Having blown in fiberglass or cellulose insulation into stud cavities works great for the first couple of years. But as the heating and cooling cycles go by moisture is allowed to migrate into the stud cavities with cellulose it make hard clumps losing R-value. When the house is shaken with the wind (jets) or ground vibrations (heavy trucks or railroad cars passing by) this vibrates the insulation down leaving hollow pockets of air or no R-value of insulation.
This will happen at the top of all the walls and under all the windows as well as where wiring is run through the wall, the wiring holds up the insulation from settling
downward but below the wiring there again is no insulation.
Using an Open Cell insulation this sprays in place and bonds to the studs wires and wall sheathing locking it in place.
The only draw back with Open Cell insulation is trying to fish wire into new outlets it’s hard to do.
While fiberglass is easy just move it to the side pull the wire into place and install your electrical box, O by the way installing wire this way losses all you r-value in that stud cavity by moving the insulation you have created a void on the one side and on the other side you have pushed in to much insulation and have less R-value.
What is R-Value and what R-Value do I need?
Insulation is rated in terms of thermal resistance, called R-value, which indicates the resistance to heat flow. The higher the R-value, the greater the insulating effectiveness. The R-value of thermal insulation depends on the type of material, its thickness, and density.
In the case of Icynene these are the facts:
Thermal Resistance R 3.6/in x thickness of stud
Heat flow reduction through 1.0″ = 72.7%
Heat flow reduction through 3.5″ = 92.2%
Heat flow reduction through 5.5″ = 95.0%
Heat flow reduction through 10.0″ = 97.3%
What does this mean?
Example-Look at your living room wall let’s remove a 14″ x 14″ piece of sheetrock & poly on the insides and on the out side let do the same size and location, remove the siding and wall sheathing so on both sides of the wall we can see the insulation.
Now lets say it’s —2° below 0 and on the inside it’s 7° degrees.
Standing out side dip your hands into water and place them on the siding just above the hole how long will be able to stand there before your hands freeze?
Lets do the same with a house made of Icynene Insulation. Again how long before your hands freeze?
A Fiberglass insulation — Never and instead your hands should be dry in under 6 minutes at —2° below °. Above the hole the temp should be on a calm day about 5°
A Icynene Insulation- in about 30-40 Seconds major frost burn should start.
The deference is that fiberglass insulation slows the air movement down inside the stud space while Icynene creates millions of little air pockets but not allowing them to move.
Fiberglass insulation with out poly and/or wallboard on the in side and wall sheathing on the outside is really a very poor type of insulation in and of it’s self.