Civil Engineering Reference
In-Depth Information
Note that insulation only provides reduction of heat loss (or gain) through the
building fabric. Equally important is the energy lost through ventilation and
glazing (hence the need for integrated design).
Since the operational energy of buildings is gradually reducing, as a result
of the new energy efficiency standards, the energy embodied in the produc-
tion of materials and the construction process becomes more relevant. This is
why significant effort is dedicated to reducing the life cycle impact of insulat-
ing materials and it is reasonable to expect a larger diffusion of products with
high recycled content or deriving from natural sources which can be sustainably
regenerated.
A further field of innovation is the improvement of materials' thermal perfor-
mance (i.e., reducing the heat flow per thickness unit). Improving the behaviour
of the insulating material (or system) with respect to conduction, convection and
radiation would reduce the thickness required to reach high performances. This
would benefit refurbishment/retrofitting operations in particular, where the thick-
ening of existing walls would reduce internal floor area or expand the external
walls beyond the building boundaries.
Below are some examples of innovative insulating materials or systems aiming
to improve performance and minimise space requirements.
Insulating panels with IR shield
Traditional insulation materials resist the heat flow by reducing transmission from con-
duction and convection. It is possible to influence radiation transmission by reducing the
passage of infrared radiation (emissivity). This is obtained applying selective/reflective
layers to a material—usually invisible, thin metallic coatings applied by vapour deposi-
tion. An example of this can be found in low-emissivity glazing.
As this technology is not dependent on the backing material, it can also be used in
the production of insulating materials, e.g. in the form of modified polystyrene. Thermal
conductivity values can be reduced by 20 % (
λ
=
0.040 W/m K for standard EPS,
λ
=
0.032 W/m K for modified EPS).
Another possibility is adding small capsules of graphite in the mix. These are also able to
reflect infrared radiation and thus reduce the overall heat flow through the insulating panel.
Aerogel insulation
Aerogel is a manufactured material with the lowest bulk density of any known porous
solid. It is derived from a gel in which the liquid component of the gel has been replaced
with a gas. The result is an extremely low-density material. Silica aerogel can be
micro-encapsulated and integrated in a blanket of reinforcing fibres. The result is a thin
(5-10 mm) insulating panel with extremely low thermal conductivity (
λ
=
0.014 W/m K
at 25 °C average temperature).
The panel can be used as external and internal insulation in walls, roofs, framing and
floors.
Vacuum insulation panels
VIP panels have thermal conductivity values that are around 1/10th of traditional insulation
materials (
λ
=
0.003 W/m
2
K). VIPs are made by sealing the thermal insulation (in general a
porous solid with low density and nano-scale porosity) in a barrier film under vacuum.
The very high performance delivered by VIPs in thin layer makes them very interest-
ing for refurbishment operations. Other fields of application include facade insulation
where volume limitations or alignments do not allow for the installation of thick external
layers.
