*Article* **Sensitivity Analysis of Window Frame ComponentsE**ff**ect on Thermal Transmittance**

#### **Giorgio Baldinelli 1,\*, Agnieszka Lechowska 2, Francesco Bianchi 3 and Jacek Schnotale 2**


Received: 6 May 2020; Accepted: 6 June 2020; Published: 9 June 2020

**Abstract:** Standard ISO 10077-2 gives the procedure to calculate thermal transmittances of window frames in 2D numerical simulations. It also introduces some examples of frame geometrical models with all necessary input data and the solutions so as to perform validation of the applied numerical tools. In the present paper, the models prepared with a commercial finite volume software of a PVC window frame were first positively validated with the results given in the Standard. An experimental test was then implemented to confirm the simulated data, with satisfactory agreement. The numerical code was used on one of the frames provided by the Standard to perform a sensitivity analysis of all the components and boundary conditions playing a role on the definition of the frame thermal transmittance, such as surface heat transfer coefficients, values of the solid thermal conductivity, emissivity and insulation properties of air gaps. Results demonstrate that the air gap properties represent the most influential parameters for the definition of the PVC window frames thermal transmittance, followed by the surface heat transfer coefficients and the PVC thermal conductivity. The rubber and the steel properties show a negligible effect on the whole frame performance. This procedure could constitute a design tool to guide the efforts of window manufacturers for the achievement of high performance products.

**Keywords:** window frames; numerical analysis; hot box; sensitivity analysis
