Multi-functional system for managing passive heat and water

Abstract

To improve heat insulating and humidity conditioning performance of a building, and improve energy efficiency.SOLUTION: A multi-functional material system can include a variable permeable layer 114A, a desiccant-containing layer 114b, and a vapor permeable support layer. The variable permeable layer can have vapor permeability increasing as relative humidity is increased. The desiccant-containing layer can be adjacent to the variable permeable layer. The vapor permeable support layer can be arranged so as to be adjacent to at least one of the variable permeable layer and the desiccant-containing layer. When the vapor permeable support layer is closer to the variable permeable layer than the desiccant layer and the relative humidity is high, water moves from the variable permeable layer to the desiccant layer in a first direction. When the vapor permeable support layer is closer to the desiccant-containing layer than the variable permeable layer and the relative humidity is high, water moves in a second direction facing the variable permeable layer from the desiccant-containing layer. When a humidity gradient is reverse, moving speed of the water in the first direction is higher than that in the second direction.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 62 / 725,446, filed Aug. 31, 2019, entitled “Construction Materials Incorporating A Multifunctional Subsystem For Passive Heat And Water Management In Building Envelopes,” which is hereby incorporated by reference in its entirety.

Background Art

[0002] Enclosures such as buildings desirably have properties such as energy efficiency, comfort, and durability at reasonable costs. However, attempting to achieve these properties simultaneously can lead to conflicts. As an example, the energy efficiency of a building can be improved by using insulation and increasing the building's airtightness. However, concerns about moisture control increase. In particular, achieving a high R-value (a measure of resistance to heat transfer) due to the insulation and airtightness of the enclosure can result in a decrease in permeability to water vapor, increasing the risk of condensation, water damage, and mold. Thus, as energy efficiency improves, durability and comfort often decrease.

Summary of the Invention

[0003] To improve moisture control, various techniques have been developed. In one aspect, the membrane of a “smart” vapor retarder exhibits permeability to water vapor that varies with relative humidity. As an example, the permeability of the membrane rapidly increases with an increase in relative humidity, allowing water to penetrate and the wall to dry, while the permeability of the membrane decreases with a decrease in relative humidity, slowing the diffusion of water vapor into the wall. However, even with a smart vapor retarder, due to diffusion, water vapor moves in the direction of decreasing humidity, so it is possible for a finite amount of water to enter the wall when the relative humidity rises externally. When the relative humidity drops, the amount of time required to remove water vapor from the wall is approximately the same as the amount of time water vapor was added to the wall. That is, when the magnitude of the relative humidity gradient across the wall is reversed, the smart vapor retarder exhibits time symmetry with respect to the ingress and egress of water vapor. Thus, it can be understood that the smart vapor retarder does not have a mechanism to preferentially suppress the ingress of water vapor compared to the egress of water vapor when the relative humidity conditions are reversed.

[0004] Desiccant-based systems are another moisture control technology in current technology. A desiccant system removes water directly from the air by adsorbing water onto the surface of a desiccant material. When the desiccant material is heated, the adsorbed water is driven off the surface of the desiccant material. This process restores the ability of the desiccant to dehumidify the air. In contrast, existing HVAC systems remove water from the air by first cooling the air below the dew point and then reheating the air to the desired temperature. Since HVAC systems require power for both cooling and heating the air during operation, they are significantly less energy efficient with respect to moisture control than existing HVAC systems. However, while desiccant-based dehumidification systems are more energy efficient compared to existing HVAC systems, they still consume energy to generate the heat required for desiccant regeneration.

[0005] It can be understood that improving the energy efficiency of a building often significantly increases the construction cost. Generally, installing additional layers for air, moisture, and temperature control greatly increases the labor cost. Therefore, a multifunctional building material that can simultaneously regulate the ingress and egress of water vapor, store and release heat, and humidify and dehumidify can improve the heat insulation and humidity control performance of a building, and improve energy efficiency while reducing the labor cost involved in construction. Furthermore, a multifunctional material that can both humidify and dehumidify without moving mechanical parts and without using electricity can further improve efficiency.

[0006] Embodiments of the present disclosure provide a multifunctional material system that addresses such problems. The first function of the multifunctional material system is the storage and release of thermal energy, similar to the function of a phase change material (PCM). Generally, a PCM can regulate temperature by absorbing latent heat when the ambient temperature rises above the phase transition temperature or by releasing latent heat when the ambient temperature drops below the phase transition temperature. Existing PCMs can undergo a phase change between a liquid state and a solid state, as in the case of paraffin, and between a hydrated state and an anhydrous state, as in the case of hydrates. The multifunctional material system can adsorb or release heat when water travels back and forth between the gaseous state and the condensed state on the surface of a substance (e.g., the boiling / condensation line of the water phase diagram). Due to this behavior similar to that of a PCM, energy efficiency can be improved by reducing the energy demand of the HVAC system by an amount equal to the latent heat transferred.

[0007] The second function of the multifunctional material system is the storage and release of water vapor like a humidity buffer. Humidity buffering, also called moisture buffering, characterizes the ability of a material to smooth out changes in relative humidity by absorbing and releasing water vapor from the ambient air. Humidity is an important determinant of human comfort, and most people prefer an environment with a relative humidity of about 35% - 60%. When the humidity is extremely high, conditions are created in which mold, mildew, and dust mites can grow. When the humidity level is extremely low, it can cause dry eyes and skin, increase the risk of respiratory problems, or increase the risk of catching a cold or influenza.

[0008] The third function of the multifunctional material system is to bias the diffusion flow of water vapor in the direction of the desiccant layer, like a water vapor diode also called a unidirectional water vapor valve. That is, the diffusion flow of water vapor in the "open" direction of the water vapor diode is permitted, and the diffusion flow in the "closed" direction of the water vapor diode is suppressed. This function of the multifunctional material system suppresses the ingress of water vapor from the external environment while enabling the discharge of water vapor from the environment inside the enclosure.

[0009] When used in a building envelope, the disclosed embodiments of the multifunctional material can reduce the installation cost compared to the case of installing another membrane layer in the building envelope. Further, in an alternative embodiment, the disclosed multifunctional material can omit either the variable permeability layer or the desiccant layer. Such a modified multifunctional material can optimize a subset of the performance advantages for different areas of a building such as bathrooms and kitchens where humidity control or water vapor transport is the main concern.

[0010] In one embodiment, a multifunctional material system can be provided that includes a variable permeability layer, a desiccant-containing layer, and a vapor-permeable support layer. The variable permeability layer can have a vapor permeability that increases with an increase in relative humidity. The desiccant-containing layer can be adjacent to the variable permeability layer. The vapor-permeable support layer can be disposed adjacent to at least one of the variable permeability layer and the desiccant-containing layer. When the relative humidity is higher adjacent to the variable permeability layer than to the desiccant layer, water moves in a first direction from the variable permeability layer to the desiccant layer. When the relative humidity is higher adjacent to the desiccant-containing layer than to the variable permeability layer, water moves in a second direction opposite thereto from the desiccant-containing layer to the variable permeability layer. The rate of water movement in the first direction is higher than that in the second direction when the humidity gradient is reversed.

