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Basement Ceiling Insulation, Anyone?

Post in 'The Green Room' started by Mr. Kelly, Jan 7, 2012.

  1. Mr. Kelly

    Mr. Kelly Member

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    Hey all...

    We have a 260 yr. old stone foundation farmhouse. We have our wood stove parked in an outside corner of the main floor.

    The basement has had "treatment" by the local energy assessment company, i.e., holes filled and caulked, etc., but the basement ceiling has no insulation.

    Do any of you folks have their basement ceilings insulated? Our basement is not freezing cold, and in some cases, due to the boiler being down there, can be fairly mild. But, I wonder if my stove pulls some of the cooler air out of the basement from the cracks in the floor and sub floor (there are many) to feed it. The stove can easily heat much of our main floor, but it's very streaky, with inconsistencies of temperature abound. I wonder if the cooler air being drawn up from the basement may contribute to this effect.

    I also wonder if I insulate the basement ceiling, will it force the air pressure upstairs to come up with fresh air somewhere else, perhaps less ideal, or cause the stove to run less efficiently due to lack of air to circulate?

    The rest of our house is moderately insulated, as we had the energy company blow in cellulose insulation into the walls, and I packed the attic reasonably tight with fiberglass batts.

    So, what do you think? Insulate the basement, pain in the rear that it would be? With old electrical wiring, I'm a little concerned about old conduit and wires someday coming into contact with fiberglass insulation... there's years of old wires and pipes running in the ceiling.

    Any thoughts are appreciated!

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  2. jharkin

    jharkin Minister of Fire

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    First a disclaimer- My opinionated side comes out on old house discussions ;) Anyway my house is a little younger than yours but similar basement situation so I have some thoughts.

    #1 When it comes to insulating basements the general rule of thumb is to insulate the walls if the space is within the conditioned envelope of hte house, and the ceiling if its outside the envelope. If you have HVAC equipment and water pipes in the basement you generally want it inside the conditioned envelope even if you are not actively heating it (to prevent frozen pipes and take advantage of standby losses to help heat the house).

    #2 Insulation is not an air barrier (except for closed cell foam and dense pack cellulose). FIberglassing the ceiling wont stop drafts. You would have to air seal that entire ceiling and weatherstrip the basement door. Then you would also have to worry about sufficient combustion air for any fueled HVAC or water heater down there if your foundation is tight.


    #3 Old stone basements are damp. You can limit it by pointing hte stones and sealing hte floor and running a dehumidifier, but it never completely goes away usually. If you insulate the ceiling you could trap moisture and start rotting the joists. I can tell from old staples that the ceiling of my basement was insulated in some areas once and all those areas have the start of dry rot. Im glad it was removed by the previous owner.


    The bad news is that insulating the walls of a stone foundation is not trivial. You have to make allowance for drainage, and you need to be able to get those walls periodically for maintenance. Buildingscience has some methods but I don't like them as they are irreversible (membranes and spray foam). Our you could put in a drainage system and then build an insulated wall inside that - but again you might need to get in there someday to repoint the stonework. No easy answer on a house this old.

    Good luck.
  3. semipro

    semipro Minister of Fire

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    Mr. Kelly,
    You'd probably get more responses if this was posted in the DIY room. There's a lot of discussion there about this sort of thing.
  4. Mr. Kelly

    Mr. Kelly Member

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    Excellent points, Jeremy. Thank you for your time and consideration.

    Perhaps, a compromise would be to insulate around the very old and deteriorated sills with batts. This is where I suspect a good chunk of the basement warm air is escaping. Any thoughts about this?
  5. MrWhoopee

    MrWhoopee Minister of Fire

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    It sounds like you need to close the holes before you worry about insulation. Think Tyvek house wrap. Once you have stopped the air movement, then it's time to think about insulation. Bear in mind that the boiler requires combustion air, so you can't seal off the basement completely from the outside. An infltration barrier under the floor might be the place to start, as long as it doesn't create a condensation problem for the flooring. Tyvek is permeable to water vapor, but restricts air movement. Don't use Visqueen/polyethylene film, it WILL cause condensation problems.
  6. velvetfoot

    velvetfoot Minister of Fire

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    I would foam the sill, not fiberglass.
  7. begreen

    begreen Mooderator Staff Member

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    +1 I'd seal and caulk the sill plate area carefully and thoroughly. Eliminate all leakage there and then insulate from the sill plate up.
  8. daveswoodhauler

