What Is an LGR Dehumidifier and When Do You Need One?

What does LGR mean?

LGR stands for low grain refrigerant. 'Grain' is an old unit for the amount of moisture in air, so 'low grain' describes the machine's goal: to send air back into the room with very little moisture left in it. An LGR is still a refrigerant dehumidifier, meaning it condenses water from the air the same way a standard unit does. The Department of Energy defines a dehumidifier as a self-contained, electrically operated assembly with a refrigerated surface that condenses moisture, a refrigerating system with an electric motor, an air-circulating fan, and a means for collecting or disposing of condensate. An LGR fits that definition, but its refrigeration circuit is arranged differently.

The key difference is a second pass over the cooling system. A conventional unit pulls in room air, cools it across the evaporator coil, collects the water that condenses, and sends the air back out. An LGR chills the air a first time, then chills it again before it leaves. That second pass pulls more water out and sends drier air into the space. For the basic physics of how the machine works, see how dehumidifiers work.

How an LGR differs from a standard dehumidifier

The practical difference shows up in what comes out of the machine. Standard portables are sized by capacity, which ENERGY STAR describes as the amount of water removed per day at test conditions, reported in pints per day. They are built to keep a room near the level health agencies recommend: the CDC advises keeping indoor humidity as low as you can and no higher than 50 percent, and notes that a dehumidifier can help. A standard unit is enough for that job.

An LGR is built for a harder job: pulling moisture out of materials, not just out of the air. When wood, drywall, carpet, and insulation get wet, they release that water slowly. Drier air at the surface keeps the moisture moving from the material into the machine. An LGR sends that drier air out of its outlet, which is why restoration drying is its classic use. The tradeoffs are real: LGRs are heavier, run longer, and need more attention to airflow and drainage than a standard portable.

Capacity numbers need context too. The Department of Energy defines performance ratings and test methods for dehumidifiers, and since 2020 portable units have been tested at 65 degrees Fahrenheit instead of 80 degrees to reflect basement conditions. ENERGY STAR notes that there is less water to remove in cooler air, which is why the newer capacity numbers are lower. A modern machine with a lower pint number can remove the same moisture as an older machine with a higher number, so compare the current pint rating and low temperature performance before you choose.

When you actually need an LGR

You need an LGR when the task is structural drying, not routine humidity control. The clearest signal is water damage: a flood, a burst pipe, or a major roof leak. The CDC says to clean up and dry out your home fully and quickly, within 24 to 48 hours after a flood, and EPA repeats that timeline for drying water-damaged areas and items to prevent mold growth. When walls, floors, and framing are soaked, you want maximum drying power.

Restoration crews also turn to LGRs in cooler, damper places where a conventional portable loses output. ENERGY STAR warns that frost can form on condensing coils when air temperature drops below 65 degrees Fahrenheit, causing the compressor to cycle on and off without removing moisture. Check the maker's stated operating range and defrost features before you rely on the machine. See auto defrost explained for how these systems work.

• Water has soaked into drywall, hardwood, subfloor, or insulation.
• You are drying a basement, crawl space, or lower level after a leak or flood.
• You need to run the machine for days with a continuous drain instead of emptying a bucket.
• A standard portable has been slow to lower humidity in a cool, damp space.

When a standard dehumidifier is enough

If your problem is ordinary dampness, a standard dehumidifier is usually the right tool. University of Minnesota Extension recommends using a dehumidifier in a damp basement to remove moisture from the air. The everyday target is the CDC's 50 percent ceiling: keep humidity as low as you can and no higher than 50 percent. A standard portable, sized for the room, will hold that level in most homes. See the basement dehumidifier guide for current recommendations.

ENERGY STAR's sizing guidance shows what counts as ordinary. For a slightly to moderately damp space, described as feeling damp with an intermittent musty odor at 50 to 75 percent relative humidity, the recommended portable capacity is 20 to 30 pints per day for a room under 2,000 square feet, and 30 pints or more for a larger room. Very damp or wet spaces need more capacity, but everyday basement dampness falls within normal portable range. For models in the common sizes, see the 50 to 99 pint guide.