[0011] In another embodiment, the vapor-permeable layer is interposed between the desiccant-containing layer and the variable permeability layer. In another embodiment, the permeability of the variable permeability layer increases substantially exponentially with an increase in relative humidity.

[0012] In another embodiment, the desiccant-containing layer is substantially homogeneous. In another embodiment, the desiccant-containing layer is a composite material including desiccant particles embedded in a matrix.

[0013] In another embodiment, the desiccant-containing layer includes a first layer having a matrix formed from a vapor-permeable binder and a second layer having a matrix formed from a variable-permeability binder, and the first layer is the variable permeability layer.

[0014] In another embodiment, at least a portion of the desiccant-containing layer is formed from a desiccant material. The desiccant material can be at least one of silica gel, zeolite, calcium oxide (CaO 2 ), calcium sulfate (CaSO 4 ), lithium chloride (LiCl), clay, or activated carbon.

[0015] In another embodiment, the vapor permeable layer is formed from polylactic acid (PLA), polytetrafluoroethylene, silicone, natural rubber, synthetic rubber, polystyrene, polymethylpentene (PMP), polycarbonate (PC), polyurethane (PU), or polymethyl methacrylate (PMMA).

[0016] In another embodiment, the variable permeability layer is formed from polyamide or polyvinyl alcohol (PVA). As an example, the polyamide can be nylon. In one embodiment, a wall assembly is provided, which can include a wall cavity, a thermal insulation material, and a multifunctional material system. The wall cavity can define a first surface adjacent to the interior of the building and a second surface adjacent to the exterior of the building. The thermal insulation material can be disposed within at least a portion of the wall cavity. In one embodiment, the multifunctional material system can include a variable permeability layer, a desiccant-containing layer, and a vapor permeable support layer. The variable permeability layer can have a vapor permeability that increases with an increase in relative humidity. The desiccant-containing layer can be adjacent to the variable permeability layer. The vapor permeable support layer can be disposed adjacent to at least one of the variable permeability layer and the desiccant-containing layer. When the relative humidity is higher adjacent to the variable permeability layer than to the desiccant layer, water moves in a first direction from the variable permeability layer to the desiccant layer. When the relative humidity is higher adjacent to the desiccant-containing layer than to the variable permeability layer, water moves in a second direction opposite to the first direction from the desiccant-containing layer to the variable permeability layer. The rate of water movement in the first direction is higher than that in the second direction when the humidity gradient is reversed. The multifunctional material system can be disposed on at least one of the first surface and the second surface of the wall cavity.

[0017] In one embodiment, a multifunctional material assembly is provided, which can include a substrate and a multifunctional material system. In one embodiment, the multifunctional material system can include a variable permeability layer, a desiccant-containing layer, and a vapor-permeable support layer. The variable permeability layer can have a vapor permeability that increases with an increase in relative humidity. The desiccant-containing layer can be adjacent to the variable permeability layer. The vapor-permeable support layer can be disposed adjacent to at least one of the variable permeability layer and the desiccant-containing layer. When the relative humidity is higher adjacent to the variable permeability layer than the desiccant layer, water moves in a first direction from the variable permeability layer to the desiccant layer. When the relative humidity is higher adjacent to the desiccant-containing layer than the variable permeability layer, water moves in a second direction opposite thereto from the desiccant-containing layer to the variable permeability layer. The rate of water movement in the first direction is higher than that in the second direction when the humidity gradient is reversed. The multifunctional material system can be disposed on at least one of the first surface and the second surface of the wall cavity. At least one layer of the multifunctional material system can be disposed on the surface of the substrate.

[0018] In another embodiment, the assembly can further include an adhesive layer interposed between the substrate and the layer of the multifunctional material system. In another embodiment, the adhesive layer is the variable permeability layer.

[0019] In another embodiment, the substrate is an oriented strand board (OSB), insulation material, gypsum board, cement board, stucco, drywall, substrate material, roofing material, cladding material, or building film. In another embodiment, the variable permeability layer is disposed on the first surface of the substrate, and the desiccant-containing layer is disposed on the second surface of the substrate facing the first surface of the substrate.

[0020] In another embodiment, the multifunctional material assembly includes a desiccant-containing layer formed from a matrix of the substrate and desiccant particles embedded in the substrate, and the variable permeability layer is deposited on the surface of the desiccant layer.

[0021] In one embodiment, a multifunctional material assembly is provided, which includes a pocketed structure, a plurality of desiccant particles, and a variable permeability layer. The pocketed structure can define one or more pockets having an open side. The plurality of desiccant particles can be disposed within each of the particles of the one or more pockets (e.g., occupying at least a portion of the volume of each pocket). The variable permeability layer can have a vapor permeability that increases with an increase in relative humidity. Also, the variable permeability layer can overlap the open side of each of the one or more pockets.

[0022] The multifunctional material assembly can also include a substrate. The variable permeability layer can be fixed to the substrate.

Brief Description of the Drawings

[0023]

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[0024] Note that the drawings are not necessarily to scale. This drawing is intended to show only typical aspects of the subject matter disclosed herein and should not, therefore, be construed as limiting the scope of the present disclosure.

[0025] This specification discusses embodiments of multifunctional material systems, as well as corresponding manufacturing methods and methods of use as building materials. However, the embodiments of the present disclosure can be adopted in other applications without limitation.

[0026] FIG. 1 shows one exemplary embodiment 100 of an operating environment in the form of a wall assembly 102. The wall assembly 102 includes a wall cavity 104 that defines a first surface or inner surface 104a adjacent to an internal environment 106 and a second surface or outer surface 104b adjacent to an external environment 110. Generally, the internal environment 106 can be a space enclosed by the air-conditioned wall assembly 102, while the external environment 110 is a non-air-conditioned space. Thus, when a multifunctional material system 114 is installed on the inner surface 104a of the wall assembly 102, the internal environment 106 can be the interior of a building room and the external environment can be the exterior of the building. However, it can be understood that embodiments of the multifunctional material system can also be used in a wall assembly that separates two internal rooms, one of which is air-conditioned and the other is not (e.g., a void or other non-air-conditioned space). In either case, a desiccant layer can be disposed at the location closest to the non-air-conditioned space / environment.

[0027] The wall assembly 102 can further include a thermal insulation material 112 disposed in at least a portion of the wall cavity 104 (e.g., between the first surface 104a and the second surface 104b). The wall assembly 102 can further include a multifunctional material system 114. As shown, the multifunctional material is disposed on the inner surface 104a. However, in alternative embodiments, the multifunctional material system can be disposed on or adjacent to opposite faces of the wall cavity (e.g., adjacent to the outer surface), or on and adjacent to both the inner and outer surfaces.

