The last piece of a proper encapsulated crawlspace. We size the unit to your cubic footage (not by guess), plumb the condensate line to daylight or a sump, and dial in the humidistat so your crawlspace holds a steady 50-55% RH year-round.
A licensed local crew — usually out in 24 to 72 hours. Written scope, fixed price, no pressure.
Dehumidifier is the single most important piece of equipment in a Marvin crawlspace and it is the piece the builders skipped on almost every custom from 2003 through 2016. That is the whole story of the Marvin partial-encapsulation crisis in one sentence. Every one of the four flagship HOAs — Firethorne, Longview, Marvin Creek, The Vineyards — has the same failure pattern: 10-mil or 12-mil vapor barrier on the ground, no dehumidifier, and by year eight the crawl is running 80 to 85 percent RH through the summer. Adding the right dehumidifier — sized to the cubic footage, on a dedicated 20-amp Union County-permitted circuit, drained properly — is the single change that takes a Marvin crawl from a mold factory to a stable conditioned space. It is what the builder should have installed the day the house was framed. It is what we retrofit into hundreds of Marvin custom crawls after the fact.
Two Julys ago I got a call from a 2011 Vineyards custom off Marvin Meadows Rd, a 5,200 SF two-story on a half-acre with two kids in elementary school. Owner had called me because both kids had persistent morning bloody noses through June and July, and her pediatrician had told her to check the indoor air. I dropped into the crawl through the exterior hatch and immediately saw the Vineyards 2011 partial builder story: 10-mil clear plastic on the ground, piers skirted, no wall termination, and a 70-pint plug-in Frigidaire dehumidifier sitting on a plywood pad on the ground next to the mechanical room. Compressor iced up. Cord unplugged. Hygrometer read 81 percent RH at 79 degrees. The Frigidaire had been running for four summers, could not keep up with a 2,400 SF crawl footprint at that clearance, iced up in the fifth summer, and the homeowner had unplugged it in frustration two years earlier. Same story I have seen 100 times in The Vineyards on the 2014-through-2018 builder-with-portable-dehumidifier stock. The intention was there. The equipment was undersized by half. The result is a crawl that runs 80-plus percent RH through August, kids' bedrooms with elevated humidity, and morning bloody noses in July.
Every Marvin dehumidifier install starts with a cubic footage calculation and a moisture load assessment. Standard Marvin custom crawl is 2,000 to 3,500 SF footprint at 44-to-48-inch clearance, which is 7,000 to 12,000 cubic feet of conditioned space. Standard load calculation adds a factor for the moisture-generating sources — HVAC ductwork condensation, radiant heat if present, wall block off-gassing, and any residual ground moisture through the vapor barrier. The result for most Marvin customs is a load that calls for a 90-to-100-pint-per-day rated unit, not the 70-pint residential portables the Vineyards builders used.
Second step is unit selection. Default spec for a Marvin custom crawl is an Aprilaire E100, Santa Fe Ultra98, or AlorAir Sentinel HDi90. All three are 100-pint-per-day commercial-grade units designed to hang from the joists or sit on a raised platform, with integrated humidistats, integrated drain pumps as an option, and MERV-13 filtration. Aprilaire has the best warranty (five years) and the easiest homeowner filter access. Santa Fe has the highest efficiency and the quietest operation. AlorAir is the value option and works fine for the load. Unit choice depends on homeowner preference and supplier availability.
Third step is unit location. On a Marvin custom crawl with 44-to-48-inch clearance, we hang the unit from the joists using vibration-isolation straps — not on the ground where it would sit in any water event, not on a shelf that has to be built. The location is chosen to minimize discharge run distance and to place the unit centrally to the crawl footprint so airflow reaches all corners. On very large crawls over 3,500 SF, we sometimes spec two smaller units instead of one large one to get better distribution.
Fourth is the electrical rough-in. Dehumidifier goes on a dedicated 20-amp GFCI circuit — no exceptions, no sharing with the crawl light or an outlet. Circuit permitted through the Union County office in Monroe as an electrical permit. Wire run is 12-2 Romex from the main panel through the joist bays to a junction box near the unit, terminated in a standard 20-amp outlet that the dehumidifier plugs into. Union County electrical inspection sign-off before we energize.
Fifth is the drain. Best case is a gravity drain to daylight through the closest exterior wall — schedule 40 PVC from the dehumidifier condensate outlet, sloped 1/8-inch per foot minimum, terminated in a landscape bed at least 5 feet from the foundation. When grade does not allow gravity drainage (about 30 percent of Marvin lots), we use a condensate pump — a Little Giant VCMA-15UL or equivalent — mounted at the unit, discharging up and out through the block wall to the same landscape bed. Condensate pump adds a second small circuit but simplifies drain routing.
Sixth is HOA notification for any exterior discharge point. Firethorne, Longview, Marvin Creek, and The Vineyards all want to see where the discharge exits the house and how the PVC will be finished. Firethorne wants notification with a site photo. Longview requires a formal ARC submission with a landscape screen designed around the discharge point — usually a boxwood cluster or a lattice panel. Marvin Creek and The Vineyards want a courtesy email. All four HOAs will approve the discharge when the plan is submitted properly and the visible PVC is painted to match the trim on the house.
Install itself runs a full day for the unit and electrical rough-in on most Marvin customs. Day one morning is the electrical rough-in — Romex pulled from the panel through the joist bays to the unit location, junction box installed, outlet wired. Day one afternoon is the unit hang and drain plumbing. Day two is inspection and startup — Union County electrical inspection in the morning, then unit energized, humidistat set to 55 percent RH, run test for a couple of hours to confirm operation and drainage.
