Living with cedar
Many cedars breed in Japan. It is reasonable, since cedar is native to Japan.
The scent of cedar is soft, and it has the property of being harmless to humans while controlling the growth of microorganisms. Utilizing this, it has long been used not only as a building material for houses, but also as a material related to eating habits such as sake barrels, miso barrels, tubs, ohitsu, and disposable chopsticks.
The structure of wood is a honeycomb-like structure, and more than half of its volume is occupied by voids containing water and air.
When you touch the wood, the cedar feels lighter and softer than the oak.
The reason is that the density is low and the volume occupied by air is large.
Cedar and Pollen
When you hear the word “cedar”, you may think of “pollen” first.
For people with hay fever, I think that some people find it irresistible to continue planting cedar, which is the cause of pollen.
However, recent cedars have been bred to prevent pollen from flying, and they are planted, so after a few years, pollen-free cedars will continue to grow around us.
Strength of cedar
Do you know what the “Young’s modulus” is?
The Young’s modulus is one of the indicators of the hardness of the material. Simply put, it means “high Young’s modulus = Material is hard” and “low Young’s modulus = Material is soft”.
And it is said that cedar is easy to bend and has a low Young’s modulus.
Some people may worry about “soft = weak?” and wonder if it is not suitable to use cedars as the foundation of a house.
However, it is when compared to tree species such as cypress and chestnut, not compared to the forces that act in home building.
There is no problem with using it as the foundation of a normal house.
Imported Douglas-fir is also common for house beams, but this is also due to the general perception that cedar is easier to bend than Douglas-fir.
However, the amount of bending is determined by the Young’s modulus and the cross-sectional area of the beam, so it will be solved if the height of the beam (beam back) can be increased a little.
Also, some people may concern that the price will increase if the beam is made larger, but the price when building a house may be lower because the price changes depending on the type of pillar and the amount of volume.
By the way, in the southern Kyushu area where many typhoons occur, cedar is generally used for the foundation and beams.
Mechanical properties of cedar
1)Strength
When measuring the strength of wood, the classification that is graded the strength based on the Young’s modulus obtained by using a bending tester etc. is called “mechanical grade classification”.
In the mechanical grade classification, the four strengths of “compression”, “tension”, “bending”, and “shear” are measured, and “how the wood breaks (cracks)” are calculated.
The grade numbers range from “E50” to “E150”, and the higher the last two digits, the stronger the strength.
As you can see from the above results, cedar belongs to the weakest group of coniferous trees, but if it is a mechanically graded product, it can be said that “cedar is strong” in many grades.
You may wonder, “Why is cedar stronger than Douglas-fir, although the Young’s modulus is lower than Douglas-fir “, but imagine rubber.
Rubber is not stiff, but it stretches easily and does not break if you try to shrink it.
2)Vertical compression performance
Even if it is a non-grade material of cedar, it meets about 4 times of the required performance as a pillar.
The load applied to one pillar in a general house is estimated to be about 1000 kg.
On the other hand, the pillar of cedar can withstand up to 4133 kg even with non-grade cedar wood with a length of 3 m and a cross section of 12 cm square. It has sufficient strength as a structural material.
Miyazaki cedar
Miyazaki Prefecture is one of Japan’s leading forestry prefectures, and in particular, the production quantity of cedar has been the highest in Japan since 1991.
One of the features of Miyazaki cedar is that it contains a lot of resin.
Since it contains a lot of oil, it was often used as a material for shipbuilding in the past.
In addition, the core material of Miyazaki cedar (red meat part) has long been known to be effective in preventing termite damage, and has been used as the foundation and pillars of houses.
Wood researchers have focused on this characteristic of Miyazaki cedar’s termite resistance, and have repeatedly researched it to find out that the components β-eudesmol, sandaracopimarinol, and 16-phy11ocladanol in the heartwood are active ingredients for killing ants.
As a result of conducting a comparison experiment of termite feeding damage by arranging Obi cedar side by side with white wood and red wood, the degree of feeding damage is lower than that of white wood and red wood, and the strength of Obi cedar against termites has been confirmed.
In addition, the oil (essential oil) contained in cedar has a mild and good scent and is used for aromatherapy.
However, termites don’t like this scent and don’t get close to it.
In addition, it is said to be effective against mites.
A study of an apartment complex found that after refurbishing floor carpets with wooden flooring, mites, which is one of the causes of allergies, decreased.
The reason seems to be that the humidity control effect of wood and the components contained in wood work effectively, and at the same time, gaps suitable for habitat have disappeared.
Living with cedar
Living with cedar is the secret to good health
Experiments with mice have shown that mice kept in wooden cages live longer and grow better than mice in metal or concrete cages.
In addition, in a survey at a welfare facility for the elderly, it is reported that facilities where a lot of wood uses had a lower incidence of influenza, injuries, and insomnia.
Living in a human-friendly wooden space may be the key to a healthy and long-lived life.
Cedar reduces stress
It is said that the ingredients contained in trees such as cedar have a calming effect on us.
Experiments using phytoncide, which is said to be the causative substance of the effect of forest bathing, have also shown that blood pressure drops and the pulse calms down.
It can be said that the space with trees is a relaxing environment.
Cedar creates a safe and comfortable environment
Wood such as cedar has the function of absorbing impact and is a gentle material that requires less shock than other flooring materials.
It also controls the humidity in the air, providing a cool living environment in the summer and a warm living environment in the winter.
In addition, it can be said to be the best material for creating a gentle and comfortable environment, such as reducing the irritation that light gives to the eyes and absorbing sound in a well-balanced manner.