[0028] The multifunctional material system 114 can include a variable permeability layer 114a with a thickness T and a desiccant-containing layer 114b with a thickness L. The variable permeability layer 114a is also referred to herein as a vapor retarder or a vapor barrier. As discussed in detail below, the desiccant-containing layer 114b can be composed substantially entirely of a desiccant material or a composite material containing a desiccant material embedded in a matrix. However, for simplicity, herein the desiccant-containing layer 114b is referred to as the desiccant layer. The desiccant layer 114b is disposed adjacent to the variable permeability layer 114a. Similarly, as discussed in detail below, the desiccant layer may be in contact with the side of the variable permeability layer or may be separated from the side of the variable permeability layer by one or more intervening layers.

[0029] Examples of materials from which the variable permeability layer 114a can be formed include polyamides (e.g., nylon), polyvinyl alcohol (PVA), and various polyions. Examples of desiccant materials from which the desiccant layer 114b can be formed include silica gel, zeolite, calcium oxide (CaO 2 ), calcium sulfate (CASO 4 ), lithium chloride (LiCl), clay, or activated carbon, among others. The thickness L of the desiccant layer 114b can be selected from the range of about 0.05 mm to about 20 mm. The thickness T of the variable permeability layer 114a can be selected from the range of about 0.001 mm to about 0.01.

[0030] In embodiments where the desiccant material has a porous structure, the pore size can range from about 0.4 nm to about 100 μm. In other embodiments, the pore size can be about 0.04 nm. In further embodiments, the pore size can be about 100 μm.

[0031] Also, the pore size of the porous desiccant material can vary with the position within the desiccant layer 114b. As an example, the pore size can decrease as it approaches a selected side of the desiccant layer 114b (e.g., the side of the desiccant layer 114b closest to the external environment 110).

[0032] The multifunctional material system 114 can be configured to perform various functions, either alone or in any combination. In one aspect, by enabling water to move in a first direction from the side of the variable permeability layer 114a to the side of the desiccant layer 114b at a significantly higher rate when the humidity gradient is reversed and water vapor is driven in the opposite direction, the multifunctional material system 114 functions as a vapor diode. In another aspect, in this context, the multifunctional material system 114 regulates temperature in a manner similar to a phase change material, except that it is a phase change between adsorbed water and water vapor within the desiccant layer 114b. In a further aspect, the multifunctional material system 114 regulates relative humidity by adsorbing more water vapor when the humidity rises and releasing water vapor when the humidity drops. These functions improve the energy efficiency, durability, and comfort of buildings. The physical principles of these functions and the estimation of the magnitude of their effects are discussed in detail below. [Vapor Diode Function] Embodiments of the vapor diode function operate as follows. When the humidity is high on the side of the variable permeability layer 114a, the permeability to water vapor, also called the transmission coefficient, increases. The desiccant layer 114b has a relatively high permeability and adsorbs the water received from the variable permeability layer 114a relatively easily. Subsequently, the water received on the side of the desiccant layer 114b evaporates into the air adjacent to the desiccant layer 114b. Conversely, when the humidity is high on the side of the desiccant layer 114b, the desiccant layer 114b absorbs and separates the water before it reaches the variable permeability layer 114a. In this way, the relative humidity of the variable permeability layer 114a, and thus the permeability of the variable permeability layer 114a, remains low. Over the humidity fluctuation cycle, a net transfer (e.g., pumping) of water occurs throughout the multifunctional material system 114. Using this modified function that does not currently exist in building materials, water can be pumped from the wall cavity 104 to the outside, thereby improving durability.

[0033] The function of the vapor diode depends on both the non - linear and asymmetric characteristics of vapor transport in the multifunctional material system 114. The non - linearity is provided by the variable permeability layer 114a whose permeability increases exponentially with relative humidity RH. Figure 2 shows the RH - dependent transmission coefficient of a smart vapor retarder formed from a polyamide material (MemBrain, Certaindeed). It can be observed that the transmission coefficient varies by two orders of magnitude.

[0034] The asymmetry is provided by the desiccant layer 114b which separates water only from one side of the variable permeability layer 114a (for example, the side of the variable permeability layer 114a closest to the desiccant layer 114b). Figure 3 shows the adsorption isotherms (adsorption as a function of relative humidity at a constant temperature) of silica gel, a non - toxic nanoporous mineral, and CaO, clay, molecular sieve, CASO 4 The plot of. Silica gel adsorbs water approximately proportionally to the relative humidity RH of the ambient air and has the ability to retain up to about 37% of its dry weight in water. Water diffuses relatively slowly inside the silica gel, which causes a delay between a humidity change on one side of the silica gel layer and the point in time when the water content starts to equilibrate on the opposite side. The diffusion constant D SG = 2x10 -11 m 2 s -1 And the scaling of the delay time with the thickness L of the desiccant layer as L 2 / 2D SG characterizes the time for the silica gel to separate water from the vapor barrier and enables the structure to modify vapor transport. As an example, when the silica gel is 1 mm, the delay time is about 7 hours, which is long enough to correct the humidity fluctuations during the day (per day). When the silica gel is 2 mm, the delay time is over about 115 days, suggesting that it can also correct the annual humidity cycle.

[0035] Fluctuations in relative humidity occur most prominently due to temperature changes. Since the ability of air to hold water vapor increases with temperature, RH and temperature are inversely correlated. As an example, assume air with a fixed water content starting at 23 °C and 40% relative humidity. As the air warms to 28 °C, the relative humidity drops to 29.7%. As the air cools to 18 °C, the relative humidity rises to 54.5%. These changes can be evaluated using a psychrometric chart or the Magnus formula. Over the same 10 °C temperature range, according to Figure 2, the transmission coefficient of the smart vapor barrier changes by about 7 times, and according to Figure 3, silica gel is expected to exchange about 13% of its dry mass in water. Both have a significant effect.

[0036] Measurements of water transport were made across a prototype multifunctional material system formed with a variable permeability layer of MemBrain (Certainteed) and a desiccant layer formed from silica gel particles. A porous, highly permeable plastic film (on the order of millimeters, e.g., about 1 - 10 mm for MemBrain) was used to hold the silica gel particles. This multifunctional material system was subjected to a humidity gradient by using it to cover the water in a wide - mouthed cup, exposing one side to about 100% RH and the other side to a laboratory environment of about 50% RH. The RH gradient was varied periodically by reversing the structure every day and exposing the opposite side to water vapor. To determine the transfer of water to the silica gel across the entire vapor barrier, the mass of the cup and the multifunctional material system were measured at regular intervals. Figure 4(a) shows a plot of the measured water flux and the transfer of pure water to the desiccant side as a function of time. The water flux from the MemBrain side to the silica gel side was more than twice the magnitude of the flux in the reverse direction over the entire cycle. Water moved to the silica gel side at an average rate of about 0.5 g -2 per day. In the context of a moderately sized house with an enclosure area of 200 m -1 this pumping rate would remove about 0.1 L per day from the walls. 2

[0037] The water transport was theoretically modeled using the finite difference method. Specifically, MATLAB (registered trademark) was employed to model the diffusion of water throughout the prototype multifunctional material system. This simulation was conducted assuming a 75-μm-thick polyamide layer as the variable permeability layer and a 200-μm-thick silica gel layer as the desiccant layer. The relative humidity varied sinusoidally on both sides of the simulated multifunctional material system with an amplitude of 20% and a period of 48 hours, at an average RH of 50%. The two sides were out of phase.

