Note: Descriptions are shown in the official language in which they were submitted.
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A WINDOW AND A WINDOW FRAME
The present invention relates to a novel window structure and further a
technique of
improving the air within a room of a building or housing.
The general shortage of energy and environmental concerns have through the
last
decades caused buildings, in which individuals or persons are staying or
working, to
be increasingly insulated in order to prevent the waste of energy and heat
from the
heated buildings to the environments during the cold seasons such as dependent
on
the location of the building or house in question, the autumn, the winter and
the
spring.
The increased insulation.of buildings, however, have caused certain health
problems, in particular relating to the lack of supply of fresh air from the
environment
or from the exterior, as most buildings or housings, unless ventilation
systems be
provided, only allow the air of the room or rooms of the building or the
housing in
question to be shifted by fresh air by opening one or more windows and
introducing
fresh cold air from the outside and in doing so, wasting the energy of the hot
air
which is allowed to escape to the environment.
Certain attempts have been rriade to provide vented window structures such as
the
structures known from US 5,475,957, US 4,572,282 and WO 92/14023. Reference
is made to the above publications and the above US patents are further hereby
incorporated in the present specification by reference.
An object of the present invention is to provide a simple and reliable window
structure which allows venting of the room of a building, in which building a
window
is positioned delimiting the room from the surroundings and in doing so, allow
a pre-
heating of the air, which is introduced into the room in order to save energy
rather
than allowing cold fresh air to be freely introduced into the room in
question.
It is a feature of the present invention that the pre-heating of air by
employing the
novei technique according to the present invention allows a saving of up to 50-
60%
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of the energy of the air which is substituted from a room or a house by fresh
air from
the outside as compared to the situation in which the air from the room is
simply
allowed to escape and is substituted by fresh unheated air which is introduced
into
the room.
It is a particular feature of the present invention that the novel technique
of allowing
pre-heated air to be introduced into the building, in particular a room of a
building,
may be established by a window structure, which, as compared to a conventional
window has the same appearance and therefore, from an architectural point of
view,
does not ruin the appearance of the building or house in question and may be
produced from high insulating pultruded profiled elements allowing the
manufacture
of a window and a window frame having the same overall dimensions as a
conventional window used in the same building or house and made from
conventional materials such as would, plastics, metal or combinations thereof.
The above object and the above advantage together with numerous other objects,
advantages and features which will be evident from the below detailed
description of
the present invention is according to a first aspect of the present invention
obtained
by a window comprising a circumferential window frame and one or more window
elements mounted in said window frame, said window frame including a first air
inlet
aperture at the bottom of said frame communicating with the exterior, and a
first air
outlet aperture communicating with the interior and further communicating with
said
first air inlet aperture through one or more air channels extending through
substantially the entire length of said hollow frame.
As will be discussed below in a technical description of a first embodiment of
the
window according to the present invention, a hollow frame is provided in which
one
or more air channels are provided extending from a bottom air inlet aperture
through
an air outlet aperture preferably positioned at the top of the window frame
for
drawing the air through the one or more air channels in which the air is pre-
heated
by heat from the wall or from the interior of the room. The hollow frame is
preferably
made from high strength and high insulating polymer materials in particular
pultruded polymer material allowing the frame to be made in a shallow
structure
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rather than in a large bulky structure, thereby allowing the overall window to
be
produced in accordance with existing architectural requirements and without
ruining
the architectural appearance of the building in which the window is mounted.
Conventionally, windows of most buildings have a rectangular or square
configuration and according to the presently preferred embodiment of the
window
according to the present invention, the window frame is of an overall
rectangular or
square configuration and comprises a bottom frame part, two opposite side
frame
parts and a top frame part. It is to be understood that the window element or
window
elements which are mounted in the window frame may be of any type well known
in
the art per se such as a single window element fixed to the window frame, a
raisable
or lowable, a tiltable or rotatably mounted window element, alternatively a
plurality of
window elements such as four or six window elements conventionally used in a
window of the kind commonly known in Denmark as "Dannebrog"-window (named
from the Danish red and white flag Danneborg) or any other structure per se.
