Huge issue with basement insulation (LONG)

I am refinishing a basement and have run into a major issue with insulation and could use guidance from professionals. I am located in Delaware, Climate Zone 4A

My basement looks like this: Block Walls, then a perimeter French Drain along the inside of the wall, then an 8 inch air gap, then 2x3 framing. The basement is 7 feet tall, about 6 feet is below grade.

The basement was previously finished in 1977. They just had that crappy wood paneling nailed to the framing and that was it. No insulation, no anything. In this setup, the basement air felt fine although it did get cold in winter. I decided to remodel.

I tore out the paneling, and then spent about 2 months doing various repairs to the basement. During this time the air all felt just fine. This is an unconditioned space, no HVAC.

I was told by various contractors that when getting ready to put drywall up, I needed to add a moisture barrier to the block walls. So I used 6 mil poly sheeting, cut in 15 foot long lengths and attached them to the top plate of wood above the concrete walls. I overlapped the seams by 24 inches on both sides and did not tape the seams. I ran the sheet all the way down the wall and tucked the bottom into my french drain. I was told this is the correct moisture barrier setup since warm air from the room could contact the cold air by the concrete block walls, which would cause condensation to form, but it would form on the plastic, and then gravity would pull that moisture down the plastic into my french drain and it gets whisked away. After the plastic was up the room still felt just fine.

I then added R-13 faced insulation in the 2x3 framing. THIS is where ALL the problems started. After doing that, the basement started to feel AWFUL, just incredibly stuffy and super sticky and humid. The air felt heavy and even light exertion would result in sweat all over your back and forehead, where it hadn’t before. It was absolutely uninhabitable down there.

I had been running a 50 pint dehumidifier this whole time. So I put 3 digital temperature and hygrometer gauges in various spots around the room, and even though the room felt stuffy, sticky, and gross, bizarrely, all three gauges confirmed the temps in the room were a stable 66-68 degrees and the humidity was a stable 34%-36%. I know those are perfectly fine humidity numbers, but the room felt like walking around in a meat locker, you just got instantly clammy and sticky and the air felt super sticky and stuffy. I tried opening windows, changing the air with a fan, changing dehumidifiers, nothing helped.

So after days and days of having various HVAC techs some by and insulation people come by and scouring the internet and posting all over, I was at my wits end. I then came across this post on this forum by user Marcel Cyr, CMI (Basement vapor barrier - #4 by mcyr) which seemed to describe my layout pretty accurately for the moisture barrier, but said I should have used UNFACED batts.

The oddity of my basement seems to be the 8 inch air gap between the concrete wall and the framing. I read in several places that you should NOT insulate the top of that gap, and the air should be able to flow between the air gap and the room to help that air “dry into the room”. So with that open, air can freely flow into that air gap, which means moisture can flow from the room to behind the insulation easily. And then it seems like it got trapped there because it could not migrate back into the room through the vapor barrier. By using faced batts I was basically collecting and concentrating moisture in between the walls, which in my imagination could have 2 possible ways to make the room feel sticky:

  1. The humid air from between the vapor barriers migrated into the room through the top or access holes, making the living space feel humid

  2. The normal humidity in the air was trapped in the living space since it was basically encircled by a blanket of more humid air along the perimeter of the wall so it could not migrate and flow.

In either case I would think that would register as high humidity on my hygrometer though. But going along this line of thinking, I tore the paper facing off the insulation (turning the faced batts into unfaced batts). I left it overnight and checked in the morning, and in the morning, there was definitely a change. In short, the stuffiness seems to be gone/greatly diminished. The room feels cooler and more “airy” if that makes sense. The feeling of “heavy air” is gone. But, the stickiness is still there, I think it feels a little less intense. It is hard to tell as this is all subjective. My hygrometers all show the same readings, which seemed odd, the only difference is the temperature uniformly dropped by 1 degree to a steady 63 vs 64 across the room.

As an experiment I put one of the hygrometers back in the 8 inch air gap, and surprise surprise, it went up 10% to 45% vs 35% in the rest of the space. So it seems like I found the mystery humidity, it was building up in the air gap, creating an envelope of humid air around the room. That seems to have prevented the normal course of air flow around the room, creating a “bubble” of stale air in the living space surrounded buy warmer, more humid air.

That also means that the insulation was up, with the vapor barrier, for 8 days and building up humidity in the air gap between the insulation and moisture barrier. I would think that now needs to dry out. In order to promote the drying out process, I pulled the top 1/2 of the insulation out of the stud cavities around the room, and the room INSTANTLY felt MUCH better. So I know taking the insulation out will solve the issue. I’m going to keep the insulation hanging down like that for a while, with the fan running to mix up all the air, and the dehumidifier running (with the windows closed) to get that excess moisture out of the air, and see how that feels.

