Energy-free refrigeration door and method for making the same

Abstract

The present invention provides a refrigeration door, and method for making the same, for controlling condensation, providing thermal insulation, with a desired amount of visible transmittance, without using electricity to heat the door. The energy-free refrigeration door of the present invention includes a door frame housing and an insulating glass unit comprising inner, middle and outer sheets of glass. A first sealant assembly disposed around the periphery of the inner and middle sheets of glass forms a first chamber between the inner and middle sheets of glass. A second sealant assembly disposed around the periphery of the middle and outer sheets of glass forms a second chamber between the middle and outer sheets of glass. A gas, such as krypton, air, or argon is held in the first and second chambers. The outer sheet of glass and inner sheet of glass each have an unexposed surface that faces the middle sheet of glass. A low emissivity coating is disposed on the unexposed surfaces of the inner and outer sheets of glass so that the glass door as a whole has a U value that prevents formation of condensation on the outer surface of the outer sheet of the glass door, without the application of electricity to heat the door, while also providing the desired evaporation rate of condensation from the inner side of the inner sheet of the glass door.

what is claimed is:  
     
         1 . A refrigeration door adapted to be mounted on a refrigerating compartment, said door comprising: 
 an inner sheet of glass including a first surface and a second surface, said first surface of said inner sheet being disposed adjacent the interior of the refrigerating compartment;    an outer sheet of glass including a first surface and a second surface, said first surface of said outer sheet being disposed adjacent the exterior environment of the refrigerating compartment;    a middle sheet of glass disposed between said inner and outer sheets of glass;    a first sealant assembly disposed around the periphery of said inner sheet of glass and said middle sheet of glass for maintaining said inner sheet and said middle sheet in spaced-apart relationship from each other;    a second sealant assembly disposed around the periphery of said middle sheet of glass and said outer sheet of glass for maintaining said middle sheet and said outer sheet in spaced-apart relationship from each other;    a first low emissivity coating adjacent the second surface of said inner sheet of glass;    a second low emissivity coating adjacent the second surface of said outer sheet of glass;    said inner sheet, outer sheet, middle sheet, first sealant assembly, second sealant assembly, and said first and second low emissivity coatings forming an insulating glass unit having a U value substantially equal to or less than 0.2 BTU/hr-sq ft-F substantially preventing the formation of condensation on said first surface of said outer sheet of glass without the application of electricity for heating said first surface of said outer sheet of glass; and    a frame secured around the periphery of said insulating glass unit.    
     
     
         2 . The refrigeration door of  claim 1 , further comprising: 
 a first chamber defined by said inner sheet of glass, said middle sheet of glass, and said first sealant assembly;    a second chamber defined by said middle sheet of glass, said outer sheet of glass, and said second sealant assembly; and    a gas disposed in said first and second chambers.    
     
     
         3 . The refrigeration door of  claim 2 , wherein: 
 said inner, said middle, and said outer sheets of glass have a thickness substantially equal to one eighth of an inch;    said inner and said middle sheets of glass being spaced apart a distance substantially equal to one half inch; and    said middle and said outer sheets of glass being spaced apart a distance substantially equal to one half inch.    
     
     
         4 . The refrigeration door of  claim 2 , wherein at least one sheet of glass is formed of Comfort Ti-PS.  
     
     
         5 . The refrigeration door of  claim 2 , wherein said first sealant assembly and said second sealant assembly each have a heat transfer rate substantially equal to or less than 1.73 Btu/hr-ft-F.  
     
     
         6 . The refrigeration door of  claim 5 , wherein: 
 said inner, said middle and said outer sheets of glass having a thickness substantially equal to one eighth of an inch;    said inner and said middle sheets of glass being spaced apart a distance substantially equal to one half inch; and    said middle and said outer sheets of glass being spaced apart a distance substantially equal to one half inch.    
     
     
         7 . The refrigeration door of  claim 2 , wherein said gas in said first chamber and said second chamber are the same.  
     
