Sun load on garage walls

See how solar gain on south- and west-facing garage walls creates afternoon heat lag, probe drift, and false confidence vs outdoor weather.

Cluttered home workshop with workbench, tools, lumber, and packed shelves
Humidity and temperature swings matter when tools, wood, and paint share the same bay. Photo: danielmee33 / Flickr. CC BY 2.0

Sun load heats opaque walls even when outdoor air temperature is moderate. Dark siding, uninsulated sheathing, and metal doors store heat that bleeds inward for hours after peak outdoor temps. Probes on sun-facing walls often peak later than the weather app suggests.

Seasonal patterns

  • Summer: Interior garage temps can exceed outdoor highs in late afternoon.
  • Winter: Low sun angle may still warm south walls on clear days.
  • Shoulder seasons: Large diurnal swing with delayed interior maximum.

Monitoring implications

Pair wall-adjacent probes with a more sheltered interior zone to separate sun-driven drift from whole-garage trends. Seasonal patterns explains how to read multi-month history without overreacting to a single hot afternoon.

Probe placement tips

Avoid mounting directly on sun-baked drywall facing south or west. A few inches of standoff inside a ventilated box still tracks wall influence without baking the sensor. Multi-zone layout helps assign one probe to the sunny wall and another to a shaded reference.