OUTSIDE WALL CONSTRUCTION FOR BUILDINGS, IN PARTICULAR PANEL

STRUCTURE DE MUR EXTERIEUR POUR BATIMENT, NOTAMMENT PANNEAU

English Abstract

To exploit solar energy, the outside wall construction for buildings has an
exterior heat insulating layer (5) between an inner wall shell (2) with an
inner heat insulating layer (3) and an largely transparent outside wall shell
(1) which is permeable to solar radiation. This heat insulating layer (5) is
bounded by a boundary surface (6) which absorbs solar radiation. The boundary
surface (6) is arranged between the outside layer (1) and the outside heat
insulating layer (5) and consists of an opaque enamel, film or coating.

French Abstract

L'invention concerne une structure de mur extérieur pour bâtiment, comportant, pour exploiter l'énergie solaire, une couche thermo-isolante extérieure (5) située entre une coque murale intérieure (2), présentant une couche thermo-isolante intérieure (3), et une coque murale extérieure (1) perméable au rayonnement solaire et transparente dans une large mesure. Cette couche thermo-isolante extérieure (5) est délimitée par une surface de séparation (6) absorbant le rayonnement solaire. Cette surface de séparation (6) est placée entre la coque murale extérieure (1) et la couche thermo-isolante extérieure (5), et est formée par un émail, une feuille ou une peinture opaque.

Claims

-9-
Claims:

1. An outside wall construction for buildings, and
more particularly a panel, in which for the exploitation of
solar energy an outer thermal insulation layer (5) is
arranged between an inner wall shell (2) having an inner
thermal insulating layer (3) and a largely transparent wall
shell (1) permeable to solar radiation, and which is defined
by a solar radiation absorbing boundary surface (6),
characterized in that the boundary surface (6) is arranged
between the outside wall shell (1) and the outer thermal
insulating layer (5) and is made to be opaque by the
application of an enamel, film or painted coating.

2. Outside wall construction according to Claim 1,
characterized in that the boundary surface (6) on its
surface, facing and/or adjacent to the outside wall shell
(1), displays a colour or structural design which when the
outside wall shell (1) is viewed from outside determines the
visual appearance of the outside wall construction.

3. Outside wall construction according to Claim 1 or
2, in which the boundary surface (6) absorbs an alpha
fraction of the solar radiation from the outer thermal
insulating layer (5), whereby the sum Rg of the thermal
transmission resistance Ra formed by the outside wall shell
(1) and the outer thermal insulating layer (5) and of the
thermal transmission resistance Ri formed by the inner wall
shell (2) with its inner thermal insulating layer (3) has a
minimum value Rgmin that is large enough so that in case of
insufficient solar irradiation and the minimum expected
outside air temperature (winter/night), the temperature at
the inner wall surface of the wall construction does not fall
below a minimum relative comfort and condensation risk value,
characterized in that the thermal transmission resistance Ra

-10-
formed by the outside wall shell (1), and the outer thermal
insulating layer (5) and their total degree of energy
permeation g, as well as the degree of absorption alpha at
the boundary surface (6) and the heat conductivity resistance
Ri formed by the inner wall shell (2) with its inner thermal
insulating layer (3), are matched to each other in such a way
that the maximum possible solar irradiation qsmax and the
maximum outdoor summer temperature Tmax expected at the
building location will produce, not only in the interior of
the wall construction but more particularly at the boundary
surface (6), at the highest a maximum temperature Ttmax that
can still be borne without damage by the materials used in
the wall construction, and at the wall inner surface
generates at the highest a maximum temperature T oimax which
persons inside the living space will still find comfortable,
so that at given values of Ra, alpha, and alpha*g (here and in
what follows, "*" indicates the multiplication sign), the
value Ri for a wall construction oriented towards south or
west falls between the limits given in the accompanying table
(Table 1):

-11-
Table 1

Solar panel: Permissible structures alpha = 0.2
Limiting criterion: Tt ~ 120° C Toi ~ 36° C

