Ok to add cellulose over blown fiberglass insulation?












2















I have an attic with blown in fiberglass insulation, probably original and 27 years old. The attic appears to have had some moisture issues in the past (bathroom vents being vented out of the soffit vents, which have been corrected) and the insulation is a little clumpy and a little dirty, but not terrible.



I want to add more insulation, but I'm not sure whether or not to use more blown in fiberglass or cellulose on top of it. I've read cellulose is the superior product. But I've read and saw videos of cellulose just being blown in on top of the fiberglass. I've read conflicting articles that says it's fine to do that and others say the cellulose will compact the fiberglass which isn't good for the existing fiberglass.



What should I do? Thanks!



Here is a pic of my current attic insulation:



enter image description here






insulation attic fiberglass







share|improve this question



























    2















    I have an attic with blown in fiberglass insulation, probably original and 27 years old. The attic appears to have had some moisture issues in the past (bathroom vents being vented out of the soffit vents, which have been corrected) and the insulation is a little clumpy and a little dirty, but not terrible.



    I want to add more insulation, but I'm not sure whether or not to use more blown in fiberglass or cellulose on top of it. I've read cellulose is the superior product. But I've read and saw videos of cellulose just being blown in on top of the fiberglass. I've read conflicting articles that says it's fine to do that and others say the cellulose will compact the fiberglass which isn't good for the existing fiberglass.



    What should I do? Thanks!



    Here is a pic of my current attic insulation:



    enter image description here






    insulation attic fiberglass







    share|improve this question

























      2












      2








      2








      I have an attic with blown in fiberglass insulation, probably original and 27 years old. The attic appears to have had some moisture issues in the past (bathroom vents being vented out of the soffit vents, which have been corrected) and the insulation is a little clumpy and a little dirty, but not terrible.



      I want to add more insulation, but I'm not sure whether or not to use more blown in fiberglass or cellulose on top of it. I've read cellulose is the superior product. But I've read and saw videos of cellulose just being blown in on top of the fiberglass. I've read conflicting articles that says it's fine to do that and others say the cellulose will compact the fiberglass which isn't good for the existing fiberglass.



      What should I do? Thanks!



      Here is a pic of my current attic insulation:



      enter image description here






      insulation attic fiberglass







      share|improve this question














      I have an attic with blown in fiberglass insulation, probably original and 27 years old. The attic appears to have had some moisture issues in the past (bathroom vents being vented out of the soffit vents, which have been corrected) and the insulation is a little clumpy and a little dirty, but not terrible.



      I want to add more insulation, but I'm not sure whether or not to use more blown in fiberglass or cellulose on top of it. I've read cellulose is the superior product. But I've read and saw videos of cellulose just being blown in on top of the fiberglass. I've read conflicting articles that says it's fine to do that and others say the cellulose will compact the fiberglass which isn't good for the existing fiberglass.



      What should I do? Thanks!



      Here is a pic of my current attic insulation:



      enter image description here






      insulation attic fiberglass




      insulation attic fiberglass






      share|improve this question













      share|improve this question











      share|improve this question




      share|improve this question










      asked 8 hours ago









      mangmang

      476




      476






















          2 Answers
          2






          active

          oldest

          votes


















          4














          Add the cellulose right on top, I have seen folks remove the old but this is crazy both materials are insulation and combined the provide a higher R value. I would caution if all the moisture issues are not taken care of cellulose will pick up moisture and hold it longer than fiberglass.






          share|improve this answer
























          • Yep. I've done it in my own home. Any insulation will compress, and you just plan for it.

            – isherwood
            5 hours ago











          • I'd like to "supplement" the current insulation with the cellulose. If it compresses, will the fiberglass lose it's existing R-value capabilities and thus require more cellulose?

            – mang
            5 hours ago



















          0














          I have also heard not to add cellulose over blown fiberglass because cellulose is heavier and will compress the fiberglass. When fiberglass is compressed it loses R-value (is a poorer insulator). Makes sense to me.



          I think the best option would be to blow more fiberglass on top as it will not compress the existing stuff too much. I know Home Depot will sell blown in fiberglass and the machine so it should be about the same as doing cellulose yourself.



          If you are set on blowing cellulose, you could probably put it right on top but just know it will compromise the effectiveness of the existing insulation. If you blow enough cellulose as if you had no existing insulation it will give you the R-value you need.



          I agree the trying to remove the existing blown in will be hard and not worth it.






          share|improve this answer





















          • 1





            Any new insulation will compress what's underneath. That's not a reason to not do it, and it's not a reason to not use cellulose.

            – isherwood
            5 hours ago






          • 1





            @isherwood but cellulose is heavier than fiberglass. When you calculate how much of either blown-in to use, the manufacturer with take into account how much it compresses. Since fiberglass is so sensitive to the voids inside it (that is how it works as insulation), compressing it too much is bad.

            – auujay
            4 hours ago











          • Cellulose is fine to use. I used it in my attic, the OP is asking if mixing them with fiberglass on the bottom is not recommended. I don’t have personal experience with mixing them but the argument for not putting cellulose over blown fiberglass makes sense to me.

