Sources & evidence
Home Moisture Lab separates physics calculations from general moisture-control guidance. The calculator itself uses published psychrometric relationships; the practical guidance below is anchored to public-health and building-moisture sources rather than product marketing.
Indoor humidity and moisture control
U.S. Environmental Protection Agency — Mold, Moisture and Your Home
EPA recommends keeping indoor relative humidity below 60% and ideally around 30–50% where possible. It also stresses fixing water sources and drying wet materials quickly rather than treating humidity as the only variable.
U.S. EPA — Biological Contaminants and Indoor Air Quality
EPA describes three core principles: control water sources, control indoor humidity and condensation, and use appropriate materials in areas that may get wet.
Dampness and microbial growth
World Health Organization — Indoor Air Quality: Dampness and Mould
WHO's review emphasizes prevention or minimization of persistent dampness and microbial growth in interior surfaces and building structures. Home Moisture Lab therefore does not turn a single RH reading into a health diagnosis.
Calculation method
Dew point is calculated using a Magnus-type approximation. Surface RH is derived by comparing the room vapor pressure with saturation vapor pressure at the selected or measured surface temperature. Estimated surface temperatures use a simplified steady-state U-value approach described on the methodology page.
What the sources do not justify
These references do not make a 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 a browser model.
Source page reviewed for the initial production launch on September 21, 2026.