Open Cell Vs Closed Cell Foam Insulation

View Comments

• I understand that I should use closed cell in my below grade poured concrete basement walls due to moisture, but what about the above grade rim joist and the above grade wall in the walk out part of the basement? Could you use closed cell or do these parts of a wall need to let moisture vapor pass through?

  • Matt - I would always use closed cell foam. IMHO open cell should really never be used.

    • Thanks Todd

      • Did you mean that you would "Only" use closed cell foam, or Only use closed cell foam when dealing with moisture?

        also, is this correct:
        Expanded polystyrene foam (EPS)is open cell foam
        Extruded polystyrene foam (XPS)is open cell foam
        Polyisocyanurate is closed cell foam

        Thanks,
        Brian

        • I try to avoid open cell foam altogether to be honest. If you ever get a leak it acts like a sponge. I've seen far too many situations where open cell foam turned into a nightmare because it holds water.

          EPS - Open Cell
          XPS - Closed Cell
          Polyiso - Closed Cell

• So I can compare better, can you please tell me what the "R" values are of the products below:

  > Closed cell foam
  > Open cell foam
  > Typical standard insulation in a $250K home
  > Typical high end insulation in a $500K home

  I see R values for Open / Closed, but can't compare all of the different insulation types.

  Last question, for each R value increase, how much energy / utilities does that save a home owner on a typical home (say 2,000 square feet).

  Thanks,

  • Michael - The R values will depend on the manufacturer and thickness.

    There is no standard based on the price of a home.

    You would need to create an accurate energy model for the home to come up with those numbers.

• Hello Todd, I was very upset when I read these forums and it was brought up that EPS is open celled, due to the fact that I completed 90% of my basement insulation with this product. I did some research and EPS is supposedly closed cell phone according to everyone else. Which is it?

  And if it is closed cell, do you think I will have future problems? I have a newly built poured concrete basement. The 2" EPS has a foil facing on it and plastic facing on the other side. Thanks very much..This website has helped me with alot of projects...and has very good information. I cant wait to do the attic hatch!! :)
  Thanks,

  Dave

  • David - Are you 100% sure you used EPS? Typically the foil faced foams are either XPS or Polyiso. The confusion comes from the pure definition of EPS which includes closed cell foam balls. The balls of foam are indeed a closed cell foam. However, the structure between balls is NOT. Depending on the brand and manufacturing the porosity of EPS foam can be quite high which makes it in effect an open cell foam.

    Wiki:
    "Expanded polystyrene (EPS) is a rigid and tough, closed-cell foam. It is usually white and made of pre-expanded polystyrene beads."

    EPS-Foam Company:
    "EPS foam by its nature is mostly air, and depending on the density of the foam, there will be more or less air between the fused closed cell beads of EPS. The higher the density, the more beads and consequently the less space for air between the beads.

    There is some confusion between water absorption with EPS foam and fusion of the beads. Because of the porosity of the foam, the water absorption is a product of how much air or space there is between the closed cell beads of EPS. It is therefore possible to have foam that has low water absorption and poor fusion, which makes for a poor quality product for use as a surfboard or paddleboard product."

    Make sense?

    • Thanks for the quick reply. I will check when I get home and will send you a picture.

      All aside , tho I have 90% completed, and have not even started on the rim joists yet...I had a increase of 6 degrees F so far....my nonheated basement stays a firm 60 degrees F even with drastic temperature changes.

      Thanks,

      Dave

      • Gentlemen,

        Expanded Polystyrene (EPS) is a closed cell foam that is still permeable. What does that mean? Well at 1 inch it has a perm of 2.5 perms or if graphite enhanced expanded polystyrene is tested it will measure 3.0 to 3.5 perms. Graphite enhanced expanded polystyrene has similar R-value to extruded foams & is more cost effective. I spent 9 years with Dow & I can attest that 15, 20, & 25 psi expanded polystyrene is a closed cell foam & the fact that it is permeable helps it to maintain 95% of its stated R-value for its lifetime. Extruded polystyrene foam while a good product can't make that same claim. They limit their warranties to typically 30 years or less.

• Hello Todd my question is this i'm building a metal home and want to use spray foam insulstion and i'm getting some confusing info on the difference between open cell and closed cell foam. One company i spoke with says to use open cell on the ceiling and walls, another co. says to use 2" closed cell on the ceiling and 4" open cell on the walls. please help!!!!