     
         8 . The refrigeration door of  claim 2 , wherein said gas in said first chamber and said second chamber are not the same.  
     
     
         9 . The refrigeration door of  claim 2 , wherein said gas is selected from the group consisting of argon, krypton, and air.  
     
     
         10 . The refrigeration door of  claim 1 , wherein said insulating glass unit has a U value substantially equal to or less than 0.16 BTU/hr-sq ft-F.  
     
     
         11 . The refrigeration door of  claim 1 , wherein said outer sheet and said inner sheet each have an emissivity substantially equal to or less than 0.05.  
     
     
         12 . The refrigeration door of  claim 1 , wherein said Outer sheet and said inner sheet each have an emissivity substantially equal to or less than 0.03.  
     
     
         13 . The refrigeration door of  claim 1 , wherein said insulating glass unit has an emissivity substantially equal to or less than 0.04.  
     
     
         14 . The refrigeration door of  claim 1 , wherein said insulating glass unit has an emissivity substantially equal to or less than 0.01.  
     
     
         15 . The refrigeration door of  claim 1 , wherein said insulating glass unit has an emissivity substantially equal to or less than 0.0025.  
     
     
         16 . The refrigeration door of  claim 2 , wherein said first and second low emissivity coatings are selected from the group consisting of a titania based silver and fluorine doped tin oxide.  
     
     
         17 . The refrigeration door of  claim 2 , wherein said first and second low emissivity coatings are applied with a process selected from the group consisting of sputter coating, pyrolytic coating and spray coating.  
     
     
         18 . The refrigeration door of  claim 2 , wherein said frame is formed from a material selected from the group consisting of extruded plastic, aluminum, and fiber glass.  
     
     
         19 . The refrigeration door of  claim 1 , wherein the interior temperature of the refrigerating compartment is substantially equal to or less than minus twenty degrees Fahrenheit; the temperature of the exterior environment is substantially equal to or greater than seventy degrees Fahrenheit; and the humidity in the exterior environment is substantially equal to or greater than sixty percent; and wherein said first surface of said outer sheet of glass is substantially free of condensation.  
     
     
         20 . The refrigeration door of  claim 1 , wherein the interior temperature of the refrigerating compartment is substantially equal to or less than minus forty degrees Fahrenheit; the temperature of the exterior environment is substantially equal to or greater than eighty degrees Fahrenheit; and the humidity in the exterior environment is substantially equal to or greater than sixty percent; and wherein said first surface of said outer sheet of glass is substantially free of condensation.  
     
     
         21 . The refrigeration door of  claim 1 , wherein the interior temperature of the refrigerating compartment is substantially equal to or less than zero degrees Fahrenheit; the temperature of the exterior environment is substantially equal to or greater than seventy two degrees Fahrenheit; and the humidity in the ambient environment is substantially equal to or greater than sixty percent; and wherein said first surface of said outer sheet of glass is substantially free of condensation.  
     
     
         22 . The refrigeration door of  claim 2 , wherein at least one sheet of glass is formed of Comfort E 2 .  
     
     
         23 . The refrigeration door of  claim 1 , wherein said first sealant assembly and said second sealant assembly each have a heat transfer rate substantially equal to or less than 1.73 Btu/hr-ft-F.  
     
     
         24 . The refrigeration door of  claim 1 , wherein said first sealant assembly and said second sealant assembly each have a heat transfer rate substantially equal to or less than 1.51 Btu/hr-ft-F.  
     
     
         25 . The refrigeration door of  claim 1 , wherein said first sealant assembly and said second sealant assembly each have a heat transfer rate substantially equal to or less than 0.84 Btu/hr-ft-F.  
     