Ra .alpha. x g R1.perm Ra .alpha. x g Rl-perm
(m2K)/W (m2K)/W (m2K)/W (m2K)/W
Max Min Max Min
___________________________________________________________________
0.23 0.18 3.00 0.13 0.60 0.11 3.00 0.40
0.23 0.16 3.00 0.13 0.60 0.10 3.00 0.40
0.23 0.14 3.00 0.13 0.60 0.09 3.00 0.35
0.23 0.12 3.00 0.13 0.60 0.08 3.00 0.31
0.23 0.10 3.00 0.13 0.60 0.07 3.00 0.23
0.23 0.08 3.00 0.13 0.72 0.14 1.78 0.61
0.23 0.06 3.00 0.13 0.72 0.12 2.14 0.61
0.40 0.16 3.00 0.20 0.72 0.10 3.00 0.53
0.40 0.14 3.00 0.19 0.72 0.08 3.00 0.39
0.40 0.12 3.00 0.16 0.72 0.06 3.00 0.28
0.40 0.10 3.00 0.13 0.72 0.04 3.00 0.13
0.40 0.08 3.00 0.13 0.82 0.14 1.68 0.51
0.40 0.06 3.00 0.13 0.82 0.12 2.04 0.51
0.40 0.04 3.00 0.13 0.82 0.10 2.51 0.43
0.41 0.15 3.00 0.13 0.82 0.08 3.00 0.36
0.41 0.12 3.00 0.13 0.82 0.06 3.00 0.23
0.41 0.10 3.00 0.13 0.82 0.04 3.00 0.13
0.41 0.08 3.00 0.13 0.97 0.09 1.03 0.85
0.41 0.06 3.00 0.13 0.97 0.08 1.53 0.57
0.53 0.14 3.00 0.24 0.97 0.06 3.00 0.28
0.53 0.12 3.00 0.24 0.97 0.04 3.00 0.13
0.53 0.10 3.00 0.21 0.97 0.02 3.00 0.13
0.53 0.08 3.00 0.16
0.53 0.06 3.00 0.13
0.53 0.04 3.00 0.13

- 12 -
Table 1
Solar panel: Permissible structures alpha = 0.4
Limiting criterion: Tt ~ 120° C Toi ~ 36° C

Ra .alpha. x g R1.perm Ra .alpha. x g R1.perm
(m2K)/W (m2K)/W (m2K)/W (m2K)/W
Max Min Max Min
0.23 0.35 3.00 0.28 0.60 0.23 1.90 0.65
0.23 0.33 3.00 0.27 0.60 0.20 2.40 0.60
0.23 0.28 3.00 0.26 0.60 0.18 2.73 0.51
0.23 0.24 3.00 0.22 0.60 0.16 2.73 0.45
0.23 0.20 3.00 0.20 0.60 0.13 3.00 0.35
0.23 0.16 3.00 0.14 0.72 0.28 0.95 0.87
0.23 0.12 3.00 0.13 0.72 0.24 1.10 0.61
0.40 0.32 3.00 0.43 0.72 0.20 1.50 0.53
0.40 0.28 3.00 0.40 0.72 0.16 2.14 0.46
0.40 0.24 3.00 0.34 0.72 0.12 3.00 0.33
0.40 0.20 3.00 0.29 0.72 0.08 3.00 0.13
0.40 0.16 3.00 0.23 0.82 0.28 0.85 0.77
0.40 0.12 3.00 0.13 0.82 0.24 1.00 0.72
0.40 0.08 3.00 0.13 0.82 0.20 1.40 0.51
0.41 0.29 3.00 0.42 0.82 0.16 2.51 0.43
0.41 0.24 3.00 0.33 0.82 0.12 3.00 0.23
0.41 0.20 3.00 0.28 0.82 0.08 3.00 0.13
0.41 0.16 3.00 0.20 0.97 0.19 not possible
0.41 0.12 3.00 0.13 0.97 0.16 1.25 0.57
0.53 0.28 2.80 0.50 0.97 0.12 2.36 0.46
0.53 0.24 3.00 0.47 0.97 0.08 3.00 0.13
0.53 0.20 3.00 0.38 0.97 0.04 3.00 0.13
0.53 0.16 3.00 0.30
0.53 0.12 3.00 0.18
0.53 0.08 3.00 0.13

