Highly heat-insulated log houses with double external walls.

Taiga Company offer completely new solution for the log house heat insulation problem – double external walls and a special windproof longitudinal groove. It allow to have an ecologically friendly house made of solid wood without artificial materials used for wall heat insulation  and with heat insulation coefficient

Uwerte=0.10Wt/m grad.

Houses made of solid wood (log houses) are known to be a natural ecological product, and, therefore, they are so popular in the world. However, log houses have significant disadvantages: a) Log walls have quite a low heat insulation coefficient Uwerte=0.35–0.50, moreover, for instance, in Germany EnEV Grenzwert = U<0.25, and a house with high insulation Passivhaus-Standart=U<0.15Wt/m grad.     b) The second problem of these houses is poor windproof properties of their simple “moon” longitudinal log joints in house walls.

The table with the U-werte calculation for different log walls with additional insulation was presented to us by our German customer.

            It is simple – wooden wall thickness is on the left, mineral wool thickness is above, zones of U-werte coefficients are in the middle:  red zone – houses do not comply with new strict German standards, light-green zone – boundary permitted zone (EnEV-Grenzwert=U<0.24) and dark-green zone – zone of walls with high insulation (Passivhaus-Standart=U<0.15). So, walls of a house are supposed to be high heat-insulated if U<0.15, and they are allowed to be built if U<0.24.

            Now we see the table of U-werte for walls made of round logs with diameter 200-350 mm, which are usually used for log houses construction.

	Log Diameter	U-Werte, Wt/m grad
1	Wall - round logs of 200 mm (= a solid wooden wall of 173 mm)	0.47
2	Wall - round logs of 230 mm (= a solid wooden wall of  200 mm)	0.42
3	Wall - round logs of 300 mm (= a solid wooden wall of 250 mm)	0.33
4	Wall - round logs of 430 mm (= a solid wooden wall of 350 mm)	0.24

The table shows that no logs with diameter 200–350 mm meet new strict European standards of house insulation. Only diameters over 43 cm (generally manufacturers of houses do not use those logs) have boundary values of light-green zone Uwerte=0.24. Therefore, only walls with log diameter of 43-50 cm comply with new standards and they are within EnEV-Grenzwert U zone. However, wind-sheltering for this walls remains a serious problem.

  

So, the second problem of these houses is poor windproof properties of their simple “moon” log joints. In fact, manufacturing of houses by means of very thick logs with diameters of 40–50 cm cannot solve the heating insulation problem, additional wind-sheltering is necessary. Owing to these problems, log houses shall be additionally heat-insulated with artificial chemicals (mineral wool), protected with windproof film and finished with boards from the interior. All of those things are twice difficult to be implemented because log houses have a property to “shrink” after montage and all the additional insulation system shall be slyding. So, that sort of insulation system is expensive in addition to being ecologically harmful. After those additional “correct” insulation, a log house will comply with all the heat insulation standards, but it stops being ecologically clean, it stops breathing and its interior view is spoilt with boards (view of boards differs from view of interior log walls). Thus, “correct” insulation eliminate all main advantages of houses made of solid wood.

It may seem that the situation is hopeless and log houses have no perspective. But do not make up your mind so soon.

We offer conceptually new solutions to our customers – log houses with double external walls and special windproof longitudinal profile of log joints. The sort of houses is built in usual logs with diameter 200 mm, internal walls are ordinary (single), and external walls consist of two parallel walls, each of them is 200 mm thick. There is air with thickness 180 mm between them. Air is a perfect and absolutely free for a customer heat-insulator.

  

In fact, external walls are similar to a modern glas-packet, where glasses are two walls (each of them is 200 mm) with 150–200 mm of air between them. Simple U-werte calculation of such a “packet” consisting of three layers (log-air-log) is as follows: 1/U= 1/U1+1/U2+1/U3. And after introducing U-values as 200 mm (0.47) for logs and 180 mm (0.17) for air, we get

Uwerte=0.10Wt/m grad. !!!

