Man developed his treatments for the environmental conditions surrounding him through long and continuous experiments in the practice of construction, so he was able to identify the properties of building materials, so he used them most effectively to meet his needs and requirements .. One of the main disadvantages of concrete buildings is their poor behavior and thermal behavior, given the nature of the climate and the intensity of its heat . The best evidence of this is the curve of electricity consumption in the city of Riyadh, where electricity consumption in the summer is twice as high as in the winter . The reason for this significant increase is mainly due to the electric energy used to operate various air conditioning means, to which people are forced to expel the intense heat and windows to their homes as a result of the poor resistance of walls and ceilings to the penetration of heat from the outside .
Also, half of the facilities and power plants are mainly used to operate air conditioning systems in the summer only, which makes the utilization factor of these facilities and stations very low and consequently leads to a high cost of generation, operation and maintenance of power plants and networks .
As for what can be controlled at the individual level, the choice of exterior colors, the orientation of the building, the distribution of openings and their areas, processing and insulation of walls and ceilings exposed to the atmosphere and external climatic conditions ،
It is known that thermal insulation is the process of preventing the transfer of heat from one place to another in whole or in part by taking advantage of the properties of some materials such as poor thermal conductivity and as an increase in heat capacity and reflection property .
Insulation materials
They are those substances or a combination of substances that, if used in an appropriate way, can prevent or reduce heat transfer by various means of thermal transfer ( conduction – convection – radiation ).
Insulating materials can be mainly divided as follows :
Inorganic insulating materials composed of fibers or cells such as glass, asbestos, rock wool, calcium silicate, perlite and vermiculite .
Fibrous organic insulating materials such as cotton, animal wool, reeds or cellular such as Cork, foam rubber, polystyrene or polyurethane .
Metal insulating materials such as aluminum foil and reflective tin.
As for the forms on which the insulating materials are located, they are as follows :
Bulk insulating materials, usually in the form of granules or powder, are usually poured between walls or in any closed vacuum, and they can also be mixed with some other materials, and they are especially used to fill irregular voids .
Flexible insulating materials, which vary in their degree of flexibility and their ability to bend or compress, are usually found in the form of pieces or rolls and are usually fastened with nails and the like, such as glass wool, rock, aluminum foil and so on .
Solid materials: they are found in the form of plates with dimensions and thicknesses limited by polyurethane and polystyrene .
Liquid insulating materials pour or spray in or on the desired place to form an insulating layer and these are such as foamed polyurethane .
Characteristics of thermal insulation materials
Considering the design requirements, the choice of a particular insulating material requires, in addition to knowledge of the thermal property, knowledge of other secondary properties of the material such as water absorption, combustion and hardness ..Etc.
Thermal properties:
It refers to the thermal insulation ability of the material and is usually measured by the coefficient of thermal conductivity, the lower the coefficient of conductivity, this indicates an increase in the resistance of the material to thermal transfer . Thermal resistance is inversely proportional to the coefficient of thermal conductivity through the insulating material, which is usually carried out by all different means of transport ( conduction, load, radiation ).
As for reflective materials, because of their high ability to repel radiation and heat waves, they are considered effective materials in thermal insulation, provided that they meet an air vacuum and increase the ability of these materials to insulate by increasing their gloss and refinement .
The insulating material is often integrated with walls and ceilings, so to know the total resistance to thermal transfer, it is necessary to collect the various resistances of the wall or ceiling layers, including the resistance of the air layer adjacent to the internal or external surfaces .
The collection of these resistors is very similar to the collection of electrical resistors, they are either in parallel or in sequence and this depends on the composition of the materials in the wall or in the ceiling. In addition to the mentioned thermal properties, there are other properties such as specific heat, heat capacity, coefficient of expansion and diffusion, which must be known for each insulating material .
Mechanical properties
Some insulating materials are characterized by durability and load-bearing capacity . Therefore, it can sometimes be used to contribute to the support and loading of the building, in addition to its main purpose, thermal insulation . Therefore, the bearing force of compression, tension and shear is considered ..Etc.
The presence of water in a wet, liquid or solid form in the insulating material reduces the thermal insulation value of the material or reduces thermal resistance, and it may contribute to the rapid destruction of the material .
The effect of moisture on the material depends on the properties of the material in terms of its ability to absorb and penetrate, and also depends on the surrounding climatic conditions such as temperature and humidity ..Etc. The properties by which the effect of the material on moisture is measured are absorption and permeability .
Safety and health
Some insulating materials have certain properties, including what may endanger humans, whether during storage, transportation, installation, or during the period of use, they may cause permanent or temporary impairments in the human body, such as wounds, blisters, poisoning, pulmonary infections, or allergies in the skin and eyes, which necessitates the importance of knowing the chemical composition of the insulating material . As well as its other physical qualities in terms of combustibility and sublimation .
The voice
Some heat-insulating materials may be used to achieve some acoustic requirements such as sound absorption, dispersion and vibration absorption, so knowing the properties associated with this aspect may meet two goals by one means .
In addition to the above properties, there are properties that may be necessary when choosing the appropriate insulating material, such as knowledge of density, ability to resist shrinkage, usability, dimensional regularity, resistance to chemical reactions, available sizes and thicknesses..Etc . In addition to all the above, the economic factor finally plays an important role in making the decision, the price of the insulation material has a significant impact when choosing .
What is the right amount of insulating material
The quality of the insulating material is usually chosen by balancing its economic cost and the extent to which it meets the main and secondary requirements, but this choice does not dispense with seeking to determine the appropriate thickness of the selected material . Buildings in terms of the quality and method of the main heat gain can be divided into two types :
Buildings most of their heat gain comes through the shell or the outer shell of the building, meaning that the cooling and heating requirements are roughly proportional to the difference between the internal and external temperature . Dwellings and warehouses are usually located in this section, since the heat gained from the outside far exceeds the heat generated by various activities inside.In these buildings, increasing the thermal insulation in the outer shell of the building will necessarily reduce the amount of heat gained or lost, and therefore leads to a reduction in the energy required to remove what is gained or compensate for what is lost . In order to determine the optimal thickness of the insulating material in buildings of this type, the main determinant of this determination is the amount of the total cost, which is equal to the sum of the cost of the insulating material and the cost of the energy required to adapt the building .
Buildings whose main heat gain comes from inside them, and these buildings have the main heat gain as a result of the activities held inside them, such as factories, or as a result of the large number of users, or the heat generated by industrial lighting, such as offices, etc . In such buildings, since most of the acquisition is not primarily affected by external weather conditions, increasing the thickness of the insulation layer does not necessarily reduce the cost of energy, but may lead to its increase as well as increase the overall cost . An increase in the thickness of the insulating layer leads to the retention of the heat gained inside from its accumulation, so the cooling loads increase significantly . Therefore, buildings of this type need to be thoroughly studied by computer to determine the thermal behavior of the building throughout the year using different thicknesses of insulating material and then reach the optimal thickness.
