Dehumidifying a Large, Cold Basement
I have Poured foundation walls, I applied Grace self adhesive membrane on all exterior foundation walls, I did it myself, there are no areas sans the membrane below grade, and I applied a capillary break (Tremco paint on membrane) between the base of foundation wall and footing (as learned here on this site!) Under the gravel layer is a thick 15-Mil Vapor Barrier, taped and overlapped seams. Walls are not insulated yet, I figured I’d eventually insulate the interior side at some point (metal framing, rigid XPS caulked and taped panels). The basement is about 2,000 sq ft, temps run in the mid 50s just about all year, humidity is usually >60% on a regular basis during winter months, summer into the 80s. I am in Zone 5, Northeast, and made the mistake of installing a 120 pint a day Ultra-Aire dehumidifier, ducted to draw about 30% of air from living space and 70% from the basement with a return to basement alone. Since the dehumidifier is a typical compressor unit, the low temps do not allow it to function as it should.
The way I see it, I have a few options:
1. Heat the basement (insulate the exterior walls and maybe tap the overhead main trunks?, set up a different zone, maybe motorized dampers?, or install baseboards running them off the tankless water heater? The question then becomes best way to heat a large basement)
2. Use a desiccant dehumidifier, (I think it would have to be a large a pricey unit for the sq footage)
3. Mini-split/s (?, not too versed in this option)
4. An air-exchange system of sorts, maybe have the dehumidier draw 100% from the living space above where temps are higher and return 100% to the basement, thus causing a cycling of air – with basement doors always kept open?
Constructive input would be appreciated.
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