      d为材料的厚度，单位米，m
D is the thickness of the material, the unit meter, M

The thickness is thicker, the insulation effect is better.

Such as: the thickness of the roof extruded board is 0.03m, the roof of reinforced concrete 0.15m.
λ为材料的导热系数，单位W/M2.K
Coefficient of thermal conductivity of materials, unit W/M2.K

The lower the coefficient of thermal conductivity, the better the thermal insulation effect.

Such as: the roof board thermal conductivity is 0.029W/M2.K, the roof of reinforced concrete 1.74W/M2.K R为热阻，单位m2.K/W，R=d/λ
R for thermal resistance, unit m2.K/W, R=d/
R值与厚度成正比，与导热系数成反比。R值越高，保温效果越好。
The R value is proportional to the thickness, and is inversely proportional to the thermal conductivity. The higher the R value, the better the thermal insulation effect.

Such as: 3cm board R is 1.034, 15cm is 0.086 concrete roof
S为蓄热系数
S for heat storage coefficient

In the periodic heat, the surface temperature of the object is raised or lowered by 1 degrees Celsius. In the 1H, the surface area of the material is stored or released. Popular speaking is the ability to store heat.

Such as: plastic extruded board S is 0.54, S is 17.2 concrete roof
D为热惰性指标
D as thermal inertia index
Ｄ＝ＲＳ，Ｄ值越大，温度波在其中衰减越快，围护结构的热稳定性越好。
D = D, the greater the value of RS, the faster the temperature wave attenuation, the better the thermal stability of the envelope.

Such as: plastic extruded board D = 0.704, D = 1.479 concrete roof

The calculation of the total thermal resistance of roofing heat transfer R0, in addition to the plastic extruded board and concrete resistance 1.034+0.086, also need to plus the air inside the change resistance 0.04, and the air outside the roof for thermal resistance of 0.11. So the total thermal resistance of the case is R0
1.034+0.086+0.04+0.11=1.54m2.K/W
1.034+0.086+0.04+0.11=1.54m2.K/W

Heat transfer coefficient K=1/R.

The heat transfer coefficient of the roof K=1/1.54=0.649

Below the area energy saving requirements 0.7W/M2.K 