            – auujay
            4 hours ago











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          2 Answers
          2






          active

          oldest

          votes








          2 Answers
          2






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes









          4














          Add the cellulose right on top, I have seen folks remove the old but this is crazy both materials are insulation and combined the provide a higher R value. I would caution if all the moisture issues are not taken care of cellulose will pick up moisture and hold it longer than fiberglass.






          share|improve this answer
























          • Yep. I've done it in my own home. Any insulation will compress, and you just plan for it.

            – isherwood
            5 hours ago











          • I'd like to "supplement" the current insulation with the cellulose. If it compresses, will the fiberglass lose it's existing R-value capabilities and thus require more cellulose?

            – mang
            5 hours ago
















          4














          Add the cellulose right on top, I have seen folks remove the old but this is crazy both materials are insulation and combined the provide a higher R value. I would caution if all the moisture issues are not taken care of cellulose will pick up moisture and hold it longer than fiberglass.






          share|improve this answer
























          • Yep. I've done it in my own home. Any insulation will compress, and you just plan for it.

            – isherwood
            5 hours ago











          • I'd like to "supplement" the current insulation with the cellulose. If it compresses, will the fiberglass lose it's existing R-value capabilities and thus require more cellulose?

            – mang
            5 hours ago














          4












          4








          4







          Add the cellulose right on top, I have seen folks remove the old but this is crazy both materials are insulation and combined the provide a higher R value. I would caution if all the moisture issues are not taken care of cellulose will pick up moisture and hold it longer than fiberglass.






          share|improve this answer













          Add the cellulose right on top, I have seen folks remove the old but this is crazy both materials are insulation and combined the provide a higher R value. I would caution if all the moisture issues are not taken care of cellulose will pick up moisture and hold it longer than fiberglass.







          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered 8 hours ago









          Ed BealEd Beal

          32.5k12145




          32.5k12145













          • Yep. I've done it in my own home. Any insulation will compress, and you just plan for it.

            – isherwood
            5 hours ago











          • I'd like to "supplement" the current insulation with the cellulose. If it compresses, will the fiberglass lose it's existing R-value capabilities and thus require more cellulose?

            – mang
            5 hours ago



















          • Yep. I've done it in my own home. Any insulation will compress, and you just plan for it.

            – isherwood
            5 hours ago











          • I'd like to "supplement" the current insulation with the cellulose. If it compresses, will the fiberglass lose it's existing R-value capabilities and thus require more cellulose?

            – mang
            5 hours ago

















          Yep. I've done it in my own home. Any insulation will compress, and you just plan for it.

          – isherwood
          5 hours ago





          Yep. I've done it in my own home. Any insulation will compress, and you just plan for it.

          – isherwood
          5 hours ago













          I'd like to "supplement" the current insulation with the cellulose. If it compresses, will the fiberglass lose it's existing R-value capabilities and thus require more cellulose?

          – mang
          5 hours ago





          I'd like to "supplement" the current insulation with the cellulose. If it compresses, will the fiberglass lose it's existing R-value capabilities and thus require more cellulose?

          – mang
          5 hours ago













          0














          I have also heard not to add cellulose over blown fiberglass because cellulose is heavier and will compress the fiberglass. When fiberglass is compressed it loses R-value (is a poorer insulator). Makes sense to me.



          I think the best option would be to blow more fiberglass on top as it will not compress the existing stuff too much. I know Home Depot will sell blown in fiberglass and the machine so it should be about the same as doing cellulose yourself.



          If you are set on blowing cellulose, you could probably put it right on top but just know it will compromise the effectiveness of the existing insulation. If you blow enough cellulose as if you had no existing insulation it will give you the R-value you need.



          I agree the trying to remove the existing blown in will be hard and not worth it.






          share|improve this answer





















          • 1





            Any new insulation will compress what's underneath. That's not a reason to not do it, and it's not a reason to not use cellulose.

            – isherwood
            5 hours ago






          • 1





            @isherwood but cellulose is heavier than fiberglass. When you calculate how much of either blown-in to use, the manufacturer with take into account how much it compresses. Since fiberglass is so sensitive to the voids inside it (that is how it works as insulation), compressing it too much is bad.

            – auujay
            4 hours ago











          • Cellulose is fine to use. I used it in my attic, the OP is asking if mixing them with fiberglass on the bottom is not recommended. I don’t have personal experience with mixing them but the argument for not putting cellulose over blown fiberglass makes sense to me.

            – auujay
            4 hours ago
















          0














          I have also heard not to add cellulose over blown fiberglass because cellulose is heavier and will compress the fiberglass. When fiberglass is compressed it loses R-value (is a poorer insulator). Makes sense to me.



          I think the best option would be to blow more fiberglass on top as it will not compress the existing stuff too much. I know Home Depot will sell blown in fiberglass and the machine so it should be about the same as doing cellulose yourself.



          If you are set on blowing cellulose, you could probably put it right on top but just know it will compromise the effectiveness of the existing insulation. If you blow enough cellulose as if you had no existing insulation it will give you the R-value you need.



