U.S. patent application number 12/809655 was filed with the patent office on 2010-12-16 for building structures containing external vapor permeable foam insulation.
Invention is credited to Carlos Castro, Martin Reimers, Van-Chau Vo.
Application Number | 20100313507 12/809655 |
Document ID | / |
Family ID | 40562938 |
Filed Date | 2010-12-16 |
United States Patent
Application |
20100313507 |
Kind Code |
A1 |
Castro; Carlos ; et
al. |
December 16, 2010 |
BUILDING STRUCTURES CONTAINING EXTERNAL VAPOR PERMEABLE FOAM
INSULATION
Abstract
Attach a thermoplastic polymeric foam to multiple spaced apart
structural support members of a structure wherein the foam has a
resistance to water vapor permeability (mu) that is less than 50, a
thermal conductivity that is less than 40 milliwatts per
meter*Kelvin, a compressive strength that is greater than 80
kilopascals, and a density of 48 kilograms per cubic meter or less
to provide insulation while also providing water vapor-permeability
and structural durability to the structure.
Inventors: |
Castro; Carlos; (Madrid,
ES) ; Reimers; Martin; (Buehl-Rittlersbach, DE)
; Vo; Van-Chau; (Souffelweyersheim, FR) |
Correspondence
Address: |
The Dow Chemical Company
P.O. BOX 1967
Midland
MI
48641
US
|
Family ID: |
40562938 |
Appl. No.: |
12/809655 |
Filed: |
January 15, 2009 |
PCT Filed: |
January 15, 2009 |
PCT NO: |
PCT/US09/31038 |
371 Date: |
August 4, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61022915 |
Jan 23, 2008 |
|
|
|
Current U.S.
Class: |
52/309.4 ;
52/408; 52/741.4 |
Current CPC
Class: |
E04B 2/707 20130101;
E04B 1/26 20130101 |
Class at
Publication: |
52/309.4 ;
52/408; 52/741.4 |
International
Class: |
E04B 1/66 20060101
E04B001/66; E04C 2/20 20060101 E04C002/20; E04B 1/64 20060101
E04B001/64 |
Claims
1. A building structure comprising: a. multiple support members
spaced apart from one another so that two neighboring support
members have a space between them and each support member having
opposing inside and outside surfaces; and b. an extruded
thermoplastic polymer foam spanning the space between two
neighboring support members and attached to the outside surface of
two or more of the support members; wherein, the thermoplastic
polymer foam: (i) has a resistance to water vapor permeability that
is less than 50 according to EN 12086; (ii) a thermal conductivity
that is less than 40 milliWatts per meter*Kelvin as measured
according to EN12667; (iii) a compressive strength greater than 80
kilopascals as measured according to EN 826; and (iv) a density of
48 kilograms per cubic meter or less according to EN 1602.
2. The building structure of claim 1, wherein the thermoplastic
polymer foam has a continuous polymer phase comprising an alkenyl
aromatic polymer.
3. The building structure of claim 1, wherein the building
structure is free of a vapor barrier component having a resistance
to water vapor permeability higher than 50 as measured according to
EN12086 and that extends across two or more support members spanned
by the thermoplastic polymer foam.
4. The building structure of claim 1, wherein the thermoplastic
polymer foam has a resistance to water vapor permeability of 10 or
more.
5. The building structure of claim 1, wherein the thermoplastic
polymer foam is further characterized by having a density of 24-48
kilograms per cubic meter according to ISO 845-95.
6. The building structure of claim 1, wherein the thermoplastic
polymer foam is further characterized by having an open cell
content of 40% or more and 100% or less according to ASTM
D2856.
7. The building structure of claim 1, wherein the thermoplastic
polymer foam is further characterized by having a thickness of 50
millimeters or more.
8. The building structure of claim 1, wherein the building
structure is one or more structure selected from a group consisting
of roof structures and wall structures.
9. The building structure of claim 1, wherein the building
structure is a timber frame wall structure.
10. The building structure of claim 1, wherein the building
structure is a pitched roof structure.
11. The building structure of claim 1, wherein adjacent support
members define a cavity between them and the building structure
further comprises insulation residing in more than one cavity
between support members.
12. A method for insulating a building structure comprising the
following steps: a. providing multiple support members spaced apart
from one another so that two neighboring support members have a
space between them and each having opposing inside and outside
surfaces; b. providing an extruded thermoplastic polymer foam that
has a resistance to water vapor permeability that is less than 50
as measured according to EN12086, a thermal conductivity that is
less than 40 milliWatts per meter*Kelvin as measured according to
EN 12667, a compressive strength that is greater than 80
kilopascals as measured according to EN 826, and a density of 48
kilograms per cubic meter or less according to EN 1602; and c.
attaching the thermoplastic polymer foam to two or more of the
support members such that the foam spans the space between two
neighboring support members.