     
         26 . A refrigeration door adapted to be mounted on a refrigerating compartment, said door comprising: 
 an inner sheet of glass including a first surface and a second surface, said first surface of said inner sheet being disposed adjacent the interior of the refrigerating compartment;    an outer sheet of glass including a first surface and a second surface, said first surface of said outer sheet being disposed adjacent the exterior environment of the refrigerating compartment;    a middle sheet of glass disposed between said inner and outer sheets of glass;    a first sealant assembly disposed around the periphery of said inner sheet of glass and said middle sheet of glass for maintaining said inner sheet and said middle sheet in spaced-apart relationship from each other;    a second sealant assembly disposed around the periphery of said middle sheet of glass and said outer sheet of glass for maintaining said middle sheet and said outer sheet in spaced-apart relationship from each other;    a first low emissivity coating adjacent the second surface of said inner sheet of glass;    a second low emissivity coating adjacent the second surface of said outer sheet of glass;    said inner sheet, outer sheet, middle sheet, first sealant assembly, second sealant assembly, and said first and second low emissivity coatings forming an insulating glass unit having an emissivity substantially equal to or less than 0.04 substantially preventing the formation of condensation on said first surface of said outer sheet of glass without the application of electricity for heating said first surface of said outer sheet of glass; and    a frame secured around the periphery of said insulating glass unit.    
     
     
         27 . The refrigeration door of  claim 26 , further comprising: 
 a first chamber defined by said inner sheet of glass, said middle sheet of glass, and said first sealant assembly;    a second chamber defined by said middle sheet of glass, said outer sheet of glass, and said second sealant assembly; and    a gas disposed in said first and second chambers.    
     
     
         28 . The refrigeration door of  claim 27 , wherein: 
 said inner, said middle, and said outer sheets of glass have a thickness substantially equal to one eighth of an inch;    said inner and said middle sheets of glass being spaced apart a distance substantially equal to one half inch; and    said middle and said outer sheets of glass being spaced apart a distance substantially equal to one half inch.    
     
     
         29 . The refrigeration door of  claim 27 , wherein at least one sheet of glass is formed of Comfort Ti-PS.  
     
     
         30 . The refrigeration door of  claim 27 , wherein said gas is selected from the group consisting of argon, krypton, and air.  
     
     
         31 . The refrigeration door of  claim 26 , wherein said insulating glass unit has a U value substantially equal to or less than 0.16 BTU/hr-sq ft-F.  
     
     
         32 . The refrigeration door of  claim 26 , wherein said outer sheet and said inner sheet each have an emissivity substantially equal to or less than 0.05.  
     
     
         33 . The refrigeration door of  claim 26 , wherein said outer sheet and said inner sheet each have an emissivity substantially equal to or less than 0.03.  
     
     
         34 . The refrigeration door of  claim 26 , wherein said insulating glass unit has a U value substantially equal to or less than 0.2 BTU/hr-sq ft-F.  
     
     
         35 . The refrigeration door of  claim 26 , wherein said insulating glass unit has an emissivity substantially equal to or less than 0.01.  
     
     
         36 . The refrigeration door of  claim 26 , wherein said insulating glass unit has an emissivity substantially equal to or less than 0.0025.  
     
     
         37 . The refrigeration door of  claim 27 , wherein said low emissivity coatings are selected from the group consisting of a titania based silver and fluorine doped tin oxide.  
     
     
         38 . The refrigeration door of  claim 27 , wherein said low emissivity coatings are applied with a process selected from the group consisting of sputter coating, pyrolytic coating and spray coating.  
     
     
         39 . The refrigeration door of  claim 27 , wherein said frame is formed from a material selected from the group consisting of extruded plastic, aluminum, and fiber glass.  
     
     
         40 . The refrigeration door of  claim 26 , wherein the interior temperature of the refrigerating compartment is substantially equal to or less than minus twenty degrees Fahrenheit; the temperature of the exterior environment is substantially equal to or greater than seventy degrees Fahrenheit; and the humidity in the exterior environment is substantially equal to or greater than sixty percent; and wherein said first surface of said outer sheet of glass is substantially free of condensation.  
     
     
         41 . The refrigeration door of  claim 26 , wherein the interior temperature of the refrigerating compartment is substantially equal to or less than minus forty degrees Fahrenheit; the temperature of the exterior environment is substantially equal to or greater than eighty degrees Fahrenheit; and the humidity in the exterior environment is substantially equal to or greater than sixty percent; and wherein said first surface of said outer sheet of glass is substantially free of condensation.  
     
