Blowing In Attic Insulation: Fiberglass vs. Cellulose

[Ashyukun]

Things are finally together enough and things cleared out of the way such that I really need to tackle insulating the attic of the house we just moved into. The inspection noted that there was very little there, and it's always been MUCH hotter up on the top level of the tri-level so I've been itching to get the attic insulation taken care of so it's more livable up there and to help lower the electric bills a bit (though they are actually not bad overall, using less is always nice).

A friend and our former realtor & landlord who has done this a number of times volunteered to help me out with it and we're going to tackle it early Saturday morning. Yeah, it would be nice to not have to do it in the middle of summer, but I figure the few hours in the heat will be worth it for the rest of the summer (and those going forward) being more comfortable inside.

There is some disagreement between he and I though regarding what form of insulation to use. From the earlier blog post here and a lot of searching around on The Googles, it seems that cellulose is the way that I would want to be going on pretty much every count. My housing contractor father-in-law concurs with that and has said that they use cellulose since it insulates better and costs less than fiberglass for the same volume. Our friend/realtor though swears by fiberglass and that it's the way that I want to go.

I realize either one should be a massive improvement over the almost non-existent insulation up there at the moment- but I also want use the better of the products. What say you?

[Bourbon]

I said cellulose.  We blew that in in the middle of the night in December after we got our first house.  We were storing things in the attic and while I had no reason to get into contact with the fiberglass I knew that I'd brush against it more often that not.  I don't like that feeling, and while I've worked with Fiberglass batts before, I didn't like the idea of the loose stuff moving around. 

Cheaper and less itchy was about the extent of my decision making.  I think I read up on it at the time and got the same thing, found people swearing by both.

[Cromacster]

I recently did this and I chose cellulose.  Mostly because I didn't want to deal with the fiberglass.  I still need to go into my attic for a few more projects and I felt the cellulose was a better choice.  Both solutions work.  I believe the fiberglass has more R per inch ( I could be wrong), but also using cellulose is suing recycled material....so you can feel good about that if it tickles your fancy.

On that note, make sure you spend time air sealing all the gaps, penetrations, top plates, etc etc...  While doing insulation alone will help, prevent air from escaping into your attic will have a huge impact on the performance of your insulation.

[Ashyukun]

Yeah, I will be spending some quality sauna-time up in the attic before doing the actual insulaion making sure everything is as sealed as I can get, putting in baffles for vents, and maybe even adding in power drop in the ceiling for a TV we have mounted in the wall.

Head back from the brother-in-law as well who followed his dad's footsteps into home constructrion, and his vote was for the cellulose as well- so the overwhelming tide seems to be in favor of the cellulose . My guess is that landlord friend (who fixes up and rents/flips houses) has just always used fiberglass and is set in his ways regarding it.

[Stachesquatch]

We are going to have insulation blown in next month, leaning toward cellulose. 

One thing to think about- in our circumstance there are components of our heat/AC system in the attic that will be serviced/insulated as a part of a major system energy audit and the HVAC company said it was good that we contracted them to do their service first because they would not do the job if insulation had just been blown in (Maybe they assumed Fiberglass?).

Advice is- check to see if any other work (wiring upgrades, additional wiring such as for new ceiling lights, new attic vents etc.) needs to be done prior to having the insulation blown.

[Cromacster]

Advice is- check to see if any other work (wiring upgrades, additional wiring such as for new ceiling lights, new attic vents etc.) needs to be done prior to having the insulation blown.

^This.  I had a tight window to complete my insulation, but I wish I would have completed all my projects in my attic beforehand.  Not that it is impossible, but it does make things a bit more complicated with all the loose insulation.

[Ashyukun]

About the only real thing that I can think of that may need to be done in the attic (because the wife doesn't like the look of the cords hanging down from the swiveling wall-mounted TV in the LR/DR/Kitchen area) is to put in an outlet box in the ceiling to plug it in to. The house was renovated extensively before we bought it and other than the considerable lack of insulation there shouldn't be much else to worry about up there- but I'll hopefully determine that for certain this evening.

[Emg03063]

On a cost & performance basis I think they're pretty much a wash.  2 considerations:  cellulose, being denser will tend to compress existing fiberglass insulation more for any given additional R-value, so if you're applying over fiberglass, I might stick with fiberglass for that reason.  From an environmental perspective, cellulose has much less embodied energy, and is the clear winner.

[Ashyukun]

Ended up going with the Cellulose on the strength of recommendation from the house-building contractors in my wife's side of the family. Blew in 40 bags of the stuff between the two attics in the house over the course of a few hours. Frankly, I probably could have done another 20 bags without any trouble, but 40 bags should have gotten it all to about R-30 which is a massive improvement over the almost bare sheetrock ceilings.

It makes a NOTICEABLE difference on the upper floor- when the rest of the house is comfortably around 75 thanks to the AC, it used to be that you'd walk up the stairs to the top floor and just get assaulted  by the heat. I never measured it, but it HAD to be a solid 10 degrees F warmer just walking up the half flight of stairs. And THAT was with having most of the vents on the lower levels blocked off so more air went up to the top floor.

Now, the top floor is still a slight bit warmer than the rest of the house- it's always going to be that way by the simple fact of heat rising- but it's no longer just HOT and uncomfortable up there and we can now use it normally during the summer. I imagine it will be a massive help with the heating bills in the winter, and will help in the summer as well. It's ALMOST a pity I did it so soon after moving in so we won't really have a good baseline for what the electric bill was before the insulation- though I suppose the Nest's report feature should be able to show me the nitty gritty on it.

[TomTX]

Cellulose, cellulose,  cellulose! It is MUCH better than fiberglass for stopping airflow - either small gaps in the ceiling,  or convection in the insulation itself. For the same nominal R value, cellulose does a much better real world job of stopping heat flow.