13. The method of claim 12, wherein the thermoplastic polymer foam
has a continuous polymer phase comprising an alkenyl aromatic
polymer.
14. The method of claim 12, wherein the thermoplastic polymer foam
has a resistance to water vapor permeability of 10 or more.
15. The method of claim 12, wherein the thermoplastic polymer foam
is further characterized by having a density of 24-48 kilograms per
cubic meter according to EN 1602.
16. The method of claim 12, wherein the thermoplastic polymer foam
is further characterized by having an open cell content of 40% or
more and 100% or less according to ASTM D2856.
17. The method of claim 12, wherein the thermoplastic polymer foam
is further characterized by having a thickness of 50 millimeters or
more.
18. The method of claim 12, wherein the building structure is one
or more structure selected from a group consisting of roof
structures and wall structures.
19. The method of claim 12, wherein the building structure is a
timber frame wall structure.
20. The method of claim 12, wherein the building structure is a
pitched roof structure.
Description
CROSS REFERENCE STATEMENT
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/022,915, filed Jan. 23, 2008.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to vapor permeable foam,
methods of using such foam for insulation in buildings and building
structures containing such insulation.
[0004] 2. Description of Related Art
[0005] There is a need to increase the level of thermal insulation
in existing building structures without inducing vapor build-up and
condensation within the building structure.
[0006] The European Energy saving directive of 2002 requires
increasing insulation values of many building structures in
European member states to lower energy consumption. However, it is
critical to add insulation to these building structures without
increasing the likelihood of vapor condensation within the building
structures. Vapor condensation within a building structure can
cause mold, mildew and decomposition of building structure
components. Therefore, addition of any insulation to existing
houses should have necessary vapor permeability.
[0007] It is further desirable for additional insulation to have a
high compressive strength while simultaneously having a desired
level of vapor permeability. Installation of additional insulation
to existing building structures advantageously involves applying
the insulation to the outside of the building structures,
particularly roof structures so as to not disrupt the ability to
occupy the building structure. Therefore, the insulation will
desirably have enough permeability to avoid vapor condensation in
the building structure while at the same time have sufficient
compressive strength to support the weight of materials and workers
applying the insulation without damage.
[0008] Typically, increasing the vapor permeability of a polymer
foam decreases the foam's compressive strength. Similarly,
increasing the vapor permeability can lead to a lower compressive
strength and a higher thermal conductivity. Therefore, it has been
unknown whether the objective of achieving an insulating foam that
has a high enough compressive strength to support materials and
workers without damage and that has a desirable thermal
conductivity and water-vapor permeability is achievable with a
thermoplastic foam.
[0009] United States patent application US2005/0055973 discloses an
insulated structure with studs, inner and outer sheathing and an
insulation component between the studs. The outer sheathing can be
a foam. However, the reference describes no properties of the foam.
The insulation between the studs can also be a foam and that is,
preferably, highly vapor permeable with a vapor permeance of
between about 7 and 13 perms 565 ng/(Pa*s*m.sup.2) for a five inch
(127 mm) thick section. Such a vapor permeability corresponds to a
permeance relative to air of about 2.1-3.8 mu.
[0010] U.S. Pat. No. 5,996,289 and U.S. Pat. No. 6,145,255 disclose
soffit ventilation systems that can include an open cell foam in
order to allow for ventilation while preventing egress of insects
into an attic space. It is unclear whether the foam of these
patents is rigid or flexible. Moreover, a foam in such a soffit
applications desirably would have high thermal conductivity (low
insulating value) to prevent trapping of heat in an attic
space.
[0011] Great Britain patent (GB) 1396182 and GB 1396582 disclose
open cell foam structures suitable for applications requiring vapor
transmission. The foams are prepared from a solution by dissolving
a polymer into a solvent. GB 1396182 achieves an example having a
95% void volume (and a density of approximately 50 kilograms per
cubic meter (kg/m.sup.3) assuming the polymer composition has a
specific gravity of approximately one gram per cubic centimeter)
that is "tough". However, another example having 98% void volume
(approximately 20 kg/m.sup.3 density) is "soft and compressible".
Therefore, it is clear that decreasing the density of these foams
reduces their compressive strength. Hence, it is unclear what
compressive strength a foam having a density of less than 48
kg/m.sup.3 will have. Moreover, there is no discussion of thermal
conductivity or a measure of vapor permeability for these
foams.
