Attic insulation -- small job -- diy options?

[JackOfDiamonds]

I have a little 1 bay garage that I'm going to AC/heat with a mini split. From what I can tell even a 9000 BTU mini split is overkill for this small of a space, but it still seems weird not to insulate the attic. I'd like to spray some loose insulation up in there but I have a feeling I'm going to get gouged by a company on such a small job. And renting the machine from home depot is like $120 even before buying any insulation.

Should I give up and just buy some batt insulation and roll it between the studs? What kind?

If I don't insulate it at all is it any sort of condensation/mold liability? I live in a dry climate.

 

[cvairwerks]

Open studs or is their a ceiling of some sort?

 

[kaymccampbell]

The blower is free with 10 bags of fiberglass or 20 bags of cellulose. If you need less than those amounts, then I'd go with batt insulation. You can do fiberglass or rockwool.

 

[mejhaha]

Additional considerations are the weight of the blown-in and if you have soffit vents.

If your joists are on 24” centers and you blow a whole bunch of insulation this may be an issue.

If you have soffit vents you will need to figure out a way to keep the airflow unobstructed.

Just some thoughts.

 

[JackOfDiamonds]

There is drywall on the ceiling already with the typical wires running across everywhere, meaning installing batts could be tough.

 

[JackOfDiamonds]

For blown - in insulation, is fiberglass or cellulose better?

 

[pcmeiners]

From the itch prospective, cellulose is so much better. Unlike fiberglass, cellulose pack down a bit, becoming pretty air tight. Fiberglass's big fault is air travels through and around it, which lowers it's R value considerably, also the colder the ambient air temperature, the less efficient it gets. Lastly they add sodium borate to cellulose, a fire retardant and rodents do not like it. I did my mom's house, ballon frame construction..fire in the basement took out the uncovered beams/ floor above it but no fire anywhere there was cellulose.

 

[PoorUB]

One thing abut cellulose insulation is it has a life span. It is supposed to be replaced every 20-30 years. Most people it will not matter as they will sell the place and move on, but it is one reason I blew in fiberglass in my own home years ago.

 

[billconner]

Wow. Did not know that. But googling lifespan of insulation, not sure fibreglass is any better. Foam and mineral wool might be. Varying reports.

 

[pcmeiners]

"One thing abut cellulose insulation is it has a life span"

********, the ones that are saying it on google own insulation companies; How is ground up dry paper going to deteriorate ?. Accord to those companies fiberglass also has a lifespan...spun glass ( aside from paper backing) having a lifetime ?, maybe a 1000 years, maybe 2000 years, as a glass it melts over time.
What next on the expiration list..... dirt, air possibly water.
The fire I referred to in the last post, the cellulose was close to 50 years old, glad I did not know it was expired. Gee I wonder if my Vidmar cabinets have an expiration date ?

 

[lmg]

The above insulation lifespan statements are inaccurate at best. Please see attached link to a very reputable website.

What is the useful life of insulation, and why? - GreenBuildingAdvisor

In energy auditing, the useful life of blown in insulation (both fiberglass and celulose) is typically estimated to be 15 years. (in my experience) I would like some input on why that might be. My common sense is telling me it should be much longer. I read everywhere that cellulose, unlike...

www.greenbuildingadvisor.com

 

[PoorUB]

********, the ones that are saying it on google own insulation companies; How is ground up dry paper going to deteriorate ?

The above insulation lifespan statements are inaccurate at best. Please see attached link to a very reputable website.

What is the useful life of insulation, and why? - GreenBuildingAdvisor

In energy auditing, the useful life of blown in insulation (both fiberglass and celulose) is typically estimated to be 15 years. (in my experience) I would like some input on why that might be. My common sense is telling me it should be much longer. I read everywhere that cellulose, unlike...

www.greenbuildingadvisor.com

I wish I still had the information, but right on the package of cellulose insulation at the home center it recommended removal in 20 or 30 years. So it was the manufacturers recommendation. I forget the specific time period, but I remember standing there trying to decide and reading the package.

I guess all I can say is do your research and decide.

 

[lmg]

I wish I still had the information, but right on the package of cellulose insulation at the home center it recommended removal in 20 or 30 years. So it was the manufacturers recommendation. I forget the specific time period, but I remember standing there trying to decide and reading the package.

I guess all I can say is do your research and decide.

Here is the link for the cellulose insulation manufacturers association:

Cellulose Insulation Manufacturers Association

CIMA is a trade association made up of cellulose insulation producers and affiliated members dedicated to ensuring the highest quality cellulose insulation products and standards.

cellulose.org

You can contact them with any questions, contact info is there.

However they did post this under "Myths and FAQ":

If cellulose is made from recycled paper products, wouldn’t that decompose over time?​

Pursuant to the National Association of Home Builders (2007) Study of Life Expectancy of Household Components, “As long as they are not punctured, cut, or burned and are kept dry and away from UV rays, the cellulose, fiberglass, and foam used in insulation materials will last a lifetime. This is true whether the insulation was applied as loose fill, house wrap, or batts/rolls.”

Also, at the end of the Green Building Advisor discussion, there is this, which basically has the same info on cellulose insulation longevity as is stated above:

"According to NACHI, the life expectancy for most insulation is 100+ years." with this link:

https://www.nachi.org/life-expectancy.htm

The problem I have seen on blown in cellulose installed in walls, it is often installed at too low a density, and settlement occurs. I used to do insulation inspections on new homes, and we were required to do density tests.

