DIY Question for insulating a crawl space

[cabaiguan juan]

So I'm smoking a DC Lancero and doing a search for how to install insulation in the exposed crawlspace of an addition which was put on the house i bought. The previous owner had a office built onto the house, but did not insulate below the addition (inbetween the floor joists under the addition). My thought was to install batt insulation with a paper vabor barrier backing with the paper backing on the down/exposed side (stapled to the bottom of the joists) and then screwing PT plywood to the bottom of the joists as protection. The thought being that the moisture would come from below the crawl space upward to the bottom side of the addition. The paper would prevent the moisture from entering the addition from below. As i mentioned, the crawl space is exposed to the outside. However, in doing a search on the many DIY websites, most say that the insulation should face the inside to prevent moisture from inside the room to coming in contact with the insulation. I'm not sure that this applies in this case. I also read that you dont want to sandwich the insulation on both sides with vabor barrier since it would trap moisture inside the insulation which would degade the effectiveness of the insulation and potentually cause mold issues. Has any one run into this sort of situation on their own or have any idea which way i go- vabor barrier up of down?

 

[b.dawgson]

2" thick insulation foam is between my floor joists. Would be simple I think..

 

[jnknzz]

In my crawlspace, the vapor barrier is facing down. Otherwise, the moisture in the crawlspace will saturate the insulation, causing it to fall down. But, we had a vapor barrier installed over the exposed dirt and installed a dehumidifier (linky). Now our crawlspace is as dry as can be, so it doens't really matter about the insulation vapor barrier.

I'm no expert...YMMV.


Derek

 

[MoeCizlak]

Human bodies in the crawl space. There is no better insulation.

 

[cabaiguan juan]

In my crawlspace, the vapor barrier is facing down. Otherwise, the moisture in the crawlspace will saturate the insulation, causing it to fall down. But, we had a vapor barrier installed over the exposed dirt and installed a dehumidifier (linky). Now our crawlspace is as dry as can be, so it doens't really matter about the insulation vapor barrier.

I'm no expert...YMMV.


Derek

Ok, but if you were an expert, you go paper face down, right?

Human bodies in the crawl space. There is no better insulation.

true, but i dont live in Jersey.

 

[mmburtch]

The kraft is not a vapor barrier, it is intended to be on the side up against the sheetrock. Plastic sheeting is the vapor barrier you are looking for. If you are going to cover it with some sort of board, skip the kraft faced insulation. Actually, skip it anyway. You can't leave the paper side exposed due to fire codes. Use a thicker sheeting, animal proof the crawlspace and skip the wood as well.

 

[chris28054]

The paper side goes towards the floor. I know it seems odd but thats how it's installed in the crawlspace.

 

[cabaiguan juan]

The kraft is not a vapor barrier, it is intended to be on the side up against the sheetrock. Plastic sheeting is the vapor barrier you are looking for. If you are going to cover it with some sort of board, skip the kraft faced insulation. Actually, skip it anyway. You can't leave the paper side exposed due to fire codes. Use a thicker sheeting, animal proof the crawlspace and skip the wood as well.

So what would you use for insulation then? Batt? Rigid Foam boards?

 

[Breedy]

Unfaced insulation with plastic as vapor barrier.

Or you could go the same route with the plastic vapor barrier stapled to the joist and use loose fiber glass attic insulation and blow it into the space you created. Often times your local home improvement center will give you a free rental of the blowing machine if you purchase X amount of bags. Using a blower will probably require a help, but is easy.