Crawl space insulation

Discussion in 'Environmental Discussion' started by tripp, Jan 18, 2009.

  1. tripp

    tripp Which it's a 'ybrid, ain't it?

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    a'reet lads and lasses,

    The next home improvement project I'd like to investigate is insulating my crawl space. Here are the basics: The CS is about 300 sqft. The "roof" (i.e the dining room and kitchen floors) is uninsulated. The furnace duct work is not insulated. I don't know yet how well sealed the duct work is. The walls of the crawl space are roughly half above grade and half below. They are uninsulated. The floor of the CS is just dirt. The crawl space has at least a few openings to the outside air, I don't yet know how well sealed it is, but there are two intake gratings for sure. There are a number of uninsulated water pipes in the space as well.

    I'd love to hear some thoughts on the best way to improve this space to improve our NG utilization during the winter. There are some winter months when we use right about 100 therms and I'd like to improve that number as much as possible, started with the lowest hanging fruit. We've done a lot of the really easy things: wash clothes with cold water, R11 blanket on the water heater, low-flow shower head. Now I'd like to go after moderate price tag but good return projects and the crawl space seems like an obvious one. We've already upgraded the windows, did that about 4 years ago.
     
  2. KK6PD

    KK6PD _ . _ . / _ _ . _

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    Google this ... polyisocyanurate foam

    polyisocyanurate foam - Google Search Spray Foam Insulation.

    I did my attic due to extreme summer temps , 150'+. I had a company come spray the underside of the attic roof and now at blazing summer temps, the attic temp is about same as outside air temp or less! 300 ft is a small area, if you have more to do do it all at once. There are 2 types, fast set, slow set. You want to use the fast on open areas, walls before drywalling. The slow's advantage is it won't pop drywall off the studs with a fast expansion rate inside the wall void or ceiling void. It will have the best R of any insulation. It also completely fills any voids, no air infiltration on windy days. There are no emissions once dry, and will not support combustion.

    It worked for me!!

    73 de Pat KK6PD
     
  3. hyo silver

    hyo silver Awaaaaay

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    You can do several things here.

    The easiest place to start is probably with a roll of duct tape, sealing off the joins in the sheet metal. A high temperature version, not just the standard stuff, will last much longer.

    I'd say closing off the vents would be the next step, but the dirt floor presents an issue. The gasses that emanate from the bare dirt need to be kept out of your living area; hence the vents. If you covered up the dirt with plastic sheeting, held down with rocks or some gravel around the edges, then you could cover the vents too. And, crawling around to do the insulation would be much cleaner on a ground sheet.

    The water pipes are easy to do with some pipe insulation - the same kind you'd insulate your grill with! :)

    Then, some regular batts between the floor joists will take care of the crawlspace 'ceiling'. Stapling a vapour barrier to the bottom of the joists will help seal any air leaks, keeping the heat where it belongs, and the radon out of your house.

    Good luck!
     
  4. Godiva

    Godiva AmeriKan Citizen

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    This is my next big project too. But I want to hire it out. I've had enough crawling under my house to last me. And I still have to go one more time to put a phone extension in the TV cabinet. (And the occasional fix for the furnace.)

    I did the attic myself a few rolls at a time over months. I really don't want to do the same with the crawlspace. I guess I'll see how much I get back from the taxes this year.

    I really need to do something about the attic. I've got ventilation and a fan, but during the summer the fan is constantly going because the temps are over 100 degrees up there. If it were only the same as the ambient outside temperature, I'd be happy. But it's always an oven.
     
  5. jayman

    jayman Senior Member

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    Funnily enough, duct tape should *not* be used on ductwork. The tape will quickly dry out and fail, literally fall right off. There is an aluminum foil stuff that works well for ductwork, the stuff I use is made by 3M

    Larger seams and gaps should be done with mastic or with silicone sealant. Next is insulating the ductwork, which makes a huge difference

    Here in Manitoba, Radon gas ia a problem. Ideally, the sump pump pit is vented outside, and preferably a Heat Recovery Ventilator is in use to bring in fresh air 24x7. Extreme cases require power venting of the slab, eg air sparging

    According to the EPA, CO has very high potential for dangerous radon levels

    Colorado | EPA Map of Radon Zones | Radon | Indoor Air Quality | Air | US EPA

    I think with that, unless Tripp is willing to invest in a HRV, it wouldn't be wise to just cover the vents. At this point, Trip should consult a pro to determine how best to safely insulate the crawl space

    Just 6 mil vapor barrier on the ground will *not* keep the radon out. It may be safer and easier to just use the iso foam to insulate the joists, insulate the pipes, and hope for the best
     
  6. msirach

    msirach Member

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    The main trunk of your duct work is probably insulated inside. That is typical in the midwest. Keep the air off of the metal to reduce condensation/rust.