     
         42 . The refrigeration door of  claim 26 , wherein the interior temperature of the refrigerating compartment is substantially equal to or less than minus zero degrees Fahrenheit; the temperature of the exterior environment is substantially equal to or greater than seventy-two degrees Fahrenheit; and the humidity in the ambient environment is substantially equal to or greater than sixty percent; and wherein said first surface of said outer sheet of glass is substantially free of condensation.  
     
     
         43 . The refrigeration door of  claim 27 , wherein at least one sheet of glass is formed of Comfort E 2 .  
     
     
         44 . The refrigeration door of  claim 26 , wherein said first sealant assembly and said second sealant assembly each have a heat transfer rate substantially equal to or less than 1.73 Btu/hr-ft-F.  
     
     
         45 . The refrigeration door of  claim 26 , wherein first sealant assembly and said second sealant assembly each have a heat transfer rate substantially equal to or less than 1.51 Btu/hr-ft-F.  
     
     
         46 . The refrigeration door of  claim 26 , wherein first sealant assembly and said second sealant assembly each have a heat transfer rate substantially equal to or less than 0.84 Btu/hr-ft-F.  
     
     
         47 . A refrigeration door having an outer surface and adapted to be mounted on a refrigerating compartment, said door comprising: 
 a first sheet of glass;    a second sheet of glass;    a first sealant assembly disposed around the periphery of said first sheet of glass and said second sheet of glass for maintaining said first sheet and said second sheet in spaced-apart relationship from each other;    a first low emissivity coating adjacent a surface of said first sheet or said second sheet of glass;    said first sheet and second sheets of glass, said first sealant assembly, and said first low emissivity coating forming an insulating glass unit having a U value substantially equal to or less than 0.2 BTU/hr-sq ft-F; and    a frame secured around the periphery of said insulating glass unit.    
     
     
         48 . The refrigerator door of  claim 47 , further comprising: 
 a third sheet of glass;    a second sealant assembly disposed around the periphery of said second sheet of glass and said third sheet of glass for maintaining said second sheet and said third sheet in spaced-apart relationship from each other; and    wherein said insulating glass unit further includes said third sheet of glass and said second sealant assembly.    
     
     
         49 . The refrigeration door of  claim 48 , further including a second low emissivity coating adjacent a surface of said first sheet, said second sheet, or said third sheet of glass.  
     
     
         50 . The refrigeration door of  claim 49 , wherein the U value of said insulating glass unit is effective to substantially prevent the formation of condensation on the outer surface of the door without the application of electricity for heating the outer surface when the interior temperature of the refrigerating compartment is substantially equal to or less than zero degrees Fahrenheit; the temperature of the exterior environment is substantially equal to or greater than seventy-two degrees Fahrenheit; and the humidity in the ambient environment is substantially equal to or greater than sixty percent.  
     
     
         51 . The refrigerator door of  claim 47 , wherein the U value of said insulating glass unit is effective to substantially prevent the formation of condensation on the outer surface of the door without the application of electricity for heating the outer surface when the interior temperature of the refrigerating compartment is substantially equal to or less than minus zero degrees Fahrenheit; the temperature of the exterior environment is substantially equal to or greater than seventy-two degrees Fahrenheit; and the humidity in the ambient environment is substantially equal to or greater than sixty percent.  
     
     
         52 . The refrigeration door of  claim 51 , further comprising: 
 a first chamber defined by said first sheet of glass, said second sheet of glass, and said first sealant assembly; and    a gas disposed in said first chamber.    
     
     
         53 . The refrigeration door of  claim 52 , wherein said first sealant assembly has a heat transfer rate substantially equal to or less than 1.73 Btu/hr-ft-F.  
     
     
         54 . The refrigeration door of  claim 43 , wherein said gas is selected from the group consisting of argon, krypton, and air.  
     