So then: Now we have a look at the table of our German customer (at the beginning of the text) and see that our “unit” has a better Uwerte than all presented in the German table combinations of wood and mineral wool (actually it is a little more to the right from the right border of the table). The unit “log 200 mm – air 180 mm – log 200 mm” has perfect heat-insulating properties with Uwerte=0.10Wt/m grad.

Our another important solution is a complex profile of longitudinal log joints – moon+nut-und-feder (mortise and tenon).

As we have already mentioned, a “moon” longitudinal groove, which is used by the majority of manufactures of log houses, cannot be a proper wind-sheltering. A simple groove is easily blown through. 

We offer logs with a complex profile – “moon” groove + nut-und-feder (“mortise and tenon”). The photo of our log clearly demonstrates it. We borrowed that system from the Swedes. The manufacturer of our equipment and technology is a Swedish company, named Stenlund.

  

So, insulating material between logs (made of natural jute) is placed not in an simple “moon” arc, but in a complex “mortise and tenon” profile between logs. The sort of log joints becomes practically impossible to be blown through by wind. If air passes through one wall somewhere in angle joints, it will appear in the buffer area between two walls and meet one more wall on its way to the house - the second wall with exactly the same complex longitudinal joint.

Therefore, the system consisting of two walls with a complex longitudinal log profile does not demand additional insulation by means of mineral wool as well as wind-sheltering. A house of that sort will breath naturally and let its residents do the same.

An important disadvantage of houses made of thick logs with diameter 40–50 cm is the fact that they are generally built in spruce. Spruce is a fast-growing wood material, it has little pitch (pitch protects wood against humidity and decay). Finnish, Russian and other manufactures of log houses do not use spruce in house walls building, but pine only. But quantity of pine-trees with diameter 40–50 cm is so little in forests, so, manufacturers of houses made of thick logs take an easier way – they use spruce. Inexperienced customers do not understand that they are cheated. We build our houses only in pine-wood! It is essential for life durability of a house.

And finally, not last advantage of our houses with double external walls and log profile “nut-und-feder” is their lower price. With heat insulation, which is 2.5 times higher than the one 430–500 mm thick walls have, and much higher wind-sheltering “nut-und-feder” of log joints, the house has a lower price – 1.8–2.0 times cheaper than the price offered by the competitor. In fact, only external walls are built double, all internal walls will be usual, single – 200 mm.

What does it look like? Here an example of such house designed for Germany:

Internal walls naturally unary

The house in a section looks so:

The montage of that sort of houses is much cheaper. Every separate dry detail is 5–7 times lighter than a similar thick wet detail of the competitor. It means that a crane will not be needed for installation works and the process itself will not be so hard and expensive.

Log Diameter – Uwerte – Cost:

	Log Diameter	Uwerte,  Wt/m grad	cost of sq.m of the area of a wall Euro/m2	cost of sq.m of the area of the house Euro/m2
1	200mm	0.47	45	95
2	230mm	0.42	52	110
3	280-320mm	0.34	110	230
4	400-450mm	0.24	140	300
5	Logs, 2x200mm + 180mm Air	0.10	63-65	135

 

So, advantages of our double log walls system are as follows:

1) Perfect heat insulation, Uwerte=0.10 (it is less than Passivhaus-Standart, U<0.15);

2) Proper wind-sheltering systems consisting of two walls with a longitudinal log joint profile “nut-und-feder”;

3) Mineral wool and windproof films are not used for those walls, walls are composed entirely from logs, a house becomes environmentally clean and can breath properly.

4) Our houses are built only in pine-wood, while competitors use spruce, which quality is significantly poorer, for houses made of thick logs.

5) The system is able to provide a longterm external and internal natural log design of houses.

6) Construction strength of double external walls is increased.

7) The price of houses is relatively not high.

Contact us and we will build for you an ecologically clean house with proper heat insulation, which complies with the highest European standards, for a reasonable price!

 

Contacts:

tel: +7-911-230-31-72 Mr. Semyon Dimitriyev, Director General       

e-mail: info@taiga-loghouse.ru

Postal address: Russia, 188689, Leningrad Oblast, Vsevolozhsk, p. Yanino-2, d.1-A