    daveswoodhauler Minister of Fire

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    Another vote for sealing up the sill.
    I'm kinda a nerd, and I am in the process of finishing off a basement playroom for the kids.
    I wanted to track the basement temps during the winter for high, low and current temp for each day.
    In the process, I started aiming the IR gun on the walls, and most read 55 degrees or so....pointed the laser up to the sill plate area, and blammo....looking at 45 degree temps...some close to 40......spent some time just using some left over fiberglass insulation I had laying around and it did make a big difference just insulating the sill area. Sill temps are now low 50's and its a lot warmer downstairs. Another good use for the IR gun as well as taunting the cat.
    Dune likes this.
  9. jharkin

    jharkin Minister of Fire

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    I'm going to add another dissenting opinion.

    Air sealing the sill to the floor above and foundation is definitely a good idea to reduce infiltration. The work you already had done may have addressed that. Insulation , again I would be hesitant on - here is why.

    IN platform and balloon framing its commonly recommended and a very good idea to insulate the rim joist. In the rim joist area there is only about 3 inches of wood between you and the outdoors. A little bit of insulation here makes a big difference, and the sill makes a convenient shelf to stuff FG batts into.

    But you don't have platform framing - You have post and beam timber framing! Your sills are probably no less than true 6x6s (mine are 6x7 and my house is very small) and maybe as big as 12x12s... probably a dense hardwood like oak or chestnut (or maybe pine/fir if you are up north) . You have no rim joists as you floor joists are mortised into the sill itself and the floor above runs under the outside wall and buts directly to whatever studding there might be. If the siding is old you might still have 1" shiplapped sheathing board, and then shingles or clapboards. In all its not unlikely that you have a full foot of solid wood there between you and the great outdoors. You could have an effective R value of 10-15 already, so the benefits of adding more are not as big, plus if you use FG you have to figure out someway to hold it up.

    But again we get to the subject of moisture. If your sills already have significant rot at some point you are going to have to address that. Removing spray foam to cut out and replace rotten sill will be a *(&^&*^%%. Plus, with those sills sitting directly on the stonework, they will always be absorbing a bit of moisture. They MUST have a means to breath or else they will stay wet and the rot will just accelerate. Assuming the outside of the wall is sealed right, the inside is the only place they get that ventilation. So I think if you seal them in with insulation you are only going to accelerate the rot problem.

    If you haven't figured it out yet - I wouldn't do it.


    On the bright side, when you do need to fix the sill its actually very easy to do in a post and beam house so long as the rot is not around the base of one of the posts. All you need to do is put lally columns under the floor joists then you can open the wall from outside and cut out the bad sections. Build up a replacement sill beam from PT or if you want to be authentic have a sawmill cut you a new one in oak and lap joint it in. Get some steel hangar plates made up to bolt the joists to the new sill, lag bolt any braces back into place, button up the wall and you are done. We did a 6 foot section on my house in a weekend with 2 guys.
  10. firewoodjunky

    firewoodjunky Member

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    I am definitely no expert on these matters, but I just installed Reflectix on part of my basement ceiling and it has made a significant difference in my house. The portion that I put the Reflectix on was wide pine flooring with no subfloor, hence the air was just being drawn up into the main house. This portion is about a third of my basement. I have a furnace down there that heats my hot water and occassionally runs early in the am when the VC is running out of steam. It's usually around 50 degrees or so down there all year long. Typical NE cellar, a bit damp, the dehumidifier runs in the summer months, usually in the winter the basement is about 40 or 50 percent humidity.

    It's pretty short money, glued onto firring straps with construction adhesive. My house is pretty darn old, with two subsequent additions so there is NO way that I could excessively tighten it up without encapsulating the whole thing in a giant blob of foam.

    Just my two cents.
  11. Mr. Kelly

    Mr. Kelly Member

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    All great suggestions, folks. However... lots of ??? remain, with no easy answers!

    My gut tells me not to insulate up the sills. Yes, as inferred, our basement is VERY wet. Our foundation pretty much sits in water for a good chunk of the year, with standing water in our sump hole (and our sump pump running) regularly. And... we live at the crest of a hill! Go figure.

    Anyway, I have been running a dehumidifier most of the summer, which really has helped in the dampness of the basement. I do feel that if I tighten up the flow of air down there that I might be asking for rot trouble.