You also gain efficiency without going commercial. ENERGY STAR certified dehumidifiers use about 20 percent less energy than a similarly sized conventional unit while removing the same amount of moisture. For a machine that runs for months, that difference matters more than the extra drying muscle of an LGR. If you are replacing an old unit, remember that capacity ratings changed under the new test, so a smaller-looking pint number can still match your old machine. See the ENERGY STAR certified guide for efficient choices.

What to check before choosing an LGR

If you decide an LGR is justified, compare published specs rather than marketing language. Capacity comes first: look at the pint-per-day rating under the current DOE test conditions and match it to the wet materials you are drying. In restoration work, drying speed matters, so place the machine close to the wet area with clear airflow around it.

Drainage is next. An LGR that runs for days will fill a bucket quickly, so the plan should be a continuous drain hose to a floor drain, sump, or condensate pump. Check whether the machine has a built-in pump or relies on gravity draining. See pump versus gravity drain for set-up options. Then look at the operating range: ENERGY STAR warns that frost can form below 65 degrees Fahrenheit, so review the maker's stated range and any automatic defrost feature.

Finally, efficiency. The current metric is the integrated energy factor, or IEF, measured in liters of water removed per kilowatt-hour of energy consumed, with higher meaning better. Compare IEF values before choosing, because an LGR is a machine that runs long and hard. See IEF explained for the details.

Bottom line: pick by job, not by label

Ask what the machine has to do. If the answer is keeping a basement under 50 percent humidity, a standard portable is the right buy. If the answer is drying soaked building materials after flooding, an LGR is the restoration tool. EPA's advice is the useful frame: fix the water problem, clean up mold, and dry water-damaged areas within 24 to 48 hours. An LGR helps you meet that deadline after a failure; a standard unit helps you avoid the situation in the first place.

For routine basement, crawl space, and room dehumidification, start with standard sizing and efficiency. For large commercial jobs, a high-capacity standard machine may be better than an LGR when the goal is whole-space humidity control. See the commercial dehumidifier guide for that tier.

What to pick for your use

Questions

What does LGR stand for?

LGR stands for low grain refrigerant. It is a two-stage refrigerant dehumidifier that cools the air twice before sending it back into the room, which produces drier outlet air than a standard one-coil machine. It is the type of dehumidifier commonly used for restoration drying after water damage.

Is every commercial dehumidifier an LGR?

No. Commercial dehumidifiers are a broad category that includes standard refrigerant machines, high-capacity portables, and whole-home units. LGR refers specifically to the low-grain refrigerant design that re-cools air for a lower leaving humidity. Restoration crews typically choose LGRs for structural drying, while a standard commercial unit can be the right choice for large spaces that only need humidity control.

Do I need an LGR to prevent mold in a basement?

Usually not. Mold control is moisture control, and the everyday prevention target is keeping indoor humidity at 50 percent or below, according to the CDC. A properly sized standard dehumidifier handles that job. An LGR becomes relevant after water damage, when the goal is to dry wet materials quickly and keep them dry.

How fast do I need to dry a space after a flood?

CDC and EPA both say to dry water-damaged areas and items within 24 to 48 hours to prevent mold growth. If mold has already grown and covers more than about 10 square feet, EPA advises following professional remediation guidance rather than handling it with a small cleanup.

Are LGR dehumidifiers more energy efficient?

Efficiency is measured with the integrated energy factor (IEF), in liters of water removed per kilowatt-hour. A higher IEF means a more efficient machine. ENERGY STAR certified units use about 20 percent less energy than a similarly sized conventional unit, so compare IEF numbers and certifications on any machine, LGR or standard.

Can I use a standard dehumidifier after a small leak?

Yes. Any refrigerant dehumidifier removes moisture, and a standard portable is a reasonable start for a small, damp area. For soaked drywall, wood, or carpet, drying within 24 to 48 hours is critical, and an LGR will send much drier air into the wet materials. If the damage is extensive, professional drying equipment is the safer choice.