Can I Use Rigid Foam Insulation in My Attic?

Rigid foam insulation is an effective solution to insulate your attic, as it prevents heat transfer between the attic and living spaces and boosts energy efficiency in your home.

There are various kinds of rigid foam insulation on the market, and each has its benefits and drawbacks. Finding the right type for you depends on factors like budget, space requirements, DIY-ability, or hiring professional insulation installers, as well as climate.

Extruded Polystyrene (XPS)

XPS foam board insulation is an ideal choice for new construction, offering rigid yet moldable insulation that can easily fit wall cavities, angles, projections, or tight corners. In addition, its energy efficiency has been demonstrated through studies by Franklin Associates, who concluded that using XPS  in any home or commercial building saves more energy over its lifespan than was consumed manufacturing it!

XPS rigid foam is typically blue or pink in hue with a smooth plastic surface and provides an R-value of R-5 per inch, unlike expanded polystyrene (EPS).

Furthermore, unlike its counterpart, it won’t absorb water like its counterpart does and thus helps avoid mold or rot problems that might otherwise arise from humidity issues.

Simple to install and relatively lightweight, this wall system can be cut with any utility knife on a flat, sturdy surface like a sawhorse without special cutting tools or equipment. Furthermore, its resistance to fire makes it highly reliable; no melting, scorching, or toxic fume emission after prolonged exposure to high temperatures.

Polyisocyanurate (PIC)

Polyiso, more commonly known by its acronym PIR insulation, is currently in high demand due to a nationwide shortage of many building materials. PIR is an open-cell rigid foam insulation material consisting of an inner core of organic and inorganic materials held together by isocyanate or polyol bonds.

EPP foam is similar to XPS in appearance but differs due to being thermoset foam that doesn’t melt when exposed to flame or heat, is more moisture-resistant, and can be used in many wall and roof assembly designs. Furthermore, EPP features foil faces on each side, which makes it more effective at blocking moisture than standard six mil polyethylene foams.

Foam insulation comes in an extensive variety of R-values and service temperatures and offers many advantages over fiberglass batt insulation, such as not losing insulating value when wet and being resistant to mold, vermin, and fungus growth.

Furthermore, its design allows it to shed water rather than absorb it, making it less inviting as an inviting home for mice or insects.

Polyurethane (PU)

Polyurethane (PU) is an impressive polymer with characteristics combining plastic and rubber properties, making it a highly flexible yet resilient material for many different uses.

Stretchable yet mouldable into rigid insulation boards, polyurethane has numerous applications as an insulation board material, as well as being resistant to water, oils, and petroleum products – making PU an advantageous and versatile material with many potential uses. PU also boasts excellent resistance against wear and tear and durability against moisture penetration and weather exposure.

Rigid foam insulation is used in both new homes and existing buildings as it offers significant cost-cutting opportunities while simultaneously decreasing energy use, condensation risk, and mold growth. Rigid foam is an eco-friendly product and helps lower energy bills significantly while protecting against condensation and mold growth in the home.

Combining Rigid Foam Insulation and Fiberglass Batts

Fiberglass batt insulation is an economical and popular insulation commonly found in walls, floors, ceilings, and rim joists. Available either as blanket form or pre-cut rectangles that fit standard framing dimensions, fiberglass batt insulation can be purchased from most home improvement stores and installed professionally by experienced installers. Due to the potential release of particles that could potentially enter the air when disturbed, installers should wear gloves, long-sleeved shirts, pants, and goggles during installation for their own safety and optimum performance.

Combining rigid foam insulation with traditional fiberglass batts is possible when installed correctly; the key is not compressing the fiberglass insulation too tightly, as that could reduce its R-value and allow moisture into walls.

A 4-mil plastic sheeting vapor barrier must also be present to prevent condensation and mold growth in walls. Sheep’s wool can also be added for an excellent moisture-resistant natural insulation option with excellent R-value properties that is treated with borate to make it fire-resistant and prevent pests from entering walls.


Installation is usually straightforward with rigid foam insulation. Its flexible form enables users to cut it to fit around wires, junction boxes, and bracing using either a fine saw or utility knife, but there can be one key drawback of using rigid foam insulation: its presence may cause skin and eye irritation upon contact with them; moreover, it is highly flammable so a fire barrier such as gypsum board should also be employed as protection from its flames.

Utilizing rigid foam insulation in your attic can be a cost-effective and energy-efficient solution to improve the comfort and efficiency of your home. As we’ve explored throughout this article, rigid foam insulation offers numerous benefits, including its high R-value, moisture resistance, and ease of installation.

By taking the time to assess your specific needs, choose the right type of rigid foam insulation, and ensure proper installation, you can significantly reduce heat loss and make your living space more comfortable year-round. While the upfront costs might be higher than traditional insulation materials, the long-term energy savings and improved indoor comfort make it a worthy investment.

All in all, whether you’re looking to lower your energy bills, reduce your carbon footprint, or enhance the overall quality of your home, rigid foam insulation is a versatile option worth considering for your attic insulation project.

FAQs About Rigid Foam Insulation

Q1: What is rigid foam insulation, and how does it differ from other insulation materials?

A1: Rigid foam insulation is known for its high-insulating properties and rigid structure. It differs from other insulation materials, such as fiberglass or cellulose, in that it is not flexible and maintains its shape.

Q2: What are the different types of rigid foam insulation available?

A2: There are several types of rigid foam insulation, including expanded polystyrene (EPS), extruded polystyrene (XPS), and polyisocyanurate (polyiso). Each type has its unique properties and applications.

Q3: How do I choose the right type of rigid foam insulation for my project?

A3: The choice of rigid foam insulation depends on factors like the desired R-value, moisture resistance, and the specific application. EPS is cost-effective and has good moisture resistance, while XPS is known for its high R-value. Polyiso is suitable for projects requiring high thermal performance.

Q4: What are the advantages and disadvantages of using rigid foam insulation in my home?

A4: Rigid foam insulation offers high thermal resistance, excellent moisture resistance, and durability. It can improve energy efficiency, reduce heat loss, and enhance the overall comfort of your home. On the other hand, certain types of rigid foam insulation are flammable and can release toxic fumes when exposed to fire. Special fire-resistant coatings or barriers may be necessary in applications where fire safety is a concern.

Q5: Can rigid foam insulation be used in the attic?

A5: Yes, rigid foam insulation can be used in the attic. It’s a compelling choice for insulating the attic space and can help control heat gain and loss, making your home more energy-efficient.

Q6: Is rigid foam insulation environmentally friendly?

A6: Rigid foam insulation can be environmentally friendly, depending on the type and manufacturing process. Some types may contain recycled materials, while others are manufactured with blowing agents with lower global warming potential.

Q7: What is the typical installation process for rigid foam insulation?

A7: Rigid foam insulation is usually installed by cutting it to fit the desired space, securing it with adhesive or mechanical fasteners, and sealing gaps with appropriate materials. It’s essential to follow manufacturer guidelines for proper installation.

Q8: Can I install rigid foam insulation, or should I hire a professional?

A8: DIY installation is possible for those with the necessary skills and tools. However, for more complex projects or when unsure about installation, it’s advisable to consult or hire a professional insulation contractor.

Q9: How does the cost of rigid foam insulation compare to other insulation materials?

A9: Rigid foam insulation can be more expensive upfront than other materials. Still, it often offers long-term savings due to its energy efficiency and durability, making it a wise investment in many cases.

Q10: Are there any safety precautions I should know when using rigid foam insulation?

A10: Safety precautions include wearing appropriate protective gear during installation, ensuring proper ventilation, and following safety guidelines for the specific type of rigid foam insulation.

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