-13-
Table 1
Solar panel: Permissible structures alpha = 0. 6
Limiting criterion: Tt ~ 12O° C Toi ~ 36° C

Ra .alpha.xg R1.perm Ra .alpha. x g R1.perm
(m2K)/W (m2K)/w (m2K)/W (m2k)/W
Max Min Max min
0.23 0.53 3.00 0.44 0.60 0.34 1.07 0.73
0.23 0.49 3.00 0.42 0.60 0.30 1.15 0.70
0.23 0.42 3.00 0.40 0.60 0.27 1.90 0.62
0.23 0.36 3.00 0.33 0.60 0.24 2.73 0.51
0.23 0.30 3.00 0.30 0.60 0.20 3.00 0.40
0.23 0.24 3.00 0.19 0.72 0.42 not possible
0.23 0.18 3.00 0.13 0.72 0.36 not possible
0.40 0.48 2.46 0.65 0.72 0.30 1.10 0.71
0.40 0.42 3.00 0.60 0.72 0.24 2.14 0.61
0.40 0.36 3.00 0.51 0.72 0.18 3.00 0.39
0.40 0.30 3.00 0.43 0.72 0.12 3.00 0.13
0.40 0.24 3.00 0.31 0.82 0.42 not possible
0.40 0.18 3.00 0.19 0.82 0.36 not possible
0.40 0.42 3.00 0.09 0.82 0.30 1.00 0.72
0.41 0.44 2.92 0.64 0.82 0.24 1.68 0.61
0.41 0.36 3.00 0.54 0.82 0.18 3.00 0.29
0.41 0.30 3.00 0.42 0.82 0.12 3.00 0.13
0.41 0.24 3.00 0.36 0.97 0.28 not possible
0.41 0.18 3.00 0.20 0.97 0.24 1.25 0.95
0.53 0.42 1.47. 0.72 0.97 0.18 1.66 0.57
0.53 0.36 2.33 0.65 0.97 0.12 3.00 0.13
0.53 0.30 2.80 0.52 0.97 0.06 3.00 0.13
0.53 0.243.00 0.38
0.53 0.183.00 0.24
0.53 0.123.00 0.13



-14-

Table 1
Solar panel: Permissible structures alpha = 0.8
Limiting criterion: Tt ~ 120° C Toi ~ 36° C

Ra .alpha. x g R1.perm Ra .alpha. x g R1.perm
(m2K)/W (m2K)/W (m2K)/W (m2K)/W
Max Min Max Min
0.23 0.70 3.00 0.54 0.60 0.46 not possible
0.23 0.66 3.00 0.51 0.60 0.40 0.83 0.73
0.23 0.56 3.00 0.44 0.60 0.36 1.62 0.65
0.23 0.48 3.00 0.40 0.60 0.32 2.26 0.58
0.23 0.40 3.00 0.33 0.60 0.26 2.73 0.40
0.23 0.32 3.00 0.25 0.72 0.56 not possible
0.23 0.24 3.00 0.19 0.72 0.48 not possible
0.40 0.64 1.27 0.78 0.72 0.40 0.95 0.82
0.40 0.48 2.10 0.71 0.72 0.32 1.78 0.61
0.40 0.40 3.00 0.60 0.72 0.24 3.00 0.39
0.40 0.32 3.00 0.51 0.72 0.16 3.00 0.13
0.40 0.24 3.00 0.37 0.82 0.56 not possible
0.40 0.24 3.00 0.27 0.82 0.48 not possible
0.40 0.16 3.00 0.13 0.82 0.40 0.85 0.72
0.41 0.58 1.26 0.77 0.82 0.32 1.68 0.51
0.41 0.48 2.92 0.64 0.82 0.24 3.00 0.36
0.41 0.40 3.00 0.50 0.82 0.16 3.00 0.13
0.41 0.32 3.00 0.39 0.97 0.38 not possible
0.41 0.24 3.00 0.22 0.97 0.29 not possible
0.53 0.56 not possible 0.97 0.26 0.95
0.53 0.48 0.80 0.72 0.97 0.24 1.53 0.46
0.53 0.40 2.80 0.58 0.97 0.16 3.00 0.13
0.53 0.32 3.00 0.47 0.97 0.08 3.00 0.13
0.53 0.24 3.00 0.30
0.53 0.16 3.00 0.13