     
         55 . The refrigeration door of  claim 47 , wherein said insulating glass unit has a U value substantially equal to or less than 0.16 BTU/hr-sq ft-F.  
     
     
         56 . The refrigeration door of  claim 47 , wherein said insulating glass unit has an emissivity substantially equal to or less than 0.04.  
     
     
         57 . The refrigeration door of  claim 47 , wherein said insulating glass unit has an emissivity substantially equal to or less than 0.01.  
     
     
         58 . The refrigeration door of  claim 47 , wherein insulating glass unit has an emissivity substantially equal to or less than 0.0025.  
     
     
         59 . The refrigeration door of  claim 47 , wherein the interior temperature of the refrigerating compartment is substantially equal to or less than minus twenty degrees Fahrenheit; the temperature of the exterior environment is substantially equal to or greater than seventy degrees Fahrenheit; and the humidity in the exterior environment is substantially equal to or greater than sixty percent; and wherein the outer surface of the door is substantially free of condensation.  
     
     
         60 . The refrigeration door of  claim 47 , wherein the interior temperature of the refrigerating compartment is substantially equal to or less than minus forty degrees Fahrenheit; the temperature of the exterior environment is substantially equal to or greater than eighty degrees Fahrenheit; and the humidity in the exterior environment is substantially equal to or greater than sixty percent; and wherein the outer surface of the door is substantially free of condensation.  
     
     
         61 . A refrigeration door having an outside surface and adapted to be mounted on a refrigerating compartment, said door comprising: 
 a first sheet of glass;    a second sheet of glass;    a first sealant assembly disposed around the periphery of said first sheet of glass and said second sheet of glass for maintaining said first sheet and said second sheet in spaced-apart relationship from each other;    a first low emissivity coating adjacent a surface of said first sheet or said second sheet of glass;    said first sheet and second sheets of glass, said first sealant assembly, and said first low emissivity coating forming an insulating glass unit having an emissivity substantially equal to or less than 0.04 substantially preventing the formation of condensation on the outside surface of the refrigeration door without the application of electricity for heating said outer surface; and    a frame secured around the periphery of said insulating glass unit.    
     
     
         62 . The refrigerator door of  claim 61 , further comprising: 
 a third sheet of glass;    a second sealant assembly disposed around the periphery of said second sheet of glass and said third sheet of glass for maintaining said second sheet and said third sheet in spaced-apart relationship from each other; and    wherein said insulating glass unit further includes said third sheet of glass and said second sealant assembly.    
     
     
         63 . The refrigeration door of  claim 62 , further including a second low emissivity coating adjacent a surface of said first sheet, said second sheet, or said third sheet of glass.  
     
     
         64 . The refrigeration door of  claim 61 , further comprising: 
 a first chamber defined by said first sheet of glass, said second sheet of glass, and said first sealant assembly; and    a gas disposed in said first chamber.    
     
     
         65 . The refrigeration door of  claim 64 , wherein said first sealant assembly has a heat transfer rate substantially equal to or less than 1.73 Btu/hr-ft-F.  
     
     
         66 . The refrigeration door of  claim 65 , wherein said gas is selected from the group consisting of argon, krypton, and air.  
     
     
         67 . The refrigeration door of  claim 61 , wherein said insulating glass unit has a U value substantially equal to or less than 0.16 BTU/hr-sq ft-F.  
     
     
         68 . The refrigeration door of  claim 61 , wherein said insulating glass unit has a U value substantially equal to or less than 0.20 BTU/hr-sq ft-F.  
     
     
         69 . The refrigeration door of  claim 61 , wherein said insulating glass unit has an emissivity substantially equal to or less than 0.01.  
     
     
         70 . The refrigeration door of  claim 61 , wherein insulating glass unit has an emissivity substantially equal to or less than 0.0025.  
     
