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ADaniLion 07-14-2011 08:47 AM

Attic Insulation - am I crazy to want this?
Hello :)
I am having a few contractors come over to provide estimates for attic insulation. The last three contractors all managed to steer me toward blown-in insulation, which I don't want. They seem to think that what I'm asking for is wrong. Could someone just confirm that what I want is reasonable before this next person comes tonight? I'm offering cash on the spot and flexible schedule...and I just don't understand why everyone wants me to put blown-in cellulose?

What I want is Johns Manville unfaced rolled over existing faced fiberglass. The reason for this is because I plan to install at least a wide cat walk (perhaps floor the whole thing) and, eventually, a whole-house fan. I do go into my attic to maintain fans/ducts, etc. and worry that blown-in will cover the joists so completely that no one will be able to find them to step on them, not to mention the fibers that will be blown around when the attic fan runs...

Am I crazy to ask for this? Thanks, as always!!:no:

josall 07-14-2011 11:20 AM

Assuming that when you say you might floor it all off you are going to use it for storage, if so what size are your ceiling joists and are they capable of handling the load. How much insulation do you have now? If you are wanting to add insulation directly on top of your existing insulation and leave the tops of your joists exposed ( you need to cover them) you would be wasting your money. The efficient application would be to run the new insulation perpendicular to your old insulation. If you blew in your own insulation, an additional R-38 (almost 11" thick) for each 1,000 square feet it would cost you $642. If you just floor it off you will limit yourself too the R factor you can get.. As far as duct maintenance if done properly you shouldn't need to do anything for 30-40 years. Your motors etc. just build cat walks to them.

ADaniLion 07-14-2011 11:44 AM

The joists are tall, over 12" but I did not measure.
The current insulation is about R-19, faced fiberglass. If I ask for the new rolled insulation to run perpendicular to the joists rather than in between them, there will be an air gap between the current insulation and the new insulation in between each joist. Is that OK?

Do I then ask them to put the new insulation in between the joists only where the catwalk will be?

I'm just curious why the tops of the joists need to be covered?

The main reason for a cat walk is to get to the fan for maintenance/bee hive removal, etc. The only reason I'd eventually floor the whole thing is so that I can hear if my roof leaks. It will need to be replaced in a few years. Since every new roof I've had installed (5 different homes in 5 different states) has leaked a little somewhere at first, I just worry that if the new roof leaks onto fluffy insulation, I won't hear it or know anything about it until it starts to affect the plaster ceilings.

Thank you very much!!!!

josall 07-14-2011 02:20 PM

You would want to fill your joist cavity up before running it perpendicular. Covering the joist just makes a better seal to prevent energy loss.

DrHicks 07-14-2011 02:41 PM

They want to blow in insulation because it's easier, and is a better return for their time.

The bottom line is that what you want as a homeowner, is what they should provide - assuming it's not wrong, against code, or unsafe.

Why not just buy the rolls (or bats) and do it yourself? It really is not that difficult and you may very well save quite a bit of money. Measure the width of your joists (16" or 24" OC), and get the appropriate insulation. Depending on where you live, an addition layer of R19 should be quite adequate but, as "josall" said, run it between the joists.

DannyT 07-14-2011 02:50 PM

if you have to worry about a new roof leaking get a better installer. if you are not home and the roof leaks you won't hear it either.

Jackofall1 07-14-2011 04:03 PM

Put your walkway down first, then blow in cellulose. At least that way if you have access your attic you will know where to walk. I agree with a previous post that a new roof should not leak, and as for a exhaust fan, once the insulation is settled in a correctly sized fan will not disturd it.


SPS-1 07-14-2011 09:52 PM

If you go up into your attic occasionally, I don't like the loose fill either. The loose fill ends up getting kicked, pushed, blown, whatever, and ends up all over the place. Some places end up high, others with minimal insulation.
Not that it going to make a great difference in heat loss, but I rather like to see a nice level surface in my attic.

Gary in WA 07-16-2011 09:16 PM

"and I just don't understand why everyone wants me to put blown-in cellulose?" ----- because it's much better;


No air pockets or movement;

The attic fan (beware the problems) should be ducted directly to the exterior.

Air seal the attic first;


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