If it feels good I will pop the insulation back in and see what that does, hopefully without the vapor barrier there will not be a humidity buildup in that air gap. If it still feels good I will proceed to drywall, if it gets humid again then it seems basement walls with air gaps simply don’t work with insulation, I will trash it all and just drywall with no insulation.

So, after all that, my questions:

  1. If there is an air gap between the foundation walls and the framing, is it correct to have a moisture barrier hanging over the walls tucked into the French Drain, then the air gap, then unfaced insulation in the framing?

  2. If so, why is the stickiness feeling persisting with the (now unfaced) insulation in place? Do I just need to let the insulation air dry for a few days to release any trapped humidity? The insulation does not feel damp or wet at all (nor does the concrete wall or moisture barrier for that matter everything feels bone dry except my skin when I am down there)

  3. If after a few days of drying I put the insulation back up and the room still feels fine, then would a Concrete Block → Moisture barrier → Air gap → unfaced insulation → drywall setup is OK?

  4. If the unfaced insulaiotn does work and I need to put it back in place, I need something to help hold it in place and prevent it from falling into the 8 inch air gap. Previously the paper facing was stapled up an thats what help it in place. Can I use those metal insulation supports to keep the insulation from “falling into” the wall? Being 2x3 construction I don;t have the full surface area of a 2x4 to friction fit the insulation into.

  5. If putting the unfaced insulation back up recreates the problem, WTF is going on?

  6. With the insulation out of the framing the room feels fine again, if I cannot get any sort of insulation working, is it OK to just drywall over the framing and leave it uninsulated? I will be using the moisture resistant purple board drywall, and the room has no moisture problems. If I do that, should I keep or remove the poly moisture barrier?

I stopped reading at this point.

Did any of those repairs include repairing the foundations walls ON THE EXTERIOR??

You can throw all the money in the world at the problem, but if you never make the correct repairs, you will never solve the problems you are trying to avoid!


I stopped reading at this point.

Did any of those repairs include repairing the foundations walls ON THE EXTERIOR ??

You can throw all the money in the world at the problem, but if you never make the correct repairs, you will never solve the problems you are trying to avoid!

The foundation walls did not require any repairs. The “repairs” I did (which weren’t really fixing broken things but more enhancements) were interior upgrades, installing a new 20 Amp circuit to power all the of the outlets in the room (they had just tapped into an existing 15 amp circuit and it would not have run what I want to run down there), adding framing around the windows, in a new closet, and around the main support beam and HVAC trunks (the previous job took a lot of shortcuts with the framing, for the windows and closet they just shoved paneling in place and for the HVAC and support beam they dropped the ceiling super low to cover it up and it was a head banger), and framing out openings for access panels so plumbing cleanouts could be reached once the drywall was in (they had just paneled them up so they were inaccessible)

None of that work had anything to do with the insulation or the issues I ran into. I just mentioned that work to show I was down there for 2 months daily with no insulation or walls in place and the air quality was fine.

1 Like

And you know this HOW??

And you know this HOW ??

Observation? I’m not sure what you are saying here. Walls as is, no insulation, everything fine. Walls as is, insulation, problem The walls are not problem, the insulation is.

What you have described in your post is a much debated topic, how to properly insulate basement walls. What most people can agree on though, is that spray foam applied directly to the interior foundation, from floor to top of rim joist, is the method that creates the least amount of problems.


What you have described in your post is a much debated topic, how to properly insulate basement walls.

It seems the confusing point is the air gap. If the air gap was not there, then it seems to be a consensus to use R10 Foam boards directly against the concrete block and the stud walls directly against the foam and done.

However, since I have an 8 inch gap between the concrete and the framing, that seems to be a different situation. I’m actually wondering is I need any insulation at all at this point. Here is my thought:

I would think the 8 inch air gap would give it plenty of space for any moisture to dry into. The top of the wall is open to the room, so there is air movement on both sides of the wall. So there is ample opportunity for any moisture to dry.

If any water got through the wall (it never has but never say never), it would either run down the wall and into the drain, or just evaporate into the air that is exchanged with the room itself due to the top of the wall being open to the room.

Similarly, if any warm air hit the cold concrete and condensed, gravity would either pull it down the wall, or it would evaporate into the air gap.

