Sign In to join the community | Help
Build & Remodel

reinsulating the attic

I need to add insultation to the attic. I assessed the existing insulation. Whether the the ceiling joists are 2X6 or 2X8, most of the attic has visible space to fill in, a good inch or 2 in most places. The existing material is the original 42 year old insulation. It is dirty and dustry and does not fill the cavity between the joists. We plan to add flooring to use the attic as storage space. What to do...

1. Add insulation on top (parallel) to the existing material, filling the space.

2. Roll perpendicular to the existing insulation

3. Just blow more right on top.

4. Remove and start over...


What do you suggest?

Also, what do I do about wires and electrical boxes from the ceiling below?


Looking forward to getting started!


Not what you were looking for ? Try posting a question
Posted 2012-01-03T18:02:55+0000  by Rob13 Rob13

Hey Rob,


Rob having said you are going to utilize your attic as a storage space  your best option in my option would be to add rolls of unfaced fiberglass insulation over the top of your existing material.


You don’t want to use paper or foil faced –these act as a vapor barrier and placing them on your attic deck with paper or foil side up could very possibly create moisture problems.


How much (thick) of fiberglass can you roll over existing stuff depends on how much can it be compressed down. In other words before purchasing insulation I would do a simple test and push existing stuff down, with moderate pressure, and see how much room it is going to clear out on the side of the joist.


My guess it’s going to be at least half of the joist depth.


If you budget permits it wouldn’t be a bad idea to install attic decking at the same time you’re doing insulation. It is going to make it easier for you to move around and in also it’s going to keep the new stuff in place.


Question #2


If you where to install new insulation perpendicularly to the ceiling joists it would make it very  difficult for you to install attic decking .I would roll the new stuff in the direction of the  ceiling joist so that you have fastening points for the attic decking.





You are going to achieve higher insulating value with unfaced rolls than with 2” inches of blow in insulation. If you were to clear half of the joist depth you could easily install R19 (5.5”) there versus 2”inches of blow in (R5-7).




Old stuff still has significant insulating value you just need to top it off so you can get most of it. Removing it would be waste of time and material in my opinion.


As far as the ceiling boxes go you need to provide an access to the ones that cannot be accessed from bellow. Easy way to do this is to use 6” sheet metal duct  pipe placed in vertical position or you can use something called SmartCap. SmartCap Attic Recessed Light Cover is a pre-assembled, easy to install, fire rated recessed light cover that simply unfolds into a cap over non-IC rated light fixtures in the attic.


If you want you can also  fire stop around the boxes with the fire rated caulking.


Hope this helps Rob and feel free to ask questions if anything sounds unclear to you.



Posted 2012-01-03T20:58:20+0000  by George_HD_CHI

Thanks for the quick reply. What do you mean by 


As far as the ceiling boxes go you need to provide an access to the ones that cannot be accessed from bellow. 


all the electrical ceiling boxes are for ceiling fixtures and can all be accessed from below. I was concerned about heat or fire safety and not wanting to roll the insulation over the boxes.


I also have another insulatin question. Our bedrooms are over the garage. The floors are cold. There is some insulation in the floor/ceiling. How do you suggest adding insulation. I do not want to tear down, insulate and reinatall the sheetrock.

What are my options? 

Posted 2012-01-04T04:04:20+0000  by Rob13

Hello Rob13.


SteelToes is not in today, but maybe I can help you.


The issue with electrical boxes is access.  If all the boxes open into the ceilings, then you have no action needed.  There is no problem with rolling insulation over the backs of electrical boxes.  What George was referring to are those occasions where junction boxes are installed in an attic.  This is often done to branch circuits off to different rooms,  The boxes in this case face up in the attic, and access must be maintained when more insulation or if flooring is installed.  Also, he mentioned a solution for insulating around can light fixtures, which is a different issue from electrical boxes.  Apparently neither are a problem in your case.


Secondly, the insulation issue...


If your floors over the garage are cold, then what insulation you already have is not working well.  The first thing I would want to do is find out what insulation is there, and whether a vapor barrier against the bedroom floor exists.  I would start by cutting a fist sized hole in the garage ceiling to check that out.


If you find a vapor barrier and just a thin layer of insulation, then it is possible to cut numerous holes between joists (both entrance and exit) and use blown-in insulation to hopefully fill in the gap between the ceiling and the insulation set against the floor.  I have never seen this done working against gravity before and the dozens of holes that need patching certainly would not be easy.


Skimming the ceiling with foam board AND adding another layer of drywall as a fire barrier is a second option.

The R value improvement here will not be very high.


Installing a drop ceiling and filling the gap with batts of unfaced insulation is another option.

You lose a lot of space by doing this. 


If you do not find a vapor barrier up against the bedroom floor, then I would pull the ceiling down completely and apply the highest R value faced insulation for the space available and then put up a new drywall ceiling.  In the long run this may actually be the easiest and most effective solution, even though you don't want to do that.  Remember that the facing goes against the heated bedroom floor, not against the garage ceiling drywall.


I hope this helps,




Posted 2012-01-06T14:55:35+0000  by Chris_HD_CHI
Not what you were looking for ? Try posting a question