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Thoughts on dense packing plaster walls?

Kjmass1 Member Posts: 241
1940's Colonial with plaster and lathe walls, no insulation in walls. We just replaced all of the falling apart single pane windows with Harvey replacements (U factor of .30). Boiler is a Penco NG, probably 20+ years old but seems to work fine, just not very efficient. As part of our attic is finished/heated space, our energy audit recommended spraying open-cell in the rafters first, then if needed pack the walls.

MassSave program offsets $2000 for the walls. What are peoples thoughts on insulating the walls? I've read so many contradictory posts about vapor barriers, settling, rotting sills, etc. Walls are in good shape (at least 1" thick concrete board was found in the kitchen, not sure about the rest of the exterior walls.) Some interior walls have lathe, some have wire mesh. Aluminum siding over wood. Just trying to get some input on if it makes sense to do the dense pack right away, or wait and maybe put that money towards a new boiler.

Thanks in advance, just trying to tighten up this home as much as we can!


  • Gordy
    Gordy Member Posts: 9,546
    Envelope first

    So long as the boiler is in good shape. Then when you are ready for a new one heat loss won't need to be compensated for.
  • ChrisJ
    ChrisJ Member Posts: 15,437
    Dense packing

    Not sure what dense packing is but if its the sprayed in paper stuff I wouldn't do it. Too many complaints about it and the fact it absorbs moisture just seems bad to me.

    I don't know about yours, but the walls in my 150 yr old house are only clap board on the outside and I've heard that is a bad combination with the blown in paper stuff. My walls are staying empty until I figure out a better alternative.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • Kjmass1
    Kjmass1 Member Posts: 241
    dense pack

    It's much better than the old style of blown-in. Supposedly it doesn't settle as badly and does better with moisture.

  • kcopp
    kcopp Member Posts: 4,386
    In my 200+ yr....

    old home I used rock/ mineral wool.

    I was concerned about disturbing the out side shinhgles, foam insulation and vinyl too.  I opted to have them drill from the inside and blow in from there. Worked pretty well.

     I then sprayed the sills w/ spray foam.
  • Kjmass1
    Kjmass1 Member Posts: 241
    from the inside

    Yeah they drill holes between the studs on the inside to pack the cellulose.
  • vaporvac
    vaporvac Member Posts: 1,520
    Rock wool...

    I'd appreciate hearing how well that is working out... superbly I would imagine. My old Chambers stove is insulated with rock wool and it "Cooks with the gas turned off"! It really stays completely cool so i can only imagine how well that would work inside a house.
    Two-pipe Trane vaporvacuum system; 1466 edr
    Twinned, staged Slantfin TR50s piped into 4" header with Riello G400 burners; 240K lead, 200K lag Btus. Controlled by Taco Relay and Honeywell RTH6580WF
  • SWEI
    SWEI Member Posts: 7,356
    Dense pack rocks

    when done by a properly trained applicator, the results can border on amazing.
  • MDNLansing
    MDNLansing Member Posts: 297

    What is on the exterior of the house? Without a tight vapor barrier you'll absorb moisture in the insulation. If you use something resistant to moisture it will help, but moisture will still collect in there. If your house is brick, leave it alone. Insulating a brick home without a good vapor barrier will wick moisture through the brick and pop the faces off when it freezes. I ave a three story home with an unused third floor and see tremendous benefit from insulating the second floor ceilings / third floor floors. I laid it in from the third floor when I hard all the flooring up and there is a dramatic difference. Heat loss through the exterior walls is there, but insulating it can cause serious problems and damage without a good vapor barrier. You don't want moisture in the walls.
  • Kjmass1
    Kjmass1 Member Posts: 241
    wood siding

    The home originally had wood siding. Previous owners sided over top with aluminum. I've heard people rave over open cell in the rafters...heat can't leave the house in the winter and stays cooler in the summer.
  • Paul48
    Paul48 Member Posts: 4,469

    I believe open-cell(Icynene) has to be covered, because of its fire rating. It also soaks up water like a sponge. I'm not sure about the requirements for closed-cell (Urethane), but it will not absorb water, and you could use less. 1/2lb vs. 2 lb
  • Canucker
    Canucker Member Posts: 722
    edited December 2013
    Should be

    fine without a vapour barrier. Cellulose insulation isn't like fibreglass, it won't lose its insulating ability with some moisture in it. As long as the wall can dry in at least one direction, it will be ok.(We're talking vapour, not bulk water. Leaks are very bad and must be fixed) You can find just about all the info you'll need in the article below and its assorted links.

    You can have it good, fast or cheap. Pick two
  • Roland_18
    Roland_18 Member Posts: 147

    For your reading pleasure. Tons of info here:

  • Kjmass1
    Kjmass1 Member Posts: 241

    for all the information. How much energy loss is there with the walls? Would the new windows and insulating the attic account for 80% of my loss and the walls are the last 20%? Or is it much greater than that? Guess I'm trying to determine how much insulating the plaster walls will really help me.
  • mcsteamy
    mcsteamy Member Posts: 77

    Insulate the walls and the attic if you want the best ROI, and get an energy audit to help find leaks. 

    Dense pack cellulose is just fine in the walls, although it is true that it can cause paint adhesion problems because you lose the vent channel behind the siding.  Will it cause the walls to rot out?  No--not unless you somehow have water infiltration happening in the walls.  Simple vapor passage will not cause rot issues.  No vapor barrier?  Think again--what do you think all of those layers of old oil paint are?  A vapor barrier.