So is a moisture barrier even needed? And, since the wall is open on top and air can travel back and forth, is there a point to insulating at all? I tested with my digital thermometer and hygrometer and the temp behind the wall in the air gap and the temp in the room are the same, so obviously the insulation isn’t really doing anything.

What I’m saying here is, you’ve stated that you have an interior perimeter french drain system in the basement. (A huge RED FLAG to professional inspectors who not only look at obvious defects, but at the clues that point to issues that are conducive to material defects). Those type systems are typically installed because water is entering the basement through cracks/damages in the walls, ON THE EXTERIOR of the walls! They are a band-aid at best. Unless you have actively investigated the sub-grade areas of the exterior foundation walls, you have no clue as to their actual condition.

With that being said, I’m done here. I’ve given too much time to a non-person already. What are you afraid of that you have to use a non-name? Not exactly exhibiting any degree of trust, but you expect us to tell you how to fix your perceived problems. Hire a foundation professional and quit wasting peoples time.


It as installed when the house was built. After I demo’d i had a professional waterproofing company inspect my walls and grading outside and used his water sensor thing and he said I had no water issues. Again, I don’t have water issues, so why are you fixated on water issues?

And “investigate the sub grade exterior of the walls”? Yeah, let me go get my backhoe and start excavating around my house. That’s certainly an appropriate course of action.

With that being said, I’m done here. I’ve given too much time to a non-person already. What are you afraid of that you have to use a non-name? Not exactly exhibiting any degree of trust, but you expect us to tell you how to fix your perceived problems. Hire a foundation professional and quit wasting peoples time.

If you think that is an appropriate way to talk to someone, you should look into a new job, preferably one where you do not have to interact with other people. If you think ranting, raving, and insulting a homeowner is appropriate behavior for a home inspector, you are a disgrace to your profession.

I’ll be sure to go to Google and leave a review for your website ( and link them to this thread so they can be aware what kind of narcissistic, arrogant, aggressive “inspector” they are thinking of hiring and make sure they go somewhere else.

I would say no. The insulation is not doing much of anything for you in this case, except stifling air movement.

1 Like

To the OP
This forum is for home inspectors to share information. It is not a help forum for DIY folks to get free advise. Consult with a foundation contractor, as has been suggested.

I really cant understand how your post even made it to this forum!


I did check the temps and the temp in the basement, and the temp behind the wall are the same. So I think I agree with you. If the temp’s are the same on both sides of the insulation obviously the insulation isn’t doing anything.

What are your thoughts on keeping/removing the moisture barrier?

I posted here because there were other threads that homeowners had posted and got feedback from home inspectors. I thought this might be a community where folks could come to get advice from knowledgeable people.

In my opinion, it too would not be useful and would only serve to limit air movement.

In my opinion, it too would not be useful and would only serve to limit air movement.

Thanks, can you give an explanation of why you think that/your thought process?

I am leaning in that direction because when the basement was originally finished it had nothing behind the walls and it was fine for 44 years. All of the framing looks like it was installed yesterday, there is no water damage, no mold, no problems of any sort.

I wanted to add insulation since in the winter it gets cold (in the summer it feels fine)

The purpose of insulating the foundation is to keep the interior foundation surface warm. A cold foundation surface will transfer heat out of the room. Insulation placed 8" off the surface and open at the top will not keep the foundation surface warm and is therefore not useful. Putting a vapor barrier on the foundation surface in this scenario does nothing to warm the surface and may actually harm your foundation over time. If you want to insulate your foundation, my recommendation is spray foam as I mentioned above, or foam board is next best, but be meticulous about sealing all air gaps.

So the reason I was told to put the plastic up (they were careful to call it a moisture barrier, not a vapor barrier) was so if any condensation occurred due to dissimilar temperatures, it would form on the plastic and gravity would pull it into the french drain, preventing the moisture from building up and causing mold risk. Would you agree with that?

Also, despite the temperature being the same in the room and in the air gap, the humidity in the air gap (at least the bottom of the air gap) is a good 10% higher than in the room. What would cause that if air can move freely on both sides of the wall?

I did look into Sprayfoam and Extruded foam boards but both exceeded my budget so I am not considering them.

Thank you for the feedback, responses from folks like you was exactly what I was hoping to find, it is much appreciated.

Some of us know who you are.
Keep your promised threat & it will cost you plenty.

Keep your promised threat & it will cost you plenty.

What is wrong with you??

This message is to our fellow inspectors. This person (the OP) needs to look for a DIY advise forum. Not this forum. Ignore him!!! Please!
I mentioned this before… Why is this post here?