Winter is mold season indoors
Spokane's long winters bring snow, ice and about 72 freeze-thaw cycles in an average year, according to NOAA's engineering weather data. Homes are closed up, indoor air is warm and moist from cooking and showers, and outdoor surfaces are cold. That's a recipe for condensation, and condensation feeds mold on windows, exterior wall corners, closets on outside walls and attic sheathing.
Ice dams
NOAA's data lists a 50-year ground snow load of 42 pounds per square foot for Spokane. Heavy snow combined with heat escaping into the attic creates ice dams at the eaves, which force meltwater under shingles and into walls and ceilings. Wet insulation and sheathing in the attic, and stains near exterior walls, are common results. Fix ice dams at the source with better attic insulation, air sealing and ventilation, and have wet materials dried or removed promptly.
Basements and snowmelt
Many Spokane homes have basements. Snowmelt and spring runoff can push water through foundation cracks, floor-wall joints and window wells. Finished basements hide moisture behind carpet and drywall. If a basement smells musty, check the bottoms of exterior walls and carpet edges, and fix water entry before remediation.
Frozen pipes
Pipes in exterior walls, crawlspaces and garages can freeze and split. After a burst pipe, have wall cavities and subfloors dried and checked with moisture meters, because hidden moisture causes most post-leak mold.
Disposal and the aquifer
Spokane's drinking water comes from the Spokane Valley–Rathdrum Prairie Aquifer, a sole source aquifer. Ask the remediation contractor what cleaning products they'll use and how waste water and debris will be disposed of. Products should be used according to their labels and kept out of storm drains.
Prevention
Use exhaust fans that vent outdoors, keep indoor humidity moderate in winter, insulate cold surfaces where condensation forms, keep gutters and downspouts clear, and grade soil away from the foundation.
Before you hire
Ask Spokane mold contractors what moisture source they've found, how they'll contain the work area, what they'll remove and clean, how they'll confirm the job is complete, and whether they recommend independent clearance testing. Use L&I's contractor lookup to check their Washington registration, bond and insurance.
Crawlspaces
Crawlspaces with exposed soil, poor drainage or blocked vents can grow mold on floor framing, and musty air from below can reach the living space. A vapor barrier over the soil, good drainage and the right ventilation or conditioning for your crawlspace design are the basics. Wet or fallen insulation should be removed and the cause fixed.
After the cleanup
Watch the repaired area through the next winter and snowmelt. Odors or new stains mean moisture is still getting in.
Bathrooms
Run bathroom fans during and for a while after showers, and make sure they vent outdoors rather than into the attic, where the moisture condenses on cold sheathing.