-15-
where in the table for alpha equal to 0.2; 0.4; 0.6 and 0.8,
each as a function of Ra (first column) and alpha*g (second
column), the permissible maximum value (third column) and
minimum value (fourth column) for R1 are compiled, and
intermediate values can be easily determined by
interpolation.

4. Outside wall construction according to Claim 3,
characterized in that the wall construction possesses the
values for alpha*g and Ra as well as the R1 value given in the
accompanying table (Table 2), which lies in the R1 range given
in Table 2 for these values of alpha*g and Ra.

-16-
Table 2

Image

E.= individual value

-17-
Table 2
Image

E. = individual value



-18-

5. Outside wall construction according to one of
Claims 3 or 4, characterized in that with the harmonization
with each other of the values Ra, Ri, alpha and alpha*g, the
expected highest possible value qsmax of solar irradiation is
calculated for each of the cardinal points of the compass
that corresponds to the directional orientation of the wall
construction.

6. Outside wall construction according to one of
Claims 1 to 5, characterized in that the colour and/or
structural design is formed by a coating applied to the
boundary surface (6).

7. Outside wall construction according to one of
Claims 1 to 5, characterized in that the colour and/or
structural design is formed by a finish applied to the
boundary surface (6).

8. Outside wall construction according to one of
Claims 1 to 7, characterized in that the boundary surface (6)
on its surface facing the outer thermal insulating layer (5)
displays an essentially plain pattern for carrying the colour
and/or structural design.

9. Outside wall construction according to one of
Claims 1 to 8, characterized in that the colour design is
formed of monochrome or polychrome colour fields or areas.

10. Outside wall construction according to one of
Claims 1 to 9, characterized in that the structural design is
formed by a surface with a relief-type configuration.

11. Outside wall construction according to one of
Claims 1 to 10, characterized in that the outside wall shell
(1) consists of single-layer glass or of multi-layered
insulating glass of different constructions.

Description

CA 02239883 1998-06-08



Outside Wall Construction for Buildinqs,
More Particularly a Panel
The invention consists of an outside wall construction
for buildings, more particularly a panel, in which for the
exploitation of solar energy an exterior thermal insulating
layer, bounded by a boundary surface which absorbs solar
radiation, is arranged between an inner wall shell having an
inner thermal insulating layer, and a largely transparent
wall shell which is permeable to solar radiation.
In a wall construction of this type as known to art from
WO 95/10741, the thermal transmission resistance of the
outside wall shell and its total energy permeability, as well
as the thermal transmission resistance formed by the inner
wall shell with its inner thermal insulating layer, are
matched with each other in such a way that the solar energy
absorbed by the boundary surface under the possible maximum
expected solar irradiation, and the maximum expected summer
outside temperature, do not generate high temperatures in the
interior o~ the wall construction that would be damaging to
materials in the wall construction, and that temperatures
which result, at their maximum, will still be felt to be
comfortable by persons inside the living space. As a rule
such a matching re~uires an adjustment of the coefficient of
thermal transmission k and the total energy conductance
rating g of the transparent outside wall shell, which is
generally ~ormed by glazing, so that their k and g values
o~ten leave insu~icient leeway ~or creating the most
desirable design o~ the visual appearance o~ the outside wall
construction in the wall and window breast area, as perceived
by an outside observer, by configuring the outside wall
shell.
The invention responds to the ~irst partial objective of
creating a wall construction of the kind described at the
outset so that the visual appearance of the wall construction
as seen from without, given even an already existing
configuration of the transparent outside wall shell, can be
affected and determined in whatever way desired. In

