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homebild

08:38PM | 08/06/04
Member Since: 01/28/03
694 lifetime posts
"I don't know if you misunderstood either, but a plastic sheet against the inside of a concrete wall is the least correct way to keep moisture from leaking into a basement through a block or concrete wall."

Again, based upon Piffin's reply he is worng and demonstrates he has little understanding of basement water/moisture problems and how to correct them no offense.

A plastic sheet on the inside of a basement masonry wall is one of the BEST ways to not only control liquid water fron entering a basement living space but also one of the best ways to channel water below the basement slab so long as the sheeting can be placed below the slab before pouring.

All due respect to Piffin but I see his basement vapor barrier information as "all wet" and he has yet to demonstrate anything differently or correctly.

Domino

07:27PM | 08/07/04
Member Since: 07/30/04
2 lifetime posts
Vapor barriers or vapor retarders are incapable of allowing foundation walls to dry to the interior. This is an issue. Simply leaving off interior vapor barriers and vapor retarders will not work due to the issues associated with interior vapor diffusion. Additionally, these two methods are incapable of being constructed in an airtight manner using typical production trades and materials and therefore are unable to address the air leakage wetting mechanism. The problems with these two common approaches to interior basement insulation manifest themselves in mold, decay and odors. Approaches to basement construction must not result in mold, decay and odors. The experience acquired by the Building Science Consortium has been reflected in changes that have been made to the Builder’s Guide Cold Climate (Lstiburek, 2001) as well as those for Builder’s Guide Hot-Dry & Mixed-Dry Climate (Lstiburek,2000) and Builder’s Guide Mixed-Humid Climate (Lstiburek,2001).

****** ALL ****** recommended basement interior insulation strategies involve placement of a layer of rigid foam insulation against the foundation wall.

The moisture sensitive interior wood framing and paper faced gypsum board are no longer in contact with the major moisture source – the concrete or masonry foundation wall such as can occur with water trapped behind POLYETHYLENE installed directly against foundation wall.

Moisture dynamics must be considered in detail before insulating a basement wall. Materials used to insulate a basement wall must be selected based on their ability to control the flow of moisture and air as well as heat. Selecting the wrong type of insulation or placing it in the wrong wall assembly often leads to moisture accumulation with subsequent material deterioration and growth of mold. A damp or wet basement that is improperly insulated will lead to deterioration of the building and promote conditions that worsen indoor air quality. A basement wall will remain dry only if it is built to handle all the different ways in which water can move into and through basement walls. Since walls will at times get wet in spite of good design and construction, BASEMENT WALLS MUST ALSO BE ABLE TO DRY. Drying typically means TOWARDS THE INTERIOR.

Basement walls can be wetted by liquid water (bulk flow and capillary suction) and water vapor. However, once materials become wet, they can typically dry only by the removal of water vapor either by evaporation or diffusion. Evaporation requires energy but insulation decreases the flow of energy. Insulated walls cannot dry as easily as uninsulated walls.

The rate at which water vapor moves through materials is “permeability”. Individual water molecules can move easily through permeable materials even if the materials do not permit air flow through them. Other materials are said to be semi-permeable to water vapor because they permit the passage of water molecules at a much slower rate. Materials that allow very little water vapor to pass through them are classified as impermeable. Air transport of water vapor requires an air pressure differenceas well as a pathway or opening between the areas of differing air pressure.

******A vapor barrier on the interior would prevent the walls from drying should they ever get wet.******

Insulating only on the interior side of basement walls presents problems because of ground water and the alternating direction of the vapor drive discussed above. The fact that ground temperature at various depths frequently is much colder than either exterior or interior air temperatures means that condensation can occur on the interior surface of the foundation wall. The interior basement insulation and the finished wall assembly are subjected to potentially significant moisture loads from vapor driven from both the exterior and the interior at different times of the year. While the building industry in the United States has become preoccupied in the past decade with vapor diffusion and vapor barriers in building assemblies, the problem of air-transported water vapor is often ignored. This is unfortunate because air-transported moisture is generally much more of a problem than is the diffusion of water vapor. Air transported moisture can quickly lead to deterioration in moisture sensitive materials. The entire consideration of water vapor has been complicated and confused by the fact that some materials can block the flow of air (an air barrier) as well as the flow of vapor (a vapor barrier). Some research in basement insulation systems has attributed moisture accumulation to vapor diffusion when airflow was not controlled. An effective air barrier is required in basement walls.

