Installation Instructions

SABIC Innovative Plastics 23
Overglazing
Installing Lexan Thermoclear sheet in front or behind
the existing glazed window provides additional energy
savings. For effective insulation, the best results are
obtained when leaving a 20-50 mm air gap between
the existing glazing and the Lexan multi-wall sheet.
Double Lexan Multi-wall sheet Units
Extremely low U-values can be obtained by double-
glazed multi-wall Lexan sheet units. A combination
of Lexan Thermoclear sheet outside and Lexan
Thermoclear sheet inside, with an air gap of 20-50
mm will dramatically reduce the heat loss factor in
applications such as curved and pitched roof lights.
Energy Loss Calculations
The need to reduce energy consumption, and therefore
energy costs, is one of the highest priorities in any
business today. Substantial savings of more than 50%
are possible when installing Lexan Thermoclear sheet
instead of mono-layer glass. When calculating according
to the guidelines given in the DIN standard 4701, an
average annual saving of between 0.9 - 1.3 litres of
oil or 1.0 - 1.5 m
3
of gas per m
2
of glazing area will be
obtained by decreasing the U-value by 0.1 W/m
2
K.
Table 13 shows the minimum and maximum amount of
savings of fuel consumption per m
2
glazing area when
the U-value is decreased by varying amounts.
Calculation example
Annual fuel saving when glass is replaced by Lexan
Thermoclear sheet.
Data:
4 mm glass, U-value - 5.8 W/m
2
K
10 mm Lexan Thermoclear sheet, U-value – 3.0 W/m
2
K
U-value difference: 5.8 - 3.0 = 2.8 W/m
2
K. As shown
in Table 12, the minimum and maximum amount of
annual fuel savings per m
2
glazing area are:
25.2 – 36.4 litres of oil
28 – 42 m
3
of gas
Thermal Properties
Table 11: Overglazing
Glass
Thickness inch
Air space
inch
Thermoclear sheet
Thickness inch
U-value
BTU/ft2 hr F
0,16 0,79 - 1,97 0,24 (2RS) 0,382
0,16 0,79 - 1,97 0,31 (2RS) 0,368
0,16 0,79 - 1,97 0,39 (2RS) 0,347
0,16 0,79 - 1,97 0,39 (3TS) 0,298
Installing Lexan Thermoclear sheet in front or behind the existing glazed window provides additional energy
savings. For effective insulation, the best results are obtained when leaving a 20-50 mm air gap between the
existing glazing and the Lexan multi-wall sheet.
Table 12: Double Lexan Multi-wall sheet Units
Thermoclear
sheet outside
Air gap
inch
Thermoclear sheet
inside
U-value
BTU/ft2 hr F
0,24 (2RS) 0,79 - 1,97 0,18 (2RS) 0,322
0,31 (2RS) 0,79 - 1,97 0,18 (2RS) 0,313
0,39 (2RS) 0,79 - 1,97 0,24 (2RS) 0,284
0,63 (3TS) 0,79 - 1,97 0,24 (2RS) 0,250
0,63 (3TS) 0,79 - 1,97 0,31 (2RS) 0,245
0,79 (5RS) 0,79 - 1,97 0,24 (2RS) 0,210
0,79 (5RS) 0,79 - 1,97 0,31 (2RS) 0,204
Table 13
U-value
difference
BTU/ft2 hr F
Annual saving per 10,8 ft2 glazing area
Oil - Gallon Gas - ft
3
0,02 0,24-0,35 35-53
0,04 0,48-0,69 71-106
0,05 0,72-1,04 106-159
0,07 0,96-1,38 141-212
0,09 1,19-1,72 177-265
0,11 1,43-2,07 212-318
0,12 1,67-2,41 247-371
0,14 1,91-2,75 283-424
0,16 2,14-3,1 318-477
0,18 2,38-3,44 353-530
0,21 2,86-4,13 424-636
0,25 3,33-4,81 494-742
0,28 3,81-5,5 565-848
0,32 4,28-6,19 636-953
0,35 4,76-6,87 706-1059
0,39 5,24-7,56 777-1165
0,42 5,71-8,25 848-1271
0,46 6,19-8,93 918-1377
0,49 6,66-9,62 989-1483
0,53 7,14-10,31 1059-1589
0,56 7,61-10,99 1130-1695
0,60 8,09-11,68 1201-1801
0,63 8,56-12,37 1271-1907
0,67 9,04-13,06 1342-2013
0,70 9,52-13,74 1413-2119
Note:
The exact amount of annual fuel savings is strongly dependent upon the building
type, location and regional environmental conditions. Local authority engineering
departments usually have ofcial data relating to average temperature differences
throughout the year.