WEIGHT OF CELLULOSE INSULATION BLOWN-IN OVER …



WEIGHT OF CELLULOSE INSULATION BLOWN-IN OVER SHEETROCK

|QUESTION FROM CHERYL TRAVIS IN KNOXVILLE, KY: | ANSWER FROM THE INSULATION DOCTOR: |

| |[pic]Regarding your question about the weight of the cellulose on 24" trusses, |

|We want to add insulation to our attic, and are considering cellulose.  However |the weight should not be a problem in this application.  You stated that you |

|the ceiling trusses are on 24" centers and the ceiling sheetrock is only nailed |would like to increase your R-value to R-38.  Your current R-value with the |

|to the truss. (The house was built in 1965.).  There is currently about 2.5 |2-1/2" of cellulose is approximately R-8.  Therefore, you would need to add an |

|inches of cellulose in the attic and we would like to get the R-value to R-39.  |R-30.  This would be adding approximately 8-1/4".  The weight ratio per square |

|Is it likely that the added weight of the new cellulose would cause the ceiling |foot of 8-1/2" of cellulose is usually .97 pounds per square foot.  This should |

|to sag? |not cause a problem.  |

| |  |

|     |I would recommend adding an R-40 which would bring you to the maxiumum |

|  |insulation and the point of diminishing returns on your investment.  An R-40 |

|  |would be 11.15" with a rate ratio of approximately 1.29 per square foot.  (If |

|  |your drywall has been properly installed, which is glued and screwed, it is |

|  |capable of carrying a weight load of approximately 2 lbs). |

|  | |

|  |Note:  You also will want to add baffles for ventilation inside the attic and |

|  |beware of walking on the trusses and putting all your weight on one truss.  It |

|  |is imperative that you distribute yours or the installers weightload on more |

|  |than one truss at a time.  This can be accomplished by sliding a few boards into|

|  |the attic and walking on them.  You will need to be careful not to approach the |

|  |end of any board or it will flip and maybe cause you to fall through the |

|  |ceiling. |

|CONTINUED QUESTION: |ANSWER FROM THE INSULATION DOCTOR: |

| | |

|Thanks for the information below, but the specs for my application are a little |In response to your question regarding the 1/2" sheet rock and the weight of the|

|different. |cellulose insulation.  1/2" sheet rock on a 24" on-center trussed ceiling is |

|The house was built around 1965 and the sheetrock seems to have been nailed |considered standard by today's building standards.  The fact that the sheet rock|

|rather than screwed & glued. I'm assuming it is 1/2 sheetrock. |is not screwed may not be relevant to any significant difference in the weight |

|This means the weight load capacity is lower than the 2.2 lb per sq. foot listed|load.  More than likely your sheet rock was installed with more nails AND |

|below. |GLUE.  In that era, glue was always used.  The advantage in today's method of |

|Assuming 1/2 sheetrock nailed* on joists on 24 inch centers, What would the |screwing the sheet rock is that it requires fewer fasteners. |

|weight load capacity be? | |

| |If you are still concerned with the weight load, you have the option to consider|

| |installing blown-in fiberglas insulation.  For example, an R-30 fiberglas |

| |weightload per square foot is .531 or an R-40 the weightload would be under |

| |.786.  This is considerably less weight. |

| | |

| |Bruce Jones |

| |The Insulation Doctor   |

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