Note: Descriptions are shown in the official language in which they were submitted.
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Water drain reservoir
The present invention relates to a water drain reservoir, the use of a water
drain
reservoir, and a method of dissipating surface water.
Precipitation such as rain, snow, sleet, hail and the like results in surface
water
which needs to be disposed of. Buildings commonly have guttering which
collects
precipitation which has fallen on a roof. The guttering is connected to a
drainpipe and
the resulting water can be disposed of via mains drainage.
Increasingly, it is desirable for the surface water to be disposed of without
the use
of mains drainage. One option is that the water can be harvested in a rain
water butt
which can then be used for watering a garden.
EP1818463 discloses a different solution of a water drain tank or channel
module
made of a plastic box with open lattice walls covered by a water-permeable geo-
textile
material. This water drain tank or channel module is surrounded by sediment
and
releases the water from the box in a controlled way. The geo-textile material
is required
to prevent sediment from entering the tank or module.
DE 29611700U1 discloses the use of coarse gravel as part of a system to
manage the water content of soil.
DE2155594 discloses a water drain reservoir made of open-pored foam, such as
polyurethane. It is difficult to make a foam with a 100 % open foam structure.
The lower
the degree of open-pores, the less water a foam structure can hold. The less
water the
foam structure holds, the larger it needs to be to hold a given amount of
water. The
reduced water holding capacity of a foam substrate means that it is only able
to buffer a
low level of water. A disadvantage of foam water drain reservoirs is that if
the ground
water level is high, the foam water drain reservoir can float in the water,
and thus rise out
of the ground.
There is a need for a device that can store surface water and gradually
dissipate this
to the ground. Further, there is a need for a device that does not become
contaminated with
sediment from the ground. Further, there is a need for a device that can be
installed without
being wrapped in a geo-textile material. Further, there is a need to improve
the storage
capability of the device so that a device stores more water per volume.
Further there is a
need for a device which remains in the ground when the ground water level
rises. Further
there is a need to increase the buffering capacity of such a device, that is
the difference
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between the maximum amount of water that can be held, and the amount of
water that is retained when the device gives off water. It is also desirable
to
provide such a device which is environmentally acceptable and economical in
terms of its production. The present invention solves the above detailed
problems.
Summary of Invention
In a first aspect of the invention, there is provided a water drain reservoir
comprising a coherent man-made vitreous fibre substrate (MMVF substrate) and
a conduit having two open ends, wherein the MMVF substrate comprises man-
made vitreous fibres bonded with a cured binder composition, wherein a first
open end of the conduit is in fluid communication with the MMVF substrate.
In a second aspect of the invention, there is provided use of a water drain
reservoir comprising a coherent MMVF substrate and a conduit with two open
ends, wherein the MMVF substrate comprises man-made vitreous fibres bonded
with a cured binder composition, wherein a first open end of the conduit is in
fluid
communication with the MMVF substrate, as a water dissipating system wherein
the water drain reservoir is positioned in the ground, whereby water flows
along
the conduit and is absorbed by the MMVF substrate, wherein the water is
dissipated by the MMVF substrate into the ground.
In a third aspect of the invention, there is provided a method of
dissipating surface water comprising providing a water drain reservoir
comprising a coherent MMVF substrate and a conduit with two open ends,
wherein the MMVF substrate comprises man-made vitreous fibres bonded with a
cured binder composition, wherein a first open end of the conduit is in fluid
communication with the MMVF substrate, positioning the MMVF substrate in the
ground wherein surface water flows along the conduit and is absorbed by the
MMVF substrate and wherein the water dissipates from the MMVF substrate into
the ground.
Detailed description of the invention
MMVF substrates are known for numerous purposes, including for sound
and thermal insulation, fire protection and in the field of growing plants.
When
used for growing plants, the MMVF substrate absorbs water to allow plants to
grow. When used for growing plants, it is important that the MMVF substrate
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does not dry out. In the field of growing plants, an MMVF substrate is
normally
used instead of soil to grow plants. EP 1961291A1 discloses a coherent mineral
wool growth substrate. It describes the use of film-forming additives to
prevent
the top section of the growth substrate from becoming too dry and the lower
section of the growth substrate from becoming too wet. US 5,417,786 discloses
a plant growing medium comprising mineral fibres and lignite. Lignite is an
agent for increasing the water retention ability of the plant growing medium.
The
relative capillarity of soil and an MMVF substrate is not important in the
field of
growing plants. W001/23681 discloses the use of MMVF substrate as a sewage
filter.
