Contents
In recent years, when building a house or repairing it, much attention has been paid to energy efficiency. With the already existing fuel prices, this is very important. And it seems that further savings will become increasingly important. In order to correctly select the composition and thickness of materials in the pie of enclosing structures (walls, floors, ceilings, roofs), it is necessary to know the thermal conductivity of building materials. This characteristic is indicated on the packaging with materials, and it is necessary at the design stage. After all, it is necessary to decide what material to build walls from, how to insulate them, how thick each layer should be.
What is thermal conductivity and thermal resistance
When choosing building materials for construction, it is necessary to pay attention to the characteristics of the materials. One of the key positions is thermal conductivity. It is displayed by the coefficient of thermal conductivity. This is the amount of heat that a particular material can conduct per unit of time. That is, the smaller this coefficient, the worse the material conducts heat. Conversely, the higher the number, the better the heat is removed.
Materials with low thermal conductivity are used for insulation, with high – for heat transfer or removal. For example, radiators are made of aluminum, copper or steel, as they transfer heat well, that is, they have a high thermal conductivity. For insulation, materials with a low coefficient of thermal conductivity are used – they retain heat better. If an object consists of several layers of material, its thermal conductivity is determined as the sum of the coefficients of all materials. In the calculations, the thermal conductivity of each of the components of the “pie” is calculated, the found values are summarized. In general, we get the heat-insulating ability of the building envelope (walls, floor, ceiling).
There is also such a thing as thermal resistance. It reflects the ability of the material to prevent the passage of heat through it. That is, it is the reciprocal of thermal conductivity. And, if you see a material with high thermal resistance, it can be used for thermal insulation. An example of thermal insulation materials can be popular mineral or basalt wool, polystyrene, etc. Materials with low thermal resistance are needed to remove or transfer heat. For example, aluminum or steel radiators are used for heating, as they give off heat well.
Table of thermal conductivity of thermal insulation materials
To make it easier for the house to keep warm in winter and cool in summer, the thermal conductivity of walls, floors and roofs must be at least a certain figure, which is calculated for each region. The composition of the “pie” of walls, floor and ceiling, the thickness of the materials are taken in such a way that the total figure is not less (or better – at least a little more) recommended for your region.
When choosing materials, it must be taken into account that some of them (not all) conduct heat much better in conditions of high humidity. If during operation such a situation is likely to occur for a long time, the thermal conductivity for this state is used in the calculations. The thermal conductivity coefficients of the main materials used for insulation are shown in the table.
| Name of material | Thermal conductivity W/(m °C) | ||
|---|---|---|---|
| Dry | Under normal humidity | With high humidity | |
| Woolen felt | 0,036-0,041 | 0,038-0,044 | 0,044-0,050 |
| Stone mineral wool 25-50 kg/m3 | 0,036 | 0,042 | 0 ,, 045 |
| Stone mineral wool 40-60 kg/m3 | 0,035 | 0,041 | 0,044 |
