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What Is The Best Insulation For The Exterior Walls?

What is the Best Insulation for the Exterior Walls?

foam board insulation

Insulating a home is like putting armor on it, protecting it from the elements. But with the growing call for energy-efficient living, homeowners are faced with the complex decision of determining the insulation of choice for exterior walls. In addition to immediate comfort, this choice can affect long-term energy savings, environmental footprint, and overall home valuation. While the options are varied, fiberglass and foam board insulation remain the most popular. But are they really the best exterior wall insulation materials?

What Type Of Insulation For Exterior Walls?

What Kind Of Insulation For Exterior Walls

When opting for the appropriate insulation material for your exterior walls, it is crucial to deliberate not only on the category but also the distinct characteristics that render it apt for your requirements. The efficacy of wall insulation is gauged by its R-value, denoting the material’s thermal impediment. The following exterior wall insulation options are a systematic examination of popular insulation alternatives, with sophisticated specifications to guide your choice:

fiberglass insulation
Fiberglass Insulation

Batt Insulation: Typically has an R-value ranging from R-11 to R-15 for 3.5 inches of thickness, making it suitable for standard wall cavities.

Loose Fill: Offers an R-value of about R-2.2 to R-2.7 per inch. It requires a professional blow-in process, which ensures a complete fill.

Spray Foam Insulation
Spray Foam Insulation
  • Open Cell: Has a lower density with an R-value of approximately R-3.5 per inch. It’s air-permeable and can accommodate a degree of moisture.
  • Closed Cell: Denser and more moisture-resistant, with a higher R-value of around R-6 to R-7 per inch, expanding to create an airtight seal.
Foam Board Insulation
  • Materials such as polystyrene (R-5 per inch), polyisocyanurate (R-5.6 to R-8 per inch), and polyurethane (R-5.5 to R-6.5 per inch).
  • Rigid Panels: Can be applied externally or internally to the wall cavities, often used in conjunction with other insulation to prevent thermal bridging.

Cellulose Insulation

  • Loose Fill: Provides an R-value of about R-3.2 to R-3.8 per inch. It’s treated for fire resistance and is often composed of up to 85% recycled content.

Wool Insulations

  • Natural sheep’s wool typically has an R-value of R-3.5 to R-3.8 per inch, while rock wool has an R-value of around R-3.0 to R-3.3 per inch.
  • Wool is moisture-tolerant and can absorb up to 35% of its weight in moisture without compromising its insulative properties.

Every one of these substances has the potential to notably diminish your energy expenses by upholding the preferred temperature inside your residence, resulting in decreased dependence on heating and cooling mechanisms. A proficiently insulated household has the capacity to curtail heating and cooling expenditures by as much as 15%, as per the U.S. Environmental Protection Agency.

What's The Best Insulation For Walls ?

In the realm of home insulation, the optimal insulation for walls stands as a pivotal decision that impacts not solely comfort but also enduring energy conservation and efficacy. Whether your quest is for the supreme insulation for external walls or the most efficient selections for internal dividers, grasping the diverse materials and techniques is paramount. In this context, we shall juxtapose a few leading candidates vying for the accolade of premier exterior wall insulation, scrutinizing their efficacy across an array of scenarios.

Choosing the best exterior wall insulation is not a one-size-fits-all answer. Homeowners need to consider their unique situation: local climate, home design, budget, and long-term goals. It’s also important to work with an experienced installer who can recommend the best product for specific needs.

Closed Cell Spray Foam Insulation
Closed Cell Spray Foam Insulation
  • Best Insulation for Walls: Closed cell spray foam insulation is renowned for its high R-value, which can reach up to R-7 per inch. It’s an ideal solution for creating an impermeable air seal, crucial in preventing energy leaks, making it one of the best insulation for outside walls.
  • Best Exterior Wall Insulation: Its moisture-resistant properties and strength also contribute to its status as one of the best exterior insulation options, able to withstand the environmental stresses that exterior walls face.
Fiberglass Insulation
Fiberglass Insulation
  • Best Insulation for Walls: Fiberglass, particularly in batt form, is one of the most commonly used insulations due to its cost-effectiveness and ease of installation. With an R-value ranging from R-11 to R-15 for standard wall cavities, it’s a solid choice for interior and exterior wall insulation.
  • Best Exterior Wall Insulation: When installed correctly, fiberglass batts can fill wall cavities completely, leaving no gaps, which makes it a contender for the best insulation for walls, balancing cost and performance.
Rigid Foam Insulation

When examining options for rigid foam insulation, two products that stand out for their unique properties and applications are phenolic foam boards and MGO (magnesium oxide) boards.

