Closed-Cell Foam Between Studs Is A Waste

Closed-Cell Foam Between Studs Is A Waste

When it comes to insulating stud walls, closed-cell spray foam is often seen as an attractive option. With its high R-value, it seems like the perfect choice for energy-efficient insulation. However, upon closer inspection, it becomes clear that closed-cell foam between studs may not be the best solution after all.

While closed-cell foam does offer a higher R-value per inch, the overall difference in whole-wall R-value between a wall insulated with closed-cell foam and one insulated with open-cell foam is minimal. This is because closed-cell foam is difficult to trim, resulting in gaps between the foam and the drywall. These gaps reduce the effectiveness of the insulation, making it a waste of closed-cell foam.

Not only is closed-cell foam less effective than it seems, but it is also expensive and has a higher environmental impact compared to other insulation options. For those looking for a cost-effective and energy-efficient solution, there are better alternatives to consider.

Key Takeaways:

  • Closed-cell foam between studs may not provide the expected insulation benefits due to gaps between the foam and the drywall.
  • Compared to open-cell foam, the difference in whole-wall R-value is minimal.
  • Closed-cell foam is expensive and has a higher environmental impact.
  • It is important to consider other cost-effective and energy-efficient insulation strategies.
  • Exterior rigid foam and mineral-wool insulation are alternatives worth exploring.

Understanding Whole-Wall R-Values

When it comes to insulating stud walls, it’s important to consider the concept of whole-wall R-values. This measurement takes into account the different areas of the wall with distinct R-values, providing a more accurate picture of the wall’s overall insulation effectiveness. By understanding whole-wall R-values, we can make informed decisions about the most suitable insulation options for stud walls.

In a typical wood-framed wall, approximately 25% of the wall area is occupied by studs, plates, and headers, resulting in a framing factor of 25%. The remaining 75% consists of insulated stud bays or openings for windows and doors. However, when closed-cell spray foam is used between studs, it can be challenging to trim properly, leaving a gap between the foam and the drywall. This gap reduces the foam’s effectiveness and increases heat loss through thermal bridging, despite its higher R-value per inch. Therefore, the use of closed-cell foam between studs may not provide the expected insulation benefits.

To minimize thermal bridging and achieve optimal insulation, alternative strategies such as exterior rigid foam can be considered. By adding thicker continuous insulation on the exterior side of the wall sheathing, the entire insulation’s R-value contributes to the whole-wall R-value. This approach reduces the thermal bridging effect of the studs and offers a more cost-effective insulation solution. However, it is crucial to calculate the thickness of the exterior insulation correctly to avoid moisture accumulation on the interior face of the sheathing in cold weather. Despite the need for extra detailing around windows and doors, exterior rigid foam provides excellent value for money and improved energy efficiency.

Insulation Type Pros Cons
Closed-Cell Foam Between Studs – High R-value per inch – Difficult to trim properly, leading to gaps
Exterior Rigid Foam – Provides continuous insulation – Extra detailing required for windows and doors

When it comes to insulation depth and whole-wall R-values, considering the framing factor and reducing thermal bridging is crucial. By understanding the impact of insulation choices on whole-wall R-values, we can make informed decisions about the most efficient and cost-effective insulation strategies for stud walls.

The Case for Exterior Rigid Foam

When it comes to insulating stud walls, exterior rigid foam presents a compelling alternative to closed-cell foam between studs. By adding thicker continuous insulation on the exterior side of the wall sheathing, the entire R-value of the insulation contributes to the whole-wall R-value. This effectively minimizes the thermal bridging effect of the studs, resulting in a more energy-efficient and cost-effective insulation solution.

Unlike closed-cell foam, which can be difficult to trim and often leaves gaps between the foam and drywall, exterior rigid foam offers consistent and continuous coverage. This eliminates the potential for reduced insulation effectiveness due to gaps, ensuring optimal energy performance throughout the entire wall. Moreover, the use of exterior rigid foam helps to improve the overall thermal efficiency of the building envelope, significantly reducing energy consumption and enhancing indoor comfort.

When considering exterior rigid foam insulation, it is crucial to calculate the thickness of the insulation correctly to prevent moisture accumulation on the interior face of the sheathing, particularly in colder climates. While some extra detailing may be required around windows and doors to ensure proper sealing, the benefits of exterior rigid foam, such as improved energy efficiency and reduced thermal bridging, make it a worthwhile investment for any building project.

