Crawl Space


Old 04-25-02, 11:55 AM
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Crawl Space

I am considering insulating the crawl space of my house. About 2.5 ft between ground and bottom of support beams. The entire crawl space has plastic sheeting over the dirt but the floors are freezing in cold months. What type of insulation do I use between the support beams and does paper side go against the bottom of the hardwoods or is that upside down. What is the best way to attach it to the supports.

Thank you
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Old 04-26-02, 06:23 AM
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I would seriously consider radiant barrier insulation in the crawl. I did it and it made a significant difference vs fiberglass. Do a search within this thread and you will find previous posts regarding this. If you do put fiberglass between the beams, the paper goes up, toward the heated side of the living space. But keep in mind, rodents can nest in there, it can get moldy, bad to breath in, itchy, and doesn't provide as good value/efficiency as radiant barrier sheets - which wrap around the walls - not in the beams. That way the cold air is trapped out, and the warm air is trapped in the crawl. Since my crawl has a concrete floor I don't have any additional advice on how to tackle the floor other than knowing the barrier foil should drape onto the floor to create a gap free layer.
Old 04-26-02, 11:48 AM
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The barrier that Kevin mentioned is most effective in warmer climates (read: less effective in colder weather- which is what I believe you want to address). Radiant barriers are designed to reflect radiant heat and slow its emittance. Also, It's not commonly used in crawlspaces- especially installed as a perimeter insulation.
Normally, Your floor would be insulated with fiberglass insulation between the floor joists with its air barrier towards the living area (as Kevin also previously mentioned). The fiberglass can be supported in various ways. Wire supports are probably the most common.
If you insulate your floor you must also consider insulating any exposed water pipe and ductwork located in the crawspace (it might also be wise to have the ducts sealed with a mastic paste before insulating them), blocking openings that may allow cold air to pass from the crawl space into the home (don't just rely on the insulation) and ensuring that the crawlspace is adequately ventilated.
A perimeter insulation can be installed against the foundation walls using a fiberglass with an air barrier. Kevin again is correct in saying the barrier should be facing the crawl area and extending the insulation so it lays onto the plastic sheeting. Using this method will move the thermal barrier to the foundation walls, hence you should not have to ventilate the crawlspace and insulate your water pipes and ducts. However, you will be heating the crawlspace.
You may also want to look into having these surfaces insulated with a foam type of insulation such as Icynene.
All of this work may be contingent on accessability.
Good luck.
Old 04-29-02, 08:17 PM
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I had the Radiant Barrier installed in the crawlspace for this past winter. Chicago winters are harsh. My hardwood floors above the crawl felt noticeably warmer compared to when the fiberglass was installed on the ceiling of the crawl (between the beams). I sealed up the crawlspace vents for the winter using a sandwhich of Radiant foil, Foam insulation, Radiant foil. Cut it to size, pluged up vents. In the spring/Summer I will remove that to allow ventilation. However, the moisture in the air outside that finds its way into the crawl wont cause mold to grow inside since mold can't grow on the foil of Radiant Barrier.

I also wrapped my duct works with the radiant barrier as well, but didn't need to wrap the plumbing since it no longer is cold in my crawlspace.

Do the research. Go to or any other search engine and research "Radiant Barrier Insulation." You will then need to decide what's best for you. Speaking from a new homeowner perspective, I am beyond happy. The previous owner had fiberglass "professionally" installed years ago. Since I moved in I found a dead mouse and green mold in several batts of the fiberglass. Plus it compressed in certain areas.

I had a concrete floor poured in with an 8mil vapor barrier under the concrete. I patched any possible aread where the little critters could come in and filled it with steal wool. Used spray foam around pipes leading outside, and through the floor. I use my crawl for major storage and go down there once every two week at least. Huge difference with the radiant barrier vs fiberglass. And no worries about what I'm breathing in down there. Do the research. You'll see.
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