If you rent, a portable dehumidifier is almost always the right answer. Pick one rated for your square footage, put it where the air is dampest, and empty it or run a drain hose to a floor drain. If you own or manage the building, a portable is the wrong tool — it depends on a tenant remembering to empty a bucket, and the moisture comes back the week they stop.
That is the whole decision. The rest of this page is how to tell which one you are, and what to buy in each case.
Start with who controls the unit
Dehumidifier advice usually skips this, which is why so much of it is useless. The right machine depends less on your square footage than on who is responsible for it six months from now.
- You rent and you are solving your own comfort problem. Portable. Nothing permanent gets installed in a unit you do not own, and you want to take it with you.
- You own the building, or manage it. Permanent. Every portable in every unit is a device somebody else has to maintain, and a humidity problem you hear about only after it has become a moisture complaint.
The three types, honestly compared
| Portable | In-wall | Whole-house | |
|---|---|---|---|
| Best for | Renters, one room, a temporary problem | Apartments, condos, individual units | Single-family homes, ducted buildings |
| Install | Plug it in | Recessed in the wall or mounted on it | Tied into ductwork |
| Drainage | Bucket, or a hose to a drain | Self-draining, no tank | Plumbed to a drain |
| Who maintains it | The occupant, continuously | Maintenance staff, occasionally | Maintenance staff, occasionally |
| Runs when HVAC is off | Yes | Yes | Usually not |
| Fails when | Nobody empties the bucket | Rarely | The system is off or the unit is vacant |
The last row is the one that matters in multifamily buildings. A portable is not a bad machine — it is a machine with a human dependency, and at scale that dependency is the failure.
If you rent: how to size and place one
Match the pint rating to the space and how damp it actually is, not to the largest number you can afford. A unit that is too large short-cycles; one that is too small runs constantly and never catches up.
- Put it where the damp is — usually the bathroom side of the apartment, a below-grade room, or wherever you see condensation on the windows first.
- Give it clearance. Most units pull air in on one side and exhaust on the other; against a wall or in a closet, it fights itself.
- Run a hose to a floor drain if you can. Emptying a tank by hand is the single most common reason a dehumidifier stops getting used.
- Aim for 30–50% relative humidity. A $10 hygrometer tells you whether it is working better than any spec sheet will.
If your apartment is damp enough that a portable runs constantly, that is worth telling your property manager. Persistent moisture in a unit is usually a building condition, not a housekeeping one, and it is their problem to solve.
If you own or manage the building: what changes
At one unit, a portable is fine. At forty, it is forty devices, forty tenants who may or may not use them, and no way to know which apartments are actually dry.
Innovative Dehumidifier Systems designed its wall-mounted dehumidifier for apartment buildings first — we introduced the first in-wall dehumidifier, and the IW25 has been in the field since 2011. The design follows from the problem:
- It drains itself. No tank, so there is nothing for a tenant to empty and nothing to overflow.
- It runs independently of the HVAC. It keeps working in a vacant unit, over a long weekend, and through the shoulder seasons when the air handler is off — which is exactly when humidity climbs.
- It takes a security cover. Controls stay set. In student housing and military barracks this is the difference between a specified humidity level and a suggestion.
- It installs four ways — recessed in a 2×6 wall, in an exterior sleeve in a 2×4 wall, through-wall, or mounted on the surface for block, brick and masonry — so the same unit suits new construction and retrofit. Where to install a wall-mounted dehumidifier covers the detail.
The current model, the IW-25-6, removes up to 40 pints a day and covers spaces up to 1,500 square feet, with a two-speed fan and an ozone-free bi-polar ionizer. It carries a 5-year warranty with 100% coverage, not prorated.
For portfolio operators, DehuLink Wi-Fi monitoring reports what each unit is doing, so a rising humidity reading in a vacant apartment becomes something you can see rather than something you discover.
What it looks like at scale
On a 400-unit Texas property in 2021, relative humidity fell from 78% to 56% within two hours of the units running. That is the argument for permanent equipment stated as a number rather than a promise.
More on the building-wide picture: multifamily dehumidification. For a side-by-side written for owners, developers and specifiers, see the multifamily spec guide.
What a dehumidifier does and does not do
A dehumidifier controls the humidity that mold needs to grow. Keeping indoor relative humidity in the 30–50% range is the practical reason to run one, and it is a condition you can measure.
What it will not do is fix a leak. If moisture is coming from a failed seal, a roof, a plumbing problem or grade draining toward the building, a dehumidifier manages the symptom while the cause keeps producing it. Find the source first.
Frequently asked
What size dehumidifier do I need for an apartment?
Match the pint rating to the square footage and to how damp the space actually is. A one-bedroom apartment with mild seasonal dampness needs far less capacity than a below-grade unit that stays humid year round. For permanent installations, the IW-25-6 covers spaces up to 1,500 square feet at up to 40 pints a day.
Can I install a permanent dehumidifier in an apartment I rent?
Not on your own — it is a modification to the building. If dampness is persistent, raise it with your property manager, since a permanent unit is normally an owner decision and an owner expense.
Do I still need a dehumidifier if I have air conditioning?
Often, yes. Air conditioning removes moisture as a side effect of cooling, so it only dehumidifies while it is actively running. In mild or humid shoulder-season weather the system may barely run while the air stays damp, which is when a dedicated dehumidifier earns its place.
Where should a dehumidifier go in an apartment?
Where the air is dampest and where it has clearance on the intake and exhaust sides. Windows that fog first are a reliable indicator of the damp end of the apartment.
What humidity level should an apartment be?
Between 30% and 50% relative humidity. Above roughly 60%, conditions favor mold growth; an inexpensive hygrometer tells you where you actually are.
Innovative Dehumidifier Systems is a division of Maradyne Corporation. Our units are in service in all 50 states and 9 countries. To specify equipment for a building, call (910) 579-3348.