CA 02239883 1998-06-08



accordance with the second partial objective, temperatures
inside the wall construction that might damage materials
would be dependably avoided, while at the same time ensuring
the maximum possible exploitation o~ solar energy and indoor
com~ort, and yet keeping the construction depth o~ the wall
structure as shallow as possible, and more particularly not
to be any deeper than the static requirements of the load-
carrying construction, and more particularly, ~or example,
the pillars and beams, would require.
The ~irst partial objective is met by a wall
construction with the characteristics described at the outset
satis~ied according to the invention, in that the boundary
sur~ace is arranged between the outside wall shell and the
outside thermal insulating layer and made opaque by
application o~ enamel, ~ilm or a paint coating.
In this case it is advantageous i~ the boundary sur~ace
has a colour and/or structural design on the surface that
~aces and/or adjoins the outside wall shell, and which
determines the visual aspect o~ the outside wall construction
o~ the outside wall shell when seen ~rom without.
The colour and/or structural design on the sur~ace
~acing the outside wall shell a~ects the spectral absorption
and re~lection o~ solar radiation at the boundary sur~ace and
at the same time has a surprising e~ect on the visual
appearance o~ the wall construction as seen by an observer
looking at the outside wall shell, so that the visual
appearance can be signi~icantly modi~ied by the appropriate
design o~ this surface, without having to undertake changes
in the design o~ the external wall shell itsel~, especially
as regards its k and g values.
The second partial objective is achieved by the measures
set ~orth in the characterizing clause o~ Claim 3, that is,
by an outside wall construction, in which the boundary
sur~ace absorbs a ~raction alpha o~ the solar radiation ~rom
the external thermal insulating layer, and where the sum Rg o~
the thermal transmission resistance Ra ~ormed by the outside
wall shell and the outer thermal insulating layer, and o~ the

CA 02239883 1998-06-08



thermal transmission resistance Ri ~ormed by the inner wall
shell with its inner thermal insulating layer, has a minimum
value Rqmin which is large enough so that in the absence o~
solar radiation, and with the expected minimum outside air
temperature (winter/night) the temperature at the inner wall
sur~ace o~ the wall construction never falls below a minimum
value ~or com~ort and risk o~ condensation. In Claim 3, as
in what ~ollows, the thermal conductivity resistances Ra~ R
signify respectively the sum o~ the thermal conductance
resistance l/Lambdaa or l/Lambdai o~ the wall construction
between the boundary surface or the wall outer side or wall
inner side, and the heat trans~er resistance l/alphaa on the
wall outer side, or l/alphai on the wall inner side.
Similarly, the thermal transmission resistance Rg = Ra + Ri =
l/alphaa plus l/Lambdaa + l/Lambdai + l/alphai the sum o~ the
thermal permeability resistance l/Lambdaa + l/Lambdai o~ the
total wall construction and o~ the inner or outer heat
trans~er resistances l/alphaa, l/alphai.
In the wall construction according to the invention the
absorption of incident solar radiation takes place primarily
at the boundary sur~ace bounding the transparent outer
thermal insulating layer on the side o~ the inner thermal
insulating layer, so as to produce as a rule under solar
radiation the highest temperatures inside the wall
construction. For this purpose the boundary sur~ace can be
thin, something in the nature o~ ~oil, film or a coating, so
long as it is largely impermeable to solar radiation. The
matching according to the invention o~ the quantities
described in the characterizing claims, by means o~ a
deliberately reduced value ~or the overall energy conductance
rating g o~ the outside wall shell and/or the absorption
rating alpha on the boundary sur~ace, can have the result,
achieved while continuing to maintain good exploitation o~
solar energy, that even in the case o~ maximum possible solar
irradiation, the maximum temperature value TmaXis not exceeded
in the wall construction, so that damage to materials cannot
take place. Simultaneously, by means o~ this matching