However, vapor barriers are typically not needed – particularly on the interior of basement assemblies.

The almost indiscriminate use of vapor barriers (polyethylene or vinyl wall coverings) over the past decade has caused many building failures and facilitated the growth of mold in many buildings. The permeability of materials must be considered before placing them in a particular location within a wall assembly. Otherwise water vapor may become trapped within a wall assembly where it can condense when the temperature is low enough. Any interior basement insulation strategy must successfully handle both the internal and external moisture loads. One proposed solution to this dilemma is to install a vapor barrier on both sides of the interior insulation system. The barrier against the foundation wall is often called a moisture barrier. The main problem with a double vapor barrier wall is that it cannot dry to either the inside or the outside should it ever get wet. In addition, it requires a perfect air barrier on the interior to prevent warm interior air from contacting and condensing on the cold foundation wall where it may be trapped. This type of construction should be avoided.

****** The major change in the past 20 years is the realization that a vapor barrier (usually polyethylene) on the interior side of the basement wall assembly inhibits drying of the wall more than it prevents wetting of the wall. *******

In testing walls that dried the fastest were the ones that did not have a moisture barrier against the foundation wall allowing the wall to dry to the exterior. Unfortunately this design would also allow the wall to become wet from the exterior likely causing condensation on the interior vapor barrier.

Many superficially dry walls will not remain dry when they are insulated. Many walls are dry because of “their ability to continuously evaporate soil-sourced liquid water to the inside.”

Basement wall assemblies with an interior vapor barrier can never dry if they become wet.

The widespread use of a double vapor barrier basement wall has resulted in many failures in some cases within one year of construction (Ellringer, 2002). Extruded polystyrene and cavity batt insulation, with and without a vapor barrier, covered by gypsum board were compared with walls having only a thicker layer of extruded polystyrene and an empty frame wall covered with gypsum board. The walls with an interior vapor barrier did not get wet from the interior during the winter but they did trap moisture during the summer when moisture is moving inward.

Without the vapor barrier, the fiberglass batts would remain dry if interior humidity is not excessive during the summer. Such low interior levels of relative humidity during summer conditions typically can only be achieved with active dehumidification provided by air conditioning or a dehumidifier. Walls with 3.5 inches of extruded polystyrene (XPS) and no vapor barrier performed the best. However,walls with 0.75 inches of extruded polystyrene and 3.5 inches offiberglass batt insulation in the cavity would perform well as long as interior humidity was controlled below 50 percent during the summer. Increasing the extruded polystyrene to 1.0 or 1.5 inches would improve performance even with higher interior relative humidity during the summer months. This part of the analysis assumed that the concrete wall had arelative humidity of 100 percent at the exterior temperature.

Any interior basement insulating wall system must have the following properties: It must be able to dry to the interior should it become wet since the below grade portion of the wall will not be able to dry to the exterior during any time of the year. This precludes an interior polyethylene vapor barrier or any impermeable interior wall finishes such as vinyl wall coverings or oil/alkyd/epoxy paint systems. The wall assembly must prevent any significant volume of interior air from reaching the cool foundation wall. Thus it must have an effective interior air barrier or a method of elevating the temperature of potential condensing surfaces(such as rigid insulation installed directly on the interior of concrete or masonry surfaces).Materials in contact with the foundation wall and the concrete slab must be moisture tolerant; that is the materials should not support mold growth or deteriorate if they become wet - some materials may tolerate being wet without blocking the passage of liquid water through the materials. A capillary break must be placed between these materials and moisture sensitive materials.

If a frame wall is placed interior to the rigid insulation, cavity insulation without a vapor barrier or retarder can be installed between the studs.

