Icynene Insulation

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  #1  
Old 02-26-05, 02:05 PM
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Icynene Insulation

I will be finishing an attic and plan to use 3-1/2" of spray on Icynene insulation between the roof rafters and outside wall studs. There will be no venting because there will be no unheated spaces.

This will be in Iowa where the temperature can range from below zero to over 100 degrees.

What is your opinion of this plan?
 

Last edited by fredmorrison; 02-26-05 at 02:08 PM. Reason: More Info
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  #2  
Old 02-26-05, 04:37 PM
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http://wsuonline.weber.edu/course.cm...ent_Index.html

This site discusses the purpose of attic ventilation.

http://www.eere.energy.gov/consumeri...heets/bd4.html

This site discusses Vapor Barriers. The section you want to read about is Perm Ratings.

What both sites do not discuss enough is what pertains to your situation. What attic ventilation actually does is ventilate your roof. This is because of the low vapor permeability of most roofing materials. Your application clearly violates the 5 to 1 rule. Since all heat has moisture in it, as the heat from the house travels through the insulation, when the heat reaches the roofing shingles, the heat will continue to go through but because of the low perm rating of the shingles, the moisture in the heat will be trapped underneath.

This does not happen with your walls because your siding does not violate the 5 to 1 rule.
 
  #3  
Old 02-28-05, 08:19 AM
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Fred,
If you do a search on the web for "hot roof theory" you'll find hits that pitch a non-vented attic. The arguments in general are more compelling in hot humid enviornments and in fact when I was researching this I found researchers from the south who claim that the idea of the vented attic was a Yankee trick played by the North on the South.

This past summer we gutted our house and used icynene on the walls/attic/crawlspace. The contractor did try to convince us to spray the underside of the roofdeck. We did not do that mainly because our attic was not finished space and it would be more money to spray the gable walls and the roof deck rather then just spraying the ceiling (and then of course we'd have to heat this space). Hence we did a cold roof or vented attic.

In your case you're going to use the attic. Icynene does serve as a pretty good vapor barrier since air movement is for the most part non existant. The biggest drawback to not ventilating when you use foam is the temperature of the roofdeck. If you choose to spray the underside of your roofdeck you should be aware that most shingling companies will void your warranties. Even though studies show that the difference in deck temperture between vented and unvented attics is somewhere around 5 degrees they still void the warranty.

One other thing I would note is that you're only putting R13 in the attic with 3-1/2 inches of foam. This seems inadequate to me particulary for the winter. While it's true that you'll kill almost all infiltration with the foam, the attic should have a higher R value. While I'm not a big fan of using R value to compare insulation systems I would seriously consider a higher R value here.

Scott
 
  #4  
Old 02-28-05, 11:47 AM
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Icynene

Thanks for the replys.

My findings on Icynene spray-on insulation agree 100% with Sean_Sarah's comments. And indeed I want to and may be able to increase the R-Value for the roof deck. My former attic with "cold roof" will be converted to living space with a "hot roof".

Regarding condensation, the Icynene is for all practical purposes a vapor barrier because it seals the roof deck and prevents air from carrying the moisture through to the cold shingles.

I realize that some attic spaces should be ventilated, but the problem is that building codes requiring ventilation are years behind today's technology. I understand that some regulators are giving ventilation code variances for Icynene.
 
  #5  
Old 02-28-05, 02:38 PM
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R-Value's

R-19 means 1/19 of a BTU travels through one square foot of this material an hour. Since all heat has moisture in it and the R-Value explicitly implies it does not stop heat flow, the moisture in the heat as it conducts through the Icynene will be impeded once it reaches the roofing material.

Icynene makes their claims based on air transported moisture, which has nothing to do with R-Values. Which is Conductive Heat Transfer and moisture associated problems comes from heat transported moisture.
 
  #6  
Old 03-01-05, 07:50 AM
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A couple of points: Heat does not carry moisture. It is correct to say that the process of heating something can result in a transfer of water vapor. It is incorrect to say that heat carries water vapor. Heat is a form of kinetic energy transferred as a result of a difference in temperature. Energy does not "carry" moisture.

It is correct to say as you do, that the predominant method of vapor transfer through the walls of a house is air borne water vapor. The claim made by open cell foam manufacturers like icynene is that they stop air flow and therefore stop the flow of moisture. To a large extent this is correct given that we agree that most, albeit not all moisture is transferred via air currents. If it stops the moisture laden air from entering the foam then it cannot condense at the dew point in the interior of the wall.

This is even more true with closed cell foams.

With respect to R value you're correct that R value is a measure of the resistance of a material to the flow of heat (Actually it is the inverse of the thermal conductance of a material). It only accounts for the heat transferred via conduction. It does not account for heat transfer due to convection. It is determined empirically for each material under 0 airflow conditions. Convective heat loss is primarily due to the imperfect installation of insulation, settling of insulation in wall cavities/floors etc.

The real claim of foam insulation is that it kills heat flow due to convection and does not change over time. By doing this, the R value that you buy more accurately reflects the performance of the insulation system now and in the future.

As a side benefit it stops most moisture from entering the wall cavity. This is all any vapor barrier could claim. Even low perm VDRs are subject to imperfect installation. There is however, nothing that would preclude one from installing an additional vapor barrier but the value of that barrier is dubious. In fact with a closed cell foam I would say that the additional VDR is a waste of money.
 
