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  1. #1
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    Dec 2008
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    Dayton, Ohio
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    Thumbs up Proper Crawl Space Insulation

    I recently purchased a new home and I need to insulate a crawl space. Here is some background info on the home: its located in Dayton, Ohio, Cape Cod design built in 1940, has a full finished waterproofed basement under original structure, vented crawl space under an addition built in 1996. There is little to no insulation under this addition which is my kitchen. The crawl space floor is pea gravel covered with plastic. The hvac ducts are insulated. The floor above is 1/2" plywood covered with 3/4" hardwood flooring I just installed. The hardwood replaced 3/4" particle board covered with vinyl. This floor is super cold right now. The previous owner mentioned this was a problem. He installed a baseboard heater in the kitchen to make it more comfortable. I feel this is just a band-aid for an improperly insulated crawlspace. It appears someone started to insulate it but it looks like they were installing it wrong to start with. The paper is facing down and they nailed it to the floor joist. This crawl space stays dry except for one little puddle which is either a plumbing leak or a vent leak. The puddle is always in front of a vent that is under a small porch. How should I insulate? Leave the space vented and insulate the floor, or seal it up and insulate the walls. I can easily heat this area because of the existing vents and there is also a boarded up window that accesses the original basement. I've attached a few pictures. There is plastic dryer duct going to one of the vents. It seems that this could be a fire hazzard. Should I replace this with a hard duct while I'm doing my insulating? I done some research on crawlspace insulating on the web but there are a lot of conflicting opinions. I just want to do this right the first time without causing any other problems. Also the door that you use to access the crawlspace is just a piece of plywood. I'm assuming I should try to beef this up some and add weather stripping.
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  2. #2
    Join Date
    Jan 2008
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    731

    Default Re: Proper Crawl Space Insulation

    I suggest you visit the buildingscience.com web site, the US Department of Energy web site, the US Department of Housing and Urban Development web site all offer good information much of which is specific for your geographical and climatic region.

    Looks like a block wall for the crawl space you didn't mention that don't know hollow block, filled, solid block,or what, nor footing/foundation. Don't know if that is moisture penetration at the horizontal masonry joints on that first picture to the left on the block wall and that last picture on the right but looks like it might be, nor how well it has been waterproofed or if insulated on the exterior, nor what ground level (grade) on the outside is there - but might be a problem and you'd need to determine and stop that water/moisture situation before you began esp if it is coming in via the plate (horizontal lumber on top of the block wall that the floor supports rest on).

    Up above the sill plate to the rim board/plate if dry is the first place that needs to be air sealed and insulated, if not done well anything you do to the ceiling/floor cavity above will be less than effective. The plastic on the floor isn't sealed or secured you'll find you want to address moisture issues first.

    Don't know if you want to keep it vented or you want to condition the crawl space if you're looking to condition the space along with the basement or if basement is conditioned along with it being "finished". This will influence what approach you take considering both summer extremes and winter.

    Also don't know if your particular and specific area is known for radon issues, many areas near you are. You'd want to keep that in mind also. Lots of good information on Radon remediation, sealing, etc. on those same sites as well as the US Environmental Protection Agency web site and the Federal Housing Administration subsection of the US Dept. of Housing and Urban Development site as well.

    Some of what you need to consider is if the original portion of the home is balloon construction or platform construction, looks like the addition was platformed on the crawl.

    Hope that helps with your self-education, and good luck with your project.

  3. #3
    Join Date
    Jan 2008
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    731

    Default Re: Proper Crawl Space Insulation

    Quote Originally Posted by wilsoncs3980 View Post
    There is plastic dryer duct going to one of the vents. It seems that this could be a fire hazzard. Should I replace this with a hard duct while I'm doing my insulating?
    What is this connected to (this plastic duct) the dryer? yes it should be replaced possibly re-routed depending on what it is connected to, if it is a clothes dryer then yes with smooth ridgid duct work.

  4. #4
    Join Date
    Dec 2008
    Location
    Dayton, Ohio
    Posts
    2

    Default Re: Proper Crawl Space Insulation

    Thanks for the info. I'm not sure if the blocks are filled or not. The finished part of the basement is conditioned. It is one of the warmest parts of the house. The house has been updated with blown in insulation in the walls. The basement has an everdry system. The crawl space stays very dry except that one very small puddle. Right now the crawl space is vented. We do have very large temperature extremes here in Ohio. I want to use which ever method gives me the best bang for the buck. The grade around the foundation is flat but well drained. We never have any water problems. The sump stays very dry and the previous owner just had a radon system put in the basement. That was a dryer duct running to one of the outside vents.

  5. #5
    Join Date
    Aug 2007
    Location
    The Great White North
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    Default Re: Proper Crawl Space Insulation

    First thing is get rid of the white plastic stuff and use rigid metal ducting for your dryer exhaust and don't forget to cover that duct boot with insulation that's exposed in your picture.

    There is a couple of methods I would probably use for that space.

    If you are going to use the vents then I would add insulation to the joist bays filling the entire space and either use a house warp or attach 1 inch sheets of foam insulation attached to the under side of the joists .
    The house wrap material will provide an air barrier for the insulation and the foam would prevent any air infiltration as well provide a thermo break to the joists and inprove the insulation.
    You definately want the fiberglass batts in contact to the underside of the sub floor .
    The sample of insulation in your picture is just a waste of material with the large air gap between the insulation and the floor .... it isn't doing much of anything.