CA 02239883 1998-06-08



according to the invention, it can also and to a surprising
degree be attained that the temperature at the inner surface
of the wall can never be greater than the value Toimax~ so that
this temperature and the temperature jump from the wall inner
surface to the interior room air, as determined by the heat
transmission resistance 1/alphai, lie, even during maximum
solar irradiation, in the range that persons inside the
living space will still feel to be comfortable. The values
for the thermal transmission resistance Riof the inner wall
shell required to obtain this matching are easy to achieve by
means of layer thicknesses, while the construction depth and
the design and monetary cost of the wall construction
according to the invention must together not exceed what is
in any case necessary for the value Rgminof the thermal
transmission resistance of the total wall construction, so
that even at night and under minimum outdoor temperatures
there is sufficient thermal insulation, with the result that
the temperature at the wall inner surface does not fall below
a minimum value for comfort and risk of condensation. The
possibility according to the invention of matching values by
deliberately reducing the g value of the outside wall shell
and the outside thermal insulation layer, can, in combination
with the absorbing boundary surface, additionally be
exploited taken advantage of to optimize the external
appearance of the wall construction, wherein a further
important advantage of the invention is to be found. The
reduced g values in fact reduce the view through the outside
wall shall, and also make it difficult to look in from
outside at the wall construction located behind the outside
wall shell, by which means requirements for the aesthetics of
the appearance of the wall construction can without
difficulty be met.
So as to be able to comply with the requirements set
forth earlier (maintaining specific limits for the maximum
temperature taking place in the wall construction and the
maximum inner surface temperature generated, the portion of
the solar energy incident on the boundary surface must be

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decreased by reducing the g value and/or the absorption at
the boundary sur~ace, by increasing the thermal transmission
resistance Ra o~ the outside wall shell and the inner thermal
insulating layer. Reducing g and/or alpha simultaneously
makes possible a greater expansion o~ the permissible wall
thermal transmission resistance Ri o~ the inner wall shell
both upwards and downwards.
More particularly, the matching o~ values according to
the invention is characterized in Table 1 as contained in
Claim 3 below. Versions o~ the wall construction which have
been distinguished by especially good exploitation o~ solar
energy are characterized in Claim 4 and in Table 2 contained
therein. These tables are valid ~or assumptions o~ TmaX =
120 C, Toimax= 36~ C, TamaX= 30~ C, Ti= 20~ C, where Tmax
represents the maximum expected outdoor summer temperature
and Ti the indoor temperature, ~or a south/west orientation
o~ the wall construction with a maximum expected solar
irradiation o~ q5max= 700 W/m2. Table 1 compiles permissible
maximum values (third column) and minimum values (~ourth
column) o~ Ri , for alphas equal to each o~ 0.2; 0.4; 0.6 and
0.8, as a ~unction o~ Ra (~irst column) and alpha*g (second
column). Intermediate values can easily be determined by
interpolation. Table 2, ~or selected and especially pre~erred
cases, characterizes not only the respective Ra/ alpha, g and
Ri values, but also, in the last column, suitability ~or
exploitation o~ solar energy at three levels, +, ++ and +++,
where the degree o~ bene~it increases with the number o~ plus
signs.
The values o~ Ra/ Ri , alpha and g as per Tables 1 and 2
are o~ course a ~unction o~ the value ~max of the highest
possible solar irradiation to be expected. This value varies
with the orientation o~ the wall construction to the points
o~ the compass; in southern orientation it is at its
greatest, and at its lowest with northern orientation. The
invention recommends that this directionality be exploited
according to Claim 5, that is, ~or example, by determining
the dimensions ~or a wall construction ~acing north to take

