What is rigid foam insulation good for?

Author: Chauncey Nicolas  |  Last update: Saturday, May 24, 2025

Rigid insulation is the go-to material in commercial roofing systems. It's used to insulate the building from above and create a drainage slope on flat roofs. In fact, to meet current energy codes, many commercial roofs require more than five inches of rigid insulation above the roof deck and below the roof membrane!

What are the disadvantages of rigid foam insulation?

Rigid Insulation Is Rigid!

As a result, air passes though these areas. Air traveling in an out will bring moisture with it. This can lead to a multitude of problems such as mold, mildew and rot.

What is rigid foam insulation used for?

Rigid foam insulation serves as a continuous insulation layer applied to roofs and exterior walls to reduce energy loss through framing members, leading to lower energy costs and increased comfort. It can also be used under basement slabs to lower heat loss.

What is the downside of foam insulation?

Spray foam insulation is a good insulator in terms of keeping a room warm or cool. But its many downsides outweigh the benefits. These include, making it more difficult getting a mortgage, potential health issues, environmental damage, ventilation issues and a lower home valuation.

What are the benefits of rigid insulation?

3 Benefits of Rigid Foam Sheathing
  • More effective insulation. ...
  • Better at controlling moisture When it comes to controlling moisture, rigid foam serves two functions. ...
  • Better at preventing air leaks. ...
  • Must be installed properly to limit air leaks and act as a weather-resistive barrier.

EPS, XPS & Polyiso insulation | everything you need to know

Do I need a vapor barrier with rigid foam insulation?

In general, if the foam rigid insulation is installed correctly and sealed properly, a vapour barrier may not be necessary. However, there are certain situations where a vapour barrier is recommended, such as in areas with high humidity levels or where there is a risk of moisture infiltration.

What are the disadvantages of foam board?

Disadvantages of polystyrene foam insulation board
  • EPS insulation board needs to be hung, and the construction is complicated and the cycle is long;
  • Flammable & toxic. ...
  • Poor material strength. ...
  • Limited strength and load-bearing capacity.
  • Unstable quality.

What is the best insulation for a house?

The best performance available is spray foam insulation. An attic with spray foam will perform better than blown-in can, even with an air-seal. If you choose blown-in insulation for your attic, we recommend air-sealing the attic floor first. An airtight seal maximizes the performance of insulation.

What is the life expectancy of foam insulation?

Closed-cell spray foam is exceptionally durable, lasting up to 80 years or more. Open-cell spray foam has a shorter lifespan of about 20 years. Both types excel in gap-filling, providing excellent insulation by expanding to fill cracks and crevices.

Where not to use expanding foam?

While it is hugely useful, it should not be used to solve all problems. One such example is electrical boxes. Expanding foam shouldn't be used in these locations as it could cause jams that would be expensive to repair. So avoid using it around sockets or light fixtures, or any electrical components in the property.

What is the life expectancy of rigid foam insulation?

Due to its firmness and water resistance, rigid foam insulation will generally last 100 years or more. The correct installation is essential to take advantage of the durability this product offers.

Can you walk on rigid foam insulation?

This means you can walk on rigid insulation without damaging it. Installation Method: Rigid insulation can be installed by fastening, adhering, or loose-laying modular boards to structural sheathing, studs, walls, or decking.

What is an alternative to rigid foam insulation?

For foam insulation board

Where framing is available, or if it's possible to add it, you can always substitute non-rigid insulation materials like: Fiberglass batts; Rock wool batts;. Blown-in fiberglass or cellulose, manufactured from recycled paper and similar products.

Can mold grow on foam board insulation?

Under certain environmental conditions, such as high humidity and the presence of organic pollutants, the surface of polystyrene foam may gradually accumulate moisture and nutrients, thereby providing certain conditions for the attachment of mold.

Do I need house wrap if I use foam board?

House wrap helps prevent moisture damage, but when coupled with foam siding they create an unstoppable force. Moisture Management System for your home: It's estimated that each person uses 80-100 gallons of water per day at home. Instead of that moisture becoming trapped inside the home, foam can help it escape.

Does rigid foam insulation need an air gap?

It's important to note that some insulation materials, such as spray foam, do not require an air gap. However, if you're using traditional insulation materials such as fibreglass or mineral wool, it's important to follow the manufacturer's guidelines for air gap size and placement.

What is the downside to foam insulation?

The discussion around the dangers of spray foam insulation often includes the potential for respiratory problems, particularly during the installation process and while the foam is curing. Furthermore, some spray foams can off-gas volatile organic compounds (VOCs), leading to indoor air quality issues.

Does foam board insulation lose R-value over time?

A popular rigid insulation choice, XPS features an initial R-value of R-5 per inch. That said, the long term R-values of this foam board decline over time. For example, after just 5 years, an XPS board will see its R-value fall by 10%, and even more going forward.

How long do you have to stay out of the house after foam insulation?

After curing, spray foam is a safe and inert product that is safe to live surrounded by. All off-gassing fumes will have dissipated or been ventilated out of the home after curing. So, twelve to twenty-four hours after spray foam insulation is installed, you should be able to return home.

What is the longest lasting home insulation?

Spray foam insulation is one of the most durable, effective, and reliable forms of home insulation. It can last a lifetime or longer. Because it is mold resistant and does not hold moisture, it doesn't move around and typically stays put until physically removed.

What is the best insulation for the exterior walls of a house?

EPS is most commonly used. This is the main insulation - it is normally made of either expanding polystyrene or mineral wool. Technologies such as phenolic resin insulation are also available. All of these materials are used to prevent heat escaping through walls.

What is the best insulation to keep cold out?

Fibreglass insulation is the most effective for frigid climates; it can be applied to walls, lofts, and other areas where heat may escape. Adding insulation can reduce energy costs and maintain a comfortable residence throughout the winter.

When to use rigid foam board insulation?

When should I use foam board insulation? Because of its resistance to moisture, foam board insulation is a great choice whenever and wherever there's a chance it could get wet. Examples: an exterior foundation, inside a basement against the foundation, and on the outside of a house beneath a house wrap.

Is foam board a fire hazard?

Rigid polyurethane and polyisocyanurate foams will, when ignited, burn rapidly and produce intense heat, dense smoke and gases which are irritating, flammable and/or toxic. As with other organic materials the most significant gas is usually carbon monoxide.

What's better insulation or foam board?

Making the Choice: Key Considerations. Climate: For colder or damper environments, foam board offers superior R-value and moisture resistance. Budget: Batt insulation is the go-to for cost-conscious projects.

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