| Stone mineral wool 80-125 kg/m3 | 0,036 | 0,042 | 0,045 |
| Stone mineral wool 140-175 kg/m3 | 0,037 | 0,043 | 0,0456 |
| Stone mineral wool 180 kg/m3 | 0,038 | 0,045 | 0,048 |
| Glass wool 15 kg/m3 | 0,046 | 0,049 | 0,055 |
| Glass wool 17 kg/m3 | 0,044 | 0,047 | 0,053 |
| Glass wool 20 kg/m3 | 0,04 | 0,043 | 0,048 |
| Glass wool 30 kg/m3 | 0,04 | 0,042 | 0,046 |
| Glass wool 35 kg/m3 | 0,039 | 0,041 | 0,046 |
| Glass wool 45 kg/m3 | 0,039 | 0,041 | 0,045 |
| Glass wool 60 kg/m3 | 0,038 | 0,040 | 0,045 |
| Glass wool 75 kg/m3 | 0,04 | 0,042 | 0,047 |
| Glass wool 85 kg/m3 | 0,044 | 0,046 | 0,050 |
| Expanded polystyrene (polystyrene, PPS) | 0,036-0,041 | 0,038-0,044 | 0,044-0,050 |
| Extruded polystyrene foam (EPS, XPS) | 0,029 | 0,030 | 0,031 |
| Foam concrete, aerated concrete on cement mortar, 600 kg/m3 | 0,14 | 0,22 | 0,26 |
| Foam concrete, aerated concrete on cement mortar, 400 kg/m3 | 0,11 | 0,14 | 0,15 |
| Foam concrete, aerated concrete on lime mortar, 600 kg/m3 | 0,15 | 0,28 | 0,34 |
| Foam concrete, aerated concrete on lime mortar, 400 kg/m3 | 0,13 | 0,22 | 0,28 |
| Foam glass, crumb, 100 – 150 kg/m3 | 0,043-0,06 | ||
| Foam glass, crumb, 151 – 200 kg/m3 | 0,06-0,063 | ||
| Foam glass, crumb, 201 – 250 kg/m3 | 0,066-0,073 | ||
| Foam glass, crumb, 251 – 400 kg/m3 | 0,085-0,1 | ||
| Foam block 100 – 120 kg/m3 | 0,043-0,045 | ||
| Foam block 121-170 kg/m3 | 0,05-0,062 | ||
| Foam block 171 – 220 kg/m3 | 0,057-0,063 | ||
| Foam block 221 – 270 kg/m3 | 0,073 | ||
| Ecowool | 0,037-0,042 | ||
| Polyurethane foam (PPU) 40 kg/m3 | 0,029 | 0,031 | 0,05 |
| Polyurethane foam (PPU) 60 kg/m3 | 0,035 | 0,036 | 0,041 |
| Polyurethane foam (PPU) 80 kg/m3 | 0,041 | 0,042 | 0,04 |
| Cross-linked polyethylene foam | 0,031-0,038 | ||
| Vacuum | 0 | ||
| Air +27°C. 1 atm | 0,026 | ||
| Xenon | 0,0057 | ||
| Argon | 0,0177 | ||
| Airgel (Aspen aerogels) | 0,014-0,021 | ||
| Slag | 0,05 | ||
| Vermiculite | 0,064-0,074 | ||
| foamed rubber | 0,033 | ||
| Cork sheets 220 kg/m3 | 0,035 | ||
| Cork sheets 260 kg/m3 | 0,05 | ||
| Basalt mats, canvases | 0,03-0,04 | ||
| Tow | 0,05 | ||
| Perlite, 200 kg/m3 | 0,05 | ||
| Expanded perlite, 100 kg/m3 | 0,06 | ||
| Linen insulating boards, 250 kg/m3 | 0,054 | ||
| Polystyrene concrete, 150-500 kg/m3 | 0,052-0,145 | ||
| Cork granulated, 45 kg/m3 | 0,038 | ||
| Mineral cork on a bitumen basis, 270-350 kg/m3 | 0,076-0,096 | ||
| Cork flooring, 540 kg/m3 | 0,078 | ||
| Technical cork, 50 kg/m3 | 0,037 |
Part of the information is taken from the standards that prescribe the characteristics of certain materials (SNiP 23-02-2003, SP 50.13330.2012, SNiP II-3-79 * (Appendix 2)). Those material that are not spelled out in the standards are found on the manufacturers’ websites. Since there are no standards, they can differ significantly from manufacturer to manufacturer, so when buying, pay attention to the characteristics of each material you buy.
Table of thermal conductivity of building materials
Walls, ceilings, floors, can be made from different materials, but it so happened that the thermal conductivity of building materials is usually compared with brickwork. Everyone knows this material, it is easier to make associations with it. The most popular charts, which clearly demonstrate the difference between different materials. One such picture is in the previous paragraph, the second – a comparison of a brick wall and a wall of logs – is given below. That is why thermal insulation materials are chosen for walls made of bricks and other materials with high thermal conductivity. To make it easier to select, the thermal conductivity of the main building materials is tabulated.
