Please calculate the thickness of the thermal insulation layer made of expanded polystyrene, so that the partition analyzed above would reach the value of the k-factor below 0,40 W/(m2K). The influence of the adhesive layer and the protective coating on the thermal insulation layer can be neglected here. Thermal conductivity for polystyrene is 0,04 W/(mK)
For proper thermal insulation, the k-factor should be kept less than 0,40 W/(m²K), which corresponds to a heat flow resistance of approx. 2,50 m²K/W. The difference between this value and the existing heat flow resistance must be reduced, adding one more layer of insulation.
Additional polystyrene insulation must be min. 8 cm. Glue, The reinforcing mesh and acrylic plaster have been omitted here and additionally increase the thermal insulation of the partition.
| The required resistance to heat flow through the partition | – existing resistance
heat flow through the partition |
= additional resistance of the insulating layer |
| 2,50 m²K/W | – 0,66 m²K/W | = 1,84 m²K/W |
| Heat flow resistance of the insulating layer | x thermal conductivity coefficient of the insulating material | = min. insulation layer thickness in m |
| 1,84 m²K/W | x 0,04 W/(mK) | = 0,074 m = 8 cm |
Please calculate the value of the k-factor for the partition after adding the thermal insulation layer, thickness 8 cm, made of expanded polystyrene. The adhesive layer and the coating on the thermal insulation can be omitted
Calculation of the partition's thermal insulation:
| Layer arrangement in the partition (from inside to outside) | Layer thickness in m | Thermal conductivity in W /(mK) | Thermal resistance in m²K / W |
| Internal lime-gypsum plaster | 0,015 | 0,70 | 0,02 |
| Wall made of hollow ceramic hollow bricks, bulk density 1800 kg/m3 | 0,360 | 0,81 | 0,44 |
| Cement-cement external plaster–lime | 0,030 | 0,87 | 0,03 |
| Expanded polystyrene board | 0,08 | 0,04 | 2,00 |
| = total resistance to heat flow | 2,49 | ||
| + – heat inflow coefficient (constant value) | 0,13 | ||
| + heat discharge coefficient (constant value) | 0,04 | ||
| Total thermal resistance 1 / k | 2,66 | ||
| k (heat transfer coefficient) | 0,38 W/(m²K) | ||
When insulating a wall with a plate of expanded polystyrene, even without taking into account the adhesive layer and the coating on the thermal insulation, the k-factor reaches the required value 0,38 W/(m²K).