Gray Wall Insulation Phenolic Board
Phenolic Foam Boards
  • Best Exterior Wall Insulation: Phenolic boards offer one of the highest R-values among rigid boards, typically between R-4 to R-7 per inch, making them a strong contender for the best exterior wall insulation. They are particularly effective in applications requiring both high thermal resistance and space conservation.
  • Best Insulation for Walls: Due to their fire resistance and low smoke toxicity, phenolic foam boards are often chosen for buildings where safety is paramount, contributing to their status as some of the best insulation for walls in both residential and commercial construction.
mgo board
MGO Boards
  • Best Insulation for Outside Walls: While MGO boards themselves do not insulate, they are frequently used in exterior systems for their excellent fire resistance and as a protective layer over foam insulation. Their ability to withstand severe weather conditions also makes them a viable option for the best insulation for outside walls when used in conjunction with other insulative materials.
  • Best Exterior Insulation: MGO boards complement other insulation types by enhancing durability and adding structural strength. This synergistic combination can often result in what many consider being the best exterior insulation system, offering both thermal efficiency and resilience.

Interpreting Insulation: More Than R-Values

glass fibers

While R-values (the insulation’s ability to resist heat flow) are critical, they are only the tip of the iceberg. Effective insulation also means humidity control, ease of installation, environmental impact and long-term durability.

The R-value serves as a key metric in the realm of thermal resistance, quantifying the ability of a material to impede the flow of heat. It’s a pivotal tool in the building and construction industry, offering a clear benchmark for the efficacy of insulation materials.

At its core, the concept is straightforward: a higher R-value signifies superior insulative performance. However, when assessing R-values, it’s crucial to factor in the specific conditions and locations where the insulation will be implemented, along with the nature of the heating and cooling system incorporated in the structure.

Typically, R-values are ascribed to a one-inch thickness of a given material. To illustrate, a material with an R-value of 5 implies that each inch of that material exhibits five times the heat flow resistance of an inch of air.

It’s important to underscore that R-values operate on a cumulative principle. If, for example, you have two inches of an insulation material with an R-value of 5, the aggregate R-value would tally up to 10.

The R-value plays a critical role in the design and construction of energy-efficient structures. It stands as one of the primary considerations when selecting insulation materials, underscoring its importance in sustainable building practices.

Fiberglass Insulation:

fiberglass insulation on wall

Fiberglass insulation, a key product from Owens Corning, is a thermal insulation material primarily made of glass. It is designed to trap air, slowing down the transfer of heat, and is used in a variety of applications, including automobiles and most prominently in buildings as an insulating material.

The insulation comes in different forms, often as batt insulation, or as loose fill. Both forms are versatile, with fiberglass batts available in pre-cut panels and rolls, and loose fill perfect for blowing machines. The thickness of these batts determines their thermal resistance, or R-value, with wall ranges typically between R11 and R19, and ceiling and attic ranges that can reach up to R30.

The cost of installing fiberglass insulation varies based on the location of the house, the amount of labor required, and other factors. On average, the cost of installing this insulation solution is between $0.88 and $1.64 per square foot, meaning you could expect to pay between $300 and $600, including labor costs, for a 500 square foot house.

The advantages of fiberglass insulation include:

1. Quick and easy installation: Especially when working with professionals, the installation process for fiberglass insulation is relatively quick and easy.

2. Affordability: Fiberglass insulation is one of the most cost-effective home insulation solutions.

3. Flexibility: With pre-cut panels, rolls, and loose fill options available, the installation of fiberglass insulation is incredibly flexible.