[0038] Figure 4(b) shows the simulated water flux throughout the prototype multifunctional material system and the plot of the integrated mass of water accumulating on the desiccant layer side. The water flux from the variable permeability layer side (polyamide side) to the desiccant layer side was twice the magnitude of the peak flux in the reverse direction over the entire cycle. Water accumulated on the desiccant layer side at an average rate of about 0.1 g -2 per -1 day.

[0039] Even when the humidity fluctuations on both sides are in - phase, that is, even when there is no change in humidity, it can be understood that the pumping effect provided by the function of the vapor diode acts. The only requirement for pumping is that the humidity varies periodically. As an example, when the humidity is high on both sides of the multifunctional material system 114, water vapor passes through the variable - permeability layer 114a at a high transport rate and diffuses from both sides to the desiccant layer 114b (e.g., through the adjacent air and the variable - permeability layer 114a). The distribution of water in the desiccant layer 114b can equilibrate slowly (e.g., when the desiccant layer 114b is about 1 mm thick, the time required for complete equilibration may be several hours). Then, when the humidity is low on both sides of the multifunctional material system 114, water vapor diffuses out of the multifunctional material system 114 from both sides of the variable - permeability layer 114a and the side of the desiccant layer 114b. However, the diffusion rate on the side of the variable - permeability layer 114a is significantly slower compared to when water vapor enters. Thus, when the rate of water entering and leaving through the variable - permeability layer 114a is unbalanced, as a result, a net transfer (pumping) of water in the direction of the desiccant layer 114b occurs. [Phase - change function] With the increase in temperature, the RH decreases and water evaporates from the desiccant layer 114b. Conversely, when the temperature decreases, the RH increases and the desiccant layer 114b absorbs water. In these two processes, the latent heat absorbed regulates the temperature, and the latent heat released reduces the demand of the HVAC system. This principle is the same as that of the phase - change material, except that the ambient water is in the phase that changes the substance.

[0040] For every gram of water evaporated, about 2500 J is absorbed from the environment. This means the sum of the latent heat of boiling and a small surface - binding energy. As an example, the latent - heat density of silica gel can be about 925 kJ / kg. However, in practice, only a part of this latent heat can be utilized. Generally, the desiccant layer 114b does not dry out completely and does not fill with water completely under normal operating conditions.

[0041] A more realistic estimate of the latent heat density can be based on the same 10 °C temperature change as considered previously and the fact that the adsorption isotherm in Figure 3 does not change significantly with temperature. The total amount of water adsorbed or released by the silica gel desiccant over this temperature increase is expected to be about 13% of the dry mass. This corresponds to a latent heat density of about 325 kJ / kg. In contrast, the latent heat density of commercially available phase change materials ranges from 120 kJ / kg to 220 kJ / kg. It can be understood that the desiccant material can be engineered to release the same latent heat over a narrower temperature range. That is, the adsorption isotherm needs to be steeper in the relevant RH range.

[0042] At a cost of about $1 / kg, silica gel is a relatively inexpensive desiccant material. It is possible to supply latent heat at about 320 kJ / dollar. The cost of commercially available PCMs is much higher, with the cheapest ones being sold at about 36 kJ / dollar (based on 120 kJ / kg and $1.5 / lb ($3.3 / kg)). Furthermore, when the density is ρ SG = 1280 kg / m -3 , a 1 mm thick layer of silica gel has a areal mass of 1.28 kg / m -2 and provides a latent heat of about 416 kJ / m -2 . In contrast, a commercially available gypsum board using a PCM (e.g., National Gypsum ThermalCORE) has 250 kJ / m -2 . [Humidity buffer function] A 1 mm thick silica gel desiccant has the ability to hold up to about 450 g of water per square meter of wall. However, more realistically, this value is closer to about 150 g / m -2 and represents the amount of water exchanged between the wall and the internal environment under normal conditions. In a medium-sized house, the multifunctional material system 114 can adsorb or release about 30 L of water. This significantly improves comfort, reduces the energy demand of the HVAC system, and further eliminates the need for an electric humidifier or dehumidifier.

[0043] Finally, it should be noted that silica gel is commonly misunderstood as a dangerous substance. This is due to the words "Do not eat" written on the well-known small white silica gel sachets contained in packaging (such as shoe boxes, etc.). However, silica gel itself is not toxic. Instead, a warning is displayed because cobalt(II) chloride, which is carcinogenic, is often contained in silica gel beads. Cobalt(II) chloride functions as a moisture indicator by changing color from blue to pink as the water content increases. Since there is no need to include cobalt(II) chloride in construction materials, using silica gel desiccants does not cause any obvious safety concerns. [Function control] The requirements and relative importance of the three functions of the multifunctional material system 114 may depend on the location of the building envelope where the multifunctional material system 114 is used and the climate in which the building is located. In one aspect, the ability of the multifunctional material system 114 to regulate humidity may be more desirable inside the building than outside. In another aspect, the vapor diode function may be more preferred in a humid climate than in a dry climate. To control the performance characteristics of the multifunctional material system 114, methods of adjusting manufacturing parameters or material parameters are available. This makes it possible to optimize the performance of different building materials incorporating the multifunctional material system 114 for specific applications.

[0044] The time scale for the multifunctional material system 114 to correct humidity fluctuations is set by the time scale until water diffuses through the desiccant layer 114b and reaches a steady concentration. For a continuous desiccant layer 114b of thickness L, the time scale t is obtained by the following formula.

[0045] [Number] Alternatively, the desiccant layer 114b can also be in the form of a composite material containing a plurality of desiccant particles held in proximity to each other within the matrix. In this configuration, when the diffusion rate of water in the matrix is significantly higher than the diffusion rate of water in the desiccant particles, the longest time scale at which a modification can be observed scales as the following equation.

[0046] [Number] where r is the radius of the desiccant particle. When the desiccant layer 114b is composed of desiccant particles having a size distribution, the relaxation time distribution becomes apparent from the time response of the desiccant layer 114b. When the diffusion rate of water in the matrix is significantly lower than the diffusion rate of water in the desiccant particles, the time scale becomes much longer and can be described by a percolation model.

[0047] The ability of the multifunctional material system 114 to regulate temperature, the latent heat, is proportional to the amount of water exchanged between the condensed phase and the vapor phase. Assuming sufficient time for equilibration, the latent heat that can be stored in or released from successive desiccant layers 114b is proportional to the thickness. However, assuming only a finite amount of time t, the portion of the desiccant layer 114b where the water concentration changes significantly has the following finite thickness.

[0048] [Number] The diurnal cycle sets the relevant time scale for energy efficiency applications and, as a result, sets the maximum effective thickness of successive desiccant layers 114b.