It is
further to be understood that the window pane may be single layer glass, multi
layer
or glazed window panes and further that the window frame may be made from one
material, preferably pultruded profiles, whereas the window elements may have
casements made from the same material as the window frame or from a different
material or different materials, such as wood, metal, plastics, metal and
including
insulating materials, e.g. mineral wool or glass wool or polymer materials or
combinations thereof. In this context, it is further to be understood that the
term
window frame is to be understood as the outer supporting structure of the
window,
which structure is to fixated directly or through supporting elements to the
wall of the
house or building in question. Similarly, the term a window element is to be
understood as a term defining the element comprising a transparent element
made
from glass or a multiplicity of layers of glass and included within a
circumferential
casing or casement.
For allowing the air channels included in the hollow window frame of the
window
according to the present invention to function as a chimney for allowing the
air to
move freely from the inlet aperture to the outlet aperture and in doing so, be
pre-
heated, the first air inlet aperture is preferably positioned in the bottom
frame part,
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and the at least one air channel extends along the bottom frame part, the side
frame
parts and the top frame part.
Dependent on the climatic conditions, in particular the difference in
temperature
between the exterior and the interior and also the humidity of the air and
possibly
also the overall structure of the building in question, the transfer of heat
from the
wall of the building or alternatively from the interior of the building to the
pre-heating
air channel or air channels included in the hollow window frame of the window
according to the present invention, may be limited to a heat transmission for
mainly
the surrounding wall or alternatively from the room in question. Consequently,
according to two alternative embodiments of the window according to the
present
invention, the hollow frame is insulated on its surface facing the interior
for
establishing heat transfer to the one or more air channels from the
surrounding wall
or alternatively, the hollow frame is insulated on its outer surface facing
the
surrounding wall.
For guiding and controlling the air flow through the one or more air channels,
the air
channels or the air channel may be configurated in a specific geometrical
configuration and in this context, the hollow frame may have a substantially
constant
cross section from the air inlet aperture to the air outlet aperture or may
have a
decreasing cross section or alternatively an increasing cross section for
decelerating
or accelerating the flow of air through the air channel or the air channels.
Further,
the surface of the hollow frame defining the air channel or air channels may
be
provided with a specific coating improving the heat transfer or, as discussed
above,
serving as an insulating layer or alternatively serving as an air flow
accelerating on
air flow decelerating surface coating.
The hollow frame including the at least one air channel characteristic of the
present
invention may be separated into a plurality of air channels constituting a set
of
parallel air channels or a continuous air channel and consequently, the hollow
window frame may, according to a further embodiment of the window according to
the present invention, including an interior separation wall dividing the
hollow frame
into two separate channels.
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The separate channels defined by the separation wall may constitute two
channels,
the one being a continuation of the first channel, thereby providing an air
flow
channel twice the length of a single air flow channel occupying the inner
space
5 defined within the hollow window frame. In order to improve the heat
transmission
between the air input to the room and the air allowed to escape from the room,
the
window according to the present invention, may advantageously be configurated
so
that a first channel delimited by the separation wall establishes
communication from
the first air inlet to the first air outlet and the hollow frame further
includes a second
air inlet aperture communicating with the interior and a second air outlet
aperture
communicating with the exterior, a second channel of said hollow window frame
establishing communication from the second air inlet aperture to the second
air
outlet.
In order to ensure that the heat transfer from the air to be vented from the
room in
question is used for pre-heating the air to be introduced into the room, the
first
channel is preferably positioned closest to the exterior and the second
channel is
preferably positioned behind the first channel closest to the interior.
The air flow through the second channel may be established dependent on the
actual position of the second air inlet aperture and the second air outlet
aperture in
parallel with and in the same direction and alternatively and preferable, in
the
opposite direction as compared to the air flow through the first channel.
In order to allow the individual or individuals located in the room to which
the
window according to the present invention allows the access of pre-heated air
to
close off the entry of pre-heated air provided e.g. the temperature outside
reaches
an extremely low level, the iniet/outlet aperture or apertures of the window
according
to the present invention are preferably provided with closure means for
allowing the
window to be seaied off.
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The above object and the above advantage together with numerous other objects,
advantages and features which will be evident from the below detailed
description of
the present invention is according to a second aspect of the present invention
obtained by a circumferential window frame of a window or to be used in a
window,
said window including one or more windows mounted in or to be mounted in said
window frame, said window frame including a first air inlet aperture which
communicating with the exterior and a first air outlet aperture communicating
with
the interior and further communicating with said first air inlet aperture
through one or
more air channels extending through substantially the entire length of said
hollow
frame.