The present invention provides the use of a coherent MMVF substrate as
a water drain reservoir. The man-made vitreous fibres are bonded with a cured
binder composition and the water drain reservoir can retain water within its
open
pore structure.
In use, the MMVF substrate is positioned in the ground and is preferably =
=
buried within the ground. Preferably the MMVF substrate is completely covered
with earth. Earth includes sediment, sand, clay, dirt, gravel and the like.
For
example, the MMVF substrate may be buried under at least 20 cm of earth,
preferably at least 40 cm of earth, most preferably at least 50 cm of earth.
The conduit may be an open channel, and water may flow along this
channel into the MMVF substrate. Preferably the conduit is a pipe. An
advantage of a pipe is that it is hollow and can therefore freely transport
water
underground to a MMVF substrate. Further, the wall of the pipe prevents debris
from entering the pipe.
Preferably the conduit, preferably a pipe, is positioned in fluid
communication with the top section of the MMVF substrate. This means that on
installation, the conduit is positioned in fluid communication with the top
half of
the MMVF substrate by volume. ,The conduit may be in fluid communication with
the top surface of the MMVF substrate. The conduit is preferably in fluid
communication with the top part of a side wall of the MMVF substrate. An
advantage of the conduit being positioned in fluid communication with the top
section of the MMVF is that in order to install the device, the conduit,
preferably
a pipe can be installed at a depth of the top of the device, rather than at a
depth
of the bottom of the device. This means that less effort is required to
install the
device. The conduit, preferably a pipe, is in fluid communication with the
MMVF,
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and may be in fluid communication with a system of conduits, preferably pipes
and one or more drainpipes so that water which flows off a roof, into a
gutter,
down a drainpipe can be stored within MMVF substrate during wet weather. As
the surrounding ground dries out, the water gradually dissipates
=
=
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from the MMVF substrate into the ground. The water drain reservoir thus
provides an effective way to dispose of rain water which does not put any
pressure on existing sewage systems. It is not necessary to transport the
water
elsewhere; the water is disposed of within the ground and preferably within
the
grounds of the building. It is envisaged that each property may have one, or
several, water drain reservoirs connected to their guttering systems, and thus
each property is able to dispose of this surface water within their own
grounds.
Alternatively, several properties may use the same water drain reservoir
for disposal of surface water. There may be more than one source of the water
which is dissipated by the water drain reservoir. There may be a network of
conduits, preferably pipes, which lead to the water drain reservoir.
Preferably, the water drain reservoir is provided with a conduit, preferably
a pipe, partially embedded into a MMVF substrate. This ensures that water can
flow along the conduit, and directly into the MMVF substrate. The MMVF is in
fluid communication with the conduit. It is, of course envisaged that the MMVF
substrate can butt up against the conduit, preferably a pipe, through which
rain
water will flow, in order to achieve this fluid communication. It is
preferable
however for efficiency for the conduit to be at least partially embedded into
the
MMVF substrate. The embedded part of the conduit may have an aperture in its
outer wall, preferably more than one aperture. The presence of an aperture has
the advantage of there being a greater area through which the water can flow
into the MMVF substrate.
The MMVF substrate may have a passage which extends from a first end
of the MMVF substrate, towards a second end of the MMVF substrate, wherein
the first and second ends are opposed and wherein the first end of the passage
is in fluid communication with water from the conduit, preferably a pipe. The
passage may extend 10 % to 100 % of the way through the MMVF substrate,
preferably 20 % to 99 % of the way through the MMVF substrate, preferably 50%
to 99 % of the way through the MMVF substrate, more preferably 80 % to 95 %
of the way through the substrate. The advantage of the passage is that there
is
a greater area through which the water can flow into the MMVF substrate. The
passage may have any cross-sectional shape, preferably circular, triangular or
square.
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The passage may be formed by embedding the conduit, preferably a pipe
into the MMVF substrate as described above. The conduit, preferably has an
aperture in its outer wall, preferably more than one aperture. The presence of
an aperture has the advantage of there being a greater area through which the
5 water can flow into the MMVF substrate.
The passage may be formed by a separate pipe which has at least one
aperture. The pipe is preferably a perforated plastic pipe, such as a PVC
pipe.
The pipe gives strength to the drain and prevents the passage from becoming
closed. The pipe is perforated to allow the water to drain into the passage.
