Silica nanogel for energy-efficient windows - Nanotechnology in Eco-efficient Construction - page 216

Table 10.1 Optical, thermal, and energy properties for daylighting systems
developed with semi-translucent and highly translucent aerogel granulates
(adapted from Reim et al. , 2005)

Visual directional-
hemispherical
transmittance

Solar factor
( g ) Centre U-value

Daylighting: glazing
manufactured with
two low-e glasses
(emissivity equal
to 0.08)

0.24 (semi-
transparent)
- 0.54
(translucent)

0.33 (semi-
transparent)
- 0.45
(translucent)

0.44 (90%
krypton,
12 mm) - 0.56
(90% argon,
16 mm)

Sun control: glazing
manufactured with
two low-e glasses
(emissivity equal
to 0.03)

0.19 (semi-
transparent)
- 0.38
(translucent)

0.17 (semi-
transparent)
- 0.23
(translucent)

0.37 (90%
krypton,
12 mm) - 0.47
(90% argon,
16 mm)

and, because of the low U-value, an inside surface temperature of the
aerogel glazing equal to the inside air temperature, providing good thermal
comfort conditions. During the project ISOTEG, a prototype of a new
aerogel glazing with translucent granular aerogel (Reim et al. , 2005) was
for the fi rst time integrated into the façade of the ZAE (Bayerisches
Zentrum für Angewandte Energieforschung) building in Wurzburg,
Germany (2000).
At the moment, different commercial systems with translucent aerogels
(polycarbonate panels, structural panels for continuous façades, insulated
glasses) are available on the market, offering excellent thermal perfor-
mance, a good solar heat gain and a good sound insulation, as described
below. Aerogel glazing, together with vacuum glazing, new spacer materials
and solutions, electrochromic windows, seem currently to have the largest
potential in fenestration products (Jelle et al. , 2012).
One of the main manufacturers of opaque aerogels is Aspen Aerogels
(USA). Cabot Corporation (USA) seems to be the main manufacturer of
granular translucent aerogels and it has been producing its aerogel since
2003 at its plant in Frankfurt, Germany. The translucent product manufac-
tured by Cabot, Lumira TM aerogel, formerly Nanogel ® aerogel, gained wide
acceptance across the USA and Europe for several kinds of highly insulated
daylighting systems. The product is supplied to various partners in the USA
and Europe, which developed different aerogel daylighting systems, such
as: structural composite panels for skylights and façades, structural polycar-
bonate skylight systems, polycarbonate façade systems and U-channel glass
(self-supporting systems of glass channels with an extruded metal perimeter
frame). The Lumira TM aerogels are characterized by grain size in the

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