Environmental Engineering Reference
In-Depth Information
For both green façades and living wall systems these results imply potential
energy savings for building envelopes in warmer and colder climates (Perini et al.
2011
; Ottelé
2011
). This ''technical/thermal green'' strategy of increasing exterior
insulation properties of vertical surfaces stimulates upgrading or retrofitting of
existing (under-insulated) façades without the added cost of interior or traditional
exterior insulation systems.
An experimental research conducted by Ottelé (
2011
) was set up to in order to
classify the thermal benefits of green façades or plant covered cladding systems
under boundary conditions in a so-called hotbox testing facility. For this reason, an
insulated (mineral wool) cavity wall with different (attached) vertical greening
systems was built and tested in order to distinguish the thermal effect of the green
systems. In total, there were two measurements performed with Hedera helix
(direct and indirect to the wall) and four measurements were carried out with
living wall systems (based on felt layers, planter boxes, mineral wool, and foam
substrate.
In the study, it was found that, both for the direct and indirect greening principle
lower surface temperatures of the exterior masonry were measured during summer
conditions compared to the bare wall situation. The difference of temperature for
the systems is reaching 1.7 and 1.9 C, respectively, after 8 h of heating. The
insulation material inside the bare wall moderates the prevailing temperature
difference between the outside and inside climate chamber, resulting in no tem-
perature difference for the inside climate chamber. The winter measurement after
72 h shows that the wall surface covered directly with Hedera helix is warmer
compared to the bare wall, with a temperature difference of 1.7 C. The air
temperature of the inside climate chamber is lowered with 0.7 C in the case of the
bare wall, which means that the vegetation layer slows down the rate of heat flow
through the façade, resulting in an improved R-value of the system. In the case of
the indirect facade greening system the same trend was found; a temperature
difference of 1.9 C, compared with the bare wall was found and the interior air
temperature is lowered with 1 C in the case of the bare wall.
According to this measurement some conclusions can be drawn, namely, that
the insulation material is superior compared with the green layer, and thus mini-
mizes the effect indoor. However, since the green layer protects the heat accu-
mulation in the outer layer of the masonry, less heat will be reradiated during the
evening and night, which has a positive effect on the urban heat phenomena
(lowering the urban temperature).
A stronger relation between temperature reduction and greenery was found for
the living wall systems tested, a surface temperature reduction that can be achieved
with the investigated living wall systems was between 7.2 and 10.3 C during
summer conditions. It can be noticed that the effect on the interior temperature is
also higher as well as the relation between mitigation of the urban heat island
effect.
For the winter measurements it was found that compared with the bare wall all
the greening systems contributes to a better thermal resistance of the facade.
Especially, in the case of the living wall systems higher interior room temperatures
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