    Windows, frankly, don't do all that much compared to simply repairing those already there.  Provided the windows have decent storms, the ROI for new windows is terrible compared to insulation and leak stopping.  You are headed in the right direction.
  • vaporvac
    vaporvac Member Posts: 1,520
    Least thru the windows w/ storms

    this is a great link to issues and pros of various insulations.http://www.oldhouseguy.com/blog/insulating-old-homes-toxic/

    Old house guy is a must read for owners of old or merely "vintage" homes, and his blog continues the conversation. The best links for fixing old window via the doe and parks service.
    Two-pipe Trane vaporvacuum system; 1466 edr
    Twinned, staged Slantfin TR50s piped into 4" header with Riello G400 burners; 240K lead, 200K lag Btus. Controlled by Taco Relay and Honeywell RTH6580WF
  • MDNLansing
    MDNLansing Member Posts: 297
    Just Fine

    Wood siding with aluminum over it will be just fine. You'll have plenty of air movement on both sides of the insulation. This will ensure the insulation stays relatively dry. Do plenty of research on blown in products. I've had multiple houses I've used fiberglass and cellulose on and regretted it. Mostly because of the product. It would settle and become dense which then retained a lot of moisture and was wet feeling when I ripped it out. Foam of course wont do this. You can get it "sprayed" into existing wall cavities now as well. The new Owens blown retro products are good too. I have one solid rue on this. You get what you pay for. Have a pro do it, and use a good product. A good installer will take thermal images of your walls to find as many barriers and obstructions as he can. The fly by night guys will just shoot you a low price and get in and out. Cheap stuff installed poorly shouldn't even be an option. If you have to, wait another year and save more money to do it right.
  • Kjmass1
    Kjmass1 Member Posts: 241
    that's exactly

    the article I read that gave me pause on insulating the plaster walls.
  • Roland_18
    Roland_18 Member Posts: 147

    It's more important (I think) to find and plug any points of air infiltration than to throw lots of money at insulation. Even small drafts can account for some serious heat loss.

    When I moved into my present house (1950's cape) the kitchen was uncomfortably cold in winter. I thought sub floor radiant heating would be the fix as the amount of baseboard seemed insufficient. I was wrong. The problem was fixed by installing a new weather seal on a sliding door. $$$$ saved. Plug any leaks first. My two zloty.
  • Kjmass1
    Kjmass1 Member Posts: 241

    said they use GreenFiber cellulose for the walls. Any good?
  • Canucker
    Canucker Member Posts: 722

    can be a lot of heat loss, especially at the rim joists(old houses tend to leak where they meet the foundation)

    Old layers of paint are NOT vapour barriers, they are vapour retarders. It is an important distinction to make.
    You can have it good, fast or cheap. Pick two
  • mcsteamy
    mcsteamy Member Posts: 77

    I stumbled across that article at one point to, which led me

    to do a lot of additional research on the subject.  To make a long story short, the approach by

    John Leeke or Bob Yapp is overly simplistic. 

    Building Science does a much better job, and takes a more comprehensive

    approach.  Few resources have helped my

    understanding of the issues involved more. 

    For example, http://www.buildingscience.com/documents/insights/bsi-043-dont-be-dense

    acknowledges the potential problems, but also has details on how to do it

    right.  This is good stuff. 


    “Old houses were not designed for insulation, so don’t

    bother” is terrible advice.  If you do

    it, you simply need to ensure that you do it right, and understand how water

    migration works in a structure.  Here’s

    another good BSC article:  http://www.buildingscience.com/documents/published-articles/pa-air-leaks-how-they-waste-energy-and-rot-houses.  Couple that with this British article at http://www.superhomes.org.uk/resources/interstitial-condensation-3/

    and you’ve got a very good start.  You

    have to understand where you are making moisture, how much, where you are

    removing it, and where your dew points are under various conditions.  If the house is very tightly sealed, with

    insulation in the walls (which has the advantage of increasing sealing), with

    oil paint all over the walls, the odds of problems are likely rather slim

    unless there are other major problems with the exterior envelope.


    Our current very old house is insulated to the hilt with UFFI

    foamed walls.  My last old house had dense packed fiberglass.  Neither has any problems.  The current house is not only well insulated,

    but also very well sealed.  Blower door

    testing showed infiltration on part with a reasonably well build new

    house.  Good storms and weather stripping

    make a big difference.  Our major loss

    points are on the bottom of a few windows, the fireplaces, and the rim

    joist.  So, with all that insulation (in

    6” walls), and all that sealing, where does water condense?  On the surface of the walls because the years

    of oil paint acts as an effective vapor barrier.  If it gets into the

    wall, it simply migrates out through all of the missing paint.

    Now paint loss, that’s a potential real problem.  New houses with wood siding often use a ¼”

    air gap on top of the sheating to promote paint adhesion.  However, whether this is necessary is

    debatable.  In an old house, paint is

    often so thick that the underlying substrate simply cannot carry any more.  Insulation, in that case, can be the straw

    that breaks the camel’s back.  However,

    if the paint is properly stripped, repainted with latex, and the clapboards not

    painted or caulked together (clean this intersection up with a scraper!) the

    issue is fixed properly, instead of bandaging over it by using walls for a

    massive air gap. 
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