The
embedded pipe provides support to the passage to make it more resilient or
resistant to pressure. In the absence of a pipe, the passage could become
closed due to pressure on the MMVF substrate, such as vehicles moving over
the MMVF substrate.
The passage may be formed by removing a section of the MMVF
substrate, such as by drilling. The resulting passage will be porous and thus
allow water to be absorbed into the MMVF substrate from the passage.
The MMVF substrate may comprise a first part in contact with a second
part, wherein the passage is disposed between the first part and the second
part. This means that the first part may be preformed with a groove along at
least part of the length of the MMVF substrate, and when the first part and
second parts are joined together, the passage is formed by the groove and the
second part. Alternatively the second part may have the groove. Alternatively,
both the first and second parts may have a groove and the grooves may be lined
up to form the passage when the first and second parts are joined together.
The
groove or grooves may be of any shape as required to form the passage. The
groove or grooves may therefore have a cross-section which is semicircular,
triangular, rectangular or the like.
The first and second parts of the MMVF substrate may be joined by
placing the two parts together, or using an adhesive.
The passage may be formed by a combination of the means described
above.
Preferably the cross-sectional area of the first and second ends of the
passage are in the range 2 to 200 cm2, preferably 5 to 100 cm2.
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Preferably the cross-sectional area of the first end of the passage is 0.5
% to 15 A of the cross-sectional area of the first end of the MMVF substrate,
preferably 1 % to 10%.
Preferably the cross-sectional area of the second end of the passage is
0.5 % to 15 % of the cross-sectional area of the second end MMVF substrate,
preferably 1 % to 10%.
The openings are such a small percentage of the cross-sectional area of
the ends of the MMVF substrate since the vast majority of the MMVF substrate
is used to buffer the amount of water that is conveyed to the MMVF substrate.
The larger the proportion of the MMVF substrate, the greater the volume of
water that can be buffered by a MMVF substrate of a given cross-sectional
area.
The cross-sectional area of the passage is preferably substantially
continuous along its length. Substantially continuous means that the cross-
sectional area is within 10 % of the average cross-sectional area, preferably
within 5 %, most preferably within 1 % . If necessary however, the cross-
sectional area can be varied according to the requirements of the passage to
be
smaller or larger.
The passage is may be straight through the MMVF substrate, that is, the
passage takes the most direct route towards the second end of the MMVF
substrate to allow water to take the most direct route along the passage.
The passage may follow an indirect route through the MMVF substrate to
increase the surface area of the passage so that water can drain into the MMVF
substrate at a faster rate.
There may be more than one passage through the substrate to increase
the surface area of the passage so that water can drain into the MMVF
substrate
at a faster rate. Where there is more than one passage, the passages are
preferably connected to form a network of passages so that water may flow
through the network of passages. Each passage may be in fluid communication
with a different conduit thus allowing water from different sources to be
disposed
of by the water drain reservoir.
The passage may have a triangular cross-section. When installed, the
base of the triangle is preferably parallel with the base of the MMVF
substrate.
Alternatively the passage can have a semicircular cross-section. Again, the
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base of the MMVF substrate is preferably parallel with the base of the
semicircle.
Alternatively, the passage can have a circular or a rectangular cross-section.
The advantage of these passage cross-sections is that the largest surface area
of the passage is at the lowest point which gives the largest surface area for
the
water to flow through.
The passage is preferably positioned centrally in the width of the cross-
section of the MMVF substrate. The reason that this is substantially
centrally, is
so that the flow of the water which is to be absorbed will be down the centre
of
the MMVF substrate. This has the advantage that the strength of the MMVF
substrate is maintained at the sides of the MMVF substrate. If however the
passage was arranged close to one side of the MMVF substrate, this may cause
a weakness in the structure.
Preferably the passage is offset towards a first direction. The advantage
of this is that the MMVF substrate may be installed with the passage at the
top of
the water drain reservoir to allow the water to drain into the main body of
the
MMVF substrate
In use, when the passage extends from the first end to the second end of
the MMVF substrate, the second end of the passage is preferably closed to
prevent earth from entering the passage and reducing the size of the passage.
The second end of the passage may be closed by arranging a plate over the
opening, such as an MMVF plate, a metal plate, a plastic plate or the like.
Alternatively, the second end of the passage may be plugged, such as with a
plug made from MMVF, metal, plastic or the like. The second end may be
wrapped in a geo-textile material to close the second end of the passage.
A water drain reservoir may be provided in kit form comprising a conduit
and a coherent MMVF substrate, wherein the MMVF substrate comprises man-
made vitreous fibres bonded with a cured binder composition.
