufacture of ordinary profiled timber. It is carried out on special equipment - a fully or partially automated cup-cutting line.
It is carried out in several stages:
- prefabrication;
- drilling holes for fastening edged boards;
- cup cutting;
- grooving;
- cut blanks;
- deleting leftovers;
- marking;
- insulation material;
- packaging.
Benefits
The main advantage of a double-timber house is its high energy efficiency. The thickness of its walls does not depend on the diameter of the log or timber. The insulation layer is selected in accordance with the requirements specified in generally accepted thermal engineering standards. The second advantage of the technology is the minimum wall shrinkage, which fluctuates in the range of 1-2%.
Start full operation of the house,built according to Finnish technology, it is possible upon completion of the assembly of walls and roof. Ordinary houses from a bar cannot be used immediately, since you need to wait until the tree dries and the crowns “fall” into place. In this case, there is no need to wait.
Installation of a house from a double beam is relatively simple, not laborious and does not require the use of complex construction equipment, which favorably affects the time of building a house and financial costs. In parallel with the assembly of the walls, thermal insulation work is carried out, filling the space between the boards. Walls in houses made of double timber should not be additionally insulated and finished.
Flaws
"Double beam", despite many advantages, has a number of disadvantages. The most significant include shrinkage of the insulation, but it occurs only when using mineral wool. There is also the possibility of cracks. They can form due to uneven shrinkage of the outer and inner boards used for houses built using the “double beam” technology. Reviews of builders assure that in practice such problems do not arise at all. At least there were no comments.
Experience in the domestic market
In the domestic market, the technology has been used recently, so no one can guarantee that wooden houses will fully perform their functions in our climatic conditions. You just need to trust the Finnish experience in housing construction, since they have been building houses from double timber for over 20 years and successfully operate buildings in their moreharsh climatic conditions.
It is not possible to independently build a house using this technology, since for its high-quality construction boards processed on special machines are needed. It is also necessary to cut the spikes, grooves and docking grooves intended for corner joints. Without a team of specialists and the purchase of a house kit, it will not work out in any way. Therefore, saving on financial costs is problematic.
Structural strength
Double timber technology is not comparable to conventional frame construction, where the insulation is located between two thin walls. In this case, everything is held on the bars. There is also a subspecies of this technology - "double mini-beam". Its construction is similar, but the walls are thinner.
Increased structural strength is also provided by floor beams if they are cut into walls during the construction process. In technology, only dry lumber can be used, which largely affects the strength of the house as a whole. This is due to the fact that drying the timber leads to a loss of 13% of its moisture content, due to which molecular bonds are broken. In the future, the timber will give exactly the same amount of moisture that it will absorb. Therefore, deformation will not occur.
Vapor barrier
For the construction of houses, the walls of which consist of several floors, an important issue is vapor barrier. Without its consideration, it is not recommended to carry outconstruction. Double timber is an exception, despite the fact that the walls of houses built using this technology will inevitably begin to absorb moisture after a certain time. Therefore, there is an opinion that the insulation between the bars is the place of rot formation. At the same time, construction companies specializing in the construction of houses using this technology claim that a double beam has not previously caused any problems. Owner reviews agree that it is enough to use the film only in ceilings.
But there are exceptions. Some owners are concerned about the lack of vapor barrier as such, so during construction they use a windproof membrane, which is applied after the insulation. Experienced builders are skeptical of this as it won't let the walls "breathe" freely, but they can last a lot longer.
Ecowool as wall insulation
When building a wooden house that is not impregnated with synthetic resins that are harmful to he alth, the best option would be to use a harmless insulation. The optimal material is ecowool, the main component of which is cellulose. It will not rot, shrink, or catch fire.
The calculations for the material are as follows:
- acoustic isolation - 46 dB;
- dew point - no condensation will occur under standard conditions;
- insulation – 0.13 m2 for each m2 wall;
- thermal conductivity coefficient – 0.2 W/m2.