| Material name, density | Coefficient of thermal conductivity | ||
|---|---|---|---|
| dry | at normal humidity | at high humidity | |
| CPR (cement-sand mortar) | 0,58 | 0,76 | 0,93 |
| Lime-sand mortar | 0,47 | 0,7 | 0,81 |
| Gypsum plaster | 0,25 | ||
| Foam concrete, aerated concrete on cement, 600 kg/m3 | 0,14 | 0,22 | 0,26 |
| Foam concrete, aerated concrete on cement, 800 kg/m3 | 0,21 | 0,33 | 0,37 |
| Foam concrete, aerated concrete on cement, 1000 kg/m3 | 0,29 | 0,38 | 0,43 |
| Foam concrete, aerated concrete on lime, 600 kg/m3 | 0,15 | 0,28 | 0,34 |
| Foam concrete, aerated concrete on lime, 800 kg/m3 | 0,23 | 0,39 | 0,45 |
| Foam concrete, aerated concrete on lime, 1000 kg/m3 | 0,31 | 0,48 | 0,55 |
| Window glass | 0,76 | ||
| Arbolite | 0,07-0,17 | ||
| Concrete with natural crushed stone, 2400 kg/m3 | 1,51 | ||
| Lightweight concrete with natural pumice, 500-1200 kg/m3 | 0,15-0,44 | ||
| Concrete on granulated slag, 1200-1800 kg/m3 | 0,35-0,58 | ||
| Concrete on boiler slag, 1400 kg/m3 | 0,56 | ||
| Concrete on crushed stone, 2200-2500 kg/m3 | 0,9-1,5 | ||
| Concrete on fuel slag, 1000-1800 kg/m3 | 0,3-0,7 | ||
| Porous ceramic block | 0,2 | ||
| Vermiculite concrete, 300-800 kg/m3 | 0,08-0,21 | ||
| Expanded clay concrete, 500 kg/m3 | 0,14 | ||
| Expanded clay concrete, 600 kg/m3 | 0,16 | ||
| Expanded clay concrete, 800 kg/m3 | 0,21 | ||
| Expanded clay concrete, 1000 kg/m3 | 0,27 | ||
| Expanded clay concrete, 1200 kg/m3 | 0,36 | ||
| Expanded clay concrete, 1400 kg/m3 | 0,47 | ||
| Expanded clay concrete, 1600 kg/m3 | 0,58 | ||
| Expanded clay concrete, 1800 kg/m3 | 0,66 | ||
| Ladder made of ceramic solid bricks at the CPR | 0,56 | 0,7 | 0,81 |
| Masonry of hollow ceramic bricks at the CPR, 1000 kg/m3) | 0,35 | 0,47 | 0,52 |
| Masonry of hollow ceramic bricks at the CPR, 1300 kg/m3) | 0,41 | 0,52 | 0,58 |
| Masonry of hollow ceramic bricks at the CPR, 1400 kg/m3) | 0,47 | 0,58 | 0,64 |
| Masonry of solid silicate bricks at the CPR, 1000 kg/m3) | 0,7 | 0,76 | 0,87 |
| Masonry of hollow silicate bricks at the CPR, 11 voids | 0,64 | 0,7 | 0,81 |
| Masonry of hollow silicate bricks at the CPR, 14 voids | 0,52 | 0,64 | 0,76 |
| Limestone 1400 kg/m3 | 0,49 | 0,56 | 0,58 |
| Limestone 1+600 kg/m3 | 0,58 | 0,73 | 0,81 |
| Limestone 1800 kg/m3 | 0,7 | 0,93 | 1,05 |
| Limestone 2000 kg/m3 | 0,93 | 1,16 | 1,28 |
| Construction sand, 1600 kg/m3 | 0,35 | ||
| Granite | 3,49 | ||
| Marble | 2,91 | ||
| Expanded clay, gravel, 250 kg/m3 | 0,1 | 0,11 | 0,12 |
