Home>Discussions>INSULATION & HVAC>Blown or Batt insulation under plywood in attic?
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mark75063
Blown or Batt insulation under plywood in attic?
mark75063

My 17 year old house has blown fiberglass insulation. I would like to create walkways in the attic by nailing plywood to the tops of the joists, which would obviously cover the insulation. Before doing so I would like to make sure the insulation under the plywood is the best it can possibly be. I could either add more loose fill insulation by hand, or replace all the loose fill under the new plywood with batts. I intend to add cross-members between the joists such that the area under each piece of plywood is sealed.

So my question is- what would be better for such a scenario- 17 year old blown insulation with some loose-fill added by hand (I don't have a blower or aerator), or custom fitted batts?

Thanks in advance.

Fencepost
Re: Blown or Batt insulation under plywood in attic?
Fencepost

Hand-applied loose fill is not as effective as either blown-in or batts. That's because when applying it by hand, it's impossible to get it fluffed up properly, so it remains somewhat compressed. Compressed fiberglass insulation has a lower R-value per inch.

Even if you plan to do the work yourself, get a few bids from contractors. In my part of the country, it's usually cheaper to pay someone else to do it than to buy the materials and do it yourself (I have no idea how it works out that way.)

You can rent the blower -- I think both Lowe's and Home Depot have it. Some stores (don't know about those two) will give free rental if you buy enough insulation.

mark75063
Re: Blown or Batt insulation under plywood in attic?
mark75063
Fencepost wrote:

Hand-applied loose fill is not as effective as either blown-in or batts. That's because when applying it by hand, it's impossible to get it fluffed up properly, so it remains somewhat compressed. Compressed fiberglass insulation has a lower R-value per inch.

Even if you plan to do the work yourself, get a few bids from contractors. In my part of the country, it's usually cheaper to pay someone else to do it than to buy the materials and do it yourself (I have no idea how it works out that way.)

You can rent the blower -- I think both Lowe's and Home Depot have it. Some stores (don't know about those two) will give free rental if you buy enough insulation.

Thanks very much for your reply. I plan on doing this work in conjunction with other attic projects such as installing a ceiling fan and lights. I intend to build a walkway to whatever area I will be working in to complete these other projects. I can't afford a contractor for all these projects, and renting a blower multiple times would get very expensive. So I think I will go with well fitted batts under the plywood.

Thanks again.

Fencepost
Re: Blown or Batt insulation under plywood in attic?
Fencepost

Since you'll be accessing the area multiple times, batts are probably a better option. If it gets compressed, a batt rebounds well. Loose-fill, on the other hand, once compressed stays compressed.

dj1
Re: Blown or Batt insulation under plywood in attic?
dj1

You have to know the R value required in your city, then the size of your joist before you get your insulation to fit. Make sure the plywood doesn't compress them too much.

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