The above object and the above advantage together with numerous other objects,
advantages and features which will be evident from the below detailed
description of
the present invention is according to a third aspect of the present invention
obtained
by a method of improving the air of a room of a building or a house by
allowing
fresh, preheated air from the exterior to be introduced into the room by
providing a
window according to the first aspect of the present invention, mounting the
window
in said building or housing and allow air from the exterior to be input
through said
first air inlet channel and be transmitted through said one or more air
channels
extending through substantially the entire length of said hollow frame and in
doing
so, be preheated and allow preheated air to be introduced into the room
through
said air outlet aperture.
The present invention is now to be further described with reference to the
drawings,
in which:
Fig. 1 is a perspective and schematic view of a first and presently preferred
embodiment of a window according to the present invention, and including a
frame
according to the present invention,
Fig. 2 is a vertical sectional view of the first embodiment of the window
according to
the present invention also shown in Fig. 1,
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Fig. 3 is a perspective, schematic and partly cutaway view similar to the view
of Fig.
I of the first embodiment of the window according to the present invention
illustrating the direction of airflow through the frame of the window,
Fig. 4a is a perspective and schematic view of an alternative embodiment of
the
frame according to the present invention, illustrating a different direction
of flow of
air through the frame,
Fig. 4b is a detail of the window frame shown in Fig. 4a illustrating the
opposite
directions of the airflow through the window frame,
Fig. 4c is a vertical, sectional view of the window frame shown in Fig. 4a
illustrating
the direction of flow through the window frame,
Fig. 5a is a perspective and schematic view similar to the view of Fig. 4a of
a third
embodiment of a window frame according to the present invention illustrating
the
direction of flow of air through the window frame,
Fig. 5b is a vertical, sectional view similar to the view of Fig. 4c
illustrating the
'20 direction of airflow through the window frame of the window shown in Fig.
5a,
Fig. 6a is a perspective and schematic view similar to the view of Fig. 4a of
a fourth
embodiment of a window frame of a window according to the present invention
illustrating the direction of flow of air through the window frame,
Fig. 6b is a vertical, sectional view similar to the view of Fig. 4c
illustrating the
direction of airflow through the window frame of the window shown in Fig. 6a,
Fig.7 is a horizontal, sectional view through a window structure of a window
structure including a window according to the present invention as mounted in
a
supporting wall,
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Fig. 8 is a perspective and schematic view illustrating in greater details the
airflow
through the first and presently preferred embodiment of the window frame of
the
window according to the present invention also shown in Figs. 1, 2 and 3, and
Fig. 9 is a diagram illustrating the correspondence between transmission area
of the
airflow and the temperature efficiency and also including the corresponding
text.
In Fig. 1, a first and presently preferred embodiment of a window according to
the
present invention is shown designated the reference numeral 10 in its
entirety. The
window 10 is generally of a design which is extremely common in older
buildings in
Denmark and conventionally called a"Dannebrog" window (named after the Danish
red and white flag). The window 10 includes a circumferential hollow frame 12
composed of two parallel and vertical frame parts 14, a horizontal top frame
part 16
and an opposite horizontal bottom frame part 18. The individual frame parts of
the
frame 12 are integrally joint together and provided an interior hollow space
to which
access is obtained from the exterior through a bottom aperture 20 provided
centrally
in the horizontal frame part 18.
The window 10 further comprises a vertical post 22 and a horizontal post 24
providing the overall geometrical structure of the "Dannebrog". In each of the
four
openings provided between the frame 12 and the crossing vertical and
horizontal
post 22 and 24, a total of four individual window elements are mounted,
preferably
journalled on individual hinges for allowing the windows to be opened and
closed.
The hinges, which may be concealed behind the frame, are not shown in the
drawings. In Fig. 1, a single window, the left hand lower window, is
designated the
reference numeral 26 and comprises a window casement 28 and a glazed window
30.
In Fig. 2, the window 10 is shown in a vertical, sectional view. Fig. 2
illustrates that
the top and bottom frame parts 16 and 18, respectively, are constituted by
hollow,
structural elements, in which a hollow inner space is provided. In the top
frame part
16, a hollow inner space is provided designated the reference numeral 17.
