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cbzdel 06-20-2010 09:09 PM

Remove some insulation?
My house was built in the 40's, then was updated within the past 10 years or so. I was messing around in the attic today and had to move some insulation (aprox 8-10" yellow fiberglass roll) under it is about 4-6" of rock wool.

In 10 days I am having blown in insulation put in.

So I have a couple choices, I can blow in the insulation on top of everything, or a I can remove all or some of the insulation.

Part or me wants to clean it all out because at one point there were birds and mice up there (since then it has been sealed)

Any input?

chrisn 06-21-2010 02:24 AM

I would think the guys installing the new insulation could and would answer that.

Just Bill 06-21-2010 05:38 AM

Should be OK as long as there is only one moisture barrier, next to the ceiling

cbzdel 06-21-2010 10:36 AM


Originally Posted by chrisn (Post 459207)
I would think the guys installing the new insulation could and would answer that.

I thought I would ask others just to make sure they are doing their job correct.. We all know not all contractors are the smartest.. (no offense to anyone on here tha tmay be one, there are good ones, but there are also bad ones)

Plus I am doing a city funded program so I am getting almost free insulation and new windows :thumbup: the downside to that is I have to use their pre-selected contractors.

Gary in WA 06-21-2010 09:15 PM

If the ceiling below is original plaster and lath (8# per sq.ft.) add up the additional insulation and check the span ratings for the species of ceiling joists. Drywall- 1/2" is rated to carry less than 5/8"-- depending on the span, if added later. Blown cellulose weighs way more than blown fiberglass... Rock wool is heavy.... I'm in the North end- off Sprauge-- howdy, neighbor!

Be safe, Gary

DrunkNinja 06-21-2010 09:31 PM

What the guys blowing it in will say .....
They will say blow over, only because they will not want to come back and their bosses will ask "why didn't you just tell him that he shoulda blown ova"

Get it out if its going to bug you later because its not that unlikely that in 20 years you will see a news article about rockwool causing nut cancer, kinda like asbestos. If you h8 itching leave it, if not get a garbage bin ready :ninja:

jklingel 06-22-2010 08:48 PM

The old insulation is not going to hurt anything, but like was mentioned, make sure your sheet rock can carry the extra load. If you remove the old, it will cost more to refill that space w/ blown-in, and someone has to spend time/money to take it out. Is the blown-in that much better that it warrants the time and extra expense to remove the old? Run the numbers and decide for yourself; it's your money and time. I hope you are getting cellulose blown in. I would not trust a contractor completely; ever. Make sure they don't fill the perimeter up against the roof, blocking ventilation, too. GL. j

rtoni 06-23-2010 04:16 PM

You mention mice and birds - is there a knock-down critter smell when you're up there? I'm not sure if you can tell if/where the critter damage would be concentrated in the loose rock wool. In the rolls it might be easier to see if they are chewed up or signs of nesting. Me - I would tear out those bad spots only because I would want that mess out of the building envelope -partly because I have a passionate hatred for these critters (having had to tear out vaulted ceiling for above reason) and I don't want any reminders when I'm in the area. Partly because there may be some health issues associated with old critter nests / droppings / etc? Maybe I'm being paranoid. I hate mice - did I mention that..?

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