- Material properties and features
- Scope and rules for the use of mineralized wood
- Purchase of ingredients
- Procurement of raw materials
- Insulation production technology
- Rules for laying in walls and floors
Today he will tell you how to reduce the cost of house insulation by making your own materials for thermal insulation from available raw materials. Indeed, today the leading trends in modern construction are economy and energy efficiency, although these two requirements may seem contradictory.
Material properties and features
Thermal insulation materials of various form factors are used in construction: in the form of rolls, mats or solid blocks. Today we are talking about a bulk insulation based on mineralized wood, suitable for filling cavities in walls and ceilings.
The main function of bulk thermal insulation is to eliminate convection and radiant heat transfer paths. At the same time, the thermal conductivity of the insulating layer remains minimal, both due to the small contact area between the fragments of the insulation, and due to its thermophysical properties.
A bulk heat insulator made under artisanal conditions does not differ in terms of service life, safety and heat-saving characteristics from the material produced by the factory method, since all stages of processing of raw materials can be reproduced without industrial equipment. However, this does not apply to the most modern types of loose thermal insulation, such as ecowool, which has similar properties, but differs in form factor, which makes its use more convenient..
The final performance characteristics of mineralized wood waste can be indicated by the following numbers:
- Thermal conductivity – 0.04-0.055 W / m · K (depending on humidity).
- Bulk density – 80-150 kg / m3 (depending on the size of the chips).
- Flammability – G1 (NG when using flame retardant additives).
- Service life before replacement – more than 20 years.
- Shrinkage – up to 10-15% in dry condition.
To immediately close the questions about environmental safety that arise due to the use of a wide range of chemicals – in the finished state, mineralized wood does not emit volatile compounds and the only potential harm to health (irritation of the skin and respiratory tract, allergic reactions) can only be caused by direct contact. Since in a properly arranged frame structure, the insulation is operated in a completely insulated volume, its entry into the habitable volume of the building is impossible.
Scope and rules for the use of mineralized wood
The main difficulty in using heat-insulating materials that do not have their own rigidity is the danger of caking. Similar phenomena are typical for both bulk and roll insulation. True, the albums of technical solutions explain the nuances of using factory-made materials, however, the question of the correct use of homemade mineralized chips remains open.
It is safe to say that when filling cavities in ceilings, the shrinkage of the bulk material does not have any significant effect. There is a simple reason for this: a decrease in the thickness and compaction of the horizontal heat-shielding belt leads only to a slight increase in thermal conductivity and does not in any way affect the quality of adjoining the vertical belts, thus the overall thermal protection of the building remains uninterrupted..
Problems arise when filling cavities in vertical enclosing structures, where with an increase in the height of the belt, the effect of the mass of the insulation on the lower layer also increases. When using ecowool, for example, such phenomena can be dealt with by choosing the optimal density of thermal insulation and by imparting sticky properties to it at the moment of blowing, which ensures high-quality adhesion of the filler with the frame and cladding elements.
When using mineralized wood, this approach does not justify itself. First of all, because in the manufacturing process it is extremely difficult to predict the final density of the material, and even if this could be done, it is difficult to calculate the required parameters based on the varying height and thickness of the cavities..
However, it is possible to use mineralized chips to insulate the walls of a frame house, since shrinkage occurs mainly not due to deformation of the insulator fragments, which are quite hard in themselves, but due to the spilling down of a fine fraction. In view of the above, there are three basic rules to remember:
- You should carefully adhere to the recipe and manufacturing technology, do not skimp on mineralizing ingredients.
- Both the raw material and the finished product should be sorted to get rid of fines.
- When laying bulk insulation, you should insure against shrinkage and take additional measures, which we will discuss in more detail in the final part of the article.
Purchase of ingredients
The main mineralizing additive in the preparation of insulation is Portland cement and slaked lime. The latter also serves as a dehydrator that reduces the moisture content of the finished material after preliminary drying..
Wood in its original state is not subject to mineralization with Portland cement or roman cement, the hydration of which is prevented by various water-soluble impurities contained in the tree. To normalize the process, the wood should be chemically treated, at least superficially. This, among other things, will make the wood immune to decay, inedible for insects and rodents..
During chemical processing, the following are used:
- Boric acid (H3BO3) – antiseptic and fire retardant.
- Sodium tetraborate (Na2B4O7) – antiseptic, preservative insecticide.
- Acetic acid (CH3COOH) – in a concentration over 30% converts unbound cellulose, increases porosity.
- Sodium sulfate (Na2SO4) – mineralizing reagent No. 1.
- Barium chloride (BaCl2) – mineralizing reagent No. 2.
