1. Field of the Invention
The present invention relates to movable insulation apparatus for insulating against radiant, conductive and convective heat transmission through building openings such as windows, doors, and the like. The movable insulation apparatus is designed for selectable movement to cover and uncover the opening and thereby control the amount of heat energy and light transmitted therethrough.
In recent years conservation of energy has become a subject of great national concern. As readily available and now technologically feasible sources of energy become more scarce or more expensive, the need to conserve energy from such sources becomes more acute.
A primary target for conservation efforts is energy used to control building temperatures. Indeed, it has been estimated that the heating and cooling systems of residential, industrial, and commercial buildings use approximately 25% of all energy consumed in the United States. Transparent single pane or double insulated pane windows in such buildings, however, are very poor insulators and, therefore, can lead to inefficient and thus excessive consumption of energy for building heating and cooling purposes. For example, it has further been found that in winter, the heat loss per unit area through conventional windows is typically three to ten times as great as that through adjacent walls, depending upon the type of insulation in the wall. Similarly, in summer the total heat entering through a sunlit window may be more than ten times that through the adjacent wall. (Se ASHRAE, Handbook of Fundamentals (1972); R. C. Dix and Z. Lavan, "Window Shades and Energy Conservation", Mechanics, Mechanical and Aerospace Engineering Department, Illinois Instititue of Technology, (1974)). Therefore, substantial amounts of energy can be saved if window and other glassed areas are effectively insulated. However, it is desirable to do so without permanently blocking such glassed areas in a manner that use of them for ventilation and natural lighting would be prevented.
It is further desirable that insulation for windows and other glassed areas provide high insulation value even when the area is partially opened or exposed by the insulation to allow for entry of light therethrough.
It may also be desirable or advantageous to insulate areas of buildings other than windows where the permissible thickness of insulation is limited.
2. Description of the Prior Art
Various devices have been proposed in the past for insulating windows or other such building openings. For example, U.S. Pat. Nos. 4,039,019 (Hopper) and 4,194,550 (Hopper) disclose highly effective devices that include a plurality of opaque or translucent imperforate shade sheets attached to a retracting roller mounted to horizontally span the building opening at its upper end or head. The sheets may be drawn downwardly from the roller to cover the window or may be retracted upwardly back on to the roller to uncover the window. Thus, in use, these insulating apparatus operate as do conventional window shades being drawn from the top of the window down.
A number of spacer devices are mounted with one sheet of each pair of adjacent sheets to separate those sheets, when they are drawn to cover the window, and thereby define a dead air space therebetween. The spacers are collapsible or nestable so that when the sheets are retracted onto the roller the sheet layers may be tightly compacted to constitute a cylinder having diameter not much greater than a conventional shade. A low emittance surface is associated with at least one of the sheets and faces on one dead air space. The insulating effect of the low emittance surface synergistically combines with the insulating effect of the associated dead air space to yield a substantially higher insulating value than merely the sum of the individual insulating values of the surface and dead air space. It has further been shown that an apparatus having three shade sheets constructed as described above provides eight times, and that an apparatus having five sheets provides sixteen times, greater thermal resistance (R) when drawn over a single pane window, then does the window when uncovered.
U.S. Pat. No. 4,247,599 (Hopper) discloses a composite sheet material having low emittance characteristics that may advantageously be used in the insulating shade apparatus disclosed in the Hopper patents mentioned above.
Other constructions for insulating openings such as windows are disclosed in U.S. Pat. Nos. 2,305,085 (Smith); 2,140,049 (Grauel); 2,328,257 (Butts); 2,865,446 (Cole); 1,908,989 (Lahey et al). U.S. Pat. No. 2,341,123 (Schweller) discloses a refrigerating apparatus that includes a multiple layer closure device. U.S. Pat. No. 3,952,947 (Saunders) discloses a heating and ventilating system which includes a two layer shade device, with each shade layer being retracted on a separate roller. One roller is mounted to be both vertically and horizontally displaced from the other. The top of the shade carried on the one roller is also arranged to be drawn to a location similarly horizontally and vertically displaced from the top of the shade on the other roller. Therefore, air current can flow between the shades from one side of one shade to an opposite side of the other shade and, in fact, the patent teaches that this is desirable. However, air flow between the shades reduces the efficiency of the device in insulating against heat transmission.
FIG. 9-3, page 146 in Wm Langdon, Movable Insulation (1980), discloses a reflective single layer window shade mounted between a window and storm sashes to cover a building opening.
While many apparatus have been proposed, including the highly effective apparatus disclosed in the two prior Hopper patents, all such know apparatus are characterized by certain drawbacks. In all such apparatus which are closed by being drawn from the top to the bottom of a building opening or sidewardly across a building opening, it has been found that a major portion of the insulating value is lost when such devices are even slightly opened. Accordingly, in order to open the device to see out through the opening which it insulates, a major portion of the insulating value must be sacrificed.
Known devices which are drawn from the bottom of a building opening upwardly are also characterized by certain drawbacks. For example, as noted above, the apparatus disclosed in the Saunders patent is constructed to encourage flow of air between adjacent sheets that greatly reduces its insulating value. This apparatus is also relatively complicated, requiring at least two of the retracting rollers, on for each of two sheets. The device disclosed in Movable Insulation is a single layer shade. The Schweller patent discloses a relatively complicated device having multiple retracting rollers for multiple shade sheets which is believed to be ill suited for wide scale commercial use to insulate building openings.
It is the intent of the present invention to correct certain deficiencies in known prior art apparatus.