ZEMCH 2019 International Conference Proceedings April.2020 | Page 146
Overall, 18 combination scenarios were simulated. The internal and external temperatures were
considered as 20 °C and 0 °C, respectively, to reflect winter conditions in an oceanic climate. Table 1
summarises the simulation conditions and material properties. For the purpose of the ventilation
through the trickle vent, a constant inlet/outlet ventilation was considered between outside and the
cavity between the window and the shutter. According to CIBSE Guide A (CIBSE 2015) [15], the
ventilation rate for small openings and cracks can be calculated from the equation (1):
q vc = l c k 1 (∆p) n
(1)
where, q vc is the volumetric flow rate through the crack (L.s –1 ), l c is the length of the
crack/opening (m), ∆p is the pressure difference across the opening (Pa) and k 1 is the flow
coefficient per unit length of the opening (L.s –1 .m –1 .Pa –n ). The figures for the k1, n and ∆p were
defined as 0.8, 0.6 and 0.7 respectively, using Appendix 4.A2 and Table 4.14 of the CIBSE
Guide A document [15]. The ventilation rate through a 500mm trickle vent was therefore
calculated as: 0.5 x 0.8 x (0.7) 0.6 = 0.32 L.s –1 .
Table 1. Simulation inputs and parameters
Material
Outside
Inside
Brick
Cavity insulation
Concrete
Gypsum board
Glazing
Shutter (VIP)
Shutter frame
Air cavity between
shutter and
window
Trickle vent
Thermal conductivity
(W/mK)
‐
‐
0.90
0.035
0.85
0.50
0.036*
0.006
0.5 Thickness/size
(mm)
‐
‐
100
80
140
15
20
50
50 Temperature
(°C)
0
20
‐
‐
‐
‐
‐
‐
‐
‐ 50 ,100, 150 and 200 ‐
500
* Additional inside (0.13 m 2 K/W ) and outside (0.04 m 2 K/W) surface resistance BS EN ISO 10077‐1 BSI (2017)[16]
should be considered for U‐value calculations.
3. Results and Discussion
According to the results, heat loss through the bare window was 26.65 W. The heat loss
significantly reduced by around 75%, 67%, 59% and 53% for the 50, 100, 150, and 200 mm air gap,
respectively, when the thermal shutter was deployed. Table 2 summarises the results for different
cavity widths (unventilated air cavity) when the shutter was on for a typical insulated cavity wall.
Table 2. Heat‐loss values for the shutter with insulated cavity wall and no trickle vents
Cavity width/air gap (mm)
Bare window‐base case
50
100
150
200
135
Heat loss through the window (W)
26.65
6.61
8.75
10.92
12.44
ZEMCH 2019 International Conference l Seoul, Korea