Similarly,
the bottom frame part 18 is provided with an inner space 19.
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In Fig. 3, the frame 12 is shown together with a cutaway part of the window
26. Fig.
3 illustrates in greater detail the inner passage defined within the hollow
frame 12 as
the aperture 20 of the bottom frame part 18 communicates with the inner space
19
defined within the frame part 18 and further communicates with inner spaces 15
defined within the vertical side frame parts 14 from which communication is
further
provided to the hollow top frame part 16, which is provided with an aperture
32,
through which the air input into the hollow frame 12 at the bottom as
indicated by
the arrow 34 is allowed to pass from the outside into the frame 12 and further
by
heating the air when in contact with the wall and the frame to be transported
through
the vertical hollow side frame part 14 and be input to the room in which the
window
is mounted through the top aperture 32. Below, a more detailed technical
analysis of
the properties and features of the first and presently preferred embodiment of
the
window shown in Figs. 1-3 is presented.
The technique of providing a hollow air passage from a bottom inlet aperture
facing
the environment to an inlet aperture through which the fresh outer air after
heating
of the air through passage in the hollow window frame is allowed to be
introduced
into the interior of the housing or building in which the window is mounted,
may be
modified in numerous ways by e.g. providing additional channels within the
hollow
frame 12, by providing insulating coverings within the hollow frame or by
including
heat transfer elements such as passive heaters constituted by metallic panels
or
heat sink like elements or active heaters.
In the below descriptions of alternative embodiments, components or elements
identical to components or elements described above with reference to Figs. 1-
3 are
designated the reference numeral or reference numerals identifying the element
or
component in question in Figs. 1-3. Components or elements included in the
below
alternative embodiments and described below having the same function as the
elements or components described above, however, differing geometrically from
the
above-described element or component is designated the same reference numeral
as the previously described element or component, however added a marking for
identifying the geometrical difference.
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In Fig. 4a, 5a and 6a, three alternative variants of the window frame 12 is
illustrated.
In Fig. 4a, a double passage is provided within the frame 12 as the air input
to the
hollow frame 12 through the aperture 20 as indicated by the arrow 34 is
allowed to
pass through an outer passage delimited from an inner passage by a separation
5 wall 36, which is shown in greater details in Fig. 4b allowing the input air
to pass a
first or outer passage 15a, vide also Fig. 4c, and to descend through an inner
passage 15b before the air is input to the interior of the building or house
through
the aperture 32', which is provided in the bottom frame part 18 as distinct
from the
above described first and presently preferred embodiment in which the aperture
32
10 allowing the preheated air to be input through the aperture 32 provided in
the top
frame part 16.
In Fig. 5a, the frame 12" includes the same separation wall 36 as described
above
with reference to Figs. 4a-4c, however, whereas the separation wall 36
described
above separates a single channel into two parts, the separation wall 36
provides two
separate channels, the one channel being established as an inlet channel from
the
inlet aperture 20 to the aperture 32, which channel is designated the
reference
numeral 15a and serves the same function as the inlet channel 15 described
above
with reference to Fig. 3.
A further channel constituting an outlet channel is provided behind the inlet
channel,
which outlet channel is divided into two parts establishing communication from
two
apertures 38 in the top frame part 18 and communicating with two bottom outlet
apertures 40 in the bottom frame part 16 through the channels 15b, which are
positioned behind the inlet channel 15a. The channels 15b constitute pre-
heating
channels in which the outlet air, which is guided from the interior of the
house or
building is used for pre-heating the inlet air. In the apertures 38, closures
may
preferably be provided for allowing the user to shut off the outlet air
provided an
excessive air outlet stream is established and similarly in Figs. 3, 4a and
5a, a
closure may be provided in the air inlet aperture 20 or alternatively in the
aperture
32.
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In Fig. 5b, the two channels 15a and 15b of Fig. 5a are shown in greater
details
illustrating the opposite directions of the two air streams from the interior
of the
house or building to the exterior and vice versa.