    If your branch lines are metal and uninsulated. It can be purchased at a local store such as Menards.
     
  7. qbee42

    qbee42 My other car is a boat

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    Ours are uninsulated, inside and out. On the other hand, our ductwork runs through heated basement space, so insulation is not much of an issue.

    I would heed Jayman's advice. Don't trifle with radon. Certainly you can put a vapor barrier on the floor and insulate the floor, as well as the ductwork, but you want ventilation for the crawlspace. Even without radon, moisture will build up and weird things will grow without ventilation. With radon it won't matter what sort of weird things grow.

    Tom
     
  8. chogan2

    chogan2 Senior Member

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    I can't speak to a Colorado climate, but in the South, you would never close the vents. Moisture buildup can rot the floor joists over time. I've seen it -- after a couple of decades, the joists look like they've been through a fire. Around here, you'd lay 6 mil poly on the dirt just to keep the soil moisture from migrating into the crawlspace. (Plus it makes it a lot cleaner to work in the crawlspace.)

    I've done retrofit-fiberglass-batts-between-the-joists, as a way to insulate a floor. Tedious, filthy, and fiddly do not begin to describe the process. But cheap. You'll want a dust mask, safety goggles, and gloves. Working over your head, yeah, you really need the goggles. You need batts and these little spring deelies (stiff wires) to hold the batts in place up against the subfloor. Might have to get some pipe strap or similar material if you need to let the batts hang down below the joists where the ductwork is. Get the batts that have a moisture barrier in the top surface (kraft paper or similar), place this against the bottom of the floor deck. You could, if you wanted, place poly against the floor deck. Do not place any moisture barrier over top the batts once installed (ie., stapled to the floor joists, trapping the batts between floor deck and poly). Do your best to stop the moisture at the warm surface, but then allow the backside of the insulation to be freely vented to the air. Anything but that risks having warm moist air condense inside your insulation, leading to rot. With any luck, you can cover floor, ducts, and pipes at one go.

    In terms of the quality of the results, in a retrofit application, that's clearly inferior to the isocyanurate mentioned by several others. It's just significantly cheaper. And you can do it yourself. I read up on the isocyanurate for my cathedral ceiling, and that does seem to be the way to go if you really want the highest R you can get.

    As long as the ducts and pipes are up within the floor joist spaces, I don't think I'd bother to insulate the ducts and pipes separately. I'd do whatever it took to insulate those floor joist bays. Fiberglass batt is cheap enough that you could probably insulate the bay for what it would cost to buy the pipe insulation.

    In sum:
    Fiberglass is cheap, and do-it-yourself. The materials might run $0.50/sq ft for R-19 insulation. The foam, I'm guessing would be about 4x as much to have somebody apply it. But clearly a better product in most applications.
     
  9. hyo silver

    hyo silver Awaaaaay

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    Yes, I knew that. Which is why I suggested using the "high temperature version, not just the standard stuff". Specifying aluminium is more helpful.

    What about the possibility of pouring a slab of concrete in the crawlspace? Would that seal off the radon?
     
  10. qbee42

    qbee42 My other car is a boat

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    Instead of concrete, you could try Jayman's method. I'm not sure of the science behind it, but it involves sacks of lime and freshly disturbed earth. I always wondered why he had that short handled shovel?

    Tom
     
  11. ScubaGypsy

    ScubaGypsy Live Free & Leave No Footprint

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    Are there any "green versions" of the spray foams? I'm particularly interested in no VOCs and reuse products if possible as I've been considering denim based products but have been concerned about using it in a crawl space.

    We added a Sunrise 1250 solar attic fan last summer and have been very happy with its performance. It has significantly kept the attic temperature reasonable in the summer while removing any condensation in the winter.

    SunriseFan072508b.jpg
     
  12. KK6PD

    KK6PD _ . _ . / _ _ . _

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    Polyisocyanurate foam "is" the green version. All that leeches out during spray is water vapor in the form of steam. After it sets thats it. NO formaldehyde emissions. No bad smells, it just sits there and insulates nicely!!!