A series of MMVF substrates may be connected together to increase the
volume of water that can be stored and then dissipated. These MMVF
substrates may be placed next to each other so that water can dissipate from
one MMVF substrate to the next. Alternatively, a conduit, preferably a pipe,
with
apertures can run through a first MMVF substrate, and then be at least
partially
embedded into a second MMVF substrate. The conduit may extend all the way
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through the second MMVF substrate as discussed above. This allows any water
which is not absorbed by the first MMVF substrate to flow into the second MMVF
substrate. There may also be more than two MMVF substrates connected in this
way such as 3, 4, 5, or 6.
The man-made vitreous fibres (MMVF) can be glass fibres, ceramic
fibres, basalt fibres, slag wool, stone wool and others, but are usually stone
wool
fibres. Stone wool generally has a content of iron oxide at least 3% and
content
of alkaline earth metals (calcium oxide and magnesium oxide) from 10 to 40 %,
along with the other usual oxide constituents of MMVF. These are silica;
alumina; alkali metals (sodium oxide and potassium oxide) which are usually
present in low amounts; and can also include titania and other minor oxides.
Fibre diameter is often in the range of 1 to 20 pm, preferably 3 to 5 pm.
The MMVF substrate is in the form of a coherent mass. That is, the
MMVF substrate is generally a coherent matrix of MMVF fibres, which has been
produced as such, but can also be formed by granulating a slab of MMVF and
consolidating the granulated material.
Preferably the water holding capacity of the MMVF substrate is at least
80% of the volume, preferably 80-99 `)/0, most preferably 85-95 /0. The
greater
the water holding capacity, the more water that can be stored for a given
volume. The water holding capacity of the MMVF substrate is high due to the
open pore structure and the MMVF substrate being hydrophilic.
Preferably the amount of water that is retained by the MMVF substrate
when it gives off water is less than 20 %vol, preferably less than 10 %vol,
most
preferably less than 5`)/ovol. The water retained may be 2 to 20 %vol, such as
5
to 10 %vol. The lower the amount of water retained by the MMVF substrate, the
greater the capacity of the MMVF substrate to take on more water. Water may
leave the MMVF substrate by dissipating into the ground when the surrounding
ground is dry and the capillary balance is such that the water dissipates into
the
ground.
Preferably the buffering capacity of the MMVF substrate, that is the
difference between the maximum amount of water that can be held, and the
amount of water that is retained when the MMVF substrate gives off water is at
least 60 %vol, preferably at least 70 %vol, preferably at least 80 %vol. The
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buffering capacity may be 60 to 90 %vol, such as 60 to 85 %vol. The advantage
of such a high buffering capacity is that the MMVF substrate can buffer more
water for a given volume, that is the MMVF substrate can store a high volume
of
water when it rains, and release a high volume of water as the surrounding
ground dries out. The buffering capacity is so high because MMVF substrate
requires a low suction pressure to remove water from the MMVF substrate. This
is demonstrated in the Example.
The water holding capacity, the amount of water retained and the
buffering capacity of the MMVF substrate can be measured in accordance with
EN 13041 ¨ 1999.
The water is stored in the MMVF substrate when the surrounding ground
is saturated, that is the capillary balance means that the water is retained
within
the MMVF substrate. As the surrounding ground dries out, the capillary balance
shifts, and the water dissipates from the MMVF substrate into the surrounding
ground. In this way, water is held within the MMVF substrate when the
surrounding ground is saturated. When the surrounding ground dries out, the
water dissipates from the MMVF substrate into the ground. The MMVF
substrate is then able to take on more water, when this flows down the
conduit,
preferably a pipe, into the MMVF substrate.
The structure of the MMVF substrate is such that whilst water can
dissipate from the substrate into the ground, earth does not contaminate the
MMVF substrate. This is due to the small pore size within the substrate. It is
therefore not necessary to wrap the MMVF substrate in a geo-textile to prevent
contamination. This has the advantage that on installation, the MMVF substrate
does not have to be manually wrapped in a geo-textile material by the
installer.
The wrapping step of the known water drain reservoirs is awkward and time
consuming, since it is performed at the installation stage. The water drain
reservoir of this invention overcomes this problem.
The binder may be any of the binders known for use as binders for
coherent MMVF products.
The MMVF substrate is hydrophilic, that is it attracts water. The MMVF
substrate is hydrophilic due to the binder system used. In the binder system,
the
binder itself may be hydrophilic and/or a wetting agent used.