[0012] Australian patent application AU2006203389 discloses a
perforated foam sheet suitable for insulation where moisture
permeability is desirable. The reference discloses several
embodiments of a foam that differ in cell size and, likely, other
properties. One type of foam has a cell structure whose cells are
cylindrical in shape with a diameter between about eight
millimeters and 25 millimeters. A foam with such a large cell size
will have poor thermal insulating properties due to high convection
of heat through the cells. The other type of foam in this reference
is a closed-cell foam having an average cell size of less than 0.1
millimeters and that is flexible and capable of rolling up.
BRIEF SUMMARY OF THE INVENTION
[0013] The present invention is the result of surprisingly
discovering a foam that is especially well suited for insulating a
building structure, particularly retro-insulating a building
structure, because the foam concomitantly has a vapor permeability
sufficiently high to allow water vapor to escape the building
structure while also having a low enough thermal conductivity to
serve as a thermal insulator and a compressive strength sufficient
to support materials and workers during installation.
[0014] In a first aspect, the present invention is a building
structure comprising: (a) multiple support members spaced apart
from one another so that two neighboring support members have a
space between them and each support member having opposing inside
and outside surfaces; and (b) a thermoplastic polymer foam spanning
the space between two neighboring support members and attached to
the outside surface of two or more of the support members; wherein,
the thermoplastic polymer foam: (i) has a resistance to water vapor
permeability value that is less than 50 according to EN 12086; (ii)
a thermal conductivity that is less than 40 milliWatts per
meter*Kelvin as measured according to EN12667; (iii) a compressive
strength greater than 80 kilopascals as measured according to EN
826; and (iv) a density of 48 kilograms per cubic meter or less
according to EN 1602.
[0015] Embodiments of the first aspect of the present invention may
have any one or any combination of more than one of the following
characteristics: the thermoplastic polymer foam has a continuous
polymer phase comprising an alkenyl aromatic polymer; the building
structure is free of a vapor barrier component having a water vapor
permeability value higher than 50 as measured according to EN12086
and that extends across two or more support members spanned by the
thermoplastic polymer foam; the thermoplastic polymer foam has a
resistance to water vapor permeability of 10 or more; the
thermoplastic polymer foam is further characterized by having a
density of 24-48 kilograms per cubic meter according to ISO 845-95;
the thermoplastic polymer foam is further characterized by having
an open cell content of 40% or more and 100% or less according to
ASTM D2856; the thermoplastic polymer foam is further characterized
by having a thickness of 50 millimeters or more; the building
structure is one or more structure selected from a group consisting
of roof structures and wall structures; the building structure is a
timber frame wall structure; the building structure is a pitched
roof structure; and adjacent support members define a cavity
between them and the building structure further comprises
insulation residing in more than one cavity between support
members.
[0016] In a second aspect, the present invention is a method for
insulating a building structure comprising the following steps: (a)
providing multiple support members spaced apart from one another so
that two neighboring support members have a space between them and
each having opposing inside and outside surfaces; (b) providing a
thermoplastic polymer foam that has a resistance to water vapor
permeability that is less than 50 as measured according to EN12086,
a thermal conductivity that is less than 40 milliWatts per
meter*Kelvin as measured according to EN 12667, a compressive
strength that is greater than 80 kilopascals as measured according
to EN 826, and a density of 48 kilograms per cubic meter or less
according to EN 1602; and (c) attaching the thermoplastic polymer
foam to two or more of the support members such that the foam spans
the space between two neighboring support members.
[0017] Embodiments of the second aspect can have any one or any
combination of more than one of the following characteristics: the
thermoplastic polymer foam has a continuous polymer phase
comprising an alkenyl aromatic polymer; the thermoplastic polymer
foam has a resistance to water vapor permeability value of 10 or
more; the thermoplastic polymer foam is further characterized by
having a density of 24-48 kilograms per cubic meter according to EN
1602; the thermoplastic polymer foam is further characterized by
having an open cell content of 40% or more and 100% or less
according to ASTM D2856; the thermoplastic polymer foam is further
characterized by having a thickness of 50 millimeters or more; the
building structure is one or more structure selected from a group
consisting of roof structures and wall structures; the building
structure is a timber frame wall structure; and the building
structure is a pitched roof structure.
[0018] The present invention has particular utility in insulating
building structures by either building new or by adding insulation
to existing structures in order to meet higher thermal insulting
requirements and demands while avoiding hazards associated with
retaining water within a building structure.
DETAILED DESCRIPTION OF THE INVENTION
Terms
[0019] "Multiple" means two or more.
