The first step to insulating your attic or anywhere is choosing the right insulation material for the job.
EnergyStar recommends that most Northeastern Pennsylvania residents insulate their attics with dense materials to achieve a thermal barrier rating of R60.
Generally, we recommend spray foam insulation for most attics and basements, especially if the space is removing any old insulation or has none to begin with.
Spray foam insulation provides the highest thermal resistance of any insulation material and provides air sealing qualities that can plug gaps in your exterior.
Homeowners have two options when it comes to spray foam, based on their budget and insulation needs: closed-cell foam and open-cell foam.
The former is denser and recommended for areas without existing insulation, while the latter is lighter and works well around existing insulation.
This guide will discuss the pros and cons of closed-cell spray foam vs. open-cell foam insulation so that you are properly informed to make the best decision for your home.
How Does Spray Foam Insulation Work?
Spray foam insulation is created by mixing liquid chemicals that react and expand into a foam when sprayed onto surfaces. The foam fills gaps, cracks, and cavities, forming an air-tight and energy-efficient barrier.
Compared to fiberglass batts or cellulose, spray foam provides superior performance because it creates both insulation and an air seal in one step.
Closed-cell and open-cell spray foam names refer to the internal structure of the foam bubbles, or “cells.” Open-cell has partially open structures that make it lighter and more flexible, while closed-cell has tightly packed, sealed bubbles that make it denser and more rigid.
Open Cell Spray Foam
Open cell spray foam has a sponge-like texture, making it softer, lighter, and less dense than closed cell.
Because the cells aren’t fully encapsulated, air fills the open spaces inside the foam.
- Density: About 0.5 pounds per cubic foot
- R-Value: Around 3.5–4 per inch
- Cost: Typically $0.50–$0.75 per board foot
Open-Cell Foam Benefits
- Cost-Effective: Open cell is generally cheaper than closed cell, making it attractive for budget-conscious projects.
- Sound Dampening: Its porous structure absorbs sound, helping reduce noise between rooms or from outside.
- Flexibility: The foam expands significantly when applied, filling hard-to-reach cracks and voids.
- Moisture Permeability: Open cell can allow water vapor to pass through, which helps walls “breathe” and reduces trapped moisture.
Open-cell spray foam is best used in the following applications:
- Interior walls for noise reduction
- Attics and roof decks (above-grade applications)
- Between floor joists
- Interior spaces where vapor permeability is beneficial
Closed-Cell Spray Foam
Closed-cell spray foam is much denser and more rigid. The cells are completely sealed and packed tightly together, creating a hard surface when cured.
- Density: About 2 pounds per cubic foot
- R-Value: Around 6–7 per inch
- Cost: Typically $1.00–$1.50 per board foot
Benefits
- High R-Value: Closed cell provides nearly double the insulating power per inch compared to open cell.
- Moisture Barrier: Acts as a vapor and water barrier, preventing moisture infiltration and helping protect against mold.
- Structural Strength: Its rigid nature adds extra support to walls, ceilings, and roofs.
- Durability: Extremely long-lasting, even in tough environments.
Closed cell is recommended for the following applications:
- Roof deck and attic floors
- Basements and crawl spaces (below-grade applications)
- Exterior walls exposed to the elements
- Metal buildings and pole barns
- Areas prone to flooding or moisture intrusion
- Thin assemblies where high R-value per inch is needed
Open Cell vs. Closed Cell: Head-to-Head Comparison
Feature | Open Cell Spray Foam | Closed Cell Spray Foam |
Density | ~0.5 lb/ft³ | ~2 lb/ft³ |
R-Value per Inch | 3.5–4 | 6–7 |
Cost | $0.50–$0.75/board foot | $1.00–$1.50/board foot |
Moisture Resistance | Vapor-permeable | Moisture barrier |
Sound Absorption | Excellent | Moderate |
Flexibility | Expands more, fills gaps | Rigid, structural strength |
Best For | Interior walls, attics | Basements, exterior walls, high-moisture areas |
Closed Cell vs. Open Cell Spray Foam: Which Is Right for Me
While closed-cell spray foam is generally considered a superior, standalone product, there are several instances where it may make sense to choose the lighter, budget-friendly option.
Generally, most contractors follow similar guidelines to EnergyStar and may recommend one or the other depending on what part of the home is being insulated and if existing insulation exists. For example, interior walls or basement walls with hanging fiberglass batts might only require open-cell spray foam for another layer of thermal resistance.
On the other hand, uninsulated attic decks, floors, or walls could benefit from the strength that closed-cell spray foam provides.
When deciding between open and closed cell spray foam, keep these key factors in mind:
- Climate and Moisture: For wetter climates prone to moisture intrusion, closed cell is the safer choice.
- Budget: Open cell is less expensive, but you may need thicker applications to achieve the same R-value as closed cell. Consider both upfront and long-term energy savings.
- Application Location: Basements, crawl spaces, and exterior walls benefit most from closed-cell. Open cell works well for attics, interior walls, and soundproofing needs.
- Energy Efficiency Goals: If your goal is maximum R-value in a tight space, closed-cell provides more insulation per inch. However, if you want to reinforce rigid boards or air seal around existing insulation, open-cell is preferable.
- Structural Benefits: Closed cells’ rigidity can add strength to walls and roofs, which may be important in storm-prone areas.
Common Misconceptions About Spray Foam
Spray foam insulation is becoming increasingly popular among homeowners, but several myths still persist that give homeowners pause.
One of the most common is the belief that open-cell spray foam isn’t effective because it has a lower R-value than closed-cell. In reality, open cell provides excellent air sealing and sound control, making it highly effective when used in the right locations.
Some homeowners also worry that spray foam is too dense and can lead to ventilation issues. However, spray foam contributes to a healthier, more efficient home with proper installation and ventilation.
Spray foam insulation is one of the smartest investments you can make in your home, especially when it comes to combating rising energy prices across Northeast Pennsylvania.
By understanding the differences between closed-cell and open-cell spray foam, weighing your budget, and considering your home’s unique needs, you can make an informed decision that boosts comfort, energy savings, and long-term protection.
FAQs
Can I mix open and closed cell spray foam in the same house?
Absolutely. Many homeowners use open-cell in interior walls and attics for affordability and soundproofing, while applying closed-cell in moisture-prone or exterior areas for durability.
How long does spray foam insulation last?
When properly installed, both open and closed cell spray foam can last for decades, often the lifetime of the home, without the need for replacement.
Does spray foam insulation increase home value?
Yes. Energy efficiency, durability, and lower utility costs can make a home more appealing to buyers, often boosting its resale value.
Is spray foam safe for my family?
Once cured, spray foam insulation is safe and inert. The installation process should always be handled by professionals who follow safety protocols to protect both occupants and workers.
