Why Use RIGID Insulation board On basement walls



Basement Wall Insulation Using Rigid Foam Board

FULL Article: https://www.aconcordcarpenter.com/basement-wall-insulation.html

Sealing Rim Joists: https://www.aconcordcarpenter.com/sealing-and-insulating-rim-joists.html

Best practice for basement wall insulation [best insulating and vapor barrier system] is closed-cell foam, the second-best is using foam board, especially if you’re trying to save money. Using a rigid foam board creates a good vapor barrier along with an insulation layer that won’t promote mold growth. Rigid insulation board is also called Extruded Polystyrene (XPS) insulation.

Basement Insulation Vapor Barrier

The simplest way to prevent this water vapor from entering the space is to prevent air movement [moisture] into the basement by installing a vapor barrier. When properly installed, closed-cell foam (spray or rigid foam board) acts as a vapor barrier and insulates. [poly plastic and Kraft faced insulation is not a good solution for basement vapor barriers. ] The main goal for using rigid foam board against masonry walls is to prevent air vapor movement and mold growth, while it can be the only insulation used in a basement insulation system, it’s often supplemented by fiberglass insulation.

The BEST Rigid Board To Use

There are two types of rigid board commonly used.
Extruded Polystyrene (XPS) insulation board
Polyisocyanurate (Polyiso) insulation boar

Extruded Polystyrene (XPS) insulation foam boards deliver long-term stable thermal performance of R-5 per inch. Compared to spray foam, it’s harder to install in awkward areas (for example, in a tight space where a rim joist is close to another parallel joist). Rigid foam is also fussy to install if the rim joists has a lots of wiring and pipe penetrations. But its cheaper and a popular choice if you’re doing a DIY project.

Polyisocyanurate (Polyiso) is a closed-cell, rigid insulation foam board that is bonded to facers on both sides Polyiso is most commonly used due to its fire-retardant properties. Under normal fire conditions, XPS, melts and drips while polyiso, chars over.

The foil facing also helps with the limiting of any moisture travel. Polyiso is commonly used in roof, wall, ceiling and specialty applications within commercial and residential buildings of all types.

Relocate Any Wall Obstructions

Prior to installing polystyrene insulation boards on your masonry wall you need to make sure the wall is clear of pipes, electrical wires and other obstructions. If you do run into obstructions you can start and stop your rigid foam on either side of it and fill that area with spray foam.

Use Insulation Foam Boards [XPS or Polyiso]

Install 2″ insulation foam boards in a vertical orientation, tight to the floor and top of wall or joist bay. See How To Insulate A Rim Joist.

We ensure that the boards fit together using the factory joints, and then return later to tape all seams.

Prior to installing the next insulation board, we add a thick bead of adhesive in the edge groove.

We use DAP DynaGrip construction adhesive for Styrofoam products, and to adhere the boards to masonry walls. DynaGrip is a premium high strength adhesive for heavy interior/exterior construction and remodeling projects.

This multi-material adhesive delivers a powerful instant grab to hold the vertical insulation boards and creates a durable long-lasting adhesion. We apply a zig-zag pattern of 1/2″ bead directly to the wall and press the insulation board in place.

Seal Vertical Joints With Foil Tape

Tape all vertical seams using a foil tape compatible with the foam board. This type of tape has a durable backing, coated with an aggressive acrylic adhesive that offers excellent adhesion, and sealing properties.

Seal Top and Bottom Joints With Foam

Once all of the insulation foam boards are installed to the walls, and the vertical edges have been taped we then seal the top and bottom edge. Using a Pro Series spray gun applicator we completely fill all gaps, remaining penetrations, and any air leaks using DAP Touch ‘n Foam Polyurethane Foam Sealant.

This All-Purpose sealant is a 1-component polyurethane foam sealant that dispenses approved fire-block (ICC-ES ESR-1926) foam.

Seal the Rim Joist and Sill Plate Area

The rim joist is located above grade and for many years we treated it similar to the wall insulation above, by stuffing fiberglass batt insulation in the rim joist bays. This method is no longer recognized as best practice. Best practice for rim joist and sill plate is to seal all cracks against air leakage and then insulate the area.

Frame Basement Walls

Install basement walls up tight to the 2″polystyrene insulation boards. Fiberglass insulation can then be applied to the studs walls, to increase the basement insulating R-value.

20 thoughts on “Why Use RIGID Insulation board On basement walls

  1. Is polyiso the same as EPS? I’ve seen other videos where people recommend EPS instead of XPS as XPS loses its r value over time. And the EPS is more cost effective

  2. Thank you for a great video, love the clarity and exact info and getting to the point – kept me interested; I would say I am a fan. Good job 👍🏽

  3. Great video… before even stumbling upon this I'm using the exact same method to insulate the basement by myself in my new home I'm building. I first tried using powder actuated nail fasteners to fasten the board to the masonry, but the nails kept bending or shooting through the board and ruined it. So I abandoned that and now am using construction adhesive. It's slower but it works like a champ. I will spray foam all the seems when I'm done. Fellow Wolverine here… Nice video and Go Blue!

  4. Thank you for this video. I'm looking to help my brother-in-law with his basement on his 100+ year old house. He's located near Baltimore. He said there is a Lowe's nearby. Looking on their website, there are not many options. Do you have suggestions of places to look that would have the Polyiso board with the foil facing?

  5. I bought an old southern home with a crawl space. It’s poorly insulated and very cold in winter. Can you do a video on the best insulation for a crawl space in a warm damp climate that also experiences some 20 degree temperatures?
    Does this product work in a crawl space? Thank you

  6. Am I missing something. If you spray foam and do foam boards it seems like it would cost thousands of dollars to do a normal basement.

  7. Why don't you talk about spray foam that is made with sugar. . Least chemicals, especially the fire retardant is so toxic that they have fire retardant in beds people want to get rid of the toxics xenoestrogens the estrogens. That's why people normal people people want to live longer. Don't have a microwave. Now we're having problems with electromagnetic. Sterilization a children men and women because of these Wireless Electronics of computers cell phones. People don't want fire retardant chemicals in their homes, and they're going to get cancer whole but you have a beautiful home, but you're going to die of cancer. Talk about the foam using spun sugar.

  8. My basement walls are porous cinder block/drylock. What if my basement walls leak (just a little) in 1 spot. can i still put this on the wall? Thanks

  9. Hey, thanks for the upload.. What if my walls are coated with drylock, can I use the adhesive on the drylock surface without the adhesive causing a tear in the "vapor/moisture seal" that the drylock is providing? Also, would that adhesive adhere to the drylock?

  10. If you live in an area with high ground water your cinder block needs to breath or it will disintegrate. Best bet is a vapor barrier sprayed outside and open cell inside.

  11. Rob…Rob..Rob…great video. Now can we talk about you're incredibly organized woodworking shop? Holy crap!!!

  12. Ron, never cut polyiso without a dust mask! The particles are like fine spiked crystals and attack eye membranes,lungs,and gut!

  13. Could not have said it better. As a plumber I’m on new construction daily. Large and small, com. and res. What kills me is the “good enough” attitude about what we do. Even a guy I work with who cares about his quality of work, had this just get it done attitude about his own house. It’s rampant in the industry.

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