[0020] "ASTM" refers to American Society for Testing and Materials.
ASTM test methods refer to the test method of the year noted by the
hyphenated suffix after the test method number or the most recent
test method prior to filing this application.
[0021] "Internal" and "inside" refer to a side that is most
proximate to a space defined by (hence, within) a building
structure. In a home structure, the "inside" or "internal" side is
the side facing the dwelling side of the structure that is
typically heated in cold portions of the year.
[0022] "External" or "outside" refers to a side that is opposite
the internal or inside and that is most remote from a space defined
by a building structure. The external or outside portion of a
building element is most proximate to the natural environment in
which the building structure is built.
[0023] "Span" means to extend all the way across. To span a space
between two support members means to extend from one support member
across the space to the other support member.
[0024] Resistance to water vapor permeability is in adimensional
units of "mu" or ".mu.". Each unit of mu is equal to the resistance
of water vapor permeability through standing air. Determine mu for
a given material according to the general procedure of EN
12086-95.
Foam Insulation
[0025] Thermoplastic polymer foam for use in the present invention
(the "present thermoplastic polymer foam") can be any type of foam,
including expanded polymer bead foam or extruded polymer foam.
[0026] In an expandable polymer bead process prepare a foamable
composition by incorporating a blowing agent into granules of
polymer composition (for example, imbibing granules of polymer
composition with a blowing agent under pressure). Subsequently,
expand the granules in a mold to obtain a foam composition
comprising a multitude of expanded foam beads (granules) that
adhere to one another to form a "bead foam". The granules can
experience some level of foaming prior to expansion within a mold
to form a bead foam. Alternatively, expand the beads apart from a
mold and then fuse them together thermally or with an adhesive
within a mold. Bead foam has a characteristic continuous network of
polymer skin corresponding to the surface of each individual bead
extending throughout the foam.
[0027] Extrusion processes are most desirable. Foams made from
expandable foam bead processes have a network of polymer skins
(bead skins) that define and enclose groups of cells within the
foam. Such skins are residual skins from each foam bead that
expanded to form the foam. The bead skins coalesce together to form
a foam structure comprising multiple expanded foam beads. Bead
foams tend to be more friable than extruded foam because they can
fracture along the bead skin network. Moreover, the bead skin
network provides a continuous thermal short from any one side of
the foam to an opposing side, which is undesirable in a thermal
insulating material. Extruded foams are continuous, seamless
structures free from having, for example, the network of bead skins
characteristic of expanded bead foam. An extruded foam can be a
"strand foam". That is, the extruded foam may comprise multiple
extruded strands of foam that are fused together. A strand foam has
a polymer network skin extending along the extrusion direction of
the foam but not in a direction perpendicular to the extrusion
direction. Hence, a strand foam is free of a continuous polymer
skin (which can cause a thermal short) extending all the way
through the strand foam in a direction perpendicular to the
extrusion direction as there is in an expanded bead foam.
Nonetheless, it is most desirable that the extruded foam be a
continuous, seamless structure as opposed to a bead foam structure
or other composition comprising multiple individual foams that are
assembled together in order to maximize structural integrity and
thermal insulating capability.
[0028] In an extrusion process prepare a foamable composition by
mixing a thermoplastic polymer composition and, optionally,
additives in an extruder at a temperature sufficiently high to
soften the polymer composition, and then mixing in a blowing agent
at an addition pressure sufficient to preclude appreciable
expansion of the polymer composition. It is acceptable to either
feed additives directly into the extruder or to pre-mix additives
with a polymer prior to addition to an extruder (i.e., compound it
or create a masterbatch). It is desirable to then cool the foamable
composition to a foaming temperature and then expel the foamable
composition through a die into an environment of lower pressure
than the addition pressure. As the foamable composition enters the
environment of lower pressure it expands into a polymer foam.
