ZEMCH 2015 - International Conference Proceedings | Page 273

Many industries that produce windows systems provide tools that allow users to determine the overall transmittance of the selected component . Our tool , in addition to the above , displays the heat flow and the isothermal diagram , providing a tool that measures the transmittance with a certain rigor to assess the quality of the different choices unresectable , by using the best way to mitigate the effects of the thermal bridges . The software , through a simple graphical interface , enables to select the climate data , the external frame typologies , the geometric features , the materials and the glass typologies . By starting the calculation , the instrument determines the thermal transmittance and checks the compatibility with the national regulations . The originality of this tool is that you can view the status of progress of the characteristics of the heat flow in a specific section , and immediately identify the possible points of heat loss ( thermal bridges ). In this way , the user can change the parameters to generate another solution that implements the overall performance of the exterior frame .
User interface
This tool is designed to be used by wide specialized users . After implementing the features of frame , the tool automatically generates the overall thermal transmittance and heat flow through THERM , a calculation software developed by the Lawrence Berkeley National Laboratory ( LBNL ), which analyzes the two-dimensional heat flows through different building components . A mesh automatic generator , processing the calculations according to the Finite Element Method , defines the section . The results obtained are consistent with the evaluation process developed by the NFRC ( National Fenestration Rating Council ), a non-profit organization that manages the consistency of assessment and labeling system for the energy performance of building components . The transmittance of the window is then calculated according to the following formula :
Uc , Ac : Thermal transmittance and projection of central glass area Ufr , Afr : Thermal transmittance and projection of frame area Ue , Ae : Thermal transmittance and projection of glass edge area Ud , Ad : Thermal transmittance and projection of divider area Ude , Ade : Thermal transmittance and projection of divider edge area
This method of calculation is considerably more detailed than the requirements of the UNI 10077- 2 , because are considered the mode of transfer of edge effects from the glass to the frame without resorting to tabulated values , often overestimated ( Fig . 2 ). As shown by the following formula ( UNI 10077-2 ), in fact , the thermal transmittance of the glass edge is identified with the parameter ψ , the linear thermal transmittance , whose value , provided by the same law , is selected from a limited number of examples not always representing the real situation to be evaluated .
Climate data are set through a first drop-down menu that allows you to choose the region and a second one in which to select the city . The information is downloaded directly from the database file insqllite .
Software for the heat flow evaluation of the nearly-zero houses 271