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The hydrophilicity of a sample of MMVF substrate can be measured by
determining the sinking time of a sample. A sample of MMVF substrate having
dimensions of 100x100x65 mm is required for determining the sinking time. A
container with a minimum size of 200x200x200 mm is filled with water. The
5 sinking time
is the time from when the sample first contacts the water surface to
the time when the test specimen is completely submerged. The sample is placed
in contact with the water in such a way that a cross-section of 100x100 mm
first
touches the water. The sample will then need to sink a distance of just over
65mm in order to be completely submerged. The faster the sample sinks, the
10 more
hydrophilic the sample is. The MMVF substrate is considered hydrophilic if
the sinking time is less than 120 s. Preferably the sinking time is less than
60 s.
In practice, the MMVF substrate may have a sinking time of a few seconds, such
as less than 10 seconds.
For instance, the binder, including any oil required may be hydrophobic,
such as a phenol urea formaldehyde binder.
When the binder is hydrophobic, preferably a wetting agent is additionally
included in the MMVF substrate. A wetting agent will increase the amount of
water that the MMVF substrate can absorb. The wetting agent may be any of
the wetting agents known for use in MMVF substrates that are used as growth
substrates. For instance it may be a non-ionic wetting agent such as Triton X-
100. Some non-ionic wetting agents may be washed out of the MMVF substrate
over time. It is therefore preferable to use an ionic wetting agent,
especially an
anionic wetting agent, such as linear alkyl benzene sulphonate. These do not
wash out of the MMVF substrate to the same extent.
EP1961291 discloses a method for producing water-absorbing fibre
products by interconnecting fibres using a self-curing phenolic resin and
under
the action of a wetting agent, characterised in that a binder solution
containing a
self-curing phenolic resin and polyalcohol is used. This binder can be used in
the present invention. Preferably, the wetting agent does not become washed
out of the MMVF substrate and therefore does not contaminate the surrounding
ground.
The binder of the MMVF substrate can be hydrophilic, that is it attracts
water. The effect of using the hydrophilic cured binder in the MMVF substrate
is
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that the MMVF substrate can absorb more water than when a hydrophobic
binder is used. A hydrophilic binder does not require the use of a wetting
agent.
A wetting agent can be used to increase the hydrophilicity of either a
hydrophobic or a hydrophilic binder. This means that the MMVF substrate will
absorb a higher volume of water than if the wetting agent is not present. Any
hydrophilic binder can be used.
The binder may be a formaldehyde-free aqueous binder composition
comprising: a binder component (A) obtainable by reacting at least one
alkanolamine with at least one carboxylic anhydride and, optionally, treating
the
reaction product with a base; and a binder component (B) which comprises at
least one carbohydrate, as disclosed in W02004/007615. This binder is
hydrophilic.
WO 97/07664 discloses a hydrophilic substrate that obtained its
hydrophilic properties from the use of a furan resin as a binder. The use of a
furan resin allows the abandonment of the use of a wetting agent. This binder
may be used in the present invention.
W007129202 discloses a hydrophilic curable aqueous composition
wherein said curable aqueous composition is formed in a process comprising
combining the following components:
(a) a hydroxy-containing polymer,
(b) a multi-functional crosslinking agent which is at least one selected from
the
group consisting of a polyacid, salt(s) thereof and an anhydride, and
(c) a hydrophilic modifier;
wherein the ratio of (a):(b) is from 95:5 to about 35:65.
The hydrophilic modifier can be a sugar alcohol, monosaccharide,
disaccharide or oligosaccharide. Examples
given include glycerol, sorbitol,
glucose, fructose, sucrose, maltose, lactose, glucose syrup and fructose
syrup.
This binder can be used in the present invention.
Further, a binder composition comprising:
a) a sugar component, and
b) a reaction product of a polycarboxylic acid component and an
alkanolamine component,
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wherein the binder composition prior to curing contains at least 42% by weight
of
the sugar component based on the total weight (dry matter) of the binder
components may be used in the present invention, preferably in combination
with a wetting agent.
Binder levels are preferably in the range 0.5 to 5 wt%, preferably 2 to 4
wt% based on the weight of the MMVF substrate.
Levels of wetting agent are preferably in the range 0 to 1 wt%, based on
the weight of the MMVF substrate, in particular in the range 0.2 to 0.8 wt%,
especially in the range 0.4 to 0.6 wt%.