Wall Insulation with Foam Sheathing Covered with Gypsum Board either expanded or extruded polystyrene insulating sheathing can be attached directly to the foundation wall. Since extruded polystyrene is more moisture tolerant it should be used if there is any question about the effectiveness of the external drainage system. If additional insulation is desired, cavity insulation can be installed in a frame wall built interior to the foam insulationand covered with 0.5 inch gypsum board or other thermal barrier.

Piffin

05:13PM | 08/08/04
Member Since: 11/06/02
1284 lifetime posts
Maybe I can be wrong sometimes, but as the above quotes from Joe's website demonstrate, if I am wrong on this one, the most respected and studied man in this country on this subject is also wrong.

That's life. I can live with it.

Excellence is its own reward!


Anonymous

07:06PM | 08/08/04
We all make mistakes (including me) but I would hardly characterize Lsiturbrek as 'the most respected and studied man in the country' in this matter since his advice conflicts with most all building codes for vapor barriers and proper basement contruction across the US. (maybe Piffin is in Canada?)

But after Domino's great handling of the vapor issues in a basement (with some disagreement) I thought I'd give my 2 cents toward his last response yet again:

First, vapor flow into a basement is from 2 sources:

One is from the wet ground into the basement thru the foundation...

The other is from the living space thru the framed wall toward the foundation.

Without addressing BOTH these directions of vapor flow we are all talking passed one another.

VAPOR FLOW IN THRU THE FOUNDATION:

______________________________

Vapor flow in from the soil, thru the foundation, occurs despite any temperature differentials, because the the soil outside the foundation is always generally "wetter" with more water vapor than the interior of the basement under most all conditions even when the soil vapor temperature is colder.

This means that even despite 'damproofing' of the foundation and basement temperatures being warmer, water vapor migration will be from areas of great concentration to areas of lesser concentration.

So the first major point of vapor transmission worry is at the foundation itself.

Without saying, the very best method(s) to prevent liquid and gaseous water transmission into a basement are from the outside.

Given that in most cases this cannot be done, the next best method is to deal with vapor and liquid water immediately at the foundation wall as soon as it enters the basement.

One acceptable method is to allow the water vapor to enter the foundation unabated and then deal with it from there.

This can be accomplished by the wholly acceptable technique of applying a 6mil polyethylene sheet over the foundation walls SO LONG AS this polyethylene sheet continues below the slab and footer or into a peripheral drain system so that any condensed water will not collect or pool in the basement.

Terminating the poly sheet above the slab does no good, since any vapor from without will only condense on the poly sheet and trickle down in pools on top of the slab.

This is also the drawback of using rigid foam panels directly over the foundation.

While rigid foam panels can decrease the potential for interior warm, moist air migrating outward from reaching colder masonry surfaces and then condensing (and let us not forget that the major proponents of these products are the rigid foam manufacturers themselves)...the use of rigid foam masonry panels alone does not prohibit gaseous water from without migrating inward and does not prevent this vapor from condensing between the foundation on the rigid foam and thus also trickling downward and pooling.

SO THE FIRST AND BEST ORDER OF BUSINESS IS TO ELIMINATE GASEOUS WATER/WATER VAPOR FROM ENTERING THE BASEMENT FROM THE OUTSIDE IN IN THE FIRST PLACE.

Rigid foam cannot accomplish this, but water and vapor proofing coatings on the inside of the foundation can.

By coating the inside surface of the foundation with a vapor and waterproofing paint, you achieve the very BEST of all possible foundation condensation preventions by never allowing outside vapor from collecting in the basement in the first place. A MUCH BETTER SOLUTION THAN USING FOAM PANELS.

You can STILL use foam panels in conjunction with a vapor proof coating, but foam panels should not be used alone.

VAPOR MOVEMENT IN FRAMED WALLS:

_______________________________

Domino gave a very good explanation of how warmer (usually) moisture interior air from the living space will want to migrate out thru any framed walls and why a plastic sheet should NEVER be hung in a framed wall in a basement to prevent this migration.

The fact is, that warm interior air will want to migrate out toward the foundation walls in some situations and yet in other wish to migrate in from the outside in others.