     
         71 . A method of manufacturing a refrigeration door component having an outer surface, said method comprising the steps of: 
 providing a first sheet of glass    providing a second sheet of glass;    providing a first low emissivity coating adjacent a surface of said first sheet of glass or said second sheet of glass;    disposing a first sealant assembly around the periphery of said first sheet of glass and said second sheet of glass to maintain said first sheet and said second sheet in spaced-apart relationship from each other; and    said first sheet of glass, said second sheet of glass, and said first sealant assembly forming an insulating glass unit having a U value substantially equal to or less than 0.2 BTU/hr-sq ft-F substantially preventing the formation of condensation on the outer surface of the refrigeration door component without the application of electricity for heating the door component.    
     
     
         72 . The method of  claim 71 , wherein said first sheet of glass, said second sheet of glass, and said first sealant assembly define a first chamber; and further comprising the step of disposing a gas in said first chamber.  
     
     
         73 . The method of  claim 71 , further comprising the steps of: 
 providing a third sheet of glass;    disposing a second sealant assembly disposed around the periphery of said second sheet of glass and said third of glass for maintaining said second sheet and said third sheet in spaced-apart relationship from each other; and    wherein said insulating glass unit further includes said third sheet of glass and said second sealant assembly.    
     
     
         74 . The method of  claim 73 , wherein said third sheet of glass includes a low emissivity coating adjacent a surface of said third sheet of glass.  
     
     
         75 . The method of  claim 71 , wherein said first sheet of glass is formed of Comfort Ti-PS.  
     
     
         76 . The method of  claim 71 , wherein said first sealant assembly has a heat transfer rate substantially equal to or less than 1.73 Btu/hr-ft-F.  
     
     
         77 . The method of  claim 76 , wherein: 
 said first and said second sheets of glass having a thickness substantially equal to one eighth of an inch; and    said first and said second sheets of glass being spaced apart a distance substantially equal to one half inch.    
     
     
         78 . The method of  claim 71 , further including the step of disposing said insulating glass unit in a door frame.  
     
     
         79 . The method of  claim 72 , wherein said gas is selected from the group consisting of argon, krypton, and air.  
     
     
         80 . The method of  claim 71 , wherein said insulating glass unit has a U value substantially equal to or less than 0.16 BTU/hr-sq ft-F.  
     
     
         81 . The method of  claim 71 , wherein said insulating glass unit has an emissivity substantially equal to or less than 0.04.  
     
     
         82 . The method of  claim 71 , wherein said insulating glass unit has an emissivity substantially equal to or less than 0.01.  
     
     
         83 . The method of  claim 71 , wherein said insulating glass unit has an emissivity substantially equal to or less than 0.0025.  
     
     
         84 . The method of  claim 71 , wherein said low emissivity coating is selected from the group consisting of a titania based silver and fluorine doped tin oxide.  
     
     
         85 . The method of  claim 71 , wherein said low emissivity coating is applied with a process selected from the group consisting of sputter coating, pyrolytic coating and spray coating.  
     
     
         86 . The method of  claim 72 , wherein said first sheet of glass is formed of Comfort E 2 .  
     
     
         87 . The refrigeration door of  claim 73 , wherein said first and second sealant assemblies have a heat transfer rate substantially equal to or less than 1.73 Btu/hr-ft-F.  
     
     
         88 . The refrigeration door of  claim 71 , wherein said first sealant assembly has a heat transfer rate substantially equal to or less than 1.51 Btu/hr-ft-F.  
     
     
         89 . The refrigeration door of  claim 71 , wherein said first sealant assembly has a heat transfer rate substantially equal to or less than 0.84 Btu/hr-ft-F.  
     
     
         90 . A method of manufacturing a refrigeration door component having an outer surface, said method comprising the steps of: 
 providing a first sheet of glass;    providing a second sheet of glass;    providing a first low emissivity coating adjacent a surface of said first sheet of glass or said second sheet of glass;    disposing a first sealant assembly around the periphery of said first sheet of glass and said second sheet of glass to maintain said first sheet and said second sheet in spaced-apart relationship from each other; and    said first sheet of glass, said second sheet of glass, and said first sealant assembly forming an insulating glass unit having an emissivity substantially equal to or less than 0.04 substantially preventing the formation of condensation on the outer surface of the refrigeration door component without the application of electricity for heating the door component.    
     
