QUESTION:
ECOTECT doesn't seem to have an automatic U-value, Admittance, Decrement Factor, Thermal Lag and Solar Absortivity calculator, relying on the user to input these values for newly created construction elements. Is this right ?
ANSWER:
No. ECOTECT offers you the option of entering performance data for a material directly from the manufacturer or, if you cannot get this data, generating it yourself from its individual layers or components.
There are really two issues here...
- It is usually much easier to obtain detailed technical information about the performance of a whole composite building element from the manufacturer than it is for each of the materials from which it is composed. In fact, you may find that the manufacturer will not even tell you what the components are as this may be commercially sensitive information.
- Even when you do know what type of materials are used in a product, choosing exactly the right density, specific heat and conductivity values for each layer is very difficult. For example, the values for a simple brick can vary significantly, depending on how it was fired, the type of clay in it and the mortar used. Similarly, the exact density and moisture content of an insulation material greatly affects it thermal conductivity.
Thus, in many cases it simply may not possible for you to generate a set of layers or components that, when calculated, will give you accurate values for all aspects of the total performance of a product.
However, if you a creating your own materials or have no other information, you can create a set of layers and then use the Calculate Thermal Properties button to calculate the U-Value, Admittance and Thermal Decrement values in the Properties tab.
As the Solar Absorption is dependant on the surface colour and transparency of the element, you will be prompted to update this whenever you change the external surface colour value.
Note: ECOTECT only uses the material layers when you use the Calculate Thermal Properties button. In its own calculations it uses the values from the Properties tab. However, it does use the layers when exporting materials to EnergyPlus, ESP-r and HTB2, all of which calculate their own thermal response factors for each material.