    So, I have two possible roads of approach: One pursuit would be to cover up some of holes in the ceiling with Tyvek, in the areas that have no sub floor, and lots of cracks b/w the wide pine floor boards. Perhaps, this might not completely eliminate the movement of air, but at least slow it down a bit, and allow the upstairs to hold the heat with a little more consistency, but also allow some circulation.

    The other option is to leave the basement exactly as it is. It could be worse. We're not exactly freezing, but we're not ecstatic with the consistency of heat.

    I suspect the answer lies somewhere in between.


    Jeremy: Our sills are very problematic. The house hasn't been well maintained by the previous owners, and we haven't really contributed much in that area. We've had a couple of post and beam experts over here to look at our sills, and although we could spend the money to get them fixed, as you suggested, one very knowledgeable fellow suggested that leaving them just as they are may not be the worst choice. In one corner of the house, the sill has actually sunken in below the top of the stone foundation (likely due to rot and deterioration). That whole section of the house is inches below the rest (maybe as much as 6-8"), leaving the house completely pitched in that direction. This has resulted in cracks in the plaster all over the house, floor boards on the top floor of the house buckled and warped - it's a mess. In another area of the sill, someone removed the actual sill and replaced it with concrete (in one area), and bricks in the other. I suspect there's a million reasons that these are not good fixes. So, our main expert suggested that the sunken sill may have been like that for years, maybe even a hundred, and perhaps it a good idea to just "let sleeping dogs lie". He did also suggest, if we really wanted to do something to stabilize the situation, we could get some good lolly columns installed in there correctly, through the basement floor into the ground below, to give things some stability. Right now, there's just some wooden posts set from the bottom of the floor joists that rest on the poured concrete floor below, which again is not a great situation. There are also a couple of metal lollys resting directly on the concrete floor also, again not great. But, I digress...

    Again, thanks for the input, and the suggestions. Any continued thoughts will be appreciated!

    MK
    wannabegreener likes this.
  12. begreen

    begreen Mooderator Staff Member

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    Water in the basement is bad. If you are at the crest of a hill, is the roof the source? What shape is the gutter system in and how well is rainwater lead away from the house foundation? Can a drain be put in the basement that goes to lower ground?
  13. Mr. Kelly

    Mr. Kelly Member

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    Gutters are pretty beat, and on one wall, nonexistent. My thought has always been that our house sits in a high water table, and it's too big of a problem to fix easily. A house inspector a hand full of years ago suggested an elaborate French drain all the way around the house. Sounds nice, but likely very expensive. Our sump does a pretty good job sucking up the water that seeps high under the house, so it's been fairly well managed, at least for the underachievers that we are! At some point, combating the problem, rather than the symptoms, should be a priority, but that will come after a bunch of other things that need to be done... like gutters, roof, barn repair, sills, etc.. What were we originally talking about, anyway? Oh, yeah, basement insulation...

    What Reflectix product is recommended? Would that be any better than Tyvek?

    Aren't old houses a blast??? :)
  14. jharkin

    jharkin Minister of Fire

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    Mr. Kelly...

    Ahh got it. Your way ahead of me on those sills... hope my little discussion didnt come off as a lecture. I guess I was lucky that my rot problem didn't reach any of hte posts and was easily fixable. From what you describe fixing yours right is going to involve jacking the house by the posts or plates... not fun.

    If you want them I have a looooong list of books that may give you some ideas. If your not a member already I also reccomend coming over to visit us on the oldhouseweb.com forums. There are a few guys on their that have done this kind of extensive structural work and could give better advice than me.


    Oh and I feel your pain on the wet basement. We have a high water table that averages about 6 inches below the slab and in the spring rains gets up to slab level. There is a sump and clay drain tiles but those clogged long ago. Someday I need to break up the slab and redo them but im not ready to just yet. Most annoying part is that 50 years ago the house had deeded rights to gravity drain the sump well under the street and down into a gully. But at some point that was revoked and we have to rely on a pump - which of course always goes out when we most need it in a driving rain power failure!

    The french drain is actually a decent idea if you have more time than money. The biggest expense is the labor digging the trenches... If you don't mind breaking your own back ;) it can end up quite inexpensive I think.
  15. firewoodjunky

    firewoodjunky Member

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    It's sold at Lowes - it comes in different diameter sized rolls and looks like tin foil (kind of). It's more of a foil wrapped bubble wrap. You get a minimal R Factor (R -3 or R-4), unless you have an airspace void between two applications of it, then it goes waaaay up in R-Factor (R-21). I got it to stop the basement from adding to the chimney effect in the house, so I was more interested in an air sealant type application. Like you, I have wide planked floors with no subfloor - you could feel the air being drawn into the house between the gaps ins the floorboard. I installed this, and there is a marked improvement in floor temp and reduced "drafty" feel in main living area. I used tubes of construction adhesive to install it - it's feather light stuff so it's not a bad job for one person.

