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gregsenne 10-10-2012 10:39 AM

Vented crawl space insulation
My crawl space is vented, but it has R10 blanket insulation hung against the block.
Is the insulation serving any purpose, since the crawl space is vented?
My tile floors above the crawl space are FREEZING in the winter.
And I close my vents in the winter and open them in the summer (thats what my builder told me to do).


joecaption 10-10-2012 10:42 AM

Is there any insulation in the floor joist bays?
Are the heating ducts insulated?

gregsenne 10-10-2012 10:44 AM

no and no

gregsenne 10-10-2012 10:45 AM

i remember asking my builder, why insulate the walls if there is a vent on the wall, and he said it keeps the wall from sweating.
But my builder was a complete idiot, too.

joecaption 10-10-2012 10:50 AM

You need to go back and add your location in your profile for the best ansewers as to how and what to use for insulation under that floor.
One thing that needs to be done before any insulation is to air seal any holes though the bottom plates or subflooring with expanding foam.
Is there at least a 6 mil. vaper barrier on the ground?

gregsenne 10-10-2012 10:54 AM

Ok, I updated my location on my profile. I'm in Southern Ohio.

All holes in the subfloor are sealed with the orange fire-block expanding foam. The floor of the crawl space has vapor barrier on the floor and then a bunch of gravel on top of that. There is also R49 (i believe) insulation stuffed in the floor joists just around the outside of the house. The bottom plate of the house's walls also have that blue styrofoam stuff that comes on a roll between the cinder block and bottom plate.

The crawl space stays very dry.

donavan 10-10-2012 01:14 PM

I actually am in a very similar situation as gregsenne except I bought my house that way and if I knew who my builder was I would beat him with his tools. I had been wondering about a number of different insulation option and came across the some stuff that I thought might work great for for my situation and might not break the bank either. Its called Reflectix its basically bubble wrap coated in mylar. it claims up to an R-21 insulation value and also acts as a vapor barrier. I have no experience with any of this but was wondering if this sort of thing would be a good option in both my and Gregsenne's cases. If you dont know what Im talking about look here

gregsenne 10-10-2012 02:01 PM

My builder cut every corner possible to put a buck in his pocket. i think I have the insulation there because code required insulation. It didn't matter to him whether or not it did anything, as long as it passed an inspection and was cheap.

I was thinking of blocking off my vents, and leaving the blanket insulation on the walls. I just dont know enough about this topic, and have done lots of reading, but still don't know what I should do!
To me, it would make more sense if the crawl space was not vented (I wouldn't notice the temp differences on the floor above the crawl space, wouldn't worry about freezing lines, insulating ductwork, etc). I just don't want to create a problem of the crawl space not being able to breathe. I don't honestly know if it has to. I do not have a moisture problem, at all.

donavan 10-10-2012 02:43 PM

Im pretty much of the same mind set. My crawl space is open the to the basement via and old windows so I don't know if there would be enough air flow from that to close off the vent or not. I luckily haven't had any issues with busted waterlines but I do know that the floor in my bathroom is ice cold in the winter so I need to get something going before it gets too cold.

gregsenne 10-10-2012 02:56 PM

My crawl space is not open to the rest of the basement; there is a small access door from the basement, but it is sealed and insulated. If I covered up my two outside vents, there would be NO ventilation in my crawl space.

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