     
         91 . The method of  claim 90 , wherein said first sheet of glass, said second sheet of glass, and said first sealant assembly define a first chamber; and further comprising the step of disposing a gas in said first chamber.  
     
     
         92 . The method of  claim 90 , further comprising the steps of: 
 providing a third sheet of glass;    disposing a second sealant assembly disposed around the periphery of said second sheet of glass and said third of glass for maintaining said second sheet and said third sheet in spaced-apart relationship from each other; and    wherein said insulating glass unit further includes said third sheet of glass and said second sealant assembly.    
     
     
         93 . The method of  claim 92 , wherein said third sheet of glass includes a low emissivity coating adjacent a surface of said third sheet of glass.  
     
     
         94 . The method of  claim 90 , wherein said first sealant assembly has a heat transfer rate substantially equal to or less than 1.73 Btu/hr-ft-F.  
     
     
         95 . The method of  claim 90 , further including the step of disposing said insulating glass unit in a door frame.  
     
     
         96 . The method of  claim 91 , further including the step of disposing said insulating glass unit in a door frame.  
     
     
         97 . The method of  claim 96 , wherein said gas is selected from the group consisting of argon, krypton, and air.  
     
     
         98 . The method of  claim 90 , wherein said insulating glass unit has a U value substantially equal to or less than 0.2 BTU/hr-sq ft-F.  
     
     
         99 . The method of  claim 90 , wherein said insulating glass unit has an emissivity substantially equal to or less than 0.01.  
     
     
         100 . The method of  claim 90 , wherein said insulating glass unit has an emissivity substantially equal to or less than 0.0025.  
     
     
         101 . The refrigeration door of  claim 92 , wherein said first and second sealant assemblies have a heat transfer rate substantially equal to or less than 1.73 Btu/hr-ft-F.  
     
     
         102 . The refrigeration door of  claim 90 , wherein said first sealant assembly has a heat transfer rate substantially equal to or less than 1.51 Btu/hr-ft-F.  
     
     
         103 . The refrigeration door of  claim 90 , wherein said first sealant assembly has a heat transfer rate substantially equal to or less than 0.84 Btu/hr-ft-F.  
     
     
         104 . A substantially transparent insulating glass unit having an outer surface and being for use with a refrigerating compartment residing in an exterior environment and having an interior refrigerating compartment; said insulating glass unit door comprising: 
 a first sheet of glass;    a second sheet of glass;    a first sealant assembly disposed around the periphery of said first sheet of glass and said second sheet of glass for maintaining said first sheet and said second sheet in spaced-apart relationship from each other;    a first low emissivity coating adjacent a surface of said first sheet or said second sheet of glass, and    said first sheet of glass, said second sheet of glass, and said first sealant assembly providing the insulating glass unit with a U value effective to substantially prevent the formation condensation on the outer surface without the application of a electricity to heat the outer surface of the insulating glass unit when the interior temperature of the refrigerating compartment is substantially equal to or less than zero degrees Fahrenheit; the temperature of the exterior environment is substantially equal to or greater than seventy degrees Fahrenheit; and the humidity in the exterior environment is substantially equal to or greater than sixty percent.    
     
     
         105 . The door of  claim 104 , further comprising: 
 a third sheet of glass; and    a second sealant assembly disposed around the periphery of said second sheet of glass and said third of glass for maintaining said first sheet and said second sheet in spaced-apart relationship from each other.    
     
     
         106 . The door of  claim 105 , further including a second low emissivity coating adjacent a surface of said first sheet, said second sheet or said third sheet of glass.  
     
     
         107 . The door of  claim 106  wherein the insulating glass unit has a U value that substantially prevents the formation condensation on the outer surface when the interior temperature of the refrigerating compartment is substantially equal to or less than minus forty degrees Fahrenheit; the temperature of the exterior environment is at substantially equal to or greater than eighty degrees Fahrenheit; and the humidity in the exterior environment is substantially equal to or greater than sixty percent.  
     
