Best Air Sealing Products 2026: Caulk, Foam & Gap Fillers
The complete guide to air sealing materials. We tested caulks, spray foams, backer rods, and tools to find the best products for every type of gap and crack.
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Quick Reference: Which Product for Which Gap?
Detailed Product Reviews
Great Stuff Gaps & Cracks
What We Like
- Industry standard for air sealing
- Excellent expansion and adhesion
- Paintable after curing
- Available everywhere
What Could Be Better
- Messy to apply
- Single-use (can clogs after opening)
- Over-expands if not careful
Our Verdict: The go-to spray foam for 90% of air sealing jobs. Great for gaps around pipes, wires, and electrical boxes. Buy the "Gaps & Cracks" formula for most applications—"Big Gap Filler" for larger holes.
DAP Alex Plus
What We Like
- Easy cleanup with water
- Paintable
- Flexible (won't crack)
- 35-year durability
- Great adhesion
What Could Be Better
- Not for wet areas (use silicone instead)
- Shrinks slightly as it cures
Our Verdict: Best all-purpose caulk for interior air sealing. The added silicone provides flexibility that pure latex lacks. Perfect for baseboards, door frames, and window trim.
GE Supreme Silicone
What We Like
- 100% waterproof
- 40-year durability
- Mold/mildew resistant
- Extreme flexibility
- Works on any surface
What Could Be Better
- Not paintable
- Harder to work with
- Strong odor during cure
- Requires mineral spirits for cleanup
Our Verdict: Essential for anywhere moisture is present. Use around tubs, sinks, exterior window frames, and any penetrations through exterior walls. Don't substitute latex caulk in wet areas.
Great Stuff Fire Block
What We Like
- Tested to ASTM E-136 fire standards
- Required by code in many areas
- Same ease of use as regular Great Stuff
- Orange color for easy ID
What Could Be Better
- More expensive than regular foam
- Still burns (just slower)
- Same clogging issues
Our Verdict: Required by building codes around electrical penetrations. The orange color makes inspections easy. If you're sealing around any wiring or electrical boxes, use this—not regular foam.
M-D Building Foam Backer Rod
What We Like
- Makes caulk go further
- Creates proper caulk depth
- Easy to install (just push in)
- Reusable if undamaged
What Could Be Better
- Extra step in process
- Need to buy correct diameter
- Not structural
Our Verdict: The secret weapon for professional-looking caulk jobs. Fills deep gaps so caulk only needs to be 1/4" deep. Essential for gaps larger than 1/4"—caulk alone will crack.
Newborn 930-GTD Drip-Free Caulk Gun
What We Like
- Drip-free mechanism (huge deal)
- Smooth trigger action
- 10:1 thrust ratio
- Built-in cutter and poker
- Steel construction
What Could Be Better
- More expensive than basic guns
- Heavier than plastic guns
Our Verdict: Worth every penny over a $3 gun. The drip-free feature alone saves you from constant cleanup. If you're doing any air sealing project, invest in a quality gun.
DIY Air Sealing Shopping List
Here's what we recommend for a typical whole-house air sealing project (1,500-2,500 sq ft home):
Saves $200-400/year on energy bills. Pays for itself in under 6 months.
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