fiberglass or cellulose blown in ceiling?

[gogolf0401]

I spray foamed my walls and now need to blow in insulation in the ceiling.

Looking for input on whether to use cellulose (15" or so) or fiberglass (18-19").

Planning to add 6 mil poly to the ceiling before the insulation.

Here's what I know so far:
Cellulose will settle, but is more dense than fiberglass so it will give you a greater R-value with less thickness. Costs more than fiberglass. Fiberglass doesn't settle but doesn't stop air flow that well.

Some companies don't even quote using cellulose since they claim it is bad for holding moisture.

My rafter baffles will allow for about 15" of fill at their opening against the roof and about 12" at the top of the wall, so I was wanting to go with cellulose, otherwise I'd have less R-value in those areas until I get past the end of the rafter baffles. Hoping for R50 in the ceiling.

 

[NUTTSGT]

If you spray foamed the walls, can you swing the cost of flash and fill ?

 

[Radix2]

I bought fiberglass to blow in my attics, read everything about blown in fiberglass in cold climates - took the fiberglass back and bought cellulose.

In MN, I would think cellulose is the way to go too.

 

[jvitez]

+1 on Cellulose.

Blown in fibreglass loses R-value the colder it gets. Check out the spec sheet on fibreglass, it will say to increase the thickness installed if you're in a very cold climate. Cellulose doesn't say that.

The problem with fibreglass is than convection currents occur withing the insulation itself when exposed to moving air in a ventilated attic. Cellulose settles, forms a hard crust in the top inch or two which acts as an air seal, so no convection currents.

I have high density spray foam in the walls of my house and R60 cellulose in the ceiling.

Why do some contractors push blown in fibreglass? Because its way less dusty to install.

 

[trainer]

+1 on Cellulose.

Blown in fibreglass loses R-value the colder it gets. Check out the spec sheet on fibreglass, it will say to increase the thickness installed if you're in a very cold climate. Cellulose doesn't say that.

.

The reason that more insulation is recommended in colder climates is because it gets colder there. Just like you put on more layers of clothing on when it's -20 out than when it's +40

As for the OP's question, I've used both and there is really no difference in performance.

The fiberglass was quicker and easier to install, but that was probably just because of the particular machines I rented.

The fiberglass job is 10 years old and the cellulose was 6 years ago. Both still have the same heating equipment and the heating fuel used has been pretty constant for both.

 

[DC73]

+1 on Cellulose.

Blown in fibreglass loses R-value the colder it gets. Check out the spec sheet on fibreglass, it will say to increase the thickness installed if you're in a very cold climate. Cellulose doesn't say that.

The problem with fibreglass is than convection currents occur withing the insulation itself when exposed to moving air in a ventilated attic. Cellulose settles, forms a hard crust in the top inch or two which acts as an air seal, so no convection currents.

I have high density spray foam in the walls of my house and R60 cellulose in the ceiling.

Why do some contractors push blown in fibreglass? Because its way less dusty to install.

Agreed. Building scientists generally recommend cellulose over fiberglass in situations like these. One added benefit of cellulose is that it is more environmentally friendly than fiberglass.

I prefer mineral wool insulation but I'm not aware of any ready available blow-in product, only batts.

DC

 

[Jess]

There are advantages and disadvantages to both. In older houses with no vapour barrier, air infiltration is an issue. Cellulose will pack somewhat denser than fiberglass so reduces it a bit. Dust from cellulose is a negative. I have both in rentals and for ease of application and cleanliness, I will do fibreglass again. Air sealing all the wall penetrations is a must with either. Good ventilation above either is also a must. If you have good access to the space, then mineral wool batts are an alternative.

 

[sands35]

The nice thing with fiberglass is that *if* there is a leak, you will know about it sooner. Water will run right through it rather than get absorbed.

As far as packing down and winter performance, just put in another R5 or so. Not sure if the costs are the same for R50 cellulose vs R55 fiberglass though.