[0049] As described above, by providing the desiccant layer 114b in the form of a composite material, the effective amount of latent heat available in the multifunctional material system 114 can be increased, and the matrix has a high water vapor diffusion rate. The desiccant particles must be small enough to equilibrate the water content within about 12 hours. Since water vapor can diffuse more rapidly through the matrix, the latent heat content obtained from such a desiccant layer 114b increases with thickness and exceeds the following values.

[0050]

Number

[0051]

Number

[0052] Also, the ability of the multifunctional material system 114 to regulate humidity is proportional to the amount of water that can be exchanged between the condensed and vapor phases. The same strategies as above may be used to adjust this ability.

[0053] The transmission coefficient of the variable permeability layer 114a is inversely proportional to its thickness. Thus, by manufacturing a variable permeability layer 114a of an appropriate thickness, the RH-dependent transmission coefficient curve can be scaled with a desired coefficient. Controlling the overall transmission coefficient is important because it affects how effectively the multifunctional material system 114 can utilize humidity fluctuations to pump water vapor. This is also important because it must be possible to increase the potential drying capacity of the wall assembly and thus increase the permeability in at least one direction. For example, in cold climates, wall assemblies are often designed to dry the outside, and the building exterior used as an air and weather barrier outside the substrate has a high permeability to water vapor. By replacing the building exterior with the multifunctional material system 114, the performance of the envelope can be improved without sacrificing potential drying capacity when the variable permeability layer 114a is fabricated to have a sufficiently high transmission coefficient under humid conditions. That is, when the wall cavity 104 is dry, a relatively low transmission coefficient is not a problem.

[0054] To control the performance of the multifunctional material system 114, the microstructure and properties of the desiccant material can be engineered. As an example, the pore size distribution and the hydrophilicity of the surface of the desiccant material affect the shape of the adsorption isotherm. Nanoporous materials with relatively hydrophobic surfaces adsorb little or no water until the critical humidity value of the air is exceeded. In this regard, it is energetically favorable for liquid water to condense inside the narrowest constrictions of the pores. This effect, which is controlled by capillary action, manifests at higher humidity values in larger pores. As another example, different desiccant materials preferentially adsorb water vapor in the range of RH indicated by the steepness of the adsorption isotherm (Figure 3). By effectively buffering the RH within a specific range of interest, a specific material can be selected, or alternatively, a combination of multiple desiccant materials can be adjusted to tune the range over which the mixture can efficiently buffer the RH. Thus, the material or microstructure (e.g., pore diameter) can be selected such that the relative humidity is most effectively buffered within the selected range of RH values (e.g., the slope of the adsorption isotherm is maximized within the selected RH range). [Exemplary Multifunctional Material Architectures] Embodiments of the architecture of the multifunctional material system 114 described above can be realized as a free-standing film. Figure 5A shows a multifunctional material system 500 that includes a variable permeability layer 114a adhered to a desiccant layer. As shown, the desiccant layer 114b may be substantially homogeneous.

[0055] Figure 5B shows another embodiment of the multifunctional material system 500 in the form of a multifunctional material system 550. As shown, the multifunctional material system 550 includes a variable permeability layer 114a and a desiccant layer 114b in the form of a composite desiccant layer 554 that includes a first component and a second component. As an example, the first component can be a matrix 556 and the second component can be a desiccant material 560 embedded within the matrix 556. The geometry of the desiccant material 560 can vary. In one aspect, the desiccant material 560 can take the form of a plurality of desiccant particles embedded within the matrix 556. In certain embodiments, the desiccant particles can be substantially uniform in size (e.g., diameter) and shape. In other embodiments, the desiccant particles can have a size distribution (e.g., a generally normal distribution, a binary distribution, etc.). As an example, the desiccant particle size can range from about 0.05 mm to about 5 mm.

[0056] The matrix 556 of the composite desiccant layer 552 can be formed from a material that is highly permeable to water vapor. In one embodiment, a material with a permeability greater than 5 US perms (e.g., greater than 10 perms) can be considered a vapor permeable material. Examples of the matrix 556 can include binders, foams (e.g., insulation materials), meshes, fiber mats, filaments, fabrics, cloths, drywall, substrates, coatings, structural insulated panels (SIPs). Examples of binder materials can include polylactic acid (PLA), polytetrafluoroethylene (e.g., colloidal polytetrafluoroethylene), polyurethane (thermoplastic or foamed), silicone, natural rubber, synthetic rubber, polymethylpentene (PMP), polystyrene (PS), polycarbonate (PC), polyvinyl alcohol (PVA), or polymethyl methacrylate (PMMA). Also contemplated are other polymers and resins.

[0057] The desiccant material 560 within the matrix 556 can be formed from any of the desiccant materials described above in the context of the desiccant layer 114b. Examples of desiccant materials can include silica gel, zeolite, calcium oxide (CaO2 ) Calcium sulfate (CaSO 4 ), lithium chloride (LiCl), clay, or activated carbon, or one or more thereof. Combinations of two or more different desiccant materials are also contemplated.

[0058] In a further embodiment, the multifunctional material system 114 can be modified to include one or more vapor-permeable layers (e.g., a layer with very high permeability to water vapor). In certain embodiments, these vapor-permeable layers can provide mechanical support to the multifunctional material system 114 without fundamentally changing its function. In other aspects, the vapor-permeable material forming the vapor-permeable layer can be a material with a permeability exceeding 10 US perms, and the vapor-impermeable material can be a material with a permeability less than 0.1 US perms. Examples of materials for forming the vapor-permeable layer include fabrics, meshes, fiber mats, porous materials, silicone, natural rubber, synthetic rubber, polystyrene (e.g., high-impact polystyrene (HIPS)), polymethylpentene (PMP), polycarbonate (PC), polyurethane (PU), and polymethyl methacrylate (PMMA).

[0059] FIG. 6 shows another embodiment of the multifunctional material system 114 in the form of a multifunctional material system 600. The multifunctional material system 600 is similar to the multifunctional material system 500, and a vapor-permeable layer 602 is added for support. As shown in FIG. 6, the vapor-permeable layer 602 is disposed on both sides of the desiccant layer 114b, and the variable-permeability layer 114a is disposed on one side of the vapor-permeable layer 602 closest to the internal environment 106. However, in an alternative embodiment, one or more vapor-permeable layers may be employed on both sides of the desiccant layer. In a further embodiment, the positions of the vapor-permeable layer and the variable-permeability layer may be interchanged. That is, the vapor-permeable layer(s) can be disposed in contact with the variable-permeability layer, the desiccant layer, or both. In other embodiments, the vapor-permeable layer can be configured to provide functions such as water repellency. Further, it can be understood that any embodiment of the multifunctional material system disclosed herein may include one or more of the vapor-permeable layers as needed, although not shown.

[0060] Embodiments of the vapor-permeable layer 602 can adopt various configurations. In one aspect, the mechanical properties of the vapor-permeable layer 602 can be adjusted within a specific range. Examples of mechanical properties include rigidity (e.g., having a modulus of elasticity greater than a predetermined value), flexibility (e.g., having a modulus of elasticity lower than a predetermined value or a yield stress smaller than a predetermined value), impact resistance (e.g., having a hardness greater than a predetermined value), acoustic absorption (e.g., having an acoustic attenuation greater than a predetermined value), tear resistance (e.g., having a fracture toughness greater than a predetermined value), strength (e.g., having a tensile strength greater than a predetermined value), or peel resistance (e.g., having a peel strength greater than a predetermined value).

