How humid is humid? When are mold or dust mites or or other pests likely? This tool will help you understand, be sure to expand to see what's going on in your basement or crawlspace too!

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Home Humidity Explorer

by Nate the House Whisperer

°F °C

Dew point is the number you can compare between spaces. Relative humidity just tells you how full the air is — like a bucket that grows bigger when it's warmer. Same moisture, colder room = smaller bucket = higher RH = mold risk. Use the sliders to see it happen. Click Compare at the bottom to see the risk in your basement/crawlspace.

□ Living Area

Upstairs · Main Floor

Solve for: Dew Point % RH

72°F

Temp

55%

%RH

54°F

Dew Pt
Shared

↕ actual moisture %full →

55%

□□

Warmer air holds more moisture — bigger bucket

Risk Assessment

Same
Dew
Point

□ Basement / Crawlspace

Below Grade · Cooler

❄️ Cooler Spaces Are Riskier

62°F

Temp

--

%RH

54°F

Dew Pt
Shared

↕ actual moisture %full →

80%

□□

Cooler air holds less — smaller bucket

Risk Assessment

➕ Compare with Basement / Crawlspace

natethehousewhisperer.com

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Risk category sources:

□ Mold Risk — Methodology adapted from dpcalc.org. RH thresholds calibrated to temperature-dependent mold growth curves.

□ Dust Mites — Below 50% RH, mites desiccate and die (Arlian et al., 2001). Active breeding above 65% RH; peak allergen production above 75% (LBL Indoor Air).

□ Pest Risk — Cockroaches thrive above 60% RH; termite feeding activity peaks at 70–80% RH (Yanase et al., J. Wood Sci.). EPA recommends 30–50% RH to discourage pests (EPA Biological Pollutants).

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