We are finishing our basement and our contractor suggested NOT to insulate our basement. The architect suggested we use R13 faced batt insulation so that a vapor barrier is not required. he suggested that the insulation be attached to the studs.

Suggestions please.
Thanks!

 

Well, your architect and your contractor need a bit of a tune up. First, have you had ANY moisture issues. If none, then I prefer rigid insulation strapped to the wall and finished as desired. "No vapor barrier" will allow the foundation to dry to the inside below grade and either direction above grade. Air seal the rim joist and insulate that area as desired. Here is a link for some reading.
http://www.eere.energy.gov/buildings...s/db/35017.pdf

Are you in north NJ (Pennsylvania conditions) or south NJ (the desert).

Fiberglass can be used, but not in contact with the walls and omit any VB. The most important area is the above grade down to one foot below grade. Unless you have hollow blocks, then you need to insulate all the way down.

GL
Bud

 

I agree more with Bud. Two inches of rigid EPS foam does more to insulate and produce a moistue barrier than anything else you can do. Owens-Corning has a (pink) foam with notches for furring strips. Screw the furring strips thru the foam into the foundation, and install drywall to the furring strips.

 

We do not get any water through the walls but we definitely get moisture. Some of the paint is peeling off of the concrete walls. I am concerned that the moisure will generate mold.

Our house is unique in that we have no joists. The ceiling of the basement is huge slabs of pre-fab concrete one next to the other.

Does your suggestion still hold? We are located in Northern NJ (Bergen County).

Thanks.

 

I have searched extensively for posts on FG insulation against block and this is the closest I've gotten. I need to know one thing but let me sum up my plan first.

I have hollow block with 60% of block at one foot below grade. To me this means full fiberglass insulation. After reading many, many posts and government articles, I am firm on no VB. And no paper face on the fiberglass. I don't want to use rigid foam because it's too expensive (unless spray foam is cheaper).

My question is: with no VB, and I don't want one, and no paper face. Even though the fiberglass can be "friction fit", is this "friction fit" my only insurance that the fiberglass will not "fall" or "lean", if you will, onto the block? And also I am stuck with a "convection air gap" between the insulation and block.

Once again, a double problem: How to install raw fiberglass (unfaced) AND be certain it won't ever touch the block?

 

I don't know if this is an illegal action, but I'm just lobbying to get my post read. Just posting this should answer my own question. I spent a lot of time typing it and wonder why it never even made it to the first page of "new posts". I wander if it's because it's a "quoted reply" instead of just a "reply".

 

Hi Mr O
old threads will sometimes get ignored, but I have just been busy. "Bump" with an explanation is the approach when your post hasn't been replied to and you want to kick it to the top.

Let me say, insulating and finishing a basement is one of the most frequent improvements made in a home and probably the one most frequently done wrong. It has only been in recent years with the new techniques applied during construction that I have had the pleasure of entering a finished basement and it did not smell like a basement.

That said, let's proceed. No vapor barrier, I agree. Using fiberglass, I don't totally agree. All depends upon your moisture issues. Holding it in place, yoi could use the kraft faced and cut out diamond holes to be sure it is not a vb. I would still like to see something behind it, even if just tyvek.

That convection gap is an issue. If you have moisture evaporating from below and circulating up to where the blocks are cold, you can have condensation. If you try to circulate basement air through there it gets worse. If the space is open to the basement it can become a nesting area for critters. The building science articles pretty much conclude that rigid up against the block walls is the best, and I agree. Build it out with 2x4's if you want space for electric and additional insulation, even fg.

Bud

 

I agree rigid foam board is the best.

That said, no gap behind insulation, no poly, sill sealer under p.t. plate for thermal/capillary break, air seal the drywall (ADA), water seal the exterior concrete wall, run downspouts 10' away, control indoor humidity, and air seal the rim joists. MYTH: LEAVE AN AIR SPACE BEHIND THE INSULATION IN THE BASEMENT TO AVOID CONDENSATION.
Pressure-Treated Sill Plates and the Building Code | GreenBuildingAdvisor.com

Info-401: Air Barriers
Info-408: Critical Seal (Spray Foam at Rim Joist) — Building Science Information

You probably have not read these three;1. http://www.swinter.com/services/docu...Insulation.pdf
2. http://www.buildingscience.com/docum...ent-insulation
3. The "biggest Loser" In Fiberglass Insulation.... - How To Guides - DIY Chatroom - DIY Home Improvement Forum

Gary

 

I appreciate the explanation and the time you spend helping me and others. Thank you very much.

I am familiar with "cutting" the VB to ventilate. I guess I would have to spend the little extra money to make sure the insulation is installed properly.

If you care to check my other posts/threads, you will see more about my basement. Here is a summary: house built in 1930's; full interior perimeter french drain with 2 sumps; zero moisture on walls; humidity stays at 55% all summer with a dehumidifier; runoff water is most likely the main source; 60% of walls are one foot below freeze/thaw; I'm in zone 5.

Big question now: Whats cheaper than "pink rigid insulation"? There must be a less expensive alternative; sprayed on insulation?, or even expandable polystyrene (the coffee cup material), OR could you tell me what is the thinnest acceptable pink rigid I can use for basement. Do I have to use $27.00 sheets of pink stuff, totaling, I think, $900 for my outside walls. I do want to do it the best way but am almost desperate for an alternative. Fiberglass for the same SF costs me $213.

You have pretty much convinced me that there should be no "convection gap"... Oh and I think I will skip the fiberglass if I am paying for the rigid, probably, unless I want the extra r-value which would be nice.