| Expanded clay, gravel, 300 kg/m3 | 0,108 | 0,12 | 0,13 |
| Expanded clay, gravel, 350 kg/m3 | 0,115-0,12 | 0,125 | 0,14 |
| Expanded clay, gravel, 400 kg/m3 | 0,12 | 0,13 | 0,145 |
| Expanded clay, gravel, 450 kg/m3 | 0,13 | 0,14 | 0,155 |
| Expanded clay, gravel, 500 kg/m3 | 0,14 | 0,15 | 0,165 |
| Expanded clay, gravel, 600 kg/m3 | 0,14 | 0,17 | 0,19 |
| Expanded clay, gravel, 800 kg/m3 | 0,18 | ||
| Gypsum boards, 1100 kg/m3 | 0,35 | 0,50 | 0,56 |
| Gypsum boards, 1350 kg/m3 | 0,23 | 0,35 | 0,41 |
| Clay, 1600-2900 kg/m3 | 0,7-0,9 | ||
| Refractory clay, 1800 kg/m3 | 1,4 | ||
| Expanded clay, 200-800 kg/m3 | 0,1-0,18 | ||
| Expanded clay concrete on quartz sand with porization, 800-1200 kg/m3 | 0,23-0,41 | ||
| Expanded clay concrete, 500-1800 kg/m3 | 0,16-0,66 | ||
| Expanded clay concrete on perlite sand, 800-1000 kg/m3 | 0,22-0,28 | ||
| Clinker brick, 1800 – 2000 kg/m3 | 0,8-0,16 | ||
| Ceramic facing brick, 1800 kg/m3 | 0,93 | ||
| Medium density rubble masonry, 2000 kg/m3 | 1,35 | ||
| Drywall sheets, 800 kg/m3 | 0,15 | 0,19 | 0,21 |
| Drywall sheets, 1050 kg/m3 | 0,15 | 0,34 | 0,36 |
| Plywood | 0,12 | 0,15 | 0,18 |
| Fiberboard, chipboard, 200 kg/m3 | 0,06 | 0,07 | 0,08 |
| Fiberboard, chipboard, 400 kg/m3 | 0,08 | 0,11 | 0,13 |
| Fiberboard, chipboard, 600 kg/m3 | 0,11 | 0,13 | 0,16 |
| Fiberboard, chipboard, 800 kg/m3 | 0,13 | 0,19 | 0,23 |
| Fiberboard, chipboard, 1000 kg/m3 | 0,15 | 0,23 | 0,29 |
| PVC linoleum on a heat-insulating base, 1600 kg/m3 | 0,33 | ||
| PVC linoleum on a heat-insulating base, 1800 kg/m3 | 0,38 | ||
| PVC linoleum on fabric basis, 1400 kg/m3 | 0,2 | 0,29 | 0,29 |
| PVC linoleum on fabric basis, 1600 kg/m3 | 0,29 | 0,35 | 0,35 |
| PVC linoleum on fabric basis, 1800 kg/m3 | 0,35 | ||
| Asbestos-cement flat sheets, 1600-1800 kg/m3 | 0,23-0,35 | ||
| Carpet, 630 kg/m3 | 0,2 | ||
| Polycarbonate (sheets), 1200 kg/m3 | 0,16 | ||
| Polystyrene concrete, 200-500 kg/m3 | 0,075-0,085 | ||
| Shell rock, 1000-1800 kg/m3 | 0,27-0,63 | ||
| Fiberglass, 1800 kg/m3 | 0,23 | ||
| Concrete tile, 2100 kg/m3 | 1,1 | ||
| Ceramic tile, 1900 kg/m3 | 0,85 | ||
| PVC roof tiles, 2000 kg/m3 | 0,85 | ||
| Lime plaster, 1600 kg/m3 | 0,7 | ||
| Cement-sand plaster, 1800 kg/m3 | 1,2 |
Wood is one of the building materials with relatively low thermal conductivity. The table provides indicative data for different breeds. When buying, be sure to look at the density and coefficient of thermal conductivity. Not all of them are the same as prescribed in the regulatory documents.