Key Benefits of Exterior Rigid Foam:

  • Enhanced whole-wall R-value: The continuous insulation provided by exterior rigid foam contributes fully to the overall R-value of the wall, reducing heat loss and improving energy efficiency.
  • Minimized thermal bridging: By eliminating gaps and inconsistencies, exterior rigid foam significantly reduces thermal bridging, resulting in more effective insulation and greater comfort.
  • Cost-effective solution: Despite the need for additional detailing, exterior rigid foam offers excellent value for money by providing long-term energy savings and reducing heating and cooling costs.
  • Improved building envelope performance: The use of exterior rigid foam insulation helps to create a tighter and more efficient building envelope, reducing air infiltration and enhancing overall energy performance.
Exterior Rigid Foam Closed-Cell Foam Between Studs
R-Value Consistent and contributes fully to whole-wall R-value May be reduced due to gaps and inconsistencies
Thermal Bridging Minimized Potential for increased heat loss through studs
Installation Requires additional detailing around windows and doors Different trimming challenges and potential for gaps
Cost Cost-effective in the long run due to energy savings Higher upfront cost
Environmental Impact Lower environmental impact compared to closed-cell foam Higher environmental impact

Considerations for Cathedral Ceilings

When it comes to insulating cathedral ceilings, there are a few key considerations to keep in mind. One of the main challenges with cathedral ceilings is the presence of rafter bays, which can contribute to thermal bridging. To address this issue, it is important to focus on complete insulation coverage in the rafter bays.

Unlike skimpy applications of spray foam, fully filling the rafter bays with insulation helps to minimize the impact of thermal bridging. By doing so, we can significantly reduce heat loss and improve the energy performance of the ceiling assembly.

When choosing the right insulation for cathedral ceilings, it is essential to assess the options available. Consider materials that provide effective thermal resistance and can be easily installed to cover the entire rafter bay. This will ensure a continuous layer of insulation, which is crucial for minimizing thermal bridging and achieving optimal energy efficiency.

FAQ

Is closed-cell foam between studs a waste of insulation?

Closed-cell foam is often seen as an attractive option for insulating stud walls due to its high R-value. However, when looking at the whole-wall R-value, there isn’t much of a difference between a wall insulated with open-cell spray foam and one insulated with closed-cell spray foam. This is because closed-cell foam is difficult to trim, resulting in a gap between the foam and the drywall, which reduces its effectiveness. Additionally, closed-cell foam is expensive and has a higher environmental impact compared to open-cell foam. Therefore, there are more cost-effective and energy-efficient insulation strategies to consider, such as exterior rigid foam or mineral-wool insulation.

How do I calculate the whole-wall R-value of a wall?

To calculate the whole-wall R-value of a wall, it is important to consider the different areas of the wall with distinct R-values. A typical wood-framed wall has a framing factor of 25%, meaning that around 25% of the wall area is made up of studs, plates, and headers. The remaining 75% consists of either insulated stud bays or openings for windows and doors. When stud bays are partially filled with closed-cell spray foam, the exposed portions of the studs reduce their R-value, leading to greater heat loss through thermal bridging. This means that even with its higher R-value per inch, the use of closed-cell foam between studs may not provide the expected insulation benefits.

Is there an alternative insulation strategy to closed-cell foam between studs?

Instead of using closed-cell foam between studs, an alternative insulation strategy to consider is the use of exterior rigid foam. By adding thicker continuous insulation on the exterior side of the wall sheathing, all of the insulation’s R-value contributes to the whole-wall R-value. This helps to minimize the thermal bridging effect of the studs and provides a more cost-effective insulation solution. However, it is important to calculate the thickness of the exterior insulation correctly to prevent moisture accumulation on the interior face of the sheathing in cold weather. Despite the need for extra detailing around windows and doors, exterior rigid foam offers excellent value for money and improved energy efficiency.

How should I approach insulating cathedral ceilings?

The same principles apply to cathedral ceiling assemblies when it comes to insulation. Fully filling rafter bays with insulation can help reduce the impact of thermal bridging, especially compared to skimpy applications of spray foam. By focusing on complete insulation coverage, the heat loss through thermal bridging can be minimized, resulting in improved energy performance.

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