ZEMCH 2019 International Conference Proceedings April.2020 | Page 149
Figure 3. Temperature ranges (°C) for (from left to right): bare window, window & shutter 50mm,
100mm, 150mm and 200mm ventilated air cavity under adiabatic conditions.
Figure 4. Heat‐loss ranges (W/m ) for (from left to right): bare window, window & shutter 50mm,
100mm, 150mm and 200mm ventilated air cavity under adiabatic conditions.
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4. Conclusions
Windows are one of the main areas of heat‐loss in buildings. Thermal window shutters could
significantly reduce heat‐losses through windows; however, the performance of shutters greatly
depends on various issues including the type of insulation used, thermal bridging and the ventilation
rate that itself relates to the airtightness of both the windows and shutters as well as the presence of
controlled trickle ventilators. This paper studied the effects of air cavity gap and trickle ventilation on
the performance of a window shutter made of Vacuum Insulation Panels (VIP). The results indicate
that there is a direct relationship between the air cavity sizes (between the window and shutter) and
heat losses through the windows. The heat loss through the window was reduced by nearly 50% when
the cavity between the shutter and window was reduced from 200 mm to 50 mm. This indicates the
significant effect of cold‐bridging on the performance of thermal shutters. Therefore, the additional heat
loss due to cold bridging outweighs the additional thermal resistance due to the increased air gap. The
results also indicates that overall thermal performance is slightly deteriorated when trickle vent was
introduced. The significance of trickle vent sizes and ventilation rates require more investigation. No
meaningful changes in the performance were observed for different unventilated cavity sizes when the
walls were changed to adiabatic. The results therefore indicate that to achieve the best performance for
an airtight shutter, the size of the cavity between the window and the shutter and/or the thermal
bridging through the surrounding walls should be minimised.
Conflicts of Interest: The authors declare no conflict of interest.
Thermal Performance of Vacuum Insulated Window Shutter Systems
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