What the heck is this moisture under my hearth pad?!?!

[begreen]

FWIW, we have a dehumidifier in the greenhouse in the winter set to 70% humidity. It never runs continuously, it cycles. It runs in 35º temps without issue. The main issue is that the reservoir needs to be emptied regularly or there needs to be a low drain nearby.

 

[KennyK]

2018 New England Winter Nor'easter Number Three today, this time complete with blizzard and an expected 15 to 20 inches in Boston, is giving me some time to further investigate and experiment. I went into the basement and pulled out some of the pink insulation in the joist bays of the ceiling below the hearth pad. There is no sign of moisture as far as I could tell, neither on the bottom of the sub floor nor on the insulation where it meets the ceiling (nor anywhere else around the area). I did, however, notice that the ceiling under the hearth pad was warm to touch. My heat gun gave me readings of between 92 and 97F of that area of the ceiling of the basement/bottom of subfloor underneath the first floor, and that was a minute or so after removing the insulation. For comparison, I tested two other areas below the same room but not under the hearth pad and ten or so feet further from the stove. Those readings of the basement ceiling/bottom of subfloor to first floor were 53 and 57F. So, not sure if that plays into this situation at all, but does seem like a good amount of heat is getting through the hearth pad. Is that normal? I also tested a bunch of objects in the basement with the heat gun and everything was in the mid to low 40s with a temp of 29 outside, so while I still need a thermometer for the basement, seems like no worry for pipes at least with this outside temp.

I also used my heat gun on the hearth pad itself and found that the top of the pad closest to the stove is between 116 and 120F, and further from the stove it is between 91 and 101F. The bottom of the hearth pad was between 91 and 106F, which was warmer than I expected. Is that reason for concern and/or a sign that this isn't a great hearth pad?

Finally, to the experiment... Once again there is liquid built up underneath the hearth pad, more on one side than the other. I cleaned it up and lined the bottom of the hearth pad with aluminum foil, sealing the seam between the two pieces of foil with duct tape. My theory is that if the part of the aluminum foil facing the hearth pad becomes wet, then the problem is coming from the hearth pad itself. If instead it becomes wet between the aluminum foil and the floor, then it's something to do with the humidity coming up from the basement. Does this make sense and seem like a solid experiment? I'm no scientist here!

 

[begreen]

Normal temp. A lot of heat is radiated out the front of the stove.

 

[KennyK]

Normal temp. A lot of heat is radiated out the front of the stove.

Both normal for top and bottom of hearth pad and for basement ceiling/bottom of subfloor underneath hearth pad?

 

[sportbikerider78]

My theory is that if the part of the aluminum foil facing the hearth pad becomes wet, then the problem is coming from the hearth pad itself. If instead it becomes wet between the aluminum foil and the floor, then it's something to do with the humidity coming up from the basement. Does this make sense and seem like a solid experiment? I'm no scientist here!

A better test would be just to duct tape some plastic to the floor and see if any moisture builds under it. Use plastic wrap so you can see what's going on.

 

[peakbagger]

I thought of that but wanted to simulate a bit of insulation on top of the vapor barrier

 

[coutufr]

I do not think the water is coming from the air. Can you please remove the mineral wool present under the floor where the water is? Maybe there is a cold water pipe that has some weird condensation on it or something.

 

[KennyK]

I do not think the water is coming from the air. Can you please remove the mineral wool present under the floor where the water is? Maybe there is a cold water pipe that has some weird condensation on it or something.

Not sure if it makes a difference, but it's not mineral wool insulation, rather fiberglass. In any case, there are no water pipes or any other pipes anywhere near the area where the hearth is. I'm going to give an update shortly about my experiment, as I think I'm onto something, but want to give it another day or so to make sure.

 

[coutufr]

Very interesting I am looking forward to your findings!

 

[KennyK]

It may have sat outside and soaked up moisture. Elevate it so that air can get below it and see if the stove heat will eventually dry it out.

I'm still going with the hearth pad sat outdoors theory.

Ding, ding, ding, ding, ding! Begreen, the other day I saw you wrote on a thread that everyone around here busts your chops. Well, gotta hand it to ya', you do know a thing or two - I guess that's why they keep you around!

My experiment was successful and Begreen was correct all along, the moisture is definitely coming from the hearth pad. After letting the hearth pad sit with the bottom covered in aluminum foil for the past two and half days, I just checked and here below are pics of what I saw. The floor, which has now had an aluminum foil barrier between it and the hearth pad, was totally dry (first pic). The top of the aluminum foil that was up against the hearth pad was totally wet with droplets of water (second pic). So, great news over all - no major moisture issues in my home (at least not to this level)! The bummer is I really liked the look of this hearth extension pad and I'm not sure what to do. I'll keep the bottom covered with foil for now to protect my floor, and I guess I can try to dry it out over time, but not sure I want to use it long term. I may also take off the black slate on top and use on a DYI hearth extension pad. I'm open to any ideas! Thanks everyone for all the thoughts - I learned some good things about moisture in a home along the way that I'm sure are still applicable!

 

[KindredSpiritzz]

I'd think the heat from the stove would of cooked that moisture out in no time, my floors sure get toasty around the stove. Gotta hand it to Begreen, he knows his poop.

 

[begreen]

Moisture in the insulation is trapped and can't evaporate naturally because of the tile barrier. Heat forces it to evaporate out the bottom which then condenses on the cooler surface of the floor. Throughout the summer take it outdoors on sunny, low humidity days and place it upside down, in the sun, on some 2x4's. Maybe by fall it will have dried out. Or at least leave it indoors upside down until next fall.