| dc.description.abstract | We are facing an urgent problem of reducing carbon dioxide emissions in order to
mitigate climate change. The building sector is a main source of carbon dioxide
emissions. This thesis is trying to contribute to the creation of solutions for this problem
by investigating the application of relatively new building materials, particularly highly
reflective coatings and aerogel granulate glazing facades.
Facades have an important role to play in controlling indoor climate and thus building
energy use. This thesis investigated which facade properties have an impact on reducing
heating and cooling energy demands in a common building type (office building) in
Tokyo, Japan. It was shown that walls with high reflectance and windows with low heat
gain and low heat transmittance can contribute to achieving energy efficient buildings. In
this regard, highly reflective coatings and aerogel granulate glazing systems can make an
important difference. These materials are therefore able to serve as an energy solution.
Highly reflective coatings and aerogel granulate glazing systems are still new products in
the building field. This thesis therefore experimentally provided information concerning
their durability.
Treated aluminum was investigated as a highly reflective material. New and conventional
commercial products were tested through an accelerated aging process, taking into
account heat, moisture, and solar radiation. Measurements showed that surface aging due
to these aging factors barely affected the optical properties of the treated aluminum.
Facades with highly reflective coatings can improve the durability of sealant joints
because their lower surface temperatures cause less thermal movement, i.e. less fatigue
damage. This has been examined both experimentally and theoretically.
Energy performance was simulated for aerogel granulate glazing systems. When the
spandrels of a double glazing facade (with shading) were replaced with an aerogel
granulate glazing system (without the shade), the energy performance was improved.
This was observed in the climates of Oslo, Tokyo, and Singapore, implying that aerogel
facades can introduce more daylight and improve energy performance not only in cold
regions but also in warm and hot regions. Furthermore, small aerogel granular sizes may
be preferable from an energy point of view, because smaller granular sizes feature less
solar transmittance without adverse change of thermal performance, and thus contribute
to cooling energy reduction. Thus, specific application of this material in spandrels is
proposed. It should however be noted that a triple glazing (with the shade) may be better
in this regard than an aerogel window in cold climates.
The durability of aerogel granulate was investigated experimentally. Although aerogel
granules have high permeability, suggesting that convection may occur in the aerogel
layer, the experiment showed that thermal performance does not change owing to this
process. If aerogel is exposed to moisture over many years (decades), the thermal
conductivity of aerogel granules can worsen by ~10%. Building specifications should
therefore avoid this aging effect on thermal conductivity by preventing moisture from
penetrating into aerogel granules (into the glazing cavity).
In order to avoid moisture, aerogel granulate glazing systems have a rim seal. A rim seal
is normally hidden in window frames. A main aging factor affecting rim seals is fatigue
due to wind pressure. The existence of an optimal rim seal section dimension was
indicated experimentally. Ideas to improve durability of the rim seal were also provided.
In overall, this thesis investigated energy and durability performance of highly reflective
coatings and aerogel granulate glazing systems. The thesis provides useful information
for designers considering application of these materials to a facade. | nb_NO |