    If you wanted to really reduce your cost of doing this project, you could probably use anything that is air permeable. Although you may lose the warmer floor feel if it has no R-Factor. I did a test of the floor with completed bays and non completed bays, three people who had no idea what I had done in the basement said that the completed bays felt noticeably warmer on their feet than the non completed bays.

    Good Luck!!!

    And if we didn't own older homes, what would we do with all of our free time? Relax? Golf? Fish? Hunt?
  16. Vic99

    Vic99 Minister of Fire

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    You are concerned about adding more insulation = less air flow for the furnace.

    In an old farmhouse I wouldn't worry about that. Unless you go crazy with spray foam, you probably wouldn't get every point of air infiltration. I've been in my 1920 house for 8 years. Each year I still go through at least a tube of caulking + because I find other holes somewhere in the house, but especially the basement. It's amazing.

    Also, unless you are dealing with new construction, it is often challenging to perfectly install insulation to block everything. With uneven foundations, house settling, uneven joists, protruding nails, electrical and piping, you really have to be meticulous.

    Good luck.
  17. backpack09

    backpack09 Minister of Fire

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    Put up some gutters, and point the downspouts down hill away from your house and I bet your sump pump will never run again.

    Gutters are very important to a dry basement.
  18. begreen

    begreen Mooderator Staff Member

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    Agreed. Unfortunately this house seems to have a long history of deferred maintenance. Even the best old houses can only take that for so long.
  19. jharkin

    jharkin Minister of Fire

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    Gutters will help but cant fix a high water table if that is the real problem.

    To the OP - do you get water in the sump just during and after rain or all the time? If you have standing water weeks after rain then it is likely a water table issue. That's the problem i have, standing water in the pit right now and it has not rained more than a drizzle in 2 weeks.
  20. semipro

    semipro Minister of Fire

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    Huh?
  21. begreen

    begreen Mooderator Staff Member

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    For the long term, is there enough slope to the property to do a french drain system around the house foundation?
  22. Mr. Kelly

    Mr. Kelly Member

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    Likely, but at a likely high cost. Anyone know what folks would get for installing a French drain around a 1700 sq/ft. house? In MA, that is??

    Also important to note... it's a field stone foundation.
  23. sesmith

    sesmith Member

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    The easiest and maybe the most effective way to dry out the cellar might be to put the drain around the perimeter on the inside. It's hard to seal a stone foundation from the outside.

    We installed gutters and did a french drain on the inside of our old stone foundation. It turned a nasty damp basement into a place we can actually use for storage. It does need a dehumidifier, though. We never did insulate the cellar. Many years ago, I tried using fiberglass bats under the floor of one of my rooms (installed in the cellar). It became a very large mouse nest and I ended up ripping out the insulation at a later date. I think the better solution would be to foam the stone walls after controlling the moisture. A couple of interesting articles here:

    http://www.buildingscience.com/documents/insights/bsi-041-rubble-foundations

    http://www.buildingscience.com/documents/insights/bsi-045-double-rubble-toil-trouble
  24. begreen

    begreen Mooderator Staff Member

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    First, be sure a french drain will solve the problem. It would be good to pay a pro to determine the best solution. If you are dealing with drainage on a hillside a french drain can really help. The cost would depend on whether you want to contract it yourself or hire someone. A team of a few good diggers could probably have the trenches dug in a day, day and a half. Then allow a day to install the drain and cover. (Note a lot of the dirt will not be going back in the trenches). So say 3 laborers @15 x 20 hrs = 900 + tools so say $1000 labor and tools. Materials will depend on the length of the trenching, but I would guess somewhere between 500 and 1500? Max I would estimate would be under $3K. If a contractor came in and did this, maybe $5K?

    This is not rocket science, though it is similar to sewer drain installation. Speaking of which, you want to know first that you are not going to run into preexisting piping or wiring down there. Maybe see if there is a local digging crew that works on septic in your area?

    http://www.easydigging.com/Drainage/installation_french_drain.html
  25. Mr. Kelly

    Mr. Kelly Member

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    You guys are the BEST!!

    Thanks for the input. Just a wee bit to think about.

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