[0029] Blowing agents are typically present in a combined
concentration of 0.001 mole per 100 grams of polymer to 0.5 mole
per 100 gram of polymer. Suitable blowing agents for use in an
extrusion foaming process include one or more of the following:
inorganic gases such as carbon dioxide, argon, nitrogen, and air;
organic blowing agents such as water, aliphatic and cyclic
hydrocarbons having from one to nine carbons including methane,
ethane, propane, n-butane, isobutane, n-pentane, isopentane,
neopentane, cyclobutane, and cyclopentane; fully and partially
halogenated aliphatic hydrocarbons having from one to five carbons,
preferably that are chlorine-free (e.g., difluoromethane (HFC-32),
perfluoromethane, ethyl fluoride (HFC-161), 1,1,-difluoroethane
(HFC-152a), 1,1,1-trifluoroethane (HFC-143a),
1,1,2,2-tetrafluoroethane (HFC-134), 1,1,1,2 tetrafluoroethane
(HFC-134a), pentafluoroethane (HFC-125), perfluoroethane,
2,2-difluoropropane (HFC-272fb), 1,1,1-trifluoropropane
(HFC-263fb), 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea),
1,1,1,3,3-pentafluoropropane (HFC-245fa), and
1,1,1,3,3-pentafluorobutane (HFC-365mfc)); aliphatic alcohols
having from one to five carbons such as methanol, ethanol,
n-propanol, and isopropanol; carbonyl containing compounds such as
acetone, 2-butanone, and acetaldehyde; ether containing compounds
such as dimethyl ether, diethyl ether, methyl ethyl ether;
carboxylate compounds such as methyl formate, methyl acetate, ethyl
acetate; carboxylic acid and chemical blowing agents such as
azodicarbonamide, azodiisobutyronitrile, benzenesulfo-hydrazide,
4,4-oxybenzene sulfonyl semi-carbazide, p-toluene sulfonyl
semi-carbazide, barium azodicarboxylate,
N,N'-dimethyl-N,N'-dinitrosoterephthalamide, trihydrazino triazine
and sodium bicarbonate.
[0030] The polymer foam may contain any individual or combination
of the following additives: infrared attenuating agents (for
example, carbon black, graphite, metal flake, titanium dioxide);
clays such as natural absorbent clays (for example, kaolinite and
montmorillonite) and synthetic clays; nucleating agents (for
example, talc and magnesium silicate); flame retardants (for
example, brominated flame retardants such as
hexabromocyclododecane, phosphorous flame retardants such as
triphenylphosphate, and flame retardant packages that may including
synergists such as, or example, dicumyl and polycumyl); lubricants
(for example, calcium stearate and barium stearate); and acid
scavengers (for example, magnesium oxide and tetrasodium
pyrophosphate). A preferred flame retardant package includes a
combination of hexahalocyclododecane (for example,
hexabromocyclododecane) and tetrabromobisphenol A bis
(2,3-dibromopropyl ether.
[0031] The polymer foam has a thermal conductivity of 40 milliWatts
per meter*Kelvin (mW/m*K) or less, preferably, 35 mW/m*K or less.
Lower thermal conductivity values are desirable to maximize thermal
insulating capability for the foam. The lower the thermal
conductivity of a foam, the less thickness is necessary to achieve
a given measure of thermal insulation. Measure thermal conductivity
at 10.degree. C. mean temperature according to test method EN
8301-91.
[0032] Additionally, the polymer foam has a compressive strength
greater than 80 kilopascals (kPa), preferably 120 kPa or more, more
preferably 170 kPa or more, still more preferably 200 kPa or more.
Measure compressive strength according to ASTM D-1621-04. Higher
compressive strengths are desirable in an insulating foam over
lower compressive strengths in order to provide durability during
handling, installation and use. The compressive strength of present
thermoplastic polymer foams renders them rigid foams. In contrast,
flexible foams are not suitable alternatives to the thermoplastic
polymer foams for use in the present invention. Flexible foams
necessarily have an undesirably low compressive strength in order
to flex and, therefore, cannot sustain loads in a roofing
application without deformation or inhibit racking in walls like
the present thermoplastic polymer foam.
[0033] The polymer foams of the present invention have properties
that surprisingly balance conflicting effects of achieving a low
thermal conductivity and high compressive strength (typically
achieved using a closed-cell foam with low permeability) with
achieving vapor permeability through the foam that is high enough
provide for more water vapor to permeate through the foam than is
retained from permeating through the foam.
[0034] Polymer foams of the present invention have a resistance to
water vapor permeability ("mu" or ".mu.") of 50 or less, preferably
40 or less more preferably 30 or less as measured according to EN
12086-95. The foam can have a mu value of 20 or less. Higher mu
values correspond to foams having lower water vapor permeability.
When the mu value is greater than 50 the polymer foam generally
will have too low of a water vapor transmission capability and
water condensate will likely build up proximate to a building
structure on which the foam resides. At the same time, it is
desirable not to have too low of a mu value or the thermal
insulating value of the foam becomes too low to be of value and,
typically, the compressive strength decreases. Hence, it is
desirable for the foam to have a mu value of 10 or more.