In general, for 1 ton of dried shavings or chips, the amount of required ingredients is as follows:
- Portland cement M300: 70-100 kg
- Slaked lime: 80 kg
- Quicklime (optional): 30 kg
- H3BO3: 1.5 kg
- Na2B4O7: 4 kg
- CH3COOH (30%): 5-6 l
- Na2SO4: 20 kg
- BaCl2: 20 kg
Procurement of raw materials
The raw wood itself can be purchased almost free of charge: the disposal of shavings and sawdust is a headache for woodworking enterprises. Another question is how high-quality and suitable material can be offered to you, because no one will sort the waste. There are several rules for the procurement of raw materials:
- You should choose wood species with minimal resin content – that is, predominantly deciduous.
- Sawdust is suitable only for the manufacture of floor filler, for walls you need shavings or chips.
- The raw material must be homogeneous, free from fragments of bark, twigs and various debris.
- Avoid raw materials containing fragments with traces of blue or gray mold. Drying and mineralization do not guarantee sterility, and the use of antiseptic additives leads to an unjustified increase in the toxicity of the material.
For the manufacture of insulation, illiquid residues from veneer peeling, planing waste are best suited; it is also a very good solution to use long sawdust remaining when large-sized logs are cut on large sawmills. Thus, the collection of wood waste must certainly be carried out independently, and immediately at the exit from the woodworking workshop, and not in general dumps. In some cases, it makes sense to make raw materials yourself, passing illiquid sawn timber or small logs, peeled from bark, through a garden shredder with a disc or millstone cutting body.
Before preparing the insulation, the raw materials should be kept for a long time in the open air to reduce the humidity to 15-18%. The shavings should be stored on a waterproof mat with a layer of up to 40–50 cm, sheltered from precipitation and opened in clear weather. Stir the mass periodically, lifting the most humid part of it up..
Insulation production technology
The process of wood processing and mineralization is associated with a chain of chemical reactions, which requires compliance with a number of conditions. Production should be carried out in the open air at a temperature not lower than 20 ° C. It is best to process in large portions so as not to disturb the ratio of ingredients, while mixing occasionally. The best for preparation is a concrete mixer with a volume of 0.25-0.4 m3.
It is considered technologically correct to subject wood to initial processing. First, it is wetted with acetic acid, which is diluted with water during mixing to distribute it evenly over the raw material. After completely wetting the mass, it must be kept for about an hour. Then you can add quicklime without drying and perform additional wetting with water until the chemical reaction is completely stopped. Before further actions, the raw material should be thoroughly dried in the open air..
In the second stage, internal (primary mineralization) is produced. Its essence is to fill the pores of wood with insoluble and non-leachable salts. To do this, first, the chips are soaked in a solution of sodium sulfate, then – barium chloride. In the course of the substitution reaction, crystals of sodium chloride and barium sulfate remain in the pores, the wood acquires hardness, becomes much less combustible.
In the course of two impregnations with intermediate drying, the fibers are straightened, which leads to curling of the chips. The material becomes more voluminous and can be subjected to surface (secondary) mineralization. For this, wood and Portland cement are mixed in dry form, after which the mass is gradually moistened. During the addition of water, additives are added to provide additional fire resistance and antiseptic properties. Some of the additives are poorly soluble in water, however, introduction with liquid ensures their more even distribution in the mass. After soaking in cement milk, the mass is dried – first with constant stirring before the cement hydration process begins, and then in an open area with periodic stirring to avoid the formation of large lumps. When the mass becomes almost dry, it should be manually mixed with the fluff. After exposure in the open air for a day, the insulation can be packaged and sent for long-term storage.
Important! Although most of the chemicals used in manufacturing are relatively harmless, protective clothing and personal eye and respiratory protection should be used..
Rules for laying in walls and floors
In conclusion, a few words about how to ensure the preservation of the properties of thermal insulation throughout the entire service life. To begin with, like most heaters, mineralized wood is afraid of moisture. Therefore, the cavities of the enclosing structures must be protected by a superdiffusion membrane from the outside and a vapor barrier from the inside of the room..
Laying of mineralized shavings into the floors is carried out by ordinary filling with a layer of up to 200 mm. If more insulation is required, divide the cake with a partition, for example, OSB or plywood. Although rodents do not eat such insulation, they are able to arrange nests in it, so the ends of the floors need to be sewn up tightly or use a steel mesh.
Frame walls intended for backfilling with mineralized wood must necessarily have a rigid sheathing on both sides. There are two ways to prevent shrinkage. The first one is filling the insulation with tiers up to 100 cm high, separated by supporting partitions. Thin plywood or well-stretched plastic mesh can be used as these. The second method is to lay a heater with light moisture, but with this option, you should wait up to two weeks in dry weather before installing a vapor barrier and an outer protective membrane..