Guide

Cold spaces: why the right size unit still fails

Capacity ratings are measured warm. A crawl space is not warm. This is the gap that makes a correctly sized unit look broken.

What happens as the air cools

A refrigerant dehumidifier works by cooling air below its dew point so water condenses on the coil. Cold air holds less water to begin with, so there is less to condense, and the coil itself is closer to freezing. Below roughly 65 F output starts dropping. Below about 40 F a unit without defrost will ice over and stop removing anything at all.

Read the operating range, not just the pint number

Two units both rated 70 pints can behave completely differently at 50 F. The spec sheet line to look for is the minimum operating temperature and whether it has automatic defrost. A crawl space unit needs both.

See AlorAir crawl space and basement units

Desiccant units

Desiccant dehumidifiers pull water onto a drying wheel instead of condensing it, so they keep working at temperatures where refrigerant units give up. They use more electricity for the same water in warm conditions, which is why they are the answer for cold spaces and the wrong answer for a warm basement.