LGR vs Conventional vs Desiccant Dehumidifiers
Which dehumidifier technology is right for water damage restoration? IICRC S500 specifies LGR as the baseline — here’s when pros switch to desiccant and why consumer units fail.
By Marcus Reed, IICRC WRT · Updated July 2026
Quick answer
Three technologies, and the room decides which one works. A conventional refrigerant dehumidifier is the household machine: effective in warm, humid air, and progressively useless as the space gets cold or already dry. An LGR — low grain refrigerant — pre-cools the air so it keeps pulling water at lower humidity, which is why restoration crews use them to finish a structural dry rather than just make a room comfortable. A desiccant uses a moisture-absorbing wheel instead of a cold coil, works in cold spaces where both refrigerant types stall, and is the choice for crawl spaces, unheated basements and dense materials like hardwood and plaster. If a structure is already wet, the machine matters less than the plan behind it — (888) 840-6512, answered 24/7.
Press 1 for water damage or 2 for mold, then your 5-digit ZIP. The line goes quiet for about half a minute while it connects — that is normal, stay on. Have ready: the address with ZIP, when the water started, what is wet now, and whether you have opened an insurance claim.
Side-by-Side Comparison
| Technology | Suited to | Temp Range | Efficiency | Equipment Cost | IICRC Class | Notes |
|---|---|---|---|---|---|---|
| LGR (Low Grain Refrigerant) | Most residential & commercial restoration | 33–95°F | Highest — extracts 5–8 lbs/kWh | $1,200–$3,000 | Class 1, 2, 3 | Industry standard for IICRC S500 drying. Required for insurance documentation. |
| Conventional Refrigerant | Mild humidity control, crawl spaces | 65–95°F | Moderate — 2–4 lbs/kWh | $300–$900 | Class 1, 2 | Freezes in cold environments. Not suitable for active water damage restoration below 65°F. |
| Desiccant | Cold environments, Class 4 drying, hardwood | 0–120°F | Lower — 1–2 lbs/kWh, but works in any temp | $1,500–$5,000+ | Class 4 (specialty materials) | Preferred when ambient temperature is below 55°F or when drying concrete, masonry, or hardwood floors. |
Why LGR Is the S500 Standard
The IICRC S500 Standard for Professional Water Damage Restoration specifies grain depression — the reduction in moisture content from ambient air to supply air — as the measurement of drying effectiveness. LGR dehumidifiers achieve grain depression values of 50–90 grains/lb, roughly double that of conventional refrigerant units.
This matters because insurance documentation requires psychrometric reports showing daily measurements of temperature, relative humidity, and dew point at multiple monitoring points. A job documented with consumer equipment has no verifiable drying log and may face claim disputes.
When Desiccant Wins
- →Class 4 (specialty drying): Wet hardwood floors, concrete walls, masonry require dew points below 40°F — only achievable with desiccant.
- →Cold environments: Below 55°F, LGR coils ice over and capacity drops to near zero. Desiccant operates down to 0°F.
- →Delayed response: When a homeowner waited 5+ days, structural materials absorb deeply. Desiccant’s lower dew point pulls bound moisture from concrete.
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Frequently Asked Questions
- 1Class 4 drying — intrusion into concrete, masonry, or hardwood requiring extremely low dew point
- 2temperatures below 55°F where refrigerant coils would ice over
- 3very large commercial structures where the heat output of a desiccant unit aids evaporation. They're rarely needed for typical residential flooding.
What type of dehumidifier do water damage restoration pros use?
IICRC-certified restoration contractors use LGR (Low Grain Refrigerant) dehumidifiers as the standard for most residential and commercial jobs.
LGRs extract more moisture per kilowatt-hour than conventional units and operate effectively down to 33°F. Desiccant dehumidifiers are added for Class 4 jobs (wet concrete, masonry, hardwood) or when ambient temperatures drop below 55°F.
Why can't I just use a store-bought dehumidifier for water damage?
Consumer dehumidifiers (like a typical Frigidaire or hOmeLabs unit) are conventional refrigerant units rated for 50–70 pints/day at AHAM standard conditions (80°F, 60% RH). In real water damage conditions — lower temperatures, very high humidity — they perform at 20–30% of rated capacity.
Professional LGR units extract 100–175 pints/day in actual conditions. Using a consumer unit on a flooded basement typically results in mold growth within 72 hours regardless of how long it runs.
When do restoration companies use desiccant dehumidifiers?
Desiccant dehumidifiers are specified under IICRC S500 for three scenarios:
Does my insurance care what type of dehumidifier was used?
YesIn practice. Insurance adjusters reviewing claims expect to see IICRC S500-compliant drying records with equipment logs from LGR units.
Restoration companies submit psychrometric reports showing daily moisture readings, equipment runtime, and grain depression progress. A job dried with consumer equipment will not produce these records, which can complicate or reduce claim payouts.
How many LGR dehumidifiers are needed for a water damage job?
IICRC S500 specifies one LGR dehumidifier per affected room or per AHAM-rated capacity calculation based on cubic footage and materials. For a typical 1,000 sq ft basement, a contractor might deploy 2–4 commercial LGR units plus air movers. The drying plan is documented in a psychrometric report and adjusted daily.
Who do I call right now for water damage?
Call (888) 840-6512. The line is answered 24 hours a day, seven days a week, and connects you with an IICRC-certified water damage restoration company that serves your area. Describe what you can see — where the water is coming from, how long it has been there, and whether it smells — the more specific you are, the faster the right company is on the line.
If the source is a pipe or an appliance, shut the main water valve first. Have four things ready and the call goes quickly: the address, when the water started, what is wet now, and whether you have filed an insurance claim.
Still not sure which of these is your situation? (888) 840-6512 · toll-free · answered 24/7