Sources & evidence
Home Moisture Lab separates calculated physics, site-defined comparison bands and external moisture-control guidance. This page shows which is which so a public-health recommendation is not accidentally presented as if it came from the calculator — or vice versa.
Claim-to-source map
| Claim used on this site | Where it comes from | How Home Moisture Lab uses it |
|---|---|---|
| Indoor RH should generally stay below 60%, ideally around 30–50% where possible. | U.S. EPA mold/moisture guidance | General context only. The calculator still checks the actual cold surface because condensation can occur below 60% room RH. |
| Moisture sources and wet materials should be addressed promptly; wet/damp materials are commonly recommended to be dried within about 24–48 hours. | U.S. EPA moisture guidance | Used in leak/dampness caveats, not as a calculator threshold. |
| Bathrooms should exhaust moisture outdoors or use a window when conditions allow during/after showering. | U.S. EPA indoor-air guidance | Used in the bathroom recovery workflow and troubleshooting text. |
| Persistent dampness and microbial growth should be prevented or minimized. | WHO indoor dampness and mould guidance | Supports the site's emphasis on persistent dampness rather than one isolated RH number. |
| Keep humidity low to help limit mold growth; CDC consumer guidance uses a more conservative no-higher-than-50% target. | U.S. CDC mold guidance | Shown as a public-health recommendation, not treated as proof that 51% is unsafe or that 49% prevents all condensation. |
Primary references
U.S. EPA — A Brief Guide to Mold, Moisture and Your Home
Moisture-source control, indoor RH guidance, condensation prevention and prompt drying. Open EPA source →
U.S. EPA — Biological Contaminants and Indoor Air Quality
Water-source control, humidity/condensation control and bathroom ventilation guidance. Open EPA source →
U.S. EPA — Main ways to control moisture in your home
Practical measures covering exhaust, dehumidification, cold surfaces and air circulation. Open EPA source →
World Health Organization — Guidelines for Indoor Air Quality: Dampness and Mould
Evidence review focused on persistent dampness and microbial contamination. Open WHO source →
U.S. CDC — Mold
Consumer-facing prevention guidance, including keeping indoor humidity low. Open CDC source →
What is calculated by this site instead of sourced as a recommendation?
Dew point, absolute humidity, surface RH, reverse room-RH limits and cold-snap breakpoints are calculated from the values you enter and the formulas/presets documented in the methodology. They are not copied from EPA, WHO or CDC.
The 80% surface-RH caution band is a site comparison band
Home Moisture Lab uses 80% calculated surface RH as a caution band for prioritizing surfaces. It is not presented as an EPA/WHO/CDC health threshold, a mold test, or proof that growth is present. Duration, material, local temperature and real moisture exposure are not known to the browser model.
Why public sources can quote different RH targets
Public guidance is written for different purposes and populations. EPA commonly describes below 60% RH and ideally 30–50% where possible; CDC consumer mold guidance uses a more conservative no-higher-than-50% recommendation. Home Moisture Lab does not collapse those statements into a fake universal cutoff. Its main calculation question is different: given this room air, how close is this particular surface to high local RH or dew point?
What the sources do not justify
These references do not make a browser calculator an inspection. The site cannot determine how long a surface has been damp, whether water is entering through a roof or foundation, whether a material contains hidden moisture, or whether visible material is mold. Those questions require observation, measurement or professional assessment beyond this model.
Source map reviewed September 21, 2026. Formula details and preset limitations: Methodology.