          I agree the trying to remove the existing blown in will be hard and not worth it.






          share|improve this answer





















          • 1





            Any new insulation will compress what's underneath. That's not a reason to not do it, and it's not a reason to not use cellulose.

            – isherwood
            5 hours ago






          • 1





            @isherwood but cellulose is heavier than fiberglass. When you calculate how much of either blown-in to use, the manufacturer with take into account how much it compresses. Since fiberglass is so sensitive to the voids inside it (that is how it works as insulation), compressing it too much is bad.

            – auujay
            4 hours ago











          • Cellulose is fine to use. I used it in my attic, the OP is asking if mixing them with fiberglass on the bottom is not recommended. I don’t have personal experience with mixing them but the argument for not putting cellulose over blown fiberglass makes sense to me.

            – auujay
            4 hours ago














          0












          0








          0







          I have also heard not to add cellulose over blown fiberglass because cellulose is heavier and will compress the fiberglass. When fiberglass is compressed it loses R-value (is a poorer insulator). Makes sense to me.



          I think the best option would be to blow more fiberglass on top as it will not compress the existing stuff too much. I know Home Depot will sell blown in fiberglass and the machine so it should be about the same as doing cellulose yourself.



          If you are set on blowing cellulose, you could probably put it right on top but just know it will compromise the effectiveness of the existing insulation. If you blow enough cellulose as if you had no existing insulation it will give you the R-value you need.



          I agree the trying to remove the existing blown in will be hard and not worth it.






          share|improve this answer















          I have also heard not to add cellulose over blown fiberglass because cellulose is heavier and will compress the fiberglass. When fiberglass is compressed it loses R-value (is a poorer insulator). Makes sense to me.



          I think the best option would be to blow more fiberglass on top as it will not compress the existing stuff too much. I know Home Depot will sell blown in fiberglass and the machine so it should be about the same as doing cellulose yourself.



          If you are set on blowing cellulose, you could probably put it right on top but just know it will compromise the effectiveness of the existing insulation. If you blow enough cellulose as if you had no existing insulation it will give you the R-value you need.



          I agree the trying to remove the existing blown in will be hard and not worth it.







          share|improve this answer














          share|improve this answer



          share|improve this answer








          edited 5 hours ago

























          answered 6 hours ago









          auujayauujay

          4,310133051




          4,310133051








          • 1





            Any new insulation will compress what's underneath. That's not a reason to not do it, and it's not a reason to not use cellulose.

            – isherwood
            5 hours ago






          • 1





            @isherwood but cellulose is heavier than fiberglass. When you calculate how much of either blown-in to use, the manufacturer with take into account how much it compresses. Since fiberglass is so sensitive to the voids inside it (that is how it works as insulation), compressing it too much is bad.

            – auujay
            4 hours ago











          • Cellulose is fine to use. I used it in my attic, the OP is asking if mixing them with fiberglass on the bottom is not recommended. I don’t have personal experience with mixing them but the argument for not putting cellulose over blown fiberglass makes sense to me.

            – auujay
            4 hours ago














          • 1





            Any new insulation will compress what's underneath. That's not a reason to not do it, and it's not a reason to not use cellulose.

            – isherwood
            5 hours ago






          • 1





            @isherwood but cellulose is heavier than fiberglass. When you calculate how much of either blown-in to use, the manufacturer with take into account how much it compresses. Since fiberglass is so sensitive to the voids inside it (that is how it works as insulation), compressing it too much is bad.

            – auujay
            4 hours ago











          • Cellulose is fine to use. I used it in my attic, the OP is asking if mixing them with fiberglass on the bottom is not recommended. I don’t have personal experience with mixing them but the argument for not putting cellulose over blown fiberglass makes sense to me.

            – auujay
            4 hours ago








          1




          1





          Any new insulation will compress what's underneath. That's not a reason to not do it, and it's not a reason to not use cellulose.

          – isherwood
          5 hours ago





          Any new insulation will compress what's underneath. That's not a reason to not do it, and it's not a reason to not use cellulose.

          – isherwood
          5 hours ago




          1




          1





          @isherwood but cellulose is heavier than fiberglass. When you calculate how much of either blown-in to use, the manufacturer with take into account how much it compresses. Since fiberglass is so sensitive to the voids inside it (that is how it works as insulation), compressing it too much is bad.

          – auujay
          4 hours ago





          @isherwood but cellulose is heavier than fiberglass. When you calculate how much of either blown-in to use, the manufacturer with take into account how much it compresses. Since fiberglass is so sensitive to the voids inside it (that is how it works as insulation), compressing it too much is bad.

          – auujay
          4 hours ago













          Cellulose is fine to use. I used it in my attic, the OP is asking if mixing them with fiberglass on the bottom is not recommended. I don’t have personal experience with mixing them but the argument for not putting cellulose over blown fiberglass makes sense to me.

          – auujay
          4 hours ago





          Cellulose is fine to use. I used it in my attic, the OP is asking if mixing them with fiberglass on the bottom is not recommended. I don’t have personal experience with mixing them but the argument for not putting cellulose over blown fiberglass makes sense to me.

          – auujay
          4 hours ago


















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