[0061] In a further embodiment, the decant layer 114b can include two or more layers. FIG. 7a shows another embodiment of the multifunctional material system 114 in the form of a multifunctional material system 700. As shown, the decant layer 114b includes a first decant layer 702 and a second decant layer 704. The first decant layer 702 and the second decant layer 704 can be composites including a matrix and a decant material (e.g., decant material 560) embedded therein, as described above. In certain embodiments, the matrix can function as a binder for holding the embedded decant material. As an example, the first decant layer 702 can include a matrix formed from a material as described above with respect to the variable permeability layer 114a. The second decant layer can include a matrix formed from the same material as described above with respect to the vapor permeability layer 602. Thus, the matrix of the first decant layer 702 can perform the function of the variable permeability layer 114a, as described above.

[0062] In an alternative embodiment, a single layer of the multifunctional material system 114 can provide the functions of the desiccant layer 114b and the variable permeability layer 114a. FIG. 7b shows the multifunctional material system 114 in the form of a multifunctional material system 750, including a composite desiccant layer 752 formed from a matrix of the materials as described above with respect to the variable permeability layer 114a and desiccant material 560 embedded therein. The concentration (e.g., volume fraction) of the desiccant material 560 can vary throughout the thickness. As an example, the concentration of the desiccant material 560 in the first portion 754 of the multifunctional material system 750 can be a relatively low value, and the concentration of the desiccant material 506 in the second portion 756 of the multifunctional material system 750 can be a relatively low value. In certain embodiments, the concentration of the desiccant material 560 in the high-concentration portion 756 can be about three times the concentration of the desiccant material 560 in the low-concentration portion 754. Configured in this way, the low-concentration portion 754 of the multifunctional material system 750 can effectively function as the variable permeability layer 114a, and the high-concentration portion 756 of the multifunctional material system 750 can effectively function as the desiccant layer 114b. The thickness of the low-concentration portion 754 can be in the range of about 0.001 mm to about 0.1 mm, and the thickness of the high-concentration portion 756 can be in the range of about 0.05 mm to about 20 mm. As further shown in FIG. 7, the multifunctional material system can optionally include a vapor-permeable layer 602 adhered to one or both sides of the composite desiccant layer 752.

[0063] In certain embodiments, the multifunctional material system 114 can be incorporated into a building in the form of a separate film, such as a vapor barrier or building exterior. In other embodiments, it may be desirable to add multifunctionality to the building envelope without increasing the complexity of the building envelope. Thus, the multifunctional material system can also be integrated with one or more elements of the building envelope, such as a cladding material, a substrate material, a roofing material, a thermal insulation material, an interior panel, etc.

[0064] As an example, a multifunctional material system 114 can be employed to form a functionalized building material. As shown in FIG. 8, the multifunctional material assembly 800 is formed by fixing any embodiment of the multifunctional material system 114 discussed herein to a substrate 802.

[0065] In certain embodiments, the multifunctional material system 114 can be fixed to the substrate 802 by a vapor permeable adhesive 804. The permeability of the vapor permeable adhesive 804 can be selected from the range of 5 to 100 perms. Examples of vapor permeable adhesives include polyvinyl alcohol and rubber cement. Examples of substrates include those that are vapor permeable and can include oriented strand board (OSB), insulation (e.g., rigid foam insulation), gypsum board, cement board, stucco, drywall, subflooring, roofing, siding, or a building membrane, or another building material. When configured in this way, all three functions of the multifunctional material system 114 can operate if the substrate 802 and the adhesive 804 are permeable to water vapor.

[0066] In a configuration where at least one of the substrate or the adhesive is relatively impermeable to water vapor and functions as a vapor barrier (e.g., having a permeability of less than 0.01 perms), the multifunctional material system may cease to function as a vapor diode. However, the temperature and humidity regulation functions may be retained.

[0067] In an alternative embodiment, the adhesive can be omitted and other mechanisms can be employed to fix the substrate to the multifunctional material system. In one aspect, nails, screws, or other fastening mechanisms can be employed. In another aspect, a boundary can exist between the substrate and the multifunctional material system (e.g., the variable permeability layer). Within the boundary, the variable permeability layer can expand within the substrate and mechanically lock therein, the substrate can expand within the variable permeability layer and mechanically lock therein, or a combination thereof can occur.

[0068] In a further alternative embodiment, the functions of the adhesive 804 and the variable permeability layer 114a can be combined into a single layer. FIG. 9 shows an embodiment of the multifunctional material assembly 800 in the form of a multifunctional material assembly 900 that includes a substrate 802, a desiccant layer 114b, and a variable permeability adhesive layer 902. The variable permeability adhesive layer 902 is inserted between the substrate 802 and the desiccant layer 114b and is configured to attach the desiccant layer 114b to the substrate 802. The variable permeability adhesive is further configured to provide the function of the variable permeability layer as described above. Examples of variable permeability adhesives can include polyvinyl alcohol (PVA) and rubber paste. By combining multiple functions (adhesiveness and variable permeability) into the variable permeability adhesive layer 902, the number of layers required to achieve all three functions of the multifunctional material system 114 within the multifunctional material assembly 900 can be reduced. This simplification can reduce the manufacturing cost of the multifunctional material assembly 900.

[0069] In a further embodiment of the multifunctional material assembly 800, the variable permeability layer 114a and the desiccant layer 114b may be separated from each other by one or more intervening layers. FIG. 10 shows another embodiment of the multifunctional material assembly 800 in the form of a multifunctional material assembly 1000. As shown, the substrate 802 is inserted between the variable permeability layer 114a and the desiccant layer 114b. Thus, the variable permeability layer 114a and the desiccant layer 114b are located on opposite sides of the substrate 802. When configured in this way, if the substrate 802 is permeable to water vapor, the function of the multifunctional material system 114 can be maintained. Optionally, one or more vapor permeable layers 602 may be inserted between the variable permeability layer 114a and the desiccant layer 114b.

[0070] FIG. 11 shows the multifunctional material assembly 800 in the form of a multifunctional material assembly 1100 that includes a composite desiccant layer 1102 in which the desiccant material 560 is embedded in a matrix formed from the material of the substrate 802. A variable permeability layer 114a is further attached to one side of the composite desiccant layer 1120. As described above, the substrate can be formed from materials including oriented strand board (OSB), thermal insulation (e.g., rigid foam insulation), gypsum board, cement board, stucco, drywall, subfloor, roofing material, cladding material, or building film. By combining the function of the desiccant material 560 with the additional functions of the substrate 802, the number of layers required to achieve all three functions of the multifunctional material system 114 and the functions of the substrate 802 can be reduced. This simplification can reduce the manufacturing cost of the multifunctional material assembly 1100.