Placing a plastic sheet in a framed wall never makes sense in a basement precisely for those reasons.

And while placement of rigid foam panels directly over the foundation walls will prevent condensation of water flowing outward by 'warming' the foundation surface, using foam panels without also vapor proofing the surface beneath only meets half the problem.

I have no idea where Lstirbrek gets his ideas since they violate all know acceptable building practice and code requirement for basements.

Unless his research affects certain locations it makes no sense for most of the US.

(And I will gladly be proven wrong)

But getting back to and addressing Domino's original question about placing 'fanfold' on the foundation then framing to it....

Unless you also water and vapor proof the foundation beneath the rigid foam beforehand....

AND unless you also install a kraft paper facing in the basement wall studs in front of the foundtaion walls...

AND unless you keep the framing at least an inch or two away from the foundation wall including the rigid foam...

It should not be done and may violate your State's building code.

_________________

As for Piffin, if you think I have handled you or your argument cheaply or worngly and did not offer you a fair shake...I will apologize in advance and still request further correction.

I do not consider this forum an arena by which any of us should disembowel the other for the public's pleasure.

I participate to be educated in as much as I strive to educate and if we all draw blood along the way, so be it.

Please, however, do not take my own personality quirks or disagreements as anything personal.

I'm an emotional, zealous type of guy and not fond of being proven wrong...but equally zealous and emotional for the truth when I am...

Respectfully submitted to Piffin, Domino and anyone else who wanders in...

And if you can enlighten me on Lsturbrek, I'll be glad.

Anonymous

06:25AM | 08/20/04
I'm starting to finish my basement this month and I want to be careful how I proceed. I've been reading through the various arguments posted here relating to vapor control and I've been visiting buildingscience.com's website for about 6 years now and their vapor control advice makes sense. I certainly does not make sense to place a vapor barrier on the warm, moist interior side of a basement wall and trap moisture inside the wall assembly which can enter through the concrete. That much is clear. Anyone thinks this is ok only needs to read the first posting in this thread to see what can happen.

However, it also seems to make sense that I could avoid the process of gluing foam board insulation to my concrete wall (approx 35, 4x8 sheets in my case), by applying 6ml plastic vapor barrier directly to the concrete wall (a fraction of the time and cost), and build the wall assembly to the inside of the plastic with low-cost batt insulation. Further, since my region is considered "cold climate", I am considering building a 2x4 studed wall with 16" centers about 3 inches away from the concrete wall. I could then install 20" R11 batt insulation behind every second wall cavity, overlapping behind each stud. I would then place another 15", batt between the studs, alternating R11 & R20. This would have a similar effect to gluing the foam board behind the wall assembly, but would take far less time & cost to install.

Does this make sense to anyone? Has anyone ever tried this approach? I'm a "layman" when it comes to construction but if you agree with the principles as set out in www.buildingscience.com, you would also agree that this approach might also work as well.

Jeff

BV002019

01:04PM | 09/05/13
I have stud walls installed in my basement about 3 inches from the concrete block exterior walls. I have limited money that I can spend fixing up my basement. What I want to know is can I install drywall over the stud walls without insulating inside the studs? I do know that I probably should put a 6 mil vapor barrier on the stud wall facing the room before I install the drywall is this correct?...thanking you in advance for an answer.....Brad

BV002020

01:07PM | 09/05/13
I have stud walls installed in my basement about 3 inches from the concrete block exterior walls. I have limited money that I can spend fixing up my basement. What I want to know is can I install drywall over the stud walls without insulating inside the studs? I do know that I probably should put a 6 mil vapor barrier on the stud wall facing the room before I install the drywall is this correct?...thanking you in advance for an answer.

BV002840

08:40PM | 12/21/13
Recently purchased house with one wall partially below ground. Wall is concrete and over time enough moisture has found its way through the wall to cause moisture resistant paint to flake off on inside of wall. Should I dig earth from around outside of wall and install some type of moisture shield between concrete wall and dirt?

BV003096

09:45AM | 01/23/14
How do I get the 6 mil plastic to stay up against wall I stapled at top and put liquid nails but when glue dried it released from wall???
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