 

[davidw221]

I used Roxul batt R30, 15.25" wool insulation, easy to cut, friction fit, really nice, I back in the day used to insulate new and consisting homes, use cellulose and fiberglass, I'd thought I'd try this product, I'm really impressed, will use it again, and recommend this product to anyone.

 

[jvitez]

Roxul is a superb product, no question, much better than fibreglass batts. I used
Roxul in the walls of my garage.

However, blown-in insulation is better in a ventilated attic space as it fills in every nook and cranny so you get no voids like you can with batts.

 

[Dragfluid]

Cellulose in the attic for sure. Less expensive (especially if you buy it right) and if you buy quality product, the dust is minimal. Plus, as previously stated, it gets into every spot up there.

Gogo, where are you at? There's a cellulose manufacturer in Loretto that I bought all of mine from. I dense packed it in the walls too, so I bought quite a bit. (42x72x16) http://www.insolutionmfg.com/index.html
Nice, clean stuff, and a hell of a lot cheaper than the box stores! It got delivered on a semi.

 

[Strouty]

Threads like this are very informative, thanks for sharing guys.

 

[awdblazer]

way up north to everyone
i went blown in fibreglass
the fibreglass is no itcy
if it gets wet, it dries
no dusty at all
super easy to install (owens corning atticat) cut bag in half feed half bag into hopper (bag and insulation) and then pull plastic out
went from a r12 approx to r60 in less than an hour in a 1000sqft house (including going to get the blower and returning it)
did it 2 winters ago, local utility paid for all the insulation all i had to pay for was the baffles and rental of the blower

 

[acer66]

would mineral wool be an option?

 

[gogolf0401]

Cellulose in the attic for sure. Less expensive (especially if you buy it right) and if you buy quality product, the dust is minimal. Plus, as previously stated, it gets into every spot up there.

Gogo, where are you at? There's a cellulose manufacturer in Loretto that I bought all of mine from. I dense packed it in the walls too, so I bought quite a bit. (42x72x16) http://www.insolutionmfg.com/index.html
Nice, clean stuff, and a hell of a lot cheaper than the box stores! It got delivered on a semi.

I'm near Fargo ND. I am leaning towards cellulose just because I can get more r value with less since I only have 12" near the soffit.

 

[Denwood]

If you have the ceiling exposed and can do very good job air sealing with the poly, cellulose would be my pick. We did 2" of sprayfoam in the attic over a balloon framed/plaster lathe ceiling to air seal, and then added R60 of cellulose over that.

Previous to the foam air seal, there were frost issues in the attic so everything in there had to be sucked out. After the foam/cellulose, it was tight, and warm over last Feb. with a -20C average temp.

The cellulose does see less convective heat loss at very low temps. I also like that it's pretty much 100% recycled material. For what it's worth, because it's denser, it also dampens sound better.

 

[TooMuchHair]

Fiberglass for sure! The problems associated with fiberglass regarding convective losses and loss of R value in cold temps have been addressed by the manufactures of today's fiberglass blown in products. In the beginning of fiberglass for blown in they were cutting the waste batt style material in cubes to use with the blowers. This laid in with considerable air flow space which did cause problems. ALL OF THIS IS NOW FIXED! EVEN THOUGH THE CELLULOSE PEOPLE CONTINUE TO FEED THE INTERNET WITH THIS OLD INFO.

http://www.structuretech1.com/wp-content/uploads/2011/07/OwensCorning.pdf

 

[cowboyjosh]

Use to insulate all the attics in my homes I build with blown in fiberglass, now days I switched to cellulose and even over topped the fiberglass in my attic with cellulose. I still insulate walls with fiberglass batts though.

 

[gogolf0401]

Use to insulate all the attics in my homes I build with blown in fiberglass, now days I switched to cellulose and even over topped the fiberglass in my attic with cellulose. I still insulate walls with fiberglass batts though.

What made you switch?

 

[ddawg16]

Use both?.....blow in to fill the cavities between studs? The lay batts on top of the blown-in