Literature Review on Building Envelope, Heating and ... - Beeshive.org

Domestic Hot Water: An instantaneous electric water heater supplied hot water.
Energy Budget: The all-electric super-insulated house did not require supplemental heat
for most of the year. In January 2004, which included two cloudy weeks and
temperatures as low as -23ºC (-10ºF), the total electricity consumption for all household
uses including heating was 340 kWh.
Innovative Wall Assemblies
This section reviews innovative wall assemblies for cold climates and a hot, humid
climate. Some assemblies reviewed are still in the conceptual state.
Cold Climate
Transparent Insulation Materials
These materials, such as granulated silica aerogel and honeycomb or capillary sheet, are
used to fill the space between two layers of glass to enhance the insulation level of
windows. Lien et al. (1997) investigated the application of transparent insulation
materials in low-energy dwellings in northern regions of Norway. The climate in northern
Norway is characterized by four months of dark and the coldest period with little or no
solar radiation. Solar energy can, however, be used the rest of the year as heating is
needed in the spring and the fall, and sometimes in the summer.
To reduce heat losses during the winter and make use of solar heat in the spring and the
fall, the windows should have both high thermal resistance and high transmittance of
solar radiation. This is achieved by using transparent insulation materials. Capillary
(circular polycarbonate or polymethacrylate or glass tubes) and honeycomb (angular
plastic tubes, usually square shape) are among the most promising transparent insulation
materials, because of the combination of both high transmittance of solar radiation and
good thermal resistance. The capillary structures reduce convection losses, while
increasing solar radiation transmission, because all reflections are directed inward
through the capillaries. The capillary or honeycomb material is placed perpendicular to
the glass of a window or to the absorber of a solar collecting wall. It is possible that most
of the building envelope would consist of transparent insulation materials, which Lien et
al. (1997) referred to as “daylight walls.”
Calculations indicated about 20% savings in heating and ventilating energy for a twostorey
row house, 108 m 2 (1165 sq. ft.) floor areas, with windows and daylight walls with
capillary materials of three different thicknesses. The energy savings potential was
especially promising for the coldest climate zone in Norway, where the problem of
overheating is small and the energy saving potential is good. Table 9 lists the U-values
used in Lien et al. (1997).
Transparent insulation materials affect light distribution in the room, depending on the
type of material, its thickness, and the sun angle. The capillary material spreads direct
daylight in a cone shape and distributes it to certain areas of the floor, walls, and ceiling
of a room depending on the incoming angle of incidence. Aesthetics depend on the size
of the capillaries and the way the materials are cut. If the capillaries have a 1 mm (0.04
PERD-079: Task 2 - <strong>Literature</strong> <strong>Review</strong> 74