Ecowool is blown dry into the space between the beams. Heightshould be no more than three meters. The procedure is carried out in stages. But here certain difficulties arise: ecowool is blown into the “double beam” in the same way as inside the frame walls. If the wells of the latter are closed and it is not difficult to achieve the required density, then the material is more filled up and, as a result, may settle. Experienced builders have found a way out of this situation and use a special blowing machine. Recently, mineral wool has found great use.
Mineral wool as insulation
The material is reliable, environmentally friendly and relatively cheap. If mineral wool is used as a heater, then it is necessary to organize a vapor barrier of the room (this is not done for ecowool). In addition, over time, it caking and, as a result, empty cold cavities are formed in the walls. Therefore, the material will have to be coated with an antiseptic inside and out.
Sawdust
For wall insulation, it is recommended to use stale sawdust. If you have only fresh ones on hand, then you can soak them for a day in lime and only then knead them. The procedure is as follows: m2 sawdust and two bags of cement are poured into the mixer. Everything is moistened a little, mixed, poured into the space between the walls and rammed. A significant drawback of the material is mice, mold or dampness.
Bulk pulp
The material effectively performs the task of wall insulation. Often during construction, insulation is not used at all, since it is believed that the air itselfin itself is an excellent heater. But it is important to understand that it serves as thermal insulation only when it is motionless. This is the task of other materials: they create a large number of cavities with "still" air.
Polyurethane foam is sometimes used, but it is relatively expensive and therefore not widely used in construction. At the same time, the material releases toxic substances and after a certain time is destroyed.
Box walls are insulated with flax fiber. Chopped straw or other material that does not cake over time is also suitable. It is also important to remember its compatibility with wood.
Stages of building a house using the "double beam" technology
Reviews convince us that self-construction of a house will only come at a loss to its quality, so you can’t do without specialists. Building a house includes the following steps:
- Sketch development (project). It includes the selected construction plan, drawing the facade of the building, and the choice of architecture. Usually firms specializing in the sale of building materials offer services for the creation of house designs, so you can turn to them for help. You can also find a suitable plan on the Internet, but this is not always the best option.
- Creating a working version of the project. Designers take into account all your wishes and draw a diagram of all the products needed for construction. A working draft can be done free of charge. But this will only happen if you sign with the firmconstruction contract. In the case when you want to start preparing all the necessary documentation, and not a full-fledged construction, the service will cost about 400 rubles/m2 (in Moscow).
- Preparation of parts for a timber house kit. This is one of the most difficult and demanding stages of building houses using the “double beam” technology. Feedback from builders says that it takes an average of 1 month to build a house with a total area of over 100 m2, not taking into account the complexity of its architecture.
- Construction erection. This is the final stage at which the assembly of the product is carried out. No nails or glue are used on it, but only “customize” all knots and connections. Locking joints provide high strength and durability of the structure.
Cost
Houses built using the “double beam” technology are more expensive than solid wood log cabins. The average price of 1 m2 of an insulated wall will cost 5,500 rubles. The cost of a solid beam with a thickness of 150 mm will be cheaper - 3,500 rubles. But it is important to understand that a beam even 20 cm thick requires insulation.
Double insulated wall technology provides a complete structure that does not need additional work and therefore cost.
For comparison, let's make a simplified estimate for a wall made of profiled timber. As already noted, the average cost of a “bare” wall 15 cm thick is 3,500 rubles/m2. Insulation, for example, 20 cm of ecowool, costs 800rub/m2. Work on the installation of the frame, as well as clapboard lining - an additional 600 rubles / m 2. That is, additional work on the insulation of a log house from a bar will cost approximately 1,400/m2. As a result, 4,900 rubles/m2 is the price that will have to be paid for m2 into a house made of double timber. Reviews at the same time convince that the relatively small difference in price is not so significant, since the technology has a large number of advantages.