| Name | Coefficient of thermal conductivity | ||
|---|---|---|---|
| Dry | Under normal humidity | With high humidity | |
| Pine, ale across the grain | 0,09 | 0,14 | 0,18 |
| Pine, spruce along the grain | 0,18 | 0,29 | 0,35 |
| Oak along the grain | 0,23 | 0,35 | 0,41 |
| Oak across the grain | 0,10 | 0,18 | 0,23 |
| Cork tree | 0,035 | ||
| Birch | 0,15 | ||
| Cedar | 0,095 | ||
| Natural rubber | 0,18 | ||
| Maple | 0,19 | ||
| Linden (15% moisture) | 0,15 | ||
| Larch | 0,13 | ||
| Sawdust | 0,07-0,093 | ||
| Tow | 0,05 | ||
| Oak parquet | 0,42 | ||
| Artificial parquet | 0,23 | ||
| Panel parquet | 0,17 | ||
| Fir | 0,1-0,26 | ||
| Poplar | 0,17 |
Metals conduct heat very well. They are often the bridge of cold in the design. And this must also be taken into account, to exclude direct contact using heat-insulating layers and gaskets, which are called thermal breaks. The thermal conductivity of metals is summarized in another table.
| Name | Coefficient of thermal conductivity | Name | Coefficient of thermal conductivity |
|---|---|---|---|
| Bronze | 22-105 | Aluminum | 202-236 |
| Copper | 282-390 | Brass | 97-111 |
| Silver | 429 | Hardware | 92 |
| Lead | 67 | Steel | 47 |
| Gold | 318 |
How to calculate wall thickness
In order for the house to be warm in winter and cool in summer, it is necessary that the building envelope (walls, floor, ceiling / roof) must have a certain thermal resistance. This value is different for each region. It depends on the average temperature and humidity in a particular area.
In order for the heating bills not to be too large, it is necessary to select building materials and their thickness so that their total thermal resistance is not less than that indicated in the table.
Calculation of wall thickness, insulation thickness, finishing layers
Modern construction is characterized by a situation where the wall has several layers. In addition to the supporting structure, there is insulation, finishing materials. Each layer has its own thickness. How to determine the thickness of the insulation? The calculation is easy. Based on the formula:
R is thermal resistance;
p is the layer thickness in meters;
k is the thermal conductivity coefficient.
First you need to decide on the materials that you will use in construction. Moreover, you need to know exactly what type of wall material, insulation, finish, etc. will be. After all, each of them contributes to thermal insulation, and the thermal conductivity of building materials is taken into account in the calculation.
First, the thermal resistance of the structural material is considered (from which the wall, ceiling, etc. will be built), then the thickness of the selected insulation is selected according to the “residual” principle. You can also take into account the thermal insulation characteristics of finishing materials, but usually they go “plus” to the main ones. So a certain reserve is laid “just in case”. This reserve allows you to save on heating, which subsequently has a positive effect on the budget.
An example of calculating the thickness of the insulation
Let’s take an example. We are going to build a brick wall – one and a half bricks, we will insulate with mineral wool. According to the table, the thermal resistance of the walls for the region should be at least 3,5. The calculation for this situation is given below.
- To begin with, we calculate the thermal resistance of a brick wall. One and a half bricks is 38 cm or 0,38 meters, the coefficient of thermal conductivity of brickwork is 0,56. We consider according to the above formula: 0,38 / 0,56 u0,68d 1,5. Such thermal resistance has a wall of XNUMX bricks.
- This value is subtracted from the total thermal resistance for the region: 3,5-0,68 = 2,82. This value must be “recovered” with thermal insulation and finishing materials.
All enclosing structures will have to be calculated - We consider the thickness of mineral wool. Its thermal conductivity coefficient is 0,045. The layer thickness will be: 2,82 * 0,045 = 0,1269 m or 12,7 cm. That is, in order to provide the required level of insulation, the thickness of the mineral wool layer must be at least 13 cm.
If the budget is limited, you can take 10 cm of mineral wool, and the missing will be covered with finishing materials. They will be inside and outside. But, if you want the heating bills to be minimal, it is better to start the finish with a “plus” to the calculated value. This is your reserve for the time of the lowest temperatures, since the norms of thermal resistance for enclosing structures are calculated according to the average temperature for several years, and winters are abnormally cold. Because the thermal conductivity of building materials used for decoration is simply not taken into account.