In Fig. 6a, the fourth embodiment 12" of the window frame is shown as the
window
frame 12" shown in Fig. 51 is modified by a simple reversal of the direction
of flow
through the air outlet channel 15b. In Fig. 6a, a single aperture 38' is
provided as an
inlet of the air outlet channel 15b from which inlet in the bottom frame part
18,
communication is established through the air outlet channel 15b to two outlets
40' in
the top frame part 16. In Fig. 6b, the directions of the air flowing through
the
channels 15a and 15b are illustrated.
In Fig. 7, a window 10 implemented in accordance with the presently preferred
embodiment of the window according to the present invention is mounted in a
brick
wall. In Fig. 7, the frame 12 is divided into two parts by a through-going
partition wall
36' primarily serving the purpose of reinforcing the inner wall of the frame
12. In the
channel 15, an insulating covering 13 is provided, which is applied to the
outwardly
facing panel of the frame 12 and serving to improve the insulating property of
the
outwardly facing panel of the hollow frame 12.
It is to be understood that the window 10 may be modified from the so-called
"Dannebrog" type into any conventionally single glazed window pane or multi-
sectional glazed window structure and further, it is also to be realised that
the
individual window including the casement may be made in accordance with any
architectural or functional criteria.
The window 10 including the window frame 12 may be made from any appropriate
material such as wood, plastics materials, metal in combination with
insulating
materials, e.g. wood, mineral wool or glass wool plastics materials etc. In
particular
plastics material including PVC, PE, PP, ABS or any other UV resistant or UV
resistivity improved polymer material may be used including fibre reinforced
or non-
fibre reinforced materials. Provided polymer materials, such as vinyl ester,
phenois
and epoxy resin are chosen, extrusion and in particular pultrusion processes
are
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relevant for providing the frame 12 as a composite profiled element,
preferably
made from pultruded elements exhibiting the advantageous characteristics of
high
strength, low weight and high thermal resistance.
In Fig. 8, the air flow through the window frame of the window according to
the
present invention is shown in greater detail.
In Annex 1, a detailed discussion of advantages inhered in the technique of
providing a controlled airflow through a hollow window frame is discussed in a
report
including a diagram illustrating the correspondence between transmission area
of
the air flow and the temperature efficiency and also including the
corresponding text.
Although the above description includes a detailed discussion of a single
presently
preferred embodiment and various modifications and alternatives, it is to be
understood that the present invention is by no means limited to the above
discussed
embodiments, as numerous modifications will be evident to a person having
ordinary skill in the art and such modifications are therefore to be
considered part of
the present invention as defined in the appending claims.
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AN N EX I
Characteristics of the window:
- It allows the light to enter
- It renders a lookout to the user
- It keeps the heat indoor. Two or more layers of transparent material (glass)
keeps
a gas (atmospheric air or argon) at rest whereby it to a great extent resists
the heat
transport by convection. Certain coatings on one layer of glass against the
cavity
reduces the heat transport by radiation. Glass in itself has a bigger
transmittance for
short-waved electromagnetic radiation (including visible light) than for long-
waved
electromagnetic radiation (including heat radiation at indoor and ambient
temperatures)
- The pane is secured in a window casement
- The window can normally be opened
- The window is provided with a rescue aperture
- The airing renders certain possibilities to the user, but it also requires
an active
operation in order to obtain a good quality of air without allowing too much
heat to
leave the room and in order to minimise draught from the fresh air
- It keeps down the noise from the traffic.
The air is let in through a slot in the outer side of the bottom of the window
frame, is
led up through the sides of the window frame and enters through an aperture at
the
inner side of the top of the window frame, thereby achieving
- Natural pre-heating of the outside air by 50-60% and thereby less draught
for the
user
- Reduction in the total heat loss to ventilation and through the window
- Airing without noise
- Less dust
As to the thermal aspect of the invention the construction of the window has
been
based on the following three characteristics:
1. The air current through the window frame in one window is 30 m3/h
corresponding to one person's need of fresh air
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2. The inside surface temperature of the window frame may be adapted so that
the
conditions of hyphomycete and condensation are not present 95% of the year
3. The total heat transmission coefficient of the window when the air in the
window
frame is stationary is supposed to live up to the general requirements in the
recommendations to new energy-saving provisions in the building regulations.
Consequently, the heat transmission coefficient may not exceed 1,5 W/m2 K.
The window and the window frame is constructed in consideration of acoustic
environments.