[0035] In order to achieve the desired water vapor permeability,
the polymer foam desirably has an open cell content of 40% or more,
preferably 50% or more, more preferably 60% or more. Measure open
cell content according to American Society for Testing and
Materials (ASTM) method D2856. Increasing open cell content
increases water vapor permeability. However, too high of an open
cell content can detrimentally raise thermal conductivity and lower
compressive strength. Typically the polymer foam has an open cell
content of 100% or less, more typically 80% or less.
[0036] The polymer foam can have an open cell content below 40%,
even below 30% or 20% or even 10%. The polymer foam can have an
open cell content of 0%. However, if the open cell content is too
low to achieve the necessary mu value then the foam must undergo
perforation so as to provide perforations though the foam to
increase water vapor permeability. Desirably, the thermoplastic
foams are not perforated but rather have an inherent open cell
structure (that is, an open cell structure resulting from expansion
of the cells during manufacture). Inherently open cell foams have a
torturous path through the cell structures from one side to the
other of the foam without a linear paths through from one side to
the other. In contrast, perforated foams have linear paths through
the foam from one side to the other where perforating needles
penetrate through the foam.
[0037] If the foam contains perforations, the perforation are
preferably 2 millimeters or less in diameter in order to minimize
detrimental effect on (that is, increase in) thermal conductivity.
When the perforations are 2 millimeters or less in diameter,
airflow does not occur extensively enough to effect thermal
conductivity. Nonetheless, water vapor can still permeate
effectively through the perforations.
[0038] The polymer foam has a density of 64 kilograms per cubic
meter (kg/m.sup.3) or less, preferably 40 kg/m.sup.3 or less, more
preferably 30 kg/m.sup.3 or less. Measure foam density according to
ISO 845-95. Lower density foams are desirable because they
contribute less weight to building structures, and weight can be a
particular concern for roof structures. Low density foams are also
desirable for easier handling and shipping. Typically, the polymer
foam has a density of 20 kg/m.sup.3 or more in order to ensure
sufficient compressive strength and durability.
[0039] The foam desirably has a thickness of at least 15
millimeters, preferably at least 30 millimeters and more preferably
at least 50 millimeters in order to provide optimal insulating
value and also provide structural integrity to the building
structure (for example, to provide stability against racking in
timber frame structures).
[0040] The thermoplastic polymer foam has a continuous polymer
phase that desirably comprises or consists of one or more than one
alkenyl aromatic polymer. The continuous polymer phase includes all
polymers present in the thermoplastic foam at a concentration
greater than 20 wt % based on the thermoplastic polymer foam
weight. Polymers present at a concentration less than 20 wt % of
the thermoplastic polymer foam are considered additives in the
continuous polymer phase as opposed to part of the continuous
polymer phase. For example, a continuous polymer phase may "consist
of" styrenic polymers even though there are non-styrenic polymer
additives present at a concentration less than 20 wt % of the
thermoplastic polymer foam weight.
[0041] An alkenyl aromatic polymer contains polymerized alkenyl
aromatic monomer units and includes homopolymers and copolymers
containing alkenyl aromatic monomer units (i.e., made from monomers
that include alkenyl aromatic monomers). Polystyrene (PS) based
polymers (that is, PS homopolymer and copolymers) are one
particularly preferred class of alkenyl aromatic polymers.
Particularly desirable PS polymers are PS homopolymer and PS
copolymer with acrylonitrile (styrene-acrylonitrile copolymer
(SAN)).
[0042] Typically, the present thermoplastic polymer foam is free of
a continuous polymer phase that consists of polyethylene (PE),
polypropylene (PP) or a combination of PE and PP. The modulus of
most PE and PP polymers is too low to provide a thermoplastic
polymer foam having a combination of vapor permeability,
compressive strength and thermal conductivity of the present
thermoplastic polymer foam.
[0043] The present thermoplastic foam typically has an average cell
size that is greater than 50 microns, preferably greater than 70
microns, and is more preferably 100 microns or larger, still more
preferably 200 microns or larger. The average cell size is
desirably 2000 microns or smaller, preferably 1000 microns or
smaller, more preferably 500 microns or smaller. When the average
cell size is less than 50 microns, thermal conductivity and density
tend to increase undesirably due a large amount of polymer in a
given through the foam's cross section. When the cell size exceeds
2000 microns, thermal conductivity tends to begin to increase due
to convention through the foam. Measure average cell size according
to American Society for Testing and Materials method D-3576.
Insulated Building Structure
[0044] The present thermoplastic polymer foam is useful for
insulating building structures. In particular, the thermoplastic
polymer foam offers advantages over other insulating foam when
applied to the outside of a building where thermal insulation needs
to be permeable to water vapor in order to allow vapor to escape to
the atmosphere from between the insulating foam and building
structure. Without being permeable to water vapor, insulating foam
applied to the outside to prevent water vapor build-up and
condensation between the insulating foam and building
structure.
