Air Sealing vs Insulating: Why Spray Foam Insulation Does Both Better

Air sealing and insulating are often treated as two separate steps in building construction. In practice, they work together to determine how efficiently a building performs. When air control is incomplete, insulation cannot perform at its full potential. 

As a spray foam manufacturer, Accufoam formulates insulation systems designed to function as both an air barrier and a thermal insulator when properly installed. This dual performance is what sets spray foam insulation apart from traditional insulation methods. 

What Is the Difference Between Air Sealing and Insulating? 

Air sealing prevents uncontrolled air movement through the building envelope. This includes air leakage at framing joints, penetrations, rim joists, and transitions between materials. 

Insulating slows heat transfer between conditioned and unconditioned spaces. Insulation performance is typically measured by R-value, which indicates resistance to heat flow, not resistance to air movement. 

Traditional insulation materials provide thermal resistance but do not inherently stop air leakage. Spray foam insulation addresses both functions in a single application and serves as a critical part of a comprehensive air-sealing strategy. 

Air Sealing vs Insulating: A Side-by-Side Comparison 

Function	Air Sealing	Insulating
Primary Purpose	Stops Air Movement	Slows Heat Transfer
Typical Materials	Caulks, Tapes, Membranes	Fiberglass and Cellulose
Controls Drafts	Yes	No
Maintains R-value Under Airflow	No	Limited
Controls Moisture Carried by Air	Yes	No
Performed by Spray Foam	Yes	Yes

This integrated performance is why spray foam is commonly used in high-efficiency building envelopes. 

Why Air Sealing Is Critical to Insulation Performance 

Air leakage allows conditioned air to escape and unconditioned air to enter the structure. This movement reduces insulation effectiveness and increases heating and cooling demand. 

Common issues caused by poor air sealing include: 

• Drafts and temperature inconsistencies 

• Increased energy consumption 

• Reduced HVAC efficiency 

• Moisture migration within wall and roof assemblies 

Without effective air control, insulation alone cannot deliver consistent thermal performance. 

How Spray Foam Insulation Performs Both Functions 

Spray foam insulation is applied as a liquid that expands in place, allowing it to fill cracks, gaps, and voids that are difficult to address with rigid or fibrous materials. 

When properly installed, spray foam insulation: 

• Creates a continuous air barrier 

• Bonds directly to substrates 

• Maintains consistent thermal resistance 

• Reduces reliance on secondary air sealing systems while simplifying installation 

This combination allows spray foam to function as a unified air and thermal control layer. 

Open-Cell vs Closed-Cell Spray Foam Air Sealing Performance 

Both open-cell and closed-cell spray foam provide air sealing benefits, but each is engineered for specific performance requirements. 

Open-Cell Spray Foam 

• Functions as an air barrier at proper thickness 

• Provides sound attenuation 

• Allows for bi-directional drying 

• Commonly used in wall cavities and interior assemblies 

Closed-Cell Spray Foam 

• Delivers higher R-value per inch 

• Acts as an air barrier and vapor retarder 

• Adds structural rigidity to assemblies 

• Performs well in demanding environments and limited-space applications 

Selection between open-cell and closed-cell spray foam should be based on climate zone, assembly design, vapor control requirements, and available cavity depth. 

Accufoam formulations are engineered for predictable expansion, adhesion, and curing to support consistent air sealing and insulation performance across varying jobsite conditions. 

Energy Efficiency and HVAC Performance 

By limiting uncontrolled air movement, spray foam insulation reduces heating and cooling loads on HVAC systems. This improved envelope performance helps: 

• Lower energy consumption 

• Support smaller or more efficient HVAC designs 

• Maintain stable indoor temperatures 

• Improve occupant comfort 

Effective air sealing is a foundational component of energy-efficient building design. 

Moisture Control and Long-Term Durability 

Air movement often carries moisture into wall and roof assemblies. Over time, this can contribute to condensation, mold growth, and material degradation. 

Spray foam insulation reduces moisture-related risks by limiting air infiltration and exfiltration. This added control helps protect building assemblies and supports long-term durability. 

While closed-cell spray foam also provides vapor control, both foam types reduce moisture risk primarily by limiting air movement through assemblies. 

This added control helps protect building assemblies and supports long-term durability. 

Why Manufacturer Formulation Matters 

Spray foam performance depends on chemistry, consistency, and quality control. Variability in formulation can affect expansion, adhesion, yield, and curing behavior. 

Accufoam focuses on: 

• Controlled formulation and production processes 

• Consistent material performance 

• Compatibility with real-world application conditions 

• Technical support to help contractors achieve reliable, repeatable results 

Reliable materials help contractors deliver predictable performance and long-term value to building owners. 

Key Takeaway: Why Spray Foam Does Both Better 

Spray foam insulation provides both insulation and a critical air-sealing layer, improving energy efficiency, moisture management, and overall building performance. 

This integrated approach is why spray foam insulation continues to be a preferred solution for high-performance building envelopes. 

Frequently Asked Questions 

Does insulation stop air leaks? 

Most traditional insulation materials do not stop air movement. Effective air sealing requires dedicated air barriers or a material like spray foam that seals while it insulates. 

Is spray foam insulation considered an air barrier? 

Yes. When installed at the appropriate thickness, both open-cell and closed-cell spray foam function as air barriers. 

Why is air sealing important for energy efficiency? 

Uncontrolled air leakage increases heating and cooling demand and reduces insulation effectiveness, making air sealing essential to overall building performance. 

Is spray foam insulation alone enough to fully air seal a building? 

No. Spray foam forms a continuous air barrier in wall cavities, roof assemblies, basements, and crawlspaces, but complete air sealing typically requires targeted use of 1-component foam sealants, caulks, gaskets, and weatherstripping at openings, transitions, and penetrations.