The three heat technical requirements on which the construction of the window
are
based are as follows:
1. The air current through the window frame in one window is 30 m3/h
corresponding to one person's need of fresh air
2. The inside surface temperature of the window frame may not become so low
that
hyphomycete and condensation arise
3. The total heat transmission coefficient of the window when the air in the
window
frame is stationary is supposed to live up to the general requirements in the
recommendations to new energy-saving provisions in the building regulations.
Consequently, the heat transmission coefficient may not exceed 1,5 W/m2K.
Furthermore when mounting the window it is possible to build a thermal bridge
cutting off/cold-conductor interruption in the brickwork defining the hole of
the
window.
Air current
Presumably, most residences include at least one window of a certain size, 1-2
m2
in area or 4-6 m in circumference of the window frame per habitant.
The supply of outside air necessary in order to obtain a good quality of the
air
corresponds to 25-30 m3/h per habitant.
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In order to minimise the loss of pressure in the window frame in order for the
window also to work under unfavourable conditions, the speed of the air
through the
window frame is limited to 0,5 m/s resulting in the cross section of the
single profile
of the window frame being 333x25 mm.
5
Hyphomycete and condensation
For the removal of hyphomycete and condensation clothes with chlorine may be
used. Another possibility is to remove the conditions for the formation of
hyphomycete and condensation.
The presence of condensation is not necessary for the formation of
hyphomycete,
the presence of a high atmospheric humidity is sufficient. Based on the below
assumptions:
= A "common household"
= An air current of 120 m3/h in the whole residence
it is quite simple to calculate:
If the conditions for the formation of hyphomycete are to be removed during
95% of
the heating season, the construction of the window should correspond to the
inside
surface temperature at the coldest place of the window frame not being below
14,2 C when the indoor temperature is 20 C and the outdoor temperature is 0 C.
When the outdoor temperature is higher, the lowest indoor surface temperature
must correspondingly be higher since there is then more humidity in the
outdoor air
with which the residence is ventilated. Vice versa when the outdoor
temperature is
lower.
In order to describe the above in general terms a factor which may be
translated as
"the dimensionless, indoor surface temperature, rfs; is used, which factor may
be
defined as follows:
Yfsi = T ndoor - Toutdoor
T ndoor - Toutdoor
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Said factor rfs; must be more than 0,71 If the conditions for the formation of
hyphomycete are to be removed during 95% of the heating season.
In the window the requirement to rfs; that the inside of window frame must be
very
well insulated at the bottom where the cold air is entering while it can be a
little less
insulated at the top where the air has become somewhat warmer.
The heat transmission coefficient of the window
An object of the heat transmission coefficient of the window is defined
corresponding to the general requirements in the recommendations to new energy-
saving provisions in the building regulations: Maximum 1,5 W/m2K which makes
it
necessary to insulate the window frame against the surroundings with what
corresponds to 20 mm common insulation. This also results in a minimising of
the
heat loss from the air current further out through the frame of the window
when the
ventilation is working.
The good central heat transmission coefficient of the pane and the insulation
of the
window frame are thermally connected via an overlapping of at least 30 mm
which
overlapping ends in weatherstrips at both sides. At the edge of the pane an
insulating TPS distance section is used for keeping the panes together.
The geometry of the window frame makes it obviously possible to improve the
heat
transmission coefficient further just as the heat transmission coefficient of
the pane
may also be considerably improved if a three-layer pane is chosen, possibly by
using a thinner, possibly iron-free glass so that the weight remains the same,
the
solar energy transmittance is improved and the staining is reduced.
Built-in thermal bridge%old-conductor
When the hole of the window is laid open, a slot may be cut around the
periphery of
the hole of the brickwork. Said slot may be used for mounting a thermal bridge
cutting off/cold-conductor interruption in the brickwork whereby the heat
current
around the well-insulated window frame is reduced.
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In order to obtain a good quality of the air, residences must be provided with
an air
exhauster or an ordinary outlet in the bathroom as well as in the kitchen. The
air
current through the window frame is moved by the differences of pressure
originating from the exhauster or outlet.