[0045] Typically, it is desirably to have water vapor barriers
between the inside of a structure and the structural
elements/insulation to prevent water vapor from getting trapped in
the structural elements/insulation. Water-vapor build up and
condensation can be particularly problematic when there is no such
water vapor barrier because humidity from inside the structure and
enter the structural elements and insulation. Even more problematic
is if the water-vapor cannot escape from the structural
elements/insulation. The high vapor permeability of the present
thermoplastic polymeric foam is particularly useful for applying to
structure from the outside because it allows water vapor to escape
from the structural elements/insulation within the structure.
Therefore the present thermoplastic polymeric foam is especially
suited for modifying existing structures to increase insulation
(that is, "retro-insulating" existing structures).
[0046] In general, the thermoplastic foam can be applied onto any
building structure in any manner. However, it is particularly
useful for spanning two or more ("multiple") support members of a
building structure that are spaced apart from one another. For
example, roof rafters and wall joists are examples of support
members of a building structure. The high compressive strength of
the present thermoplastic foams make the present thermoplastic
foams well suited for supporting loads even between support members
without breaking. Generally, an insulating thermoplastic foam
having a high vapor permeability like the present foam does not
have sufficient compressive strength to support loads between
support members. Hence, insulated building structures comprising
multiple support members spaced apart from one another such that
two neighboring support members have a space between them and each
support member having opposing inside and outside surfaces with the
present thermoplastic foam spanning the space between two
neighboring support members and attached to the outside surface of
two or more of the support members is unique and offers a desirable
structure having a combination of high insulating ability, high
compressive strength and vapor permeability.
[0047] In one embodiment, the thermoplastic foam is useful for
insulating, particularly retro-insulating, pitched roofs on
building structures such as houses by attaching to outside surfaces
of roof structural elements. Roof structures typically comprise
spaced apart structural elements such as rafters or furring strips
spanning rafters. These elements have opposing inside surfaces and
outside surfaces with the inside surfaces most proximate to the
attic or inside of the building structure. In many older buildings,
ventilation is sufficient through the roof and any insulation
between the rafters (for example, mineral wool) to allow water
vapor to pass through from the inside to the outside of the roof
structure. Other foam insulation, such as close-celled polymer foam
and insulation having vapor impermeable facers are not suitable for
such an application because they would trap moisture within the
attic. Even in newer buildings, a vapor barrier is typically
present proximate to the inside of the structural elements so
applying an insulation component on the outside that is impermeable
to water vapor would serve to undesirably trap moisture between the
insulation and building structural elements.
[0048] Pitched roof structures of the present invention may
comprise, in addition to the structural elements and present
thermoplastic foam, at least one of the following additional
elements: a breathable membrane and finishing elements (such as
shingles, battens and tiles) with the thermoplastic foam between
the additional element or elements and the structural elements. The
additional element or elements are desirably attached to the
thermoplastic foam, which is attached to the structural element
such that the thermoplastic foam is between the additional
element(s) and the structural elements.
[0049] The present thermoplastic polymer foam is ideally suited for
insulating wall structures from the outside, which is particularly
desirable in retro-insulating building structures. The vapor
permeability of the present thermoplastic polymer foam allows
moisture to escape. Moreover, the compressive strength of the
present thermoplastic polymer foam strengthens the wall structure
against deformation by, for example, racking.
[0050] In any of the insulated structure embodiments of the present
invention, additional insulation may be present in a cavity defined
by neighboring structural elements. For example, inter-joist or
inter-rafter cavities may contain mineral wool or fiberglass or
other fibrous insulation while the present thermoplastic polymer
foam spans the outside surface of the joists, rafters, or other
structural elements defining the cavity.
Method of Insulating a Building Structure
[0051] Prepare building structures of the present invent by
providing multiple support members spaced apart from one another so
to form a space between them and each having opposing inside and
outside surfaces, providing a present thermoplastic polymer foam
and attaching the thermoplastic polymer foam to two or more of the
support members such that the foam spans the space between two
support members. A single foam may span the space between more than
one pair of neighboring support members.
[0052] The support members can be of any composition, with common
materials being wood (for example, lumber joists and studs) and
metal (for example, metal joists and studs). Attach the present
thermoplastic foam to the support members by any means including
screws, nails, adhesives or any combination thereof. The present
thermoplastic foam may directly contact the support member or may
be separated from the support member by anything that has a vapor
permeability no less than that of the present thermoplastic polymer
foam.
