About Home Moisture Lab
Home Moisture Lab is an independent browser-based tool for comparing indoor humidity, dew point and cold-surface moisture conditions. It is built for a common homeowner problem: one RH percentage often does not explain why a window is wet, why a basement looks humid, or why a bedroom changes overnight.
The core idea is to turn a reading into a measurement workflow. The site compares rooms, surfaces and repeated snapshots instead of presenting a single universal “good humidity” number.
What it calculates
Dew point, estimated or measured surface RH, dew-point margin, reverse room-RH limits and cold-weather surface breakpoints. The formulas and preset assumptions are published on the methodology page.
What it does not diagnose
The site cannot see hidden leaks, identify mold, measure material moisture, inspect a thermal bridge or determine a health effect. Persistent wetting, damage or visible growth needs investigation beyond a browser model.
What stays on your device
Calculator readings, saved setups and measurement snapshots are handled in your browser. Saved history uses local storage. The calculator does not require an account. See the privacy notice for the full distinction between calculator data and normal site/advertising traffic.
How advertising is separated
Display advertising helps fund the site, but advertisers do not set formulas, thresholds, scores or recommendations. Home Moisture Lab does not sell a higher moisture score or sponsored calculator result. See the advertising disclosure.
Editorial rules used across the site
- Separate physics from guidance. Psychrometric calculations are documented separately from general humidity and dampness guidance.
- Show assumptions. Estimated surface temperatures are labeled as estimates because a preset cannot know the real edge, frame, wall build-up, airflow or thermal bridge in your home.
- Prefer repeated measurements to dramatic conclusions. A before/after or room-to-room comparison is usually more useful than one isolated reading.
- Link important claims to primary sources. EPA, WHO and other public sources used by the site are listed on the sources page.
- Do not turn a calculator into a health diagnosis. The site can flag moisture conditions worth investigating, not determine whether a material is mold or whether an exposure caused symptoms.
Who the tool is for
It is most useful when you have a hygrometer reading and a specific question: “Why does this window condense first?”, “Is the basement actually carrying more moisture than upstairs?”, “Did the bedroom gain moisture overnight?”, or “Did the bathroom return toward baseline after the shower?” The problem guides now include page-specific quick checks for those workflows.
How updates and corrections work
The calculator and content are versioned with the site code. When formulas, source interpretation or guide workflows change, the production build is audited for JavaScript validity, internal links, canonical URLs, sitemap coverage and live-page availability. Source-backed guidance is reviewed when the underlying public source changes or when a site claim is materially revised.
If you find a calculation issue, broken source or wording that overstates what a result can prove, use the contact page. Methodology and limitations are treated as product features, not fine print.
See the tool before trusting the claim
You can inspect the formulas and assumptions, the source-to-claim map, and then run your own room reading in the calculator.