Multifunctional system for passive heat and water management

1. A multifunctional material system, comprising:

a continuous variable-permeability layer having a vapor permeability that increases with increasing relative humidity; and

a desiccant containing layer adjacent the variable-permeability layer; and

a vapor-permeable supporting layer positioned adjacent at least one of the variable-permeability layer and the desiccant containing layer;

wherein water moves in a first direction from the variable-permeability layer to the desiccant layer when relative humidity is greater adjacent the variable-permeability layer than the desiccant layer, wherein water moves a second, opposing direction, from the desiccant containing layer to the variable-permeability layer when the relative humidity is greater adjacent the desiccant containing layer than the variable-permeability layer, and wherein a rate of water motion in the first direction is greater than a rate of water motion in the second direction when the humidity gradient is reversed.

2. The system of claim 1 , wherein the vapor-permeable supporting layer is interposed between the desiccant containing layer and the variable-permeability layer.

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

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

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

6. 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-permeable binder, and wherein the first layer is the variable-permeability layer.

7. The system of claim 1 , wherein at least a portion of the desiccant containing layer is formed from desiccant material, and wherein the desiccant material is at least one of a silica gel, zeolites, calcium oxide (CaO 2 ), calcium sulfate (CaSO 4 ), lithium chloride (LiCl), a clay, or activated charcoal.

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

9. The system of claim 1 , wherein the variable-permeability layer is formed from a polyamide or polyvinyl alcohol (PVA).

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

11. A wall assembly, comprising:

a wall cavity defining a first surface adjacent a building interior and second surface adjacent a building exterior;

a thermally insulating material positioned within at least a portion of the wall cavity; and

the multifunctional material system of claim 1 positioned on at least one of the first and second surfaces of the wall cavity.

12. A multifunctional material assembly, comprising:

a substrate; and

the multifunctional material system of claim 1 ;

wherein at least one layer of the multifunctional material system is positioned on a surface of the substrate.

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

14. The multifunctional material assembly of claim 13 , wherein the adhesive layer is the variable-permeability layer.

15. The multifunctional material assembly of claim 12 , wherein the substrate is oriented strand board (OSB), insulation, gypsum board, cement board, stucco, drywall, sheathing, roofing, cladding, or an architectural membrane.

16. The multifunctional material assembly of claim 12 , wherein the variable-permeability layer is positioned on a first surface of the substrate and the desiccant containing layer is positioned on a second surface of the substrate, opposite the first surface of the substrate.

17. The multifunctional material assembly of claim 12 , comprising:

the desiccant containing layer formed from a matrix of the substrate and desiccant particles embedded in the substrate; and

the variable-permeability layer deposited on a surface of the desiccant layer.

18. A multifunctional material assembly, comprising:

a pocketed structure defining one or more pockets having an open side;

a plurality of desiccant particles positioned within respective ones of the one or more pockets; and

a continuous variable-permeability layer having a vapor permeability that increases with increasing relative humidity, the variable permeability layer overlying respective open sides of the plurality of pockets;

wherein water moves in a first direction from the variable-permeability layer to the plurality of desiccant particles when relative humidity is greater adjacent the variable-permeability layer than the plurality of desiccant particles, wherein water moves a second, opposing direction, from the plurality of desiccant particles to the variable-permeability layer when the relative humidity is greater adjacent the plurality of desiccant particles than the variable-permeability layer, and wherein a rate of water motion in the first direction is greater than a rate of water motion in the second direction when the humidity gradient is reversed.

19. The multifunctional material assembly of claim 18 , further comprising a substrate, wherein the variable-permeability layer is secured to the substrate.