EXAMPLES
[0053] The following examples serve to further illustrate
embodiments of the present invention.
Preparation of a Thermoplastic Polymer Foam for Use in the Present
Invention
Foam Sample 1: SAN Foam
[0054] Prepare a foamable composition by feeding a blend of SAN
copolymer (80% of Mw=118,000 with Mw/Mn=2.3 and 20% of Mw=145,000
and Mw/Mn=2.2), 0.22 weight-parts per hundred weight parts
copolymer (pph) barium stearate, 0.25 pph polyethylene, 0.20 pph
copper blue phthalocyanine, 0.12 pph tetrasodium pyrophosphate and
2 pph of hexabromocyclododecane into an extruder at a temperature
of approximately 200.degree. C. to form a melt. Extrude the melt
into a mixer and inject into the melt 9.8 weight parts per hundred
weight parts of SAN copolymer of a blowing agent composition
consisting of 19 wt % carbon dioxide, 67 wt % tetrafluoroethane
(R134a) and 14 wt % isobutane (iC.sub.4) into the melt at 136 bar
pressure and mix to form the foamable composition.
[0055] Cool the foamable composition to a temperature of about
130.degree. C. and extrude through a slit die into atmospheric
pressure whereupon the foamable composition expands into a
polymeric foam (Sample 1). Table 1 identifies properties of Sample
1.
Sample 2: Polystyrene Foam
[0056] Table 1 also identifies properties for Sample 2, a
polystyrene foam.
TABLE-US-00001 TABLE 1 Property Units Sample 1 Sample 2 Thickness
mm 17 60 Density kg/m.sup.3 33.5 32.7 Cell Size mm 0.12 0.38
Compressive Strength kPa 399 372 Dimensional Stability % 0.8 1.8
Open Cell % 34.7 84.4 Thermal conductivity mW/m * K. 34.6 37.3
Water Vapor Permeability ng/m * s * Pa 4.2 9.75 Resistance to Water
Vapor mu (.mu.) 47 21 Permeability
[0057] Determine foam density according to ISO 845-95, cell size
according to ASTM D-3576, compressive strength according to ASTM
D-1621-04, foam dimensional stability according to DLT(1)5 (WD)-EN
1605, open cell content according to ASTM method D2856, thermal
conductivity at 10.degree. C. mean temperature according to EN
8301-91 and resistance to water vapor permeability according to EN
12086-95.
Example of a Roof Structure
[0058] It is desirable to be able to increase insulation of a
pitched roof of a building structure without disturbing the
occupancy within the building structure. Hence, it is desirable to
increase insulation from the outside of the building structure, but
also desirable not to create a water vapor barrier on the outside
of the structure in the process for fear of condensing water vapor
within the building structure. This example provides an
illustration of one method of installing insulation to a roof
structure comprising multiple rafters that optionally contain
insulation between the rafters.
[0059] In this example, provide a roofing structure having spaced
apart rafters, optionally containing fiberglass or mineral wool
insulation between the rafters, optionally containing a batten
structure affixed on the inside of the roof structure that provides
a level surface for plaster or plaster boards to be affixed as the
substructure for the inside walls of the structure. Battens are
also affixed to the outer surface of the structure to which roofing
material such as tiles or shingles are attached.
[0060] In this exemplary embodiment, increase the insulation of
this roofing structure by first removing the roofing material (for
example, tiles or shingles) and battens on the outside of the
rafters. Affix by means of an adhesive or mechanical fastener (for
example, nails or screws) to multiple rafters a styrene-based
polymer foam board (for example, either of Sample 1 or Sample 2)
that has a resistance to water vapor permeability that is less than
50 as measured according to EN12086, a thermal conductivity that is
less than 40 milliWatts per meter*Kelvin a measured according to EN
12667, a compressive strength that is greater than 80 kilopascals
as measured according to EN 826 and a density of 48 kilograms per
cubic meter or less according to EN 1602 so that the polymer foam
board entirely spans two or more rafters. Ideally, repeat this
process so that all of the rafters are covered with polymeric foam
and there is no spacing between polymeric foam boards. Desirably,
though not necessarily, apply a water vapor permeable membrane over
the polymeric foam boards. Desirably, apply counter battens over
the permeable membrane or polymeric foam boards. Desirably, apply
battens over the counter battens if present; or if not present
over, the permeable membrane, if present; or if neither the counter
battens nor water vapor permeable membranes are present, over the
polymeric foam. Apply roofing materials such as tiles, shingles or
metal sheet over the battens.
* * * * *