  #7  
Old 03-01-05, 12:24 PM
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Airtight and Water Shedding Systems

The Old School base their position on that all materials possess moisture. In fact most materials start out very moist; like Icynene, steel, vynal and wood. Materials must maintain a certain amount of moisture to remain stabile. Too much or too little moisture destabilizes the material. While convection is a medium that can be used to transfer moisture from one object to another, it is the process of Equilibriium Relative Humidity that accomplishes the transfer. This states that an object of lower humidity will absorb humidity from an object(s) of higher humidity until the objects are equal in humidity levels. It does not matter if the material are closed cell, low Perm Rating or a VDR. The humidity in these objects will seek and obtain equilibrium. The only difference is the time it takes for an object to absorb and expel the moisture. This is the reason why all materials are given a Perm Rating, which describes the time it takes moisture to permeate the materials.

People understand easily that all heat has moisture in it, which is not true. It is the objects that carry the moisture that the heat energy conducts through. As long as there is a temperature difference between the outside of the material and the inside, the flow of heat energy is constant. There is also an affect on the Relative Humidity of the object as the heat energy traverses the object. Psychometric charts show the behavior of moisture under different temperature conditions. For example a certain volume of air with a certain amount of moisture in it with a temperature above Dew Point will not have condensation. But if I drop the temperature to Dew Point, condensation will occur. The amount of moisture in the air did not change, the temperature did.

Equilibrium is obtained with moisture in different objects in much the same way pressure and temperature does, that is high to low. Meaning to say, the lower temperature object absorbs heat from the higher temperature object or the higher temperature object gives heat TO the lower temperature object. The high to low rule is important because it explains how moisture is extracted from the house using relative humidity and temperature.

For example, we know there are a variety of sources inside the house that produce humidity; like humans give off about 2 pounds per day, dogs about 5 pounds, cooking, showering, washing, drying and more. The flow of heat is from the inside towards the outside (high to low). As the moisture is generated inside the house, all the objects in the house increase with humidity. The walls, floors and ceilings have an increased amount of humidity. The heat energy as it goes through these objects begins to lose temperature. When it does that the Relative Humidity in these objects rise. When it reaches the outside of these objects, the Relative Humidity of these objects are very high because of the temperature drop. The cold air outside which usually has a lower Relative Humidity absorbs humidity from the higher humidity objects (High to Low). These objects by design are "Water Shedding Systems" and are specifically designed not to impede the moisture flow.

Vapor barriers must have a Perm Rating of 1 or less to qualify. Most roofing materials qualify as vapor barriers because of this. Attic ventilation primary purpose is to by-pass the low moisture vapor permeability of roofing materials. So if I apply insulation directly under roof decking, regardless of the type of insulation, it is the equivalent of having vapor barriers on both sides of the insulation. The roofing material slows down the expulsion of moisture from the house and at the same time increases the Relative Humidity because of the cold temperature. This is why the rule that any material after the vapor barrier must have a Perm Rating 5 times greater than the vapor barrier. Most all roofing materials violate this rule, attic ventilation by-passes the roofing materials to allow the cold air outside to absorb the moisture generated inside the house.

This is not the only way moisture is extracted from the house during the winter, but it is a major factor.
 
  #8  
Old 03-02-05, 07:58 AM
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An explanation of current building techniques for both vented and unvented spaces can be found at:
http://www.buildingscience.com/resou...ofs_Design.pdf

Note the differentiation made with controlling the first condensing surface when using air impermeable spray foam. Note also the differentiation between open and closed cell foams. They call this light and dense foams.

In any case I would read this as you move forward with your project. I would pay particular attention to the discussion regarding the use of a vapor barrier of 1 perm or less when using light air impermeable foam such as icynene sprayed in direct contact to the underside of the roof deck.
 
  #9  
Old 03-02-05, 01:09 PM
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While this site provides a good deal of information and they support their position with know Laws of Physics, it takes a good deal more before it becomes widely accepted.

Their argument is further supported by the fact that air can carry more moisture than heat. In fact there is a National Organization known as the American Air Barrier Association (www.aaba.com) or something like that that is attempting to convince builders to only allow their licensed Air Barrier specialists install air barriers. Right now their focus is on multi-story commercial buildings. Eventually it will become a residential application too. The problem here is theory supports their claims but there is insignificant research data to verify it. This same problem applies to radiant barriers.

Even though I am fairly versed on the effects of stack effect, wind and vapor pressure on a structure, I am not convinced that airtight wall structures applications will produce what they say. I admit I am old school who believes it's better to be safe than sorry. The young men and women rising in this industry have the philosophy of having to crack a few eggs to make an omlet. This stems from the Reagan policy of streamlining government. While this helped get drugs approved for AIDS into the marketplace, it also produced Vioxx and of course "Sick Building Syndrome".

This illustrates the vast amount of information that is out there. All of it sounds good but when closely examined, you find that it raises more questions than answers. For the lay person, you are at a lost. There is no way you can go to an organization like Oak Ridge National Laboratories and make out heads or tails of their research data. If you think lay people have it bad, Oak Ridge have their hands full. It appears that a new application comes up every day by someone and it takes years of testing for Oak Ridge to come up with a conclusion for each application. On the other hand we have the Building Science Organizations who don't have to do anywhere near the amount of testing Oak Ridge does. Who spurt out unsupportive claims and believe you have to break a few eggs to make an omlet. I will admit that there are some very good Building Performance Organizations out there, like VEIC and Proctor Engineering.

I do not wish to say anything derogatory about Building Science Organizations. Besides the fact that I personally know a lot of people in these organizations, I deeply respect and admire the work they are doing. They are by far extremely hardworking and dedicated professionals. What I want people to do with this papers; is to accept them for what they are. They are hypothesis, conjecture and unsubstantiated information. However it takes this type of Hypothesis for Labs like Oak Ridge to take notice. If a lab does take on this Hypothesis, it will take them years of testing and analysis to prove or disprove it. Even then, the lab will have to defend their findings in front of a group of their peers. The data the lab will use, usually comes in volumes. While there are those who say this process takes too long, I say I rather be safe than sorry.
 
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