4. Energy efficiency: Fiberglass insulation can help reduce heating and cooling costs by 40% to 50%.

5. Fire retardant: Fiberglass, made from recycled glass and sand, is a natural fire retardant, posing virtually no fire hazard.

6. Sound reduction: Fiberglass has natural sound-dampening properties, significantly reducing the amount of noise entering a home. This ability to reduce sound makes fiberglass a popular choice for insulation products.

7. Eco-friendly: Made from recycled materials, fiberglass is an environmentally conscious insulation alternative.

However, despite these advantages, there are some drawbacks to consider:

1. Coverage: Since most fiberglass batts are pre-cut, installation can be challenging. Odd shapes, cracks, and other anomalies can pose challenges to standard-sized fiberglass batts.

2. Air leaks: Compared to other insulation materials like spray foam, fiberglass has a lower density and may not effectively prevent air leaks.

3. Moisture protection: In areas with high humidity, fiberglass offers less moisture protection. Leaks in the roof and dampness in attics and basements can contaminate fiberglass insulation and lead to mold issues.

4. Mold: Since fiberglass can retain moisture, it can create a thriving environment for mold spores.

Fiberglass insulation, is an affordable, environmentally friendly, and flexible insulation solution. However, when considering its use, potential issues such as installation challenges, air leaks, moisture, and mold protection should be factored in.

Foam Board Insulation:

Exterior wall insulation board

Foam board insulation has a high R-value and is good at preventing thermal bridging, making it an excellent choice for exterior walls.

There’s a wide variety of foam insulation boards available on the market, with the most prevalent options being Phenolic Insulation Board (PF Board), Expanded Polystyrene (EPS Board), Extruded Polystyrene (XPS Board), and Polyisocyanurate (Polyiso Board).

Among these, the Phenolic Insulation Board stands out due to its superior R-value, a measure of thermal resistance. With an impressive R-value ranging from R-6 to R-8 per inch, the PF Board outperforms its EPS and XPS counterparts and is on par with, if not superior to, the Polyiso Board.

But the advantages of Phenolic Insulation Board don’t stop at thermal efficiency. It’s also renowned for its remarkable fire resistance, outshining the other three types of panels. Furthermore, when it comes to moisture resistance and dimensional stability, the PF Board holds the upper hand, making it a reliable choice in a variety of climates and conditions.

Most importantly, Phenolic Insulation Boards are champions of environmental sustainability. They boast a low Global Warming Potential (GWP) and an Ozone Depletion Potential (ODP) of zero, making them a truly eco-friendly insulation choice.

While the Phenolic Insulation Board may come with a higher price tag, its superior performance and environmental credentials make it a compelling choice for those seeking the best in insulation technology.

Pros: Excellent moisture resistance, ideal for wet climates. It is stiff and prevents sagging or settling. Certain types can also act as vapor barriers.

Cons: Some types may be flammable and may release toxic fumes when burned. Over time, it degrades if exposed to sunlight.

Beyond the Mainstream:

Spray Foam Insulation: This insulation is applied in liquid form and expands on contact, filling gaps. Although expensive, it provides an excellent R-value and forms its own moisture barrier.

Cellulose Insulation: Made from recycled paper with fire protection treatment. Its dense composition gives it excellent noise reduction, but over time it settles.

Mineral Wool: This is a fire-resistant insulation that also offers good sound insulation.

Environmental and Financial Impact:

Both fiberglass and foam board insulation have their environmental footprints. Producing foam boards with ecologically conscious practices can reduce greenhouse gas emissions. However, both materials offer long-term energy savings that can offset their initial environmental costs.

Stay with Us: Pioneering Superior Insulation Performance

At the forefront of insulation technology, our products blend tradition and innovation. With unparalleled expertise, we promise not only quality products, but also instruction tailored to each homeowner’s unique situation.

Ready to embark on the journey to a warmer, more energy-efficient home? Work with our team for a total insulation consultation based on your unique requirements.

Exterior wall insulation board production line

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