CA 02239883 1998-06-08



into account a significantly lower value for q5maxthan for a
south-facing construction, so as in this way to make possible
considerably lower k and keqvalues for the wall construction
than would be obtained by using the q5maxvalue for a south-
facing construction.
The lower solar radiation received by the outside wall
shell, through a deliberate reduction of the value for
alpha*g (here and in what follows, "*" indicates the
multiplication sign), is optimally exploited according to the
invention by adjusting the heat penetration coefficient k =
1/Raof this wall shell material, thus limiting the
correspondingly reduced k value for heat loss from the
absorbent boundary surface outwards through the outer
transparent thermal insulating layer and the outside wall
shell.
In another preferred embodiment of the invention the
colour and/or structural design can be formed by applying a
coating to or by sur~a~ ~inishing of ~he bo-un~ary ~urface.
An especially preferred embodiment is characterized in that
the boundary surface, on its surface turned towards the outer
thermal insulating layer, has an essentially plain pattern to
act as a base for the colour and/or structural design. The
color design can be created from monochrome or polychrome
colour blocks, and the structural design by a relief-type
surface configuration.
Further, according to the invention, the outside wall
shell can be formed from a single thickness of glass or by
multi-layered insulating glass of various configurations.
The following more particularly describes, by means of
figures, one embodiment of the invention: Figures 1 and 2
depict a cross-section through the wall construction of a
wall panel according to the invention in a simple schematic
presentation, in which the outside wall shell in Fig. 1 is
made from single-thickness glass and in Fig. 2 from
insulating glass.
This outside wall shell is identified as "1" in the
figure and can be constructed in many different ways, more

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particularly as single, double or even triple glass panes, in
which incidentally thermal protection and/or solar protection
coatings as well as coatings affecting the g value may be
present, and which need not be described here in greater
detail. Starting from the inside living space shown to the
right of the drawing, the panel possesses an inner wall shell
2, to which an inner thermal insulating layer 3 belongs, and
which on its inner side can be sealed off by a largely
moisture-proof wall surface 4, for instance of sheet metal.
The outside wall shell 1 adjoins, on the side ~acing the
inner living space, an outer thermal insulating layer 5,
which like the outside wall shell 1 can be permeable to solar
radiation and is constructed for the most part of one air
layer, but may also consist of transparent glass, transparent
plastic, transparent capillary panels and the like. The
outside wall shell (1) is separated from the outer thermal
insulating layer 5 by a boundary surface 6, which can consist
of enamel, film, paint or the like and in which solar
radiation is absorbed.
To influence and control as desired the visual
impression that an observer gathers from the outside, in the
drawing looking towards the outside wall shell 1, that is
proceeding from the left, the boundary surface 6 can be
provided on the surface facing the outside wall shell 1 with
a colour and/or structural design, which affects the spectral
absorption and reflection of solar radiation in such a way
that the desired visual impression of the outside wall
element emerges when viewed from outside. More particularly,
this colour and/or structural design can be formed by an
additional coating or by surface finishing o~ the boundary
surface 6. The boundary surface 6 can also be provided on
its surface turned towards outside wall shell 1 with an
essentially flat pattern to carry the colour and/or
structural configuration. The colour configuration can be
formed by colour panels or by areas that possess different
colours. They can however also be in a monochrome finishing
extending over the entire panel surface. The structural

CA 02239883 1998-06-08



con~iguration can ~or example be achieved by applying a
relie~-type finish to the sur~ace o~ the underlying base
sur~ace 7.
According to the invention it is recommended there be an
optimal matching o~ the respective k values and g values to
the requirements at hand, more speci~ically in consideration
o~ the maximum temperature combinations TtmaX and Toimax
occurring at the absorbing boundary sur~ace 6, and easily
derived ~rom the Tables.
The permissible assignments of Ra/ alpha, g and Ri ~or
south- and west-oriented wall sur~aces are compiled in Tables
1 and 2 in the manner already explained above. Between the
alpha, Ra~ and g to be given, the or the two cited limiting
values, Ri can be ~reely selected. The case-by-case
attainable exploitation o~ solar energy is given in the ~inal
column of Table 2, where the evaluation rests on the
~ollowing basis where kstatiC= l/Rg
The standard is in each case a south-oriented wall:

x = good (kequ = 0.16-0.25 W/m2K, keqU < 1/2 k5tatiC)

xx = ve~ good (kequ = 0.06-0.15 W/m2K,kequ<1/3kstatic)

xxx = excellent (kequ = 0.05 W/m2K,kequ <1/8k5~tic).

Representative Drawing