Loss of pressure and regulation
An ordinary outlet naturally depends on wind and weather, but in most
circumstances a sufficient forward pressure will be present. When the weather
is
calm, when the outdoor and the indoor temperatures are more or less the same,
it
might very well (like always) happen that the forward pressure is too low. In
these
situations, however, there is no need of pre-heating the ventilating air, and
the users
can just open the windows as they normally do.
Energy-saving exhaustion
The power consumption when ventilating is described in the building
regulations as
"the specific power consumption", SEL. In the recommendations to new energy-
saving provisions the requirement to air exhausters is that they do not exceed
1000
J/m3.
It is, however, possible to create a balanced mechanical ventilation through
heat
recurculation (and thus a high loss of pressure) where SEL is less than 1500
J/m3. It
is therefore expected that air exhausters, which are supposed to yield a far
smaller
pressure, may be produced with a SEL which is far below the requirement of
1000
J/m3.
PRE-HEATING OF THE WINDOW FRAME
In the solid frame of an ordinary window the amount of hot air flowing into
the frame
(from the warm indoor climate) is the same as the amount of hot air flowing
out of
the frame (to the colder surroundings).
This is also the case in a hollow frame with stagnant air.
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In the window according to the present invention, however, cold, fresh outdoor
air is
introduced through the hollow frame, thus reducing the difference of
temperature
between the cavity and the cold surroundings, and correspondingly the heat
loss
that way. On the other hand the heat loss from the warm indoor climate
directly to
the inside surface of the frame rises. However, the major part of the heat
loss is
used for increasing the temperature of the cold, fresh air.
The interesting size of the temperature efficiency, i.e. the amount of air
being pre-
heated in relation to the indoor and outdoor temperatures. Said temperature
efficiency is just called the efficiency, abbreviated "e" and is calculated as
follows:
e = Tindoor - Toutdoor
Tindoor - Toutdoor
The above calculation indicates that the efficiency would be 100% is it were
possible
to heat up the air current to the same temperature as the indoor air
temperature.
When heating up the air from 0 to 10 C when the outdoor temperature is 0 C
and
the indoor temperature is 20 C, the e=50%.
Theory against empiricism
The results of the measurements turned out to be a little further more
positive than
the estimates - applying the same geometry, amounts of air, etc. the
measurements
resulted in a slightly higher efficiency: The air was simply pre-heated more
than
expected.
The most significant single-parameter as to the efficiency is the relationship
between the heat-transmitting are (between the indoor air and the cavity, i.e.
the
inside of the frame) and the current by volume through the cavity: The bigger
heat-
transmitting area and the smaller current by volume, the bigger efficiency.
Therefore, the efficiency is also illustrated by the very factor in Figure 9
which
compares results of measurements to estimates.
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In the estimates a somewhat bigger area per current by volume than in the
tests
was anticipated, and, consequently, the calculated efficiencies of the
estimates were
also the highest.
A simple, linear extrapolation (which is considered to be reasonable within
the
present field) shows, however, that at least just as high efficiencies would
have
been measured if a corresponding area had been available for the test.
Based on the above-mentioned calculations and tests it must be presumed that a
pre-heating of the outdoor air with a temperature efficiency of 50 - 60% can
be
achieved.
The results have been reached without including any solar contribution. A
considerable incident solar radiation would of course contribute to a further
pre-
heating of the air.
OPTIMIZATION OF THE WINDOW
The development of the window has not yet been terminated. The construction is
to
be further optimised, including:
= Minimisation of the heat transmission from the air current to the outer side
of the
frame: Theory and tests have proved that a slight roughness on the surface of
the cavity reduces the friction between the surface and the air current. Thus
the
"contact" between the surface and the air current becomes less convex, and the
heat transmission is reduced. The result is shown in the Figure of the results
of
measurements.
= The thermal bridge cutting off/cold-conductor interruption in the brickwork
is to
be optimised: The depth of the slot and the amount needed before reducing the
effect.
= Development of a thermal bridge/cold-conductor secured closing device for
the
air current.
= Development of constant volume current regulator.
= For future use in new residences the window is to be further developed
resulting
in a halving of the heat transmission coefficient. The aim is 0,8 W/m2/k.
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On the other hand, a maximisation of heat transmission from the inside of the
frame
to the air current is not interesting, since it is necessary to insulate the
inside of the
frame in order to keep a sufficiently high surface temperature on the surface
5 towards the room.
