Alaska ranked No. 1 in nation for mold risk in homes

Published 10:31 am Tuesday, July 7, 2026

Alaska’s lakes and average annual humidity are fueling a silent mold crisis in homes.

The state ranks number one in the nation for mold risk in homes, according to an independent study conducted by New York-based residential and commercial exterior contracting company Besroi Roofing & Siding.

The company used publicly available environmental and geographic data for the mold risk analysis to help property owners understand regional exposure.

Alaska’s Mold Risk Score was 96.69 out of 100 — 53.1 percent above the national average of 63.13 and 26.47 points ahead of second-place Louisiana. The score is built from the average annual relative humidity (70 percent weight) and lake density per square mile (30 percent weight), and each variable is then normalized against its national maximum, weighted, and summed to produce a composite score.

Alaska is 12th nationally with an average annual humidity of 70.5 percent, but has the highest lake density index in the country and is the only state to reach the maximum density index, with over three million lakes and 5.26 lakes per square mile — 3.6 times the next-densest state.

“In Alaska, water is never far from the door — it gathers across the open tundra, fills the countless basins left behind by ancient glaciers, and drifts inland as a cool, persistent dampness from the surrounding seas,” the study read.

“Inside the state’s homes, that moisture finds every quiet corner, settling beneath roof decks and into walls that rarely have the chance to fully dry.”

Besroi Roofing & Siding added that mold is not a passing inconvenience but a feature of the landscape itself, shaped by a geography that is defined by water at every turn, and that understanding the environment is the first step toward protecting the homes built within it.

Alaska stands apart even among its closest U.S. neighbors, leading the nearest Pacific state, Washington, by 27.42 points and outscoring last-place Arizona by 59.79 points.

“The gap between Alaska and the nation’s driest states is enormous,” Besroi Roofing & Siding stated. “It beats every bottom-ten state by more than 36, almost entirely because of its lakes.”

Top 10 most mold-prone states with Mold Risk Score

1. Alaska: 96.69

2. Louisiana: 70.22

3. Kansas: 69.86

4. Michigan: 69.69

5. Washington: 69.27

6. Florida: 68.93

7. Wisconsin: 68.74

8. Mississippi: 68.60

9. New York: 68.59

10. Oregon: 68.19

Alaska sits far above the top-10 average of 71.88, and no other state comes within 26 points. It is also the only one in the group driven by lakes rather than humidity.