=Exterior Walls.=--As for the exterior surface of the building, this should be brick, the lighter the color the better, making absorption of heat less probable. When building reinforced concrete frame with curtain walls, the design should be such that the brick work entirely covers the concrete frame, since it is very difficult to obtain tight joints abutting beams and columns when attempting to build panels of brick in concrete framing. It is desirable to prevent air and moisture leakage. [Illustration: FIG. 31.--GROUND PLAN OF A FREEZER AND STORAGE BUILDING.] _Qualities in Brick._--In the selection of brick sufficient attention is rarely paid to the obtaining of brick burned approximately to vitrification. The presence of salt, as is frequently noticed on exterior walls of packing houses adjacent to floor lines, indicates that brine has been percolating the walls, due to their porosity. In the same manner water will pass through the opposite direction, and very far disqualify the insulation materials unless they be non-absorbing, and even these are lessened in value owing to the accumulating moisture. _Wall Construction._--All kinds of tile and plaster or concrete exteriors should be avoided, since it is impossible to prevent shrinkage cracks which permit percolation of water, eventually shelling off plastered surfaces and deteriorating insulation. _Ventilation._--In northern climates it is desirable to take advantage of the winter air when it equals or is lower in temperature than the rooms where product is stored, or when empty to air and cleanse an apartment. For convenience in this it is advisable to locate refrigerator windows in the same line to permit ready flow through the room; these being put on hinges similar to a door. _Insulation._--When undertaking to construct buildings fire proof, problems in insulation are encountered. The more dense or heavier the material used in building, the more cold radiated from all surfaces unless effectually cut off. In ordinary type of construction the various floors rest on exterior walls and in no way is it possible to prevent a very great loss of cold being carried through the floors, thence to the walls and dissipated thereby. Such matters are not trivial in their importance. At one wholesale distributing market deterioration in insulation during six or seven years has necessitated the doubling of refrigerating machine service and the volume of business is practically the same. To obviate this the remedy seems to be to surround the building on all sides and cover the roof with an encasing of insulation, putting an exterior covering of brick or impervious material over this to protect the insulation, and to prevent moisture coming in contact with the insulation. It is just like dropping a small box within a larger one, the space between the sides being the insulation.