What is the Best Rim Joist Insulation? (Spray Foam vs Foam Board vs Fiberglass )

Rim Joist Insulation

Eco Spray Insulation - Rim Joist Insulation

What is foam board insulation?

Foam board insulation is a great alternative to the very common fiberglass batt insulation in most of our homes. It has a higher R-value per inch of thickness, is resistant to moisture, and is easy to work with.

There are a few different types of foam board insulation:

  • Expanded polystyrene (EPS). This is the same thing that your disposable cup of coffee is made of and used to protect fragile items in their packaging. It has an R-value of 4 per inch of thickness and is the cheapest type of foam board insulation. EPS is used under roofing, over foundation walls, and under the siding.
  • Polystyrene extruded. This foam board insulation is made of rigid pink or blue panels that can be found at home centers in many different thicknesses. It is thicker than EPS and provides a higher R-Value rating of 5 per inch of thickness. This foam board insulation is available with straight or tongue-and-groove edges to help reduce air movement. It is available in all size configurations to accommodate a number of different applications. One common use of extruded polystyrene foam boards is for base insulation panels.
  • Polyiso (Polyisocyanurate). This is a thicker and more expensive foam board insulation. It provides an R-value of 6 per inch of thickness and is often foil-faced to help reflect radiant heat. Polyiso comes in several thicknesses and is used over house sheathing beneath the siding or in attic spaces where its reflective properties are very effective.

Rim Joist Foam Board Insulation: Pros and Cons

Rim Joist Foam Board Insulation Pros:

  • Some rigid foam products are water resistant. This helps to reduce the build-up of moisture and the growth of mildew.
  • Expanded polystyrene board is the only type that does not use HCFCs in its production, making it a greener choice.
  • Expanded polystyrene board is the cheapest foam board product on the market. The expanded board is made from mold to contain small foam beads.
  • Extruded polystyrene foam is cheap, lightweight, and easy to use. Extruded polystyrene foam is produced when the liquid foam is continuously expelled through the die and expands during the cooling process. This produces a closed cell insulation of rigid foam.

Rim Joist Foam Board Insulation Cons:

  • To prevent air flow, joints between sheets and boards must be taped.
  • The sheets must be customized to fit the joist rim area.
  • Air bubbles inside the expanded polystyrene board stop heat transfer, but may accumulate moisture, making it ineffective.
  • Polyiso may suffer from reduced isolation over time.
  • Foam boards are slightly more expensive than traditional insulation materials.

Rim Joist Fiberglass Insulation: Pros and Cons

Fiberglass is an insulation material made of plastic that is reinforced with extremely fine glass fibers. 

Fiberglass is considered a traditional form of insulation found in the walls, attics, crawling space, and rim joists of older homes.

Rim Joist Fiberglass Insulation Pros:

  • Fiberglass is cheap compared to other rim joist insulation materials.
  • Fiberglass can be a Do-It-Yourself project for an experienced homeowner.

Rim Joist Fiberglass Insulation Cons:

  • Fiberglass, according to Home Construction Improvement, does not do as good a job in isolating the rim joist.
  • Fiberglass insulation in the rim joist is prone to mold problems as it holds condensation against the wood leading to mold and decay formation.
  • Because the fiberglass batts are air permeable, the material does nothing to prevent warm, humid interior air from coming into contact with the rim joist.
  • When fiberglass in the rim joist is disturbed, it can release particles into the air that can be inhaled, causing coughing, nosebleeds, and other respiratory problems. When the material comes into contact with the skin, small particles may lodge in the pores causing rashes, irritation, and itching.
  • If the fiberglass insulation in the rim joist has to be disturbed, it should be the person near the area.
  • Should wear protective gear such as gloves, a long-sleeved shirt, pants, and goggles.

Rim Joist Spray Foam Insulation: Pros and Cons

Spray foam insulation will fill every nook and cranny in the rim joist as it creates an air barrier that will seal the area to stop any outside air from entering.

The main ingredients of spray foam insulation are water-soaked and organic chemical compounds derived from petroleum extracts.

Rim Joist Spray Foam Insulation Pros:

  • Spray foam insulation does not retain water, so any moisture near the rim joist would not promote mold or mildew growth in the area. 
  • Spray foam is not a food source for pests that can be found near the rim joist.
  • Spray foam creates an air seal that prevents outside air from entering and reduces drafts near the floorboard.
  • Spray foam insulation is safe for the environment.
  • The material is Class One Fire Rated, making it safe for your home.

Rim Joist Spray Foam Insulation Cons:

  • A homeowner may not want to install spray foam insulation on his own in the rim joist, but instead, choose to hire an experienced contractor.
  • Some spray foam brands have a slight odor after they have been applied. It is important for homeowners to note which spray foam brand is being installed in their homes. 
  • Spray foam insulation tends to be a more expensive material compared to other traditional forms of insulation used for joist rims.

More Benefits of Rim Joist Insulation

If you’re planning to add more insulation to your home, make sure the band joist is one of the locations you’re addressing. There are several benefits of boosting home insulation (including the rim joist). It helps to:

  • Lower energy bills: proper insulation is one of the most important features of an energy-efficient home. By keeping the air conditioned inside where you want it, you’re going to end up maintaining a comfortable home more easily and at a lower expense.
  • Improve comfort: If you’ve ever sat next to the window, you’ll appreciate how uncomfortable outdoor air infiltration can be. A well-insulated rim joist helps keep the basement at a comfortable, steady-state temperature on par with the rest of the house.
  • Contribute to a healthier environment: whenever you reduce energy consumption, you will certainly save money, but you will also do your part for the environment! If a lower carbon footprint is your goal, insulation is a step in the right direction.

Why should you choose Eco Spray Insulation?

  • Good price/quality ratio and value for your money 
  • Highest R-Value 
  • The best products in the market
  • Provide comfort for your whole house
  • As a professional company, we take a lot more care of each customer
  • Friendly helpful service
  • We try really hard to satisfy our clients 
  • We believe in renewable energy solutions
  • We promote energy efficiency
  • We have the best experts that will give you different options so you can ensure your home.

If you need a free estimate just contact us at (416) 860-6664 or email us at [email protected].

We are here to give you solutions!

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