 

The foam boards cost about 50 cents per board foot. Spray foam is going to run you at least $1 per board foot.

 

"Water sealing" the exterior wall is the killer. There goes 20 grand out the window. Or rent a backhoe.
Has anyone here "done this themselves"?

 

Unless you have the finger action of a brain surgeon, hire the excavation. One short circuit between the brain and the wrong finger will send the bucket into the foundation and crack it. Pros do it like playing a piano, and it looks simple. Years of experience.

 

Thanks chandler, I like the way you put that. You really put me in my place. Now I wonder has anyone ever dug a 900SF house by hand?

 

I just spent 5 grand for an interior french drain which is working great. The cellar humidity level went from 90%+ to a constant 55% with the dehumidifier on. Before the drain, if laundry (clean) laid on floor for one day it would pick up a mildew smell. Everything that would absorb the mildew smell in the cellar had to be thrown away. Now everything is nice and dry, even the walls.

Now the dryness of the basement seems to have made us forget about how unusable and smelly it was before the drain, now we want to take it to the next level and make it a finished basement. But we can't.

We are told by experts on the forum and government articles on correct basement finishing procedures that we should now go outside (to me this is only insurance) and spend a ton of money to make sure our walls stay dry by sealing the walls.

I'm thinking the insurance costs 20 grand to dig the perimeter of the house; the finishing costs 1 to 2 grand in materials. Get a mold detector and rebuid if it ever goes off. My phone battery is running out , I have to go.

Is there anyone with a clean smelling, finished basement with 2 inch rigid foam glued to the walls (as part of their system) with unsealed exterior wall and an interior french drain(only) for insurance?

Please no other responders. If I get none, I will have to post a title that better attracts the friend I am looking for on the forums.

 

So what you are looking to do is dismiss scientific research and try to find at least one person that will tell you what you want to hear? Am I understanding this correctly?

 

drooplug -

I agree since the "look for someone that agrees" is counterproductive.

Unfortunately, the poster did not realize the the interior drains already in place reduced/eliminated the excess moisture under the slab and around the foundation. I guess that goes hand-in-hand with the strange concept of "R-value" maximization.

In many situations a interior drain is superior to an exterior drain and is not just "insurance" especially since it has improved everything and it is not details. - Been around basements for 40 years it still always amazes me.

Dick

 

It's still scientific.

Science (from the Latin scientia, meaning "knowledge") is an enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the world.[1][2][3][4] An older meaning still in use today is that of Aristotle, for whom scientific knowledge was a body of reliable knowledge that can be logically and rationally explained (see "History and etymology" section below).[5].

This is the wikipedia definition. I like the "testable explanation" part. Some people want to learn from their mistakes. I don't want to "dismiss scientific research" but maybe just test it a little. Or maybe I am slightly ignorant.

Some of the explanations for the research I am having trouble with; one that is sinking in that the next poster mentioned is the important relation between r-value and moisture levels including humidity. I apologize if I came off a little too skeptical. I can be - not much fun, a little bit dumb, and a whole lot mental= fun-da-mental lol.

I tend to not understand things without a dialogue. Unfortunately, it comes off as argumentative.


So, now, more dialogue anyone? Time for confession. Point in hand, after the french drain was installed, a control was established. Everything dried up, to a degree - no liquid, except the A/C condenser was sweating enough to cause black mold, efforescence, and stuff to show up on inside of basement wall. I deverted it but it makes me realize how vulnerable the interior structure would be to mainly the m word -MOLD.

So now I'm beginning to realize the importance of sealing the outside of the wall. I think I'm just going to have to do the basement one room at a time, digging up the exterior as I go. I simply can't afford to do the whole basement at once, not in the budget.

 

Droo, I do realize the moisture is reduced; I put in the int. french drain, ten(10) years after I moved in. But what is your position on the exterior?

Also, I was suggesting the exterior drain is the insurance, not the interior drain.

Now, I wonder how much would sealing the exterior wall decrease interior humidity, while consequently increasing interior r-value?

 

It is obvious - just sealing the interior wall does not provide any additional insulation, but it can reduce the moisture and make the HVAC system many times more efficient.

The R-value concept is a bit of a convenient advertising gimmick and is not a concept used blindly by people that understand the real thermodynamics.

The gap between the basement wall system and the interior living space is really worthless (as referenced by GBR earlier) because the gap air is the same temperature (or close to) the living space temperature and the important thing to remember is the definition of the effective R-value is based on the temperature differential between the difference between the 2 sides of the material over a very short term and can be meaningless or almost zero.

Obviously, with a 900 sf area as a living space it will be climate controlled to control air flow, humidity and temperature and this allows true control of the lower living level and benefit from the long term thermal inertia of the surrounding soil and provide air control (temperature and humidity).

The thermal inertia concept is not that common in the U.S. because it does not lend itself to simplistic advertising and tests (long term cycles) are very costly. Generally, the concept term is a dynamic hot box with programmed thermal cycles over a long period of time). Every insulation manufacturer has run these tests privately at the facilities capable of testing it, but they own the results and they control who sees them. Internationally, the concept is widely understood and implemented. When I showed a group of 15 Russian engineers our typical residential construction they were very polite and then explained what they thought they were seeing and the problems.

Dick

 

Sorry, I meant the condensation that drips from the air conditioner OUTSIDE the house was leeching, if you will, down through the outside earth, through the block foundation wall, and ending up on the inside of basement wall showing up as mold and efforesence.

 

Concretemasonry,
But I was talking about the outside of the foundation wall. And how this will ultimately prevent chance production of mold of the interior insulation system, specifically between the rigid and the block. Pleas read prior posts.