    Do the Google, I first out about this product years ago when "This Old House" started to use it!!! It works VERY WELL!!

    Good Luck de Pat KK6PD
     
  13. tripp

    tripp Which it's a 'ybrid, ain't it?

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    Thanks everybody for the input! Kudos to Tom for not taking us off subject. Pouring concrete is out of the question, that'd cost a fortune. I was planning to get a pro out, but I wanted to have some idea of what the possibilities would be before talking with someone. I'm more than happy to do some of the grunt work myself (sealing ducts with mastic, insulating ducts, etc) but defo want some professional advice so that I don't waste time and money or do something that might cause damage. I'm really not too worried about moisture, our house sits on bedrock (sandstone) and I would imagine that the moisture content is pretty darn low (could always measure with the proper kit), never-the-less, it's still a concern and my assumptions may well be wrong. The radon issue is an excellent point and yes, Jayman, radon levels can be quite shocking around here. I'll be sure to post some before and after pics. Getting a sense of how effective all this will be is gonna be tough because temps can vary wildly here from year to year.
     
  14. Godiva

    Godiva AmeriKan Citizen

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    I've got a tall attic and vents at both ends of the gable. So I installed a fan at one end to draw the air through. It is programmable and is set to come on when the attic reaches either 90 degrees or 100 degrees, I don't remember. But during the summer it runs a lot and the attic is an oven.
     
  15. Godiva

    Godiva AmeriKan Citizen

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    You don't just get moisture from whatever your house is sitting on. The warm air flows under the house and it cools. There's moisture content in the air. I would never block the vents under my house. But I will insulate under the floor. I was hoping just to use the rolls of stuff that is covered in plastic and then use the flexible braces to hold it up. Maybe do the pipes with pipe insulation. (That is...someone else will do it for me.)
     
  16. tripp

    tripp Which it's a 'ybrid, ain't it?

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    The relative humidity here is almost always quite low, hence the 30+ deg temperture drops when it rains in the summer. I remember a nice little storm cell that hit us this summer. The temp dropped from ~95 deg F to ~65 deg F in about 10 minutes! It was quite nice.

    Moisture is an issue, but not the biggest concern. The radon is going to require ventilation so we'll keep the vents undisturbed.
     
  17. icarus

    icarus Senior Member

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    If your crawl space is uninsulated and vented, and your ducts are un insulated your are losing a HUGE mount of heat.

    The current code (In most places) is R-19 glass batts between the floor joists, held in place with spring wires or lathe strips. A vapor barrier should be on the heated side of the batt face. A layer of 6 mil visqueen should be placed over the soil in the crawl, extending up the side foundation walls 6" or so. The foundation should be vented at a ratio of ~ 1/150. These vents could be closed in the winter.

    In many parts of the country, radon from the soil is an issue, so a radon monitor should be bought, and tested, and extra venting should be installed as needed.

    The ducts should be insulated with proper duct insulation, although I think forced air space heat is not a preferred solution, I would rather have zoned space heaters.

    Icarus
     
  18. patsparks

    patsparks An Aussie perspective

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    Where I live if you block vents under a timber floor house the termites move in.
    My home is on a concrete slab.
     
  19. jayman

    jayman Senior Member

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    Contrary to popular belief, regular concrete is not airtight or moisture proof. Indeed, the current practise around here now for concrete slabs is, after backfilling, tamping, and piling, is to put down a 2 inch structural foam underlay. This helps to reduce frost jacking/heaving

    Beaver Plastics Terrafoam inert closed cell expanded polystyrene

    Beaver Plastics Dynavoid

    Particularly if you want a heated slab, this product is a MUST

    Beaver Plastics insulworks hydronic heating insulation

    Before these products were available, folks used to lay 6 mil vapor barrier over the tamped earth before pouring the slab. But even then, moisture would wick up through tears or breaks in the barrier

    Consider the average basement is concrete, and is usually a hot spot for radon entry. The only reliable way to keep radon levels down is to directly vent the sump pump pit, and in extreme cases, power vent the actual slab with air sparging

    When my home in Tuxedo was new, I had it tested for radon and it was "moderate." After venting the sump pit and power venting the slab, the reading was almost nil

    A particular danger of radon is that it is odorless and is cummulative over time. Radon is generally thought to be responsible for at least 10% of all lung cancer cases in Canada.
     
  20. jayman

    jayman Senior Member

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    That's to get rid of the evidence .... erk ... I mean .... um .... NO COMMENT
     
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