Looking for help on this design: Anyone experienced in HVAC feel free to chime in.
I've got a 2.5k room in a 12x9 and a 4k room in a 18x10 in my basement. In between the two rooms is a lung room which also has our gas water heater and furnace. I haven't taken the measurements of this space 10in and 8in exhausts were causing our appliances to go out, so we cut some intakes for combustion air. They now stay lit, however the water heater is backdrafting, especially when its too cold out. I am now at wits end and our temps are high as it is. I am thinking about installing a minisplit in the lung room, and having active intakes into the grow room in a similar fashion to DonJuanMatus, but using the lung room as my cooling supply instead of outdoor air. The active intakes would cause negative pressure in the lungroom, but positive pressure in the grow rooms, causing the air in the grow rooms to get pushed back into the lung room and mix with the cool air in the lung room before getting sucked back in to the grow space. Now, I still have those passive intakes we cut for the water heater and furnace... I assume the negative pressure will still pull fresh air from upstairs through these, but since its under negative pressure in the basement it will keep our smell from leaking upstairs? I'd say the lung room is probably 35-50% of our basement, and the two grow spaces take up the rest. 2500cf of grow space and approx 2000cf of lung room or more. I'd go with 24000 btu in the lung room... Main concern is water heater back draft. will the positive pressure causing passive exhaust BACK into the lung room neutralize the negative pressure in the lung room and solve our water heater back draft? I turned the exhaust off and left the active intakes on, it made positive pressure and pushes air back into the lung room so I feel like our water heater will work under this condition?
