I was looking at having high density cellulose added to my walls. My walls have fiberglass batts in them now but not sure the r value.THe basement has r-11 so im assuming the upstairs does as well. some contractors are saying adding cellulose to a existing wall is worse because when they ad the tube it pulls on the batts bunching them up thus creating spots where the cellulose wont go and it will create voids and will have a ill effect on insulating the walls. Other companies say it is awesome and I will notice a difference right away. I have found many videos and postings showing how it is done and how it works but not much if it has any negative effects. Has anyone had any experiences or suggestions? I dont want t spend the mpney if it will make the walls worse or not have any effect.
thank you in advance
If you had no insulation in your walls now then I'd say go for it. But your walls are already insulated - 2x4 walls are either R-11 or R-13 with R-13 being more common for houses built i the last 12-15 years. High density cellulose doesn't add that much R-value as it too will be about R-13 in a standard 2x4 wall. Where the HD cellulose works better is that it seals any openings.
But adding it to a cavity that is already filled with fiberglass means that you will not get a solid fill with the cellulose plus you will compress the fiberglass, making it less efficient. You will not pick up any R-value but will gain some crack sealing.
You can probably gain as much efficiency by sealing all through-wall holes around wiring and pipes, plus removing door and window trim to install expanding foam between jambs and framing.
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