 

[daws87]

I did about 30 bags of blown in cellulose this last winter. Took me and a buddy about 3-4 hours when it was all said and done (picking up machine/blowing in/returning machine).

HD does a free rental for the blower if you buy 20 bags or more. I'd advise that you air seal any gaps/cable drops/etc with spray foam beforehand and make sure you install baffles if you have soffit vents so you don't block airflow into the attic.

I went up the night before with a sharpie marker and headlamp to mark every few rafters with a line for how deep I wanted the insulation to be.

It's messy and you'll be sore but relatively easy. Made a massive difference in my gas bill (installed a gas heater a couple months before this insulation project).

 

[pcmeiners]

"I wish I still had the information, but right on the package of cellulose insulation at the home center it recommended removal in 20 or 30 years."

Still call it ********, not you the industry, I read a few references to insulation lifetime. How else are they going to sell insulation twice in a home owner's life. Nowadays everything is marked with expiration dates. Wonder if honey is now marked with an expiration date?

 

[kaymccampbell]

Something I'll add. If you blow in either, blow in a foot more than you want. I blew in 3+ feet and got a touch more than 2 feet after a year or so.

 

[engineer2]

If you use cellulose, you need to mouse proof the attic. They love to tunnel through it and make nests.

 

[mike93lx]

For such a small space, I'd buy rolls of Batts and not screw around with a blower. You'll be done a lot faster, with a lot less mess and in one trip to the store

 

[juddspaintballs]

I've never tested this out, but apparently you can buy the minimum quantity of insulation bags from Home Depot or Lowes to get the rental of the blower for free, use what you need, and return the unused bags of insulation without incurring the charge of the rental.

 

[JackOfDiamonds]

For such a small space, I'd buy rolls of Batts and not screw around with a blower. You'll be done a lot faster, with a lot less mess and in one trip to the store

In my experience I bought rock wool batts with no kind of facing or vapor barrier on them, they were just 4-foot long batts to go in a 2x4 wall.

I've also seen rolls of fiberglass insulation that have paper facing on them.

For an attic, would I want the kind with paper on it, or the plain batts? And if you get the paper, which side is the paper supposed to face -- into the attic, or toward the room (downward)?

 

[mike93lx]

Vapor barrier/retarder goes to the warm side because that is where the moisture is. So towards the room in a cold climate

 

[JackOfDiamonds]

Here in Idaho we have all seasons...it's always pretty dry though.

What about getting rigid foam panels and putting them on top of the rafters...leaving empty cavity between the sheetrock and foam panels? Would that be a horrible thing to do?

 

[mike93lx]

Here in Idaho we have all seasons...it's always pretty dry though.

What about getting rigid foam panels and putting them on top of the rafters...leaving empty cavity between the sheetrock and foam panels? Would that be a horrible thing to do?

Why would you do that and not fill the cavity?

 

[juddspaintballs]

I did use batts of rockwool in the last small insulation job I did in an attic. The attic scuttle was in the middle of the house almost 50' away from where I needed the insulation and it would have been another 15' or so to sit the unit outside and run it through a window. It was easier to just shove bags of insulation up through the scuttle and lay them out in the attic. I did a double layer where they laid in between the trusses and then I turned them 90 degrees when I put the other layer on so there were no gaps at all.

 

[JackOfDiamonds]

Why would you do that and not fill the cavity?

Because it would be really easy to just lay sheets of foam on top of the rafters...cutting it into 14.5" strips and putting between the rafters would be a lot more work and wouldn't interrupt the thermal bridge of the rafters either.

 

[mike93lx]

Because it would be really easy to just lay sheets of foam on top of the rafters...cutting it into 14.5" strips and putting between the rafters would be a lot more work and wouldn't interrupt the thermal bridge of the rafters either.

I wouldn't use foam board between the joists.

Dont reinvent the wheel. Just use insulation designed for the application. Lay in some Batts and then put foam board on top of you want to spend the money. I'd just fill the cavity with fiberglass then put another layer on top, perpendicular

 

[pcmeiners]

"If you use cellulose, you need to mouse proof the attic. They love to tunnel through it and make nests."

Not just cellulose, you should see my attic with blown fiberglass, about 1 million holes from chipmunks.
Ps found a mouse nest made of pink insulation in my basement, seems mice like the pink insulation over the bland white fiberglass insulation, go figure.

If you go with foam board between the joists, go to your first bank and get a home loan , you will need it.

 

[engineer2]

If I told my wife how many mouse tunnels I've found in our wall and attic, she'd want to sell the house.

 

[kaymccampbell]

If you use cellulose, you need to mouse proof the attic. They love to tunnel through it and make nests.

Rodentia are much less fond of the borate treated cellulose. And it doesn't stink in damp weather. Now, the ammonium sulfate treated stuff, the rodents like it, and it smells like pissy diapers in humid weather.

The ammonium sulfate stuff is more common, and cheaper. You have to be sure to pick the correct packaging to get the borate stuff. It's usually only available as lift gate delivery, and not in the store.

 

[engineer2]

Pretty sure we have the pissy diaper kind. If we ever sell, I'll go into the attic and cover up the tunnels.