Adding Attic Insulation

I live in an old N.O. house that had no insulation in the attic and when I decided to insulate it I priced the rolls of insulation needed it was actually much cheaper to have a company come out and blow in insulation to a depth of around 12 inches into my attic.

This is not cellulose insulation but fiberglass pieces that were blown in the attic in one morning. Two guys showed up and 1 got in the attic with the large hose and 1 on the ground with the hopper he filled with the insulation that was blown in.

The only place the insulation is a bit compressed is where I've walked the joists to do stuff in my attic.

No way in hell I'd want to put rolls of insulation up in an attic, especially with summer approaching.

When we got our heater replaced in February I got the crew to blow in insulation at the same time. Their rate was $1 per square foot of the house. I am sure it would have been a lot cheaper to do it myself, but it was well worth it to pay somebody else to do it. Our roof is so low and the attic so cramped I would had to have army crawled around and would not have done a good job. It probably would have taken me 5 times as long as well. If we were still in our old house where I could easily walk around the entire attic I would have done it myself in a heartbeat.

I have a buddy who did blow in his own and bought the insulation from Home Depot and got the free blower rental. The employee there told him to buy enough insulation to qualify for the free rental and if he didn’t use all the insulation to just return what he did not use and they still would not charge for the rental.

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1. Is the research I've done correct that max depth for attic insulation in S. Louisiana is 16“?

1a. Should I put the full max height?

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The recommended R Value is between R-30 and R-38. Using loose fill cellulose insulation, that's around 10 inches.

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2. Will it be much cheaper to do myself? How much (guesstimate)?

2a. If not, what would a company charge?

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Yes. Depends on a lot of factors but blow and go +$400. Doing the job right +$1200.

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3. Is there a formula for how many (bales?) of insulation I'll need?

3a. What R value should I buy?

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R-value = 38 – Existing R-value = Needed R-value

Measure the existing insulation. A conservative estimation is R-3/inch. Each package of blow in insulation has an estimated value of R-3.7/inch and a coverage area of 40 sq. ft.

Let's say your average insulation was 7 inches.

R-value needed = 38 – 21 = 17

Lowes and HD carry R-19 cellulose

Let's say 2,000 sq ft/40 = 50 packages should be more than enough to get you covered.

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4. Any suggestions, tips or guidance?

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Doing the job right requires more than blowing insulation in thin spots. I understand not wanting to pay $1,500 - $2,000 for professionals to do it. If you DIY it though, take the time to do the extra things like raking the existing insulation back and air sealing the envelope for thermal bypass leaks.

This means sealing recessed lighting, wiring or pipe holes, electrical boxes, and gaps around the top plates and gypsum board. Insulation doesn't prevent leaks into your attic. It just slows them down.


Check your duct work for leaks while you're up there. While I was up in my attic I found a penetration in the damn supply plenum, flapping around as if it were a vent.

Make sure you have your soffit vents protected so you're not blowing insulation into them and blocking air flow.

Lastly, PPE. You're going to be spending some decent time in your attic no matter the scope of the job you plan on doing. There's a lot more nasty stuff blowing around up there than just insulation so dress accordingly.