Hello
We recently purchased a home that was built in 1964 and have been working on improvements. We have a family room that, from what we understand, was originally intended to be a sun room that has been finished. This room is not piped into the heating/cooling in the rest of the house and is heated by a gas fireplace.
There is a crawl space under this room that is dirt and it has a small access panel. There is no insulation underneath the flooring in the crawl space. We pulled up the corner of the carpeting and found that the padding and flooring are moderately wet. We know now that we need to pull the carpeting off the floor and probably insulate the underneath of the flooring. Any advise regarding the type of insulation we should use or anything else regarding this newly found dilemma would be greatly appreciated!

There are a whole lot of things that could be going on here. First off, the wet carpet - could be:

1. Moisture from the gas fireplace. Especially if the room is not vented well a gas fireplace generates a lot of moisture. The thing is, all the carpet should be equally damp. If it's only wet in that one corner, then something else is going on.

2. Moisture from the crawl space. To get to the point that it is making the carpet and pad wet, there will have to be a lot of standing water in the crawl space. Also, there will be evidence of mold on joists and subflooring. Here too, most or all of the carpet will be damp, not just one corner.

3. Exterior siding / window / door leak. This is probably the most likely thing to cause one corner of the carpet to get wet. Check for leaking gutters & downspouts in that area, poorly caulked siding or windows.

4. Random plumbing leak. Possible but less likely. Simply take a look at your water meter. If the meter is turning with all the water off, then you have a leak somewhere.

Moving past the wet carpet and into the crawl space. The area should have foundation vents on at least two sides to give some cross ventilation. There should be a 6 mil thick poly vapor barrier covering the entire dirt surface. If you already have a lot of moisture there or standing water then you may need to add a low-volume fan or even a sump pump system. All this depends on how wet the crawl space is.

Insulation is simply fiberglass batts held between the joists with wire "tiger teeth" hangers. You don't mention what part of the country you are in but most recommend R-19 insulation for floors. Use a faced insulation, with the paper side facing up towards the living space.

Thank you so much for your replies! We live in northeast Ohio and I wasn't clear on the area of wetness. So far, it seems to be along all walls and a good ways into the whole room. We are trying to get by with not pulling up the carpet until spring due to the lack of insulation underneath.

You gave me lots to look into and thank you again! Forgot to mention that the gas fireplace is ventless so I am thinking maybe that is the culprit. Just unsure how to vent at this point.

I'm no expert as Jaybee is so take this for what it's worth. Are there any gutters around this room's roof that might be leaking, given that this is the time of the year when the dreaded ice dams can occur and cause leakage down the exterior walls? In my case the leakages sometimes seep along the floor.

If your fireplace is propane and unvented for every gallon of propane burned, 1.64 pounds of water is produced.

In liquid form that is 25 ounces of water per gallon of propane used.

Just crack a window or by a demumidifier.
Far cheaper then replacing the fireplace and add a vent.

It's sounding like the most likely cause is the ventless fireplace. You'd be amazed as to how much water one of those things can generate. I agree with Joe - a simple dehumidifier could solve your problems.

Since it also sounds like the room is uncomfortably cold, go ahead and take a look at the crawl space. If the crawl is dry, then you can go ahead and install some insulation in the floor without hurting anything - and getting the benefit of warmer floors right away. You don't want to insulate if you suspect the moisture is coming from below without fixing it, but if everything is just moisture from the fireplace then go ahead and insulate.

Wow! Fantastic feedback that is greatly appreciated! Thanks to everyone!
Our ventless fireplace is natural gas and somehow I had no idea that it puts out water! We are picking up a dehumidifier this evening for the room. It is pretty cozy with the fireplace but if we leave our feet on the floor for any length of time they are Popsicles. So pulling the carpet before spring is just not an option and I just hope to be able to save the flooring until then. We are going to attempt to pipe this room into the main heating/cooling this spring. Another cry for help for another day..haha.

Our gutters are a weird type with a cover over them so we are going to have to figure out how to get into them and clean them this spring. We do have tons of icicles hangin from them presently.

The appraiser noted the crawl space as being minimally damp, not enough for readjustment of appraisal. He inspected the house in October and my husband saw no wetness before the snow came. I thought that since it is dirt under there that we should do the thick plastic over it and then insulate?

I would recommend installing a 6 mil vapor barrier and R-19 faced insulation now. You might as well get the benefit of comfort this winter and start getting some payback. R-19 with tiger teeth hangers will cost you just under $1 per square foot. Depending on the area of the crawl space, maybe $25 for the VB.

The sooner you install it the sooner you have a more comfortable room.