    If you decide to not use the vents then I would insulate the walls with sheets of foam and apply batts to the joist bays ( though you likely wouldn't need to fill the whole cavity ).

    In my opinion .... I would close off the vents to the outside at least for the winter.

    Hopefully this helps.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  6. #6
    Join Date
    Dec 2008
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    5

    Default Re: Proper Crawl Space Insulation

    Quote Originally Posted by canuk View Post
    First thing is get rid of the white plastic stuff and use rigid metal ducting for your dryer exhaust and don't forget to cover that duct boot with insulation that's exposed in your picture.

    There is a couple of methods I would probably use for that space.

    If you are going to use the vents then I would add insulation to the joist bays filling the entire space and either use a house warp or attach 1 inch sheets of foam insulation attached to the under side of the joists .
    The house wrap material will provide an air barrier for the insulation and the foam would prevent any air infiltration as well provide a thermo break to the joists and inprove the insulation.
    You definately want the fiberglass batts in contact to the underside of the sub floor .
    The sample of insulation in your picture is just a waste of material with the large air gap between the insulation and the floor .... it isn't doing much of anything.

    If you decide to not use the vents then I would insulate the walls with sheets of foam and apply batts to the joist bays ( though you likely wouldn't need to fill the whole cavity ).

    In my opinion .... I would close off the vents to the outside at least for the winter.

    Hopefully this helps.
    Canuck-

    My kitchen faces south and east. On the east wall, I have a dryer vent, a downdraft vent (from oven) and a crawl vent. On the South wall, just around the corner, I have a crawl vent and a spigot. 5 holes in my house that I think make the kitchen/floor/countertops FREEZING. My cabinets in the kitchen line the east and south walls. When I open them, it is freezing in there as well. It is as if neither of these walls are insulated. The down draft vent has a single damper on the wall. That thing is the only barrier b/w the kitchen and the outside wall. The kitchen also has a 3 casement window opening, which also no doubt contributes to cold air. The Kitchen is all located above a crawl space. I have tried to block the crawl vents, but wonder if cold air just travels up the exterior walls where the crawl vents are. There is no insulation in the joist bays below, and there is no isulation where the joists meet the exterior foundation wall. I have heard that insulating the floor from below does not really help. What are your thoughts?

  7. #7
    Join Date
    Aug 2007
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    The Great White North
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    Default Re: Proper Crawl Space Insulation

    Quote Originally Posted by ScottInIndy View Post
    Canuck-

    My kitchen faces south and east. On the east wall, I have a dryer vent, a downdraft vent (from oven) and a crawl vent. On the South wall, just around the corner, I have a crawl vent and a spigot. 5 holes in my house that I think make the kitchen/floor/countertops FREEZING. My cabinets in the kitchen line the east and south walls. When I open them, it is freezing in there as well. It is as if neither of these walls are insulated. The down draft vent has a single damper on the wall. That thing is the only barrier b/w the kitchen and the outside wall. The kitchen also has a 3 casement window opening, which also no doubt contributes to cold air. The Kitchen is all located above a crawl space. I have tried to block the crawl vents, but wonder if cold air just travels up the exterior walls where the crawl vents are. There is no insulation in the joist bays below, and there is no isulation where the joists meet the exterior foundation wall. I have heard that insulating the floor from below does not really help. What are your thoughts?
    Typically the crawl space vents are located on the walls of the foundation structure that makes up the crawl space ..... in your case the area below your kitchen. These wouldn't normally have any direct influence in the cold air rising up into the walls .... unless your home is balloon framed for example.

    Insulating the floor below won't help with preventing heat loss through your cold walls ....... it will prevent the freezing floors you are experiencing and help with preventing heat loss and provide overall comfort in the kitchen space .

    In other words ... you have 2 separate considerations ..... insulate the floor below ..... insulate the walls and seal all penetrations in the walls preventing cold air leakage.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  8. #8
    Join Date
    Feb 2009
    Posts
    1

    Default Re: Proper Crawl Space Insulation

    My gfs place in Bellingham WA is a 1900 sf rancher built in 1966 with an uninsulated ventilated crawlspace. and plastic vap. barrier on the ground. Heating is by HW baseboard fed from a high-eff. boiler. Unusually, the floor is on 4"x6" beams on posts, rather than the usual joists 16 or 24 o/c. Of course the floors are quite cool and with the recent massive hike in NG prices from Cascade we have decided to insulate the crawlspace for next winter. We havent yet priced having foam sprayed in but I am guessing about $2-3k. Due to the water supply and waste lines under the floors I suppose this would be the least hassle.


    Given the spacing of the beams, installing batts would be impractical without a lot of extra framing being done. I could probably cut rigid insulation to fit, although access is somewhat limited due to the usual small metal-framed "well" at the opening to the crawlspace. I'm not sure I can get 2x8' sheets of rigid foam through there without cutting it first.


    Would using a reflective radiant barrier (such as Reflectix), stapled over the beams, be a possible alternative? I have read conflicting opinions on the real-world performance of these products. My main concern would be trapping moisture between the barrier and the underside of the floor, but leaving some openings for ventilation might prevent this (?) Im also not sure that this alone would provide enough benefit.

    Stuart

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