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turtlelearner

Remove or retain old insulation

turtlelearner
9 years ago

I need more insulation in the attic of my colonial built in 1946. The old insulation was installed more than 20 or 30 years ago, who knows? The paper is dissintegrating. I need to be better insulated because that 700 sq ft area is not retaining the temperature well enough. Should I just blow celulous over the top of the old or should I pull the old and start anew? Should I roll in fiberglass strips again or blow in celulous? What is the right way to do it?

Comments (5)

  • energy_rater_la
    9 years ago

    paper on batt insulation may disintegrate over time,
    but the batt insulation doesn't 'go bad'

    I'd air seal the attic floor at each penetration &
    any thermal bypasses, then blow blown fiberglass
    over all.

    cellulose makes a fine 'dust' that enters the house
    through the smallest of openings.

    recessed lights, attic accesses, bath fan openings
    in ceilings, return air & a/c supply boxes are all sources
    of leakage,

    complete all attic work...including mastic sealing
    ductwork before adding insulation.

    southface inst has excellent air sealing pdf's on their
    site, just do a search.

    best of luck.

  • turtlelearner
    Original Author
    9 years ago

    Thanks for the pointers!!! What material do you suggest I use to air seal the recessed lights, attic accesses, bath fan openings in ceilings, and return air & a/c supply boxes? Do you mean stuffing in more bat fiberglass insulation around those areas, or do you mean really air sealing those items? Also, I have one of those huge 1940's style metal whole house fans enclosed in a make shift box right at the attic access entrance. It sucks in outside air and creates a gentle breeze in the house in the spring and fall. however, we only use it when the smoke alarm goes off. It is counter productive when the AC or heat is running because it just sucks everything up into the attic. The problem is that It really interfers with my access to the attic. Do you suggest I remove it since it does nothing to maintain reasonable temps in my upper story rooms?

  • renovator8
    9 years ago

    Where is the house located and how deep is insulation and the attic floor joists?

  • energy_rater_la
    9 years ago

    location dictates how much insulation in attic is needed.

    I mean really air seal, not just filter air through fg batts.
    I've been at this for a long time now...and have found that
    the best product to seal many different materials..wood,
    sheetrock, metal, etc is hardcast brand #1402 mastic tape.
    what I generally do is to remove supply grill ( bath fan
    cover) & use the hardcast to seal from ceiling into the
    supply box's metal lip. hardcast is a strong tape and will
    adhere very well to clean dry surfaces...and it lasts a
    long time. (mastics have long life, unlike duct tapes
    and foil tapes)
    see attached picture on how to seal these areas
    from inside house.

    as for recessed lights, either build boxes around them
    with a minimum of 4" clearance on all sides & top & caulk
    or mastic them in place. use a razor knife to fit box tightly
    to attic floor.
    an option is to purchase air tight inserts..but its pricy at
    $15 each at box stores. (& a real pita to install until you
    get the hang of it),
    where as you can get several boxes
    out of a sheet of ductboard or sheetrock.
    if you are diy...it just takes your time.

    here in the south...the time for whole house fans is past
    very few are used due to the amount of humidity they
    bring into the house. although I have fond memories of
    the whole house fan & wisteria making my room smell
    heavenly as a child.
    we usually remove the fans, and patch sheetrock.
    or you can remove fan, leave louvers in place & from
    inside the attic use foam sheathing boards to seal the
    inside of the louvers frame..and hardcast it air tight.

    using the whole house fan for only clearing smoke...
    get a stove vent & seal the penetration tightly where it
    enters attic space.
    while you are at it...make sure bath fans have dampers
    and are vented out of attic space.

    best of luck.

  • worthy
    9 years ago

    Air-sealing is effective in any climate. Handheld cans of polyurethane spray, such as Great Gap, will work wonders in tightening the envelope.

    Identify your climate zone in the map below, then refer to the International Energy Conservation Code requirements in the table, adopted in many US states, as your target R factor.

    This post was edited by worthy on Sun, Jun 8, 14 at 9:27