Below grade heat recovery ventilator
FIELD OF THE INVENTION 
     The present invention relates to heat recovery ventilation systems for buildings and more particularly to a below grade heat recovery ventilation system. 
     BACKGROUND OF THE INVENTION 
     Adequate ventilation is of importance in any building to avoid the accumulation of noxious substances. Building ventilators are found in a number of forms. These include simple fan mechanisms drawing stale air, humid air and fumes from a kitchen, bathroom or other suitable location and discharging it to the outside. These systems include heat recovery ventilators with heat exchange for exchanging heat between discharging stale air and incoming fresh air. 
     In addition, it is known that some buildings may be subject to infiltration and accumulation of harmful radon or soil gases in below grade parts of the buildings, for example basements. Various techniques have been developed for preventing or reducing this gas infiltration or accumulation. 
     It is also known that in some soils, a loss of moisture will cause the soil to contract, causing stability problems in some buildings. 
     The present invention is concerned with a novel heat recovery system that maybe associated with a ventilation system and that also addresses the gas infiltration and soil stability problems, at least to some extent. 
     SUMMARY OF THE INVENTION 
     According to the present invention there is provided a below grade heat recovery system for a building having a below grade floor slab, said system comprising: 
     at least one inlet for receiving air; 
     an air receiver positioned below the floor slab; 
     air distribution means leading from the air receiver under the floor slab and having openings therein for discharging air therefrom; and 
     blower means for drawing air into the inlet and discharging the air into the air receiver. 
     The system may discharge all of the exhausted air into the soil under the floor slab drainage lines or it may also discharge into the conventional drainage tile. 
     The inlet may be one or more exhaust vents for receiving air from within the building. 
     Since exhaust air from the building is normally warm and humid, a portion of its energy content will be transferred to the surrounding soil beneath the floor slab and around the perimeter of the foundation. This raises the temperature of the soil and thus reduces the below grade heat loss from the basement. 
     By pressurizing the under slab drainage layer, the transport of radon and soil gas from the soil, through the slab and into the basement may be reduced. 
     The system also delivers a relatively constant supply of moisture into the soil, as moist air. In moisture sensitive soil, this will moderate fluctuations in the soil moisture content, thus moderating soil movement and foundation damage. 
     In other embodiments of the invention the inlet may be from an attic to provide attic ventilation or from outside the building to provide a &#34;precharging&#34; or storage of heat in the subsoil. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings which illustrate exemplary embodiments of the present invention: 
     FIG. 1 is a sectional view of a house equipped with a ventilating system according to the present invention; 
     FIG. 2 is a cross sectional detail of the footing and slab; 
     FIG. 3 plan view of the below slab-layout; 
     FIG. 4 is a view like FIG. 2 of an alternative embodiment; 
     FIG. 5 is a view like FIG. 3 of the alternative embodiment of FIG. 4; and 
     FIG. 6 is a schematic of the system of FIGS. 1, 2 and 3. 
    
    
     DETAILED DESCRIPTION 
     Referring to the accompanying drawings, and especially to FIGS. 2 and 3, there is illustrated a building 10, in this case a residence with a main floor level 12 containing a kitchen 14 and a bathroom 16. The house is built with a below grade basement 18. A peripheral footing 20 supports the foundation wall 22 and the edges of a floor slab 24. A conventional weeping tile 26 is installed around the footing 20. 
     The tile is covered with gravel 27 and then backfill soil 28. 
     As illustrated in FIG. 1, the kitchen 14 is equipped with a kitchen vent 30 for ventilating moisture and fumes from the kitchen. The bathroom 16 is equipped with a bathroom vent 32, likewise for ventilating moisture and other air borne materials, for example, malodorous gases, from the bathroom. The vents 30 and 32 are connected to respective ducts 34 and 36 that lead through the walls and under the main floor to join into a main duct 38 at the basement ceiling. The main duct is equipped with a blower 40 for drawing air through the vents 30 and 32. Downstream of the blower are a balancing damper 42 and a flow measuring station 44. 
     From the flow measuring station, the main duct 38 leads to a catch basin 46 in the floor slab 24. The catch basin is closed with a cover 48 that is sealed in place by a seal schematically illustrated at 49 in FIG. 2. 
     Four leader pipes 50 lead from the catch basin 46 through a bed of gravel 52 under the slab 24. These leader pipes lead to the weeping tile 26. Each pipe has a series of holes where it passes through the gravel under the slab for leading air from the ventilation system into the gravel layer. Air is also ducted through the weeping tile into the soil around the foundation wall. 
     An alternative embodiment of the present invention is illustrated in FIGS. 4 and 5 of the drawings where the footing is embedded in a more extensive gravel drain layer that extends under the floor slab around the footing, below the backfill 60. In this case, there is no weeping tile around the perimeter of the footing and the underslab leaders 64 radiating from the catch basin 66 terminate short of the footing. 
     In the second embodiment, there will be a greater pressurization of the under slab area because the exhaust air is discharged into the zone under the slab. 
     While particular embodiments of the present invention have been described in the foregoing detailed description, it is to be understood that other embodiments are possible within the scope of the invention. For example, the source of air may be a warm attic in the summer, or even an inlet for ambient air. 
     Thus, the invention is to be considered limited solely by the scope of the appended claims.