Use 1/2-inch hardware cloth on all openings

Solution

Cover windows, vents, and any small gaps in coops or hutches with 1/2-inch or 1/4-inch hardware cloth (heavy gauge welded wire mesh), securely fastened.

Explanation

Chicken wire is designed to keep chickens in, not predators out. Raccoons can tear through it or reach through the holes. Hardware cloth has smaller, stronger openings that prevent reaching and tearing. Staple or screw it securely to framing.

Notes

Ensure there are absolutely no gaps larger than 1/2 inch.