[0071] Embodiments of the multifunctional material system 114 can employ further architectures. FIG. 12 shows another embodiment of the multifunctional material system 114 in the form of a multifunctional material system 1200 with pockets. The multifunctional material system 1200 with pockets includes a pocketed frame 1202 that defines one or more pockets 1204. The desiccant material 560 (e.g., desiccant particles) can occupy at least a portion of the volume of the pocket 1204. As shown in FIG. 12, the pocketed frame 1202 defines one or more pockets 1204 that include an opening 1206 at one end. The variable permeability layer 114a can be arranged to extend across the opening(s) 1206 of the pocket(s) 1204.

[0072] In certain embodiments, the pocket 1204 contains only the desiccant material 560. That is, there is no binder or adhesive present. Thus, the walls of the pocket 1204 (e.g., the pocketed frame 1202 and the variable permeability layer 114a) simply serve to hold the desiccant material 560 within the pocket 1204.

[0073] The pocketed frame 1202 can be formed from a material that is permeable to water vapor. As an example, the pocketed frame 1202 can be made of the same materials as described above for the vapor permeable layer 602 (e.g., one or more of polylactic acid (PLA), natural rubber, synthetic rubber, polymethylpentene (PMP), polystyrene (PS), polycarbonate (PC), polydimethylsiloxane (PDM), or wood). In an alternative embodiment, the permeability of the pocketed structure can be achieved by forming the pocketed structure using a material that includes a plurality of pores. As an example, the pocketed structure can be formed from a mesh where the openings are smaller than the diameter of the desiccant particles. Further examples of materials from which the pocketed structure can be formed include one or more of fabric, fiber mat, open cell foam, or porous plastic.

[0074] FIG. 13 shows the multifunctional material system 1200 of FIG. 12 secured to a substrate 802 to form a multifunctional material assembly 1300. As shown, the variable permeability adhesive layer 902 is interposed between the substrate 802 and the pocketed frame 1202. However, in alternative embodiments, other securing mechanisms can be employed. Optionally, one or more vapor permeable layers (e.g., facing the substrate) can be provided to support the pocketed structure.

[0075] A building typically includes a building envelope that separates conditioned spaces from unconditioned spaces. The building envelope can provide a resistance to the conduction of air, water, heat, light, and / or noise. The building envelope may desirably be substantially continuous to provide the desired conduction resistance. That is, gaps present in the building envelope do not significantly affect the desired conduction resistance.

[0076] As described above, embodiments of the multifunctional material assembly 800 discussed herein can be employed as a building envelope. In situations where the substrate 802 is a relatively flexible material, the multifunctional material assembly 800 can be wrapped around the building frame. When such a flexible multifunctional assembly is wrapped so as to substantially overlap, gaps can be avoided.

[0077] In situations where the substrate 802 is a relatively rigid material, embodiments of the multifunctional material assembly 800 can be formed as panels. To provide a building envelope, the panels can be fixed to the building frame. However, it can be understood that gaps or joints may exist between adjacent panels of the multifunctional material assembly 800. These gaps, if not addressed, may allow water vapor to bypass the multifunctional material system 114.

[0078] To address potential problems with gaps between panels of the multifunctional material assembly 800, it can be employed as a building envelope. FIG. 14 shows a portion of a building envelope 1400 including a plurality of multifunctional material assemblies 800 in the form of multifunctional material panels 1402. As shown, the multifunctional material panel 1402 includes a core 1404 and a variable permeability layer 114a that extends around three sides of the core 1404 and along a portion of the fourth side so as to form a lip 1406. The side not completely covered by the variable permeability layer 114a of the core 1404 may face an air-conditioned environment (e.g., the external environment 110), while the opposite side of the core 1404 covered by the variable permeability layer 114a may face an air-conditioned environment (e.g., the internal environment 106). The core 1404 can include the substrate 802 and a desiccant layer 114b. In one embodiment, the substrate 802 and the desiccant layer 114b can be separate layers. In another embodiment, the core can be in the form of a composite desiccant layer 1102 in which the desiccant material 560 is embedded within the matrix of the substrate 802.

[0079] By applying a sealing material, a substantially vapor-tight seal 1410 can be formed along the gap 1412 between adjacent multifunctional material panels 1402. The sealing material can be any material that substantially inhibits the conduction of water vapor.

[0080] In the case of a functional material panel 1402 cut to size, a new lip can be provided along the cut edge together with the variable permeability layer 114a. Further, a damaged multifunctional material panel 1402 can be joined to other components of the multifunctional material panel 1402 after sealing its ends and the ends of the gap 1412.

[0081] The sealing material can adopt various configurations. In one aspect, the sealing material can be an adhesive vapor barrier tape that is substantially impermeable to water vapor. The lip exists to ensure that the adhesive vapor barrier tape seals against the variable permeability layer 114a. Instead of or in addition to the adhesive vapor barrier tape, a vapor-impermeable liquid sealant can be employed to form the seal 1410. In such an embodiment, the lip can be omitted.

[0082] A method of manufacturing a multifunctional material assembly for use as a building material is further provided. In a single operation, a substrate 802 is provided. As described above, examples of the substrate embodiment can include vapor-permeable, oriented strand board (OSB), insulation (e.g., rigid foam insulation), gypsum board, cement board, decorative plaster, drywall, subfloor, roofing material, cladding material, or building film, or another building material.

[0083] Layers of the multifunctional material system can be deposited on a substrate (e.g., by diffusion or spray coating) or incorporated into the substrate to form a multifunctional material assembly. In embodiments where the multifunctional material system includes multiple layers, the layers can be deposited sequentially. In certain embodiments, the multifunctional material assembly can be prepared remotely and fixed to a building frame. In other embodiments, the substrate can be attached to the building frame, and then the multifunctional material system can be sequentially deposited on the substrate.

[0084] Embodiments of the vapor permeable layer and the variable permeability layer can be deposited from an aqueous solution. When the deposited aqueous solution of the layer dries, it can adhere to an underlying layer (e.g., the other of the substrate, the variable permeability layer or the vapor permeable layer, a desiccant layer, etc.), providing a substantially continuous film of the vapor permeable layer or the variable permeability layer.

[0085] Embodiments of the desiccant layer can be performed in various ways. In one aspect, the desiccant layer can be deposited from a slurry containing a binder and desiccant particles. The desiccant particles can be one or more of silica gel, zeolite, calcium oxide (CaO 2 ), calcium sulfate (CASO 4 ), lithium chloride (LiCl), clay, or activated carbon. Examples of binders can include polylactic acid (PLA), polytetrafluoroethylene (e.g., colloidal polytetrafluoroethylene), polyurethane (thermoplastic or foamed), silicone, natural rubber, synthetic rubber, polymethylpentene (PMP), polystyrene, polycarbonate (PC), polyvinyl alcohol (PVA), or polymethyl methacrylate (PMMA). Also, other polymers and resins are contemplated.

[0086] In an embodiment of the composite desiccant layer where the matrix is a foam (e.g., polyurethane foam), the foam can be formed from the reaction of two or more components that release gas. The foam matrix may be heated and dried or self-heated by the reaction of two or more components. The deposited composite desiccant layer can adhere to the substrate when dried, providing a substantially continuous film of the composite desiccant layer.

