TECHNICAL FEATURE open area in the basement) in summer high humidity conditions. This design is approved by the Ontario Building Code as an acceptable foundation water leakage protection system. Foundation water leakage is either evaporated or drained from the envelope without causing any damage to the system or the finishing materials. It has been used as a backup to exterior foundation leakage protection systems that can or have failed. Such failures can happen when the perimeter footing weeping tile clogs up and/or there are edge sealing or other imperfections in exterior foundation surface coatings and membranes. 30 cfm (14 L/s) reduces the basement air concentration by only 12% versus 100% for the depressurized envelope (Figure 10a). It would be even less effective for 10 cfm (4.7 L/s) (Figure 10b).3 With the depressurization system properly working, these basement gas levels essentially drop 100% to a level of 0% in the basement breathing air. Conclusions At least 10% and perhaps 50% or more of building FIGURE 9 Depressurized insulated wall with fan control. Pressure Probe Into Cavity Needle Valve Sealed Cavity Sampling Tube Isn't Basement Ventilation Equally Effective? An important note to make: the infiltration energy loss from the basement is similar to the infiltration from the house aboveground, without the benefit of fresh air quality. This air contains odors and gases emitted from wet soils and concrete or other things that might incubate in the envelope. For example, the worst scenario would be a house and basement that doesn't use forced air heating. Instead, it uses point sources like electric heaters or heat pump split units. Since the only connection between levels is the stairway, the stairway is the only path for dilution of "basement gases." If the recommended envelope flow of 10 cfm to 30 cfm (to 14 L/s) is simply circulated to the basement instead of through the envelope to the outdoors, the basement contaminant gas levels remain high. A simple compartment model shows that basement contaminant gases for a contaminant free airflow of Pin Prick Hole in Poly In-Line Centrifugal Blower To Speed Controller To Electrical Panel 4 in. Dia. Duct 3/16 in. ID Plastic Tube Control Panel 4 in. Duct Exhausting Depressurization From Wall Cavity Instrumentation FIGURE 10 (a) Compartment flow and (b) CFD estimates of "basement gas" dilution. C = concentration of the containment gas. B. Concentration of Basement Gas A. 0.9200 0.8000 0.7000 0.6000 0.5000 0.4000 0.3900 0.3000 C=C1 C1=0.156 32.87 cfm 153 cfm C=0 32.87 cfm Most of House is Below 0.4 Edge Infiltration 1.5 Air Changes Per Hour for House Split Units 33 cfm From Living Room 200 in.2 Wall Leakage for The Basement Basement C=0.92 C2=0.881 CE=1 200 cfm Split Units Y X Z 24 ASHRAE JOURNAL ashrae.org APRI L 2020 33 cfm Up Stairwayhttps://ashrae.org