Attic Insulation - Fiberglass roll vs spray vs foam

Discussion in 'Insulation and Radiant Barriers' started by soparklion11, Dec 15, 2019.

Help Support House Repair Talk by donating:

  1. Dec 15, 2019 #1

    soparklion11

    soparklion11

    soparklion11

    Well-Known Member

    Joined:
    Apr 28, 2012
    Messages:
    93
    Likes Received:
    6
    I'm insulating a house in Pittsburgh (Rec attic R-49 to 60). The attic is currently devoid of insulation of any type. I want to:
    1. Seal the headers to reduce convective heat loss through the walls, ie chimney effect
    2. Insulate to R49+
    In another house, I sealed headers with caulking and other openings with great stuff.
    1. What about a closed cell spray foam - is the greater expense worthwhile - see below?
    2. Is it worthwhile to spray a sealing foam, then top with rolls of fiberglass?
    3. Are the advantages of blown-in fiberglass worth the dust and mess of install and the mess of any future ceiling work?
    4. Confirm that sealing the headers is worthwhile, whether with caulk/great stuff or insulating foam.
    Foam It Green:
    • Yields approx 602 sq feet at 1″ thick
    • R-value of 7 at 1″ thick Anti-Microbial foam
    • ~$800
     
    fastsvo likes this.
  2. Dec 15, 2019 #2

    nealtw

    nealtw

    nealtw

    Contractor retired

    Joined:
    Nov 4, 2010
    Messages:
    24,700
    Likes Received:
    3,359
    Location:
    Chiliwack BC Canada
    Sealing the attic from the house is step one.
    Confirming the venting is enough at the soffits and at or near the peak.
    1" of spray foam maybe, not sure of the great advantage for the extra $
    Attic access needs to have a good seal and needs to be insulated too.
     
  3. Dec 16, 2019 #3

    Steve123

    Steve123

    Steve123

    Well-Known Member

    Joined:
    Jul 5, 2017
    Messages:
    154
    Likes Received:
    57
    As mentioned, first need to seal all pentrations (wire holes, vent pipes, chimneys, etc.)
    Make sure your attic has proper ventillation, and don't block it with new insulation. Assuming you have sofit vents, you need to put air chutes on them to ensure airflow.
    A closed cell spray foam would be a vapor barrier, and should be very airtight. Not sure I agree that spray foam is a DIY task. If not mixed properly, you can put a toxic layer of chemicals in your attic. Also a fire risk until cured.
    I share your dislike of blown in fiberglass. But its cheap and fast, and a lot of people use it. At my place, I have the original blown in fiberglass, then two layers (at right angles) of rockwool batts.
    Yes, you can put batts over an intial layer of sprayfoam. There is a limit of how thick you can put sprayfoam in one pass anyways.
     
  4. Dec 16, 2019 #4

    Jeff Handy

    Jeff Handy

    Jeff Handy

    Well-Known Member

    Joined:
    Nov 20, 2019
    Messages:
    228
    Likes Received:
    81
    Location:
    Illinois
    Hire it out to pros, it is an itchy and messy job, and easy to screw up.

    Pros will know the codes and tricks, and maintain proper ventilation.

    I hate blown in fiberglass or cellulose, it’s difficult to walk up there again to fix anything.
    And very commonly, it plugs up many of the soffit intake vents, causing winter condensation and mold, and roasting summer attic temps.
    Even pros often cork up the soffit vents!

    Also, it gets pushed around and compressed way too easily, plus it’s hard to find a pathway through it.

    Bats are easier to pull aside and put back.
     
  5. Dec 17, 2019 #5

    nealtw

    nealtw

    nealtw

    Contractor retired

    Joined:
    Nov 4, 2010
    Messages:
    24,700
    Likes Received:
    3,359
    Location:
    Chiliwack BC Canada
    We advise people on how to do jobs that require some skill and specialized tools. Attic insulation is perfect work for a DIYer with a I can do it attitude. There are people here to help with understanding the job at hand. There may be parts of the job for pros but we are not there yet.
     
    soparklion11 and bud16415 like this.
  6. Dec 24, 2019 #6

    soparklion11

    soparklion11

    soparklion11

    Well-Known Member

    Joined:
    Apr 28, 2012
    Messages:
    93
    Likes Received:
    6
    I'm not sure what you mean by easy to screw up... I don't have soffits and therefore I don't have soffit vents. I don't plan to use spray foam...
     
  7. Dec 24, 2019 #7

    nealtw

    nealtw

    nealtw

    Contractor retired

    Joined:
    Nov 4, 2010
    Messages:
    24,700
    Likes Received:
    3,359
    Location:
    Chiliwack BC Canada
    No soffets is usually a problem, do you have a gable roof or a hip roof, do you have high vents near or at the peak?
     
  8. Jan 4, 2020 #8

    soparklion11

    soparklion11

    soparklion11

    Well-Known Member

    Joined:
    Apr 28, 2012
    Messages:
    93
    Likes Received:
    6
    Gable roof without soffits. Considering a vent in one end and a fan in the other for circulation.
     
  9. Jan 4, 2020 #9

    Jeff Handy

    Jeff Handy

    Jeff Handy

    Well-Known Member

    Joined:
    Nov 20, 2019
    Messages:
    228
    Likes Received:
    81
    Location:
    Illinois
    Without soffits, you will likely have a lot of stagnant air hanging down low.

    You might be able to add a series of small round “muffin” vents through the fascia boards.

    You just use a hole saw, then the little round vents snap in and are held by friction, or can be caulked around.

    A gable vent fan can be very effective, but make sure it has a humidistat control, so it can pull out excess humidity in winter.
    Without soffit vents, you may have condensation problems otherwise.

    And a gable vent fan can pull rain in from the other passive gable vent.

    So that needs to be considered.

    You can create a big plywood catch pan to lay on top of the insulation, any rain pulled in will eventually evaporate.
    You can cover the bottom with plastic bath paneling.

    I have had some clients with condensation problems, or hot spots in summer, where I just put a good quality box fan up in the attic and let it run almost all year.
    Setting it to blow so the attic air spins in a circle.

    With a fused plug, which many fans come with.
    And a little remote controlled socket adapter, so they can turn the fan on and off from downstairs.

    Some of these ideas might sound goofy, but they have worked well for me.

    And sorry about me saying earlier that you should hire out the insulation job, I agree it is a good money saver for a DIYer, with some research.
     

Draft saved Draft deleted

Share This Page