The MMVF product may be made in any of the ways known to those
skilled in the art for production of MMVF growth substrate products. In
general,
a mineral charge is provided, which is melted in a furnace to form a mineral
melt.
The melt is then formed into fibres by means of centrifugal fiberisation e.g.
using
a spinning cup or a cascade spinner, to form a cloud of fibres. These fibres
are
then collected and consolidated. Binder and optionally wetting agent are
usually
added at the fiberisation stage by spraying into the cloud of forming fibres.
These methods are well known in the art.
The MMVF substrate may have density in the range 60 to 200 kg/m3, in
particular in the range 130 to 150 kg/m3. The advantage of this density is
that
the MMVF substrate has a relatively high compression strength. This is
important as the MMVF substrate may be installed in a position where people or
vehicles need to travel over the ground in which the MMVF substrate is
positioned. Optionally a force distribution plate is positioned on top of the
MMVF
substrate in order to distribute the force applied to the MMVF substrate.
Preferably such a force distribution plate is not required due to the density
of the
MMVF substrate.
The dimensions of a water drain reservoir may be in the range: height 0.3
¨ 1.2 m; width 0.15 ¨ 0.8 m; and length 0.5 ¨ 1.5 m. The volume of a water
drain reservoir may be 0.025 ¨ 1.4 m3, preferably 0.05 - 1 m3, preferably 0.1
¨
0.5 m3. The typical dimensions of a water drain reservoir according to the
invention are 0.6 m x 0.2 m x 1.0 m (height x width x length). This provides a
water drain reservoir with a volume of 0.12 m3, which has proven satisfactory
for
use in relation to a typical single family house. The dimensions and thus the
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volume of a water drain reservoir may of course be varied depending on the
actual use. A plurality of water drain reservoirs may also be combined to
achieve the desired total volume as described earlier.
Brief description of figures
Figure 1 shows schematically a water drain reservoir dug into the ground and
connected to the guttering of a house, and
Figure 2 shows water retention curves for a MMVF substrate, a foam substrate
and silt loam.
Detailed description of figures
Figure 1 shows a MMVF substrate 1 that has been dug into the ground 2
in the vicinity of a house 3. The house 3 is provided with gutters 4 that
collect
water from the roof 5 and lead it to the MMVF substrate 1 via a drain pipe 6
and
a conduit 7. The conduit 7 is in fluid communication with the MMVF substrate
1.
The conduit 7 may butt up against the MMVF substrate 1, but preferably it is
partly embedded in the MMVF substrate 1 in order to ensure that debris is not
entering the conduit 7. In the part that is embedded in the MMVF substrate 1
the
conduit 7 may be provided with apertures 8 to increase the fluid communication
area between the conduit 7 and the MMVF substrate 1.
The invention will now be described in the following example which does
not limit the scope of the invention.
Example
The water holding capacity of a MMVF substrate, foam substrate and silt
loam were tested in accordance with EN 13041 ¨ 1999. The MMVF substrate
was a stone wool fibre product with a phenol-urea formaldehyde (PUF) binder
and a non-ionic surfactant wetting agent. The foam
substrate was a
polyurethane foam substrate. The results are shown in figure 2.
The MMVF substrate has a maximum water content of 90 %vol. When
the MMVF substrate gives off water, it retains about 2-5 %vol of water. This
means that the MMVF substrate has a buffering capacity of 85-87 %vol. The
foam substrate however has a maximum water content of 46-47 %vol. When
the foam substrate gives off water it retains about 27%vol of water. The
buffering capacity of the foam is therefore only 19-20 %vol. This shows that
the
MMVF substrate has a higher maximum water content than the foam substrate,
CA 02854552 2014-05-05
WO 2013/072082
PCT/EP2012/066559
14
as well as a lower water retention level. Therefore the MMVF substrate has a
higher water buffering capacity than the foam substrate. The data shows that a
foam substrate will need to be at least four times the volume of the MMVF
substrate to buffer the same amount of water.
The maximum water content of the silt loam is similar to that of the foam
substrate, and lower than the MMVF substrate. The capillarity of the silt loam
is
much higher than that of the MMVF substrate, which means you need a suction
pressure of several meters to withdraw water from the silt loam. This means
that
the soil will easily drain water from the MMVF substrate as soon as the soil
is not
saturated.
It will be appreciated by the skilled person that any of the preferred
features of the invention may be combined in order to produce a preferred
method, product, binder composition or use of the invention.