  • Mike - Metal buildings can be different that wood constructed ones. However, metal buildings are typically commercial buildings which have far better HVAC systems in place to deal with humidity.

    What type of framing?siding? finishes are you using? Without that information it's difficult at best to pass judgement.

• Hi Todd. I'm reading all of the information everywhere about the closed vs open foam. Everywhere has said use the closed if you can afford it. We have a 40yr old home in Southwest Louisiana. It's hot! 95degree days, 80/90% humidity. I recently had a bid to spray the attic, vents....and decided on the closed cell. BUT, when our A/C fan motor went out and I called our A/C guy, we talked about the two options and he said I wanted open cell NOT closed! I'm so confused. Can you shed any light on the matter?
  Thanks,
  Alicia

  • Alicia,

    I completely disagree and I'm not the only one. Take a look at the following link with an article from JLC. http://www.greenhorizon.com/files/JLC%20-%20Insulating%20Unvented%20Attics%20With%20Spray%20Foam.pdf

    Open cell will absorb moisture and cause all kinds of damage to the framing.

    Good luck.

• We're starting construction on our basement in the next few days. I want to make sure the construction company uses the right type of insulation and doesn't try to "go cheap" or use the wrong thing. So I've learned here that we should use closed cell. What R value is best? Also, can you recommend a few manufacturer's names for quality closed cell insulation with good R value?

  Thanks for your advice.

  • Tee - What detail is being used? Are they using foam board? foam spray? Both DOW and Owens-Corning are standard brands.

• Hi! My husband and I have heard conflicting views on foam insulation as well. we are building a home on a custom built flat bed trailer. It's 6in deep. We were considering closed cell but were worried about the remaining 3in air gap. And which would be better: spray foam boards or having a company spray it? Also, we weren't sure if closed or open would be a better bet. Any and all advice appreciated.

  Thanks.

  • Kurstin - I only recommend closed cell foam. Open cell foam can absorb water and that's a bad thing! Spray foam is always better than sheets, but it comes at a price. Good luck.

• 20 units of a Gatlinburg, TN complex have bathroom copper water lines in contact with the 8" block outside wall. With mid-teens temp for an extended time-the lines will freeze and rupture. I am
  assigned to find an "economical" solution. I proposed using 2"
  closed cell foam board with Hardy cement stucco covering the foam
  and trimmed with wood for esthetics. In your opinion, am I wasting
  time and money with this fix?

  • Gary - The 2" foam should work well. You lost me on the Hardi board...is that a finished exposed surface? Just curious.

• Hello:

  Thank you for your time and advice.

  I have a metal roofed Lainai. It has open cell foam blocks between to metal layers, one being the ceiling and the other the roof. It is supported by light metal I beams 16 inches apart. It is a noisy and hot situation. I spent money to replace all the windows and doors with thermo pane.

  My question has to do with installation of radiant barrier with insulation backing between the layers of the metal roof. The radiant barrier requires at least one inch space between roof and the barrier. Do you think I should remove the styrofoam all together and drape the barrier across the beams. That would give me about three inches space. Or is the open cell styrofoam porous enough to give the the spacing I need. One other thought was to remove the styrofoam, drape the radiant barrier, then replace the styrofoam over the radiant barrier and finally screw the metal panels back in place. The manufacturer, Prodex, says the radiant barrier has an R value of R16. The Prodex radiant barrier is 5mm, 13/64 inch, of polyethylene foam with layers of reflective aluminum foil on each side. Please give me your thoughts.

  Again, thank you for your expertise and time.

  Phil Ragan

  • Phillip - Radiant barriers work by deflecting radiant heat. They are usually installed below the roofing surface, but above the insulation layer (in a typically attic situation). In that application the air space prevents heat from transferring to the insulation layer. So ideally you'd have the roof, the radiant barrier, air space, then insulation, then ceiling material. For your application I'm not sure that's entirely possible. If it were my place, I'd install a continuous layer of closed cell foam over the support beams, then the roofing. Best of luck.

• I'm a contractor in Minn. Is it true that closed cell does not stop sound and have you used a combo system in walls for instance 2" closed cell and say fiberglass or open cell foam to fill the cavity to help with sound?