# Sustainable Increase in Thermal Resistance of Window Construction: Experimental Verification and CFD Modelling of the Air Cavity Created by a Shutter

## TL;DR

Adding window shutters increases thermal resistance of windows, improving building energy efficiency through reduced heat transfer.

## Contribution

Demonstrates that shutters can boost thermal resistance of windows by 2-2.5 times using experimental and CFD methods.

## Key findings

- Shutters added an air layer that significantly reduced heat transfer in double-glazed windows.
- Simulation results showed thermal resistance increased 2 to 2.5 times with shutters.
- Findings support using shutters to improve building energy performance and sustainability.

## Abstract

This study investigates, both experimentally and theoretically, the impact of incorporating window shutters on the thermal resistance of double-glazed window units, employing computational fluid dynamics (CFD) modelling. The integration of shutters, whether installed internally or externally, introduces an additional air layer that significantly influences heat transfer between indoor and outdoor environments. This effect on the thermal performance of the transparent structure was analysed through experimental measurements under real operating conditions and numerical simulations involving fluid dynamics and energy equations for the air gaps, alongside heat conduction equations for the solid components. Fourth-kind boundary conditions, considering both radiative and conductive components of the total heat flux emanating from the building’s interior, were applied at the solid–gas interfaces. The simulation results, comparing heat transfer through double-glazed windows with and without shutters, demonstrate a substantial increase in thermal resistance, ranging from 2 to 2.5 times, upon shutter implementation. These findings underscore the effectiveness of employing shutters as a strategy to enhance the energy efficiency of windows and, consequently, the overall energy performance of buildings. This research contributes to the advancement of sustainable materials for engineering applications by providing insights into the optimisation of thermal performance in building envelopes.