     
         108 . The door of  claim 106 , wherein said low emissivity coating is effective to cause the insulating glass unit to have a U value substantially equal to or less than 0.2 BTU/hr-sq ft-F.  
     
     
         109 . The refrigeration door of  claim 105 , wherein said first sealant assembly and said second sealant assembly each have a heat transfer rate substantially equal to or less than 1.73 Btu/hr-ft-F.  
     
     
         110 . The refrigeration door of  claim 104 , wherein the insulating glass unit has a U value substantially equal to or less than 0.16 BTU/hr-sq ft-F.  
     
     
         111 . The refrigeration door of  claim 104 , wherein said first sheet or second sheet has an emissivity substantially equal to or less than 0.05.  
     
     
         112 . The refrigeration door of  claim 104 , wherein the insulating glass unit has an emissivity substantially equal to or less than 0.04.  
     
     
         113 . The refrigeration door of  claim 104 , wherein the insulating glass unit has an emissivity substantially equal to or less than 0.01.  
     
     
         114 . The refrigeration door of  claim 104 , wherein the interior temperature of the refrigerating compartment is substantially equal to or less than minus twenty degrees Fahrenheit; the temperature of the exterior environment is substantially equal to or greater than seventy degrees Fahrenheit; and the humidity in the exterior environment is substantially equal to or greater than sixty percent.  
     
     
         115 . The refrigeration door of  claim 104 , wherein the interior temperature of the refrigerating compartment is substantially equal to or less than minus forty degrees Fahrenheit; the temperature of the exterior environment is substantially equal to or greater than eighty degrees Fahrenheit; and the humidity in the exterior environment is substantially equal to or greater than sixty percent.  
     
     
         116 . The refrigeration door of  claim 105 , wherein said first sealant assembly and said second sealant assembly each have a heat transfer rate substantially equal to or less than 1.73 Btu/hr-ft-F.  
     
     
         117 . A refrigeration unit including an insulated enclosure defining a compartment, a cooling system, and a door adapted mounted on an opening of said compartment, said door having an outer surface and comprising: 
 a first sheet of glass;    a second sheet of glass;    a first sealant assembly disposed around the periphery of said first sheet of glass and said second sheet of glass for maintaining said first sheet and said second sheet in spaced-apart relationship from each other;    a first low emissivity coating adjacent the a surface of said first or said second sheet of glass;    said first sheet, second sheet, first sealant assembly, and said first low emissivity coating forming an insulating glass unit having a U value substantially equal to or less than 0.2. BTU/hr-sq ft-F substantially preventing the formation of condensation on the outer surface of the door without the application of electricity for heating said first surface; and    a frame secured around the periphery of said insulating glass unit.    
     
     
         118 . The door of  claim 117 , further comprising: 
 a third sheet of glass; and    a second sealant assembly disposed around the periphery of said second sheet of glass and said third of glass for maintaining said second sheet and said third sheet in spaced-apart relationship from each other.    
     
     
         119 . The refrigeration door of  claim 117 , further comprising: 
 a first chamber defined by said first sheet of glass, said second sheet of glass, and said first sealant assembly;    a second chamber defined by said middle sheet of glass, said outer sheet of glass, and said second sealant assembly; and    a gas disposed in said first and second chambers.    
     
     
         120 . The refrigeration door of  claim 118 , wherein said first sealant assembly and said second sealant assembly each have a heat transfer rate substantially equal to or less than 1.73 Btu/hr-ft-F.  
     
     
         121 . The refrigeration door of  claim 117 , wherein the refrigeration door has an emissivity substantially equal to or less than 0.04.  
     
     
         122 . The refrigeration door of  claim 117 , wherein the refrigeration door has an emissivity substantially equal to or less than 0.01.  
     
     
         123 . The refrigeration door of  claim 117 , wherein said first sealant assembly has a heat transfer rate substantially equal to or less than 1.73 Btu/hr-ft-F.