[0087] An alternative embodiment of the composite desiccant layer can be extruded continuously. In one aspect, the desiccant layer can be extruded from a mixture of a thermoplastic polymer and desiccant particles. The desiccant particles can be one or more of silica gel, zeolite, calcium oxide (CaO 2 ), calcium sulfate (CaSO 4 ), lithium chloride (LiCl), clay, or activated carbon. Examples of thermoplastic resins include natural rubber, synthetic rubber, polylactic acid (PLA), polystyrene (e.g., high impact polystyrene [HIPS]), polymethylpentene (PMP), polycarbonate (PC), polyurethane (PU), polymethyl methacrylate (PMMA), or polyvinyl alcohol (PVA).

[0088] Exemplary technical effects of the methods, systems, and devices described herein include, by way of non-limiting examples, a decrease in the average humidity inside the wall cavity due to a water vapor pumping effect, and a resulting decrease in the risk of one or more of mold, rot, mildew, and dust mites. Further exemplary technical effects include stabilization of the relative humidity inside the enclosure, and related improvements in comfort and air quality. Additional exemplary technical effects include stabilization of the internal temperature, and when a multifunctional film is located inside the enclosure, a reduction in the energy intensity of heating and cooling. Other technical effects include further reducing the energy intensity of heating and cooling such that, when the multifunctional material system is located outside, water collected from the environment at night can be used to evaporatively cool the outer surface during the day. A further technical effect includes reducing the risk of water condensation inside the wall as a result of dampening humidity swings inside the wall cavity.

[0089] To provide a thorough understanding of the structure, function, manufacture, and use principles of the systems, devices, and methods discussed herein, specific exemplary embodiments have been described. One or more of these embodiments are shown in the accompanying drawings. It will be understood by those skilled in the art that the systems, devices, and methods specifically described herein and shown in the accompanying drawings are non-limiting exemplary embodiments, and the scope of the present invention is defined only by the claims. Features illustrated and described in connection with one exemplary embodiment can be combined with features of other embodiments. Such modifications and variations are intended to be included within the scope of the present invention. Further, in the present disclosure, components with similar names in the embodiments generally have similar characteristics, and thus, in a particular embodiment, each feature of each component with a similar name is not necessarily fully detailed.

[0090] Throughout this specification and the claims of this application, the approximating language used herein can be applied to modify any quantitative representation that can vary within a tolerance without resulting in a change in the basic functions associated therewith. Accordingly, values modified by the terms "about," "approximately," and "substantially" are not to be limited to the precise values specified. In at least some instances, the approximating language can correspond to the precision of the instrument for measuring the value. Throughout the specification and the claims, ranges can be combined and / or altered from one another, and such ranges are specified and include all sub-ranges contained therein unless the context or language specifically dictates otherwise.

[0091] Those skilled in the art will appreciate further features and advantages of the invention based on the foregoing embodiments. Accordingly, the application is not particularly limited to what has been specifically illustrated and described herein, except as defined by the appended claims. All publications and references cited herein are expressly incorporated by reference.

Claims

1. 1. A multifunctional material system comprising: a variable permeability layer that exhibits increased vapor permeability with increasing relative humidity; a desiccant-containing layer adjacent to the variably permeable layer; a vapor-permeable support layer disposed adjacent to at least one of the variably permeable layer and the desiccant-containing layer; Equipped with when the relative humidity is higher adjacent the variably permeable layer than the desiccant layer, water moves in a first direction from the variably permeable layer to the desiccant layer, and when the relative humidity is higher adjacent the desiccant containing layer than the variably permeable layer, water moves in an opposing second direction from the desiccant containing layer to the variably permeable layer, the rate of water movement in the first direction being higher than in the second direction when the humidity gradient is reversed; Multifunctional material systems.

2. 10. The system of claim 1, wherein the vapor permeable layer is interposed between the desiccant containing layer and the variably permeable layer.

3. The system of claim 1 , wherein the permeability of the variably permeable layer increases approximately exponentially with increasing relative humidity.

4. The system of claim 1 , wherein the desiccant-containing layer is substantially homogeneous.

5. 10. The system of claim 1, wherein the desiccant-containing layer is a composite comprising desiccant particles embedded in a matrix.

6. 10. The system of claim 1, wherein the desiccant-containing layer includes a first layer having a matrix formed from a vapor-permeable binder and a second layer having a matrix formed from a variable permeability binder, the first layer being the variable permeability layer.

7. At least a portion of the desiccant-containing layer is formed from a desiccant material, and the desiccant material may be silica gel, zeolite, calcium oxide (CaO ２ ), calcium sulfate (CaSO ４ ), lithium chloride (LiCl), clay, or activated carbon.

8. 10. The system of claim 1, wherein the vapor permeable layer is formed from polylactic acid (PLA), polytetrafluoroethylene, silicone, natural rubber, synthetic rubber, polystyrene, polymethylpentene (PMP), polycarbonate (PC), polyurethane (PU), or polymethylmethacrylate (PMMA).

9. The system of claim 1 , wherein the variably permeable layer is formed from polyamide or polyvinyl alcohol (PVA).

10. The system of claim 9 , wherein the polyamide is nylon.

11. 1. A wall assembly comprising: a wall cavity defining a first surface adjacent an interior of the building and a second surface adjacent an exterior of the building; an insulating material disposed within at least a portion of the wall cavity; 13. The multifunctional material system of claim 1 disposed on at least one of the first surface and the second surface of the wall cavity; A wall assembly comprising:

12. A substrate; A multifunctional material system according to claim 1; Equipped with At least one layer of the multifunctional material system is disposed on a surface of the substrate. Multifunctional material assembly.

13. The multifunctional material assembly of claim 12 , further comprising an adhesive layer interposed between the substrate and the layer of the multifunctional material system.

14. The multifunctional material assembly of claim 13 , wherein the adhesive layer is a variably permeable layer.

15. 13. The multi-functional material assembly of claim 12, wherein the substrate is oriented strand board (OSB), insulation, gypsum board, cement board, stucco, drywall, underlayment, roofing, coating, or architectural membrane.

16. 13. The multifunctional material assembly of claim 12, wherein the variably permeable layer is disposed on a first surface of the substrate and the desiccant-containing layer is disposed on a second surface of the substrate opposite the first surface of the substrate.

17. the desiccant-containing layer formed from a matrix of the substrate and desiccant particles embedded in the substrate; the variable permeability layer deposited on a surface of the desiccant layer; The multifunctional material assembly of claim 12 comprising:

18. a pocketed structure defining one or more pockets having an open side; a plurality of desiccant particles disposed within each of the one or more pockets; a variable permeability layer that has a vapor permeability that increases with increasing relative humidity, the variable permeability layer overlying each of the opening sides of the plurality of pockets; A multi-functional material assembly comprising:

19. 20. The multifunctional material assembly of claim 18, further comprising said substrate, said variably permeable layer being secured to said substrate.

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