Standard Marvin dehumidifier spec is Aprilaire E100, Santa Fe Ultra98, or AlorAir Sentinel HDi90 — 90-to-100-pint-per-day rated commercial-grade units. All three are ENERGY STAR rated, all three have integrated humidistats, and all three are sized appropriately for a 2,000-to-3,500 SF Marvin custom crawl. On very large crawls over 3,500 SF or on estate lots with specialty mechanical loads (radiant heat, geothermal manifolds), we sometimes spec two smaller units for better distribution instead of one large unit.
Mounting is joist-hung with vibration-isolation straps rated for the unit weight — typically 60 to 90 pounds. Never floor-mounted in a Marvin crawl, even with 48-inch clearance, because any wet event will pool water around the unit base and burn out the compressor. Ductwork on the dehumidifier is optional; most Marvin crawls do not need distribution ducts because the unit throws air far enough on its own to reach all corners of a standard footprint. On very deep crawls (over 40 feet in one dimension) we sometimes add a short duct extension to reach a far corner.
Electrical is a dedicated 20-amp GFCI circuit on 12-2 Romex from the main panel, terminated in a standard 20-amp outlet at a junction box near the unit. Union County electrical permit filed and inspected. Never shared with any other load. The dehumidifier can pull 5 to 8 amps under full compressor load; sharing a circuit with the crawl light or an outlet risks a trip on peak load.
Drain is gravity to daylight where grade allows — schedule 40 PVC from the condensate outlet, sloped 1/8-inch per foot minimum, terminated in a landscape bed at least 5 feet from the foundation. When gravity is not viable, a Little Giant VCMA-15UL or equivalent condensate pump mounted at the unit, discharging up and out through the block wall via 1/2-inch vinyl tubing to the same landscape bed. Filter is MERV-13 standard, homeowner-replaceable every 6 months, checked at every service call.
Humidistat set point is 55 percent RH on install. Adjustable by the homeowner but I recommend never lower than 50 or higher than 60. Lower than 50 wastes energy without improving air quality; higher than 60 approaches the dew point where condensation and mold can restart. Unit runs continuous during summer, cycles off in winter when ambient RH drops below the setpoint.
Yes — Marvin is a regular dehumidifier route. Free on-site inspection anywhere in Marvin, fixed written quote before we touch anything.
Marvin dehumidifier work is almost always retrofitting a properly-sized commercial-grade unit into a builder crawl that either has no dehumidifier at all (Firethorne, Longview, Marvin Creek stock) or has an undersized residential portable that iced up years ago (The Vineyards 2014-2018 stock) — a specific failure pattern unique to this town's custom builders.
28173. All Union County addresses covered.
Yes, and this is one of the most common Marvin calls. The 70-pint residential portable dehumidifiers the 2014-through-2018 Vineyards builders installed — Frigidaire, GE, sometimes LG — are undersized by roughly half for the 2,000-plus SF crawl footprints they were placed in. They ice up by the second summer because the compressor cannot handle a 100-percent RH environment, the coil frosts over, the unit stops removing moisture, and eventually the homeowner unplugs it in frustration. After that the crawl runs 80-plus percent RH through every summer and the underlying encapsulation (which was still the same skirted-pier, tape-on-block builder spec) fails alongside it. Fix is to remove and dispose of the portable, redo the encapsulation properly with 20-mil liner and wrapped piers, and install a real 100-pint commercial-grade unit — Aprilaire E100 or Santa Fe Ultra98 — on a dedicated 20-amp circuit.
We route to a side or rear elevation as default, paint the PVC to match the trim on the house, and submit a one-page scope to Firethorne ARC showing where the discharge exits and confirming the paint match. Firethorne wants notification for any exterior modification but has never denied a properly-submitted discharge plan in my experience. Longview is stricter and wants a landscape screen designed into the scope — boxwood cluster or lattice panel around the discharge point — but same net result, always approved when submitted correctly. On lots where the geometry forces a visible discharge on a front elevation or a fairway-facing wall, we route interior to a condensate pump and discharge into an existing plumbing stack instead, which keeps the exterior wall untouched. There is always a solution.
Depends on the unit and the moisture load, but for a standard 2,500 SF Marvin custom crawl with an Aprilaire E100 or Santa Fe Ultra98 running to hold 55 percent RH through summer, expect approximately 100 to 150 kWh per month during May through September, dropping to near zero from November through March. At current Union County residential rates that is a small monthly line item during summer and essentially free during winter. The offset is that your HVAC compressor is no longer running long cycles trying to dehumidify the second-floor return air that is being fed by a humid crawl — so overall summer HVAC electric usage typically drops enough to more than pay for the dehumidifier. Net effect on the summer electric bill is usually neutral to slightly positive.
Yes, and yes. MERV-13 filter change every six months is homeowner-serviceable — pop the front cover, slide the old filter out, drop the new one in. Aprilaire filters are available at any home improvement store; Santa Fe and AlorAir filters are usually online or through us direct. Annual service by us includes a full inspection of the unit and drain line, coil cleaning if needed, humidistat calibration check, and confirmation that the drain is running freely — most Marvin drain lines run clean but the odd one gets a hornet nest built inside the exterior termination and needs a clear-out. Full unit lifespan on a commercial-grade dehumidifier in a properly sealed crawl is 8 to 12 years; then the compressor wears out and the unit gets replaced. Aprilaire E100 has a five-year manufacturer warranty on parts and labor.
Free on-site Marvin inspection. Fixed written quote. Call (980) 227-1769 or book below.