Silica nanogel for energy-efficient windows - Nanotechnology in Eco-efficient Construction - page 213

on the density of the sample, the measured thermal conductivity was in the
0.015-0.017 W/(mK) range and it decreased to 0.009-0.011 W/(mK) in
evacuated conditions. Moreover, a fi rst prototype of an evacuated double
glazed window with aerogel in the interspace was manufactured in the
1990s (500 28 mm 3 ). A 20 mm thick aerogel pane was inserted

between two glasses, sealing the sheet units and evacuating the interspace
with the aerogel pane to a level below 5000 Pa. As expected, the same scat-
tering of light was found in the aerogel glazings as in the aerogel samples,
but excellent thermal performance was found and the thermal transmit-
tance reached a value less than 0.5 W/(m 2 K).
The very good results encouraged the research towards superinsulating
clear windows with aerogel and within the European projects HILIT
(Highly insulating and light transmitting aerogel glazing for window, EU
Non-Nuclear Energy Programme JOULE III, Contract no. JOR3-CT97-
0187, 1998-2001) and HILIT

× 500 ×

(Highly insulating and light transmitting
aerogel glazing for super insulating windows, EU Energy, Environment and
Sustainable Development Programme, Contract no. ENK6-CT-2002-00648,
2002-2005) transparent and insulating plane monolithic silica aerogel tiles
(thickness of about 15

+

1 mm) were manufactured at a pilot-scale since
2004, in collaboration with the Swedish company AIRGLASS (Jensen
et al. , 2004). Several prototypes were made, following the optimized aerogel
manufacturing process developed during the project (Fig. 10.4). A rim seal

±

￿ ￿ ￿ ￿ ￿ ￿

10.4 An aerogel window manufactured by joining four optimized
aerogel tile prototypes in a test frame (Jensen et al. , 2004).