basement moisture barrier / insullation / vapor barrier?
I am currently finishing my basement and am CONFUSED - PLEASE HELP!!! I have painted the walls with a waterproof sealer, painted the floors with an epoxy paint and have installed a 10ml plastic sheet from floor to ceiling behind my steel studs on exterior finished walls. Not all of the basement is finished, but it is all painted/sealed. I was going to install encapsulted insulation over the plastic behind my sheetrock (as someone in the home depot told me) and someone else told me to cut the vapor barrier on the insulation before installing. What do you think? I am alson confused on install and what type of installation to install above my ceiling panels for sound proofing, vapor barrier or not? If a vapor barrier, is encapsulated ok? If not, vapor barrier against flooring on top or ceiling tiles on the bottom? Any help would be GREATLY appreciated as I am ready to insulate and ROCK - finally!!! Tom I see that my posts on this forum has caused some confusion and apprehension concerning moisture in basements. I do appologize, I try very hard to avoid such reactions, unfortunately, the subject is somewhat complicated. Considering the fact that people use moisture and vapor barrier to describe the same thing and vapor barriers are applied differently in different parts of the world. The basement water proofing that you've done is considered a moisture barrier, which explicitly implies moisture cannot go either in or out through the application. In other words, water is prohibited from going through the basement walls and floor, either from the ground outside the house or humidity in the basement. Insulation does not stop heat flow, it resists it or slows it down. This explicitly implies that the heat flow is constant. Also, all heat contains moisture, which is a constant flow with the heat in this application. Therefore, heat that contains a percentage of humidity (Relative Humidity) will constantly flow through insulation. A vapor barrier is only applied to insulation and never alone. The purpose is to reduce the moisture content in the heat flow through the insulation to a percentage where the heat is incapable to condense. For example, heat that had a relative humidity level of 40% would more than likely condense once dew point temperature was reached. On the other hand, if the level was 15%, it is highly unlikely when the temp. reached dew point that it could condense because there is insufficient humidity in the heat. What's important here is there is a constant flow of heat with a percentage of humidity through the insulation. If we apply the aforementioned to your application, the probability of you experiencing a moisture problem is high. Even though the vapor barrier would reduce the percentage of humidity in the heat flow through the insulation, it is constant. Because of the water proofing to the walls and floor, this constant flow of heat with a low humidity level would have no where to go or be absorbed. Eventually this low percentage of humidity in the heat flow would increase because of this constant flow and being trapped by the water proofing (moisture barrier). Equivalent to having vapor barriers on both sides of insulation. Does this mean we shouldn't water proof basements and insulate? The answer to that is no. What we do need to understand is what will occur if we do. Your application physically traps the humidity in the insulation. The way to avoid this is to provide a drainage plane. This is a dead air space between the moisture barrier(water proofing) and the insulation. The size of the space is highly debatable. Some will say two inches and other will say two feet. In reality it really depends on the humidity levels in your area and basement. For example, if you lived in an area where heat and humidity was present most of the year or your basement was very humid, two feet. On the other hand, if you lived in an area where humidity was low or a dry basement, two inches. The ability of humidity to be absorb by its surroundings is known as Equilibrium Relative Humidity (ErH%). This applies not only to air masses but also to materials. As far as sound proofing the ceiling of the basement, it doesn't matter, dew point is highly unlikely to be reached between two conditioned spaces. I think i understand that i may be creating a problem now, but what if i score the encapsulated insulation on both sides? There is between 2 and 6 inches of room between the back of my steel studs and the 10mil plastic. I am planning on using a de-humidifier and may put a small fan in the open backed closet over my sump pump to make sure some air circulates behind the walls too. Do you think this will minimize the possibilities of condensation. You can go to http://www.eren.doe.gov/consumerinfo/refbriefs/bd4.html and read the topic PERMS It will help you understand why this product wrapped in a vapor barrier is allowed. Basically what this product has is two different vapor barriers. One side has a 5 times greater perm rating than the other side. You'll notice the difference in thickness in the plastic from one side to the other. Naturally the thicker side goes on the warm side of the insulation. Therefore, you don't have to score the plastic on the insulation. Since you already have a space between the wall and the insulation, it is unlikely you'll have a moisture problem. I don't believe you'll need the dehumidifier or the fan. The fan would probably do more for you than the dehumidifier. What would do even more for you than the fan would be to get one of those plastic covers for your sump pump well. Once covered, tape the slot closed. You'd be surprised how humidity comes into the basement through these wells by evaporation. Good luck with your project. i actually have 3 sump pump now - high water table and they all have plastic tubs and tops - from the home depot - i've sealed the slots with expandable foam and i know this should cut down a lot on the moisture in the basement. - all pipes are wrapped - all ducts are wrapped - water holding tanks wrapped and water heater wrapped - i'm trying to be thorough. Also replaced all basement windows to eliminate unwanted drafts. I think the fan will help and just to make sure I might put some pvc piping behind the insulation between the plastic to act like an air dict at the bottom of the wall - then from time to time I'll run the fan and get some circulation going back there - what do you think? You are very thorough. From a particular point of view concerning finishing the basement, it would appear you covered all the bases. To be perfectly honest with you, I agree with all you have done, which by the way is considerably more than most. However, I am involved in an industry that would not only approve of the actions you have taken, but would recommend the same actions to others. This does not go unnoticed by other professions related to the industry I'm involved in, namely Architects, ASHREA and especially Indoor Air Quality Experts (IAQ) from around the world. In fact you could say, we don't like each other very much. I feel I would be remiss as a professional if I did not point out their side, considering my statements and all you have done. I do not pretend to be an Indoor Air Quality expert, even though it has impacted my work tremendously over the last several years. From their point of view (IAQ Experts and other Professionals) and from my experience with them, they would point out that a moisture problem is now more likely in your basement than prior to all you have done. Not only the IAQ experts, all of them would state the same. I strongly suggest the you search the web for Indoor Air Quality, you will find fact sheets on this subject either on the Dept. of Energy or Environmental Protection Agency Websites. From their sites, you can ask an expert and pose you situtation to them. These are professionals, their methods and statistical analysis are beyond reproach and I respect them not only as professionals, personally. It does not mean I agree with them. Dear Sir, you deserve, no it's your right to hear from all sides concerning your situation. Afterwards, if you want my opinion, I am more than willing and able to defend my position. Francis R. Lazaro Energy Conservationist thank you for the compliment, i try to be thorough in anything i do personally or professionally. i went ahead and called Johns Manville about my situation and they told me that with the air gap between the insulation and the plastic i would probably be fine and my idea of scoring both sides would probably be a waste of time. i think i am going to go ahead as planned and monitor things closely. there are a few places i can peak behind the walls and this should help me make sure i don't have a problem. i am definitely going to run the fan from time to time in the corner of the basement where i have an open back closet over my sump pump, this should get the air moving and insure no problems develop.....by the way i am using green board for the walls, this should provide some additional help keeping the moisture from the insulation in the first place. thanks again tom
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