Looking for opinions from those who have been there, done that. The place I moved to this summer needs more attic insulation. Currently there are fiberglass batts, maybe R19 in the original part of the house and maybe R25 in the addition. Everything is for the most part easily accessible. I’m considering either rolling out fiberglass batts perpendicular to what is already there, or blowing in cellulose. I also saw a blown in fiberglass option when wandering through HD a while back. My only experience with attic insulation was feeding the blower for a friend who was adding cellulose to his attic. Didn’t seem too hard, but I was on the easy end of the job. Not necessarily looking for the cheapest or easiest, but the best return on investment. I figure at least doubling the R value will probably pay for itself in a couple years.
If you can, check any penetrations and do some sealing first. Then, pick your poison. Batts would be pretty easy, but I've heard the blown cellulose is a better insulator and shouldn't take too long if you have someone to load the hopper. Wear a respirator. I think R-38 is minimum, but more (up to about 49-50) is better. Oh, have fun.
I found a lot of cracks and gaps when I tore the drywall out of the back room. What started as removing wallpaper turned into uncovering damage from a former roof leak, finding buried junction boxes, then gutting the whole darn room and starting over. I rewired most of the place and plugged holes and any penetrations into the attic as I made them or found them (slab, no basement, so I know most every square inch of the attic by now). Probably would have been easier and cheaper to have rented a dozer and start fresh.
That's my usual fallback too, every time I start a new project here. I've kinda' gotten over it.....until next time.
Gallon of gas and a match, why rent a dozer?? I like the fiberglass over the cellulose. If you are going to have to have access I would suggest building a catwalk down the center so you can keep from compressing the insulation in the future. I just finished mine.
The main part of the house is block. I'd still have to get a dozer if I torched it. A catwalk is the plan. When I bought the place the attic was full of junk (mostly empty boxes and old carpet). Most of the floor had 1x8s nailed down over the insulation batts. About 80% of that floor got pulled up when I was running the new electrical circuits. The plan is to leave a bit of area around the attic access accessible (maybe a 5x5 area from one side of the access) for storing a couple items with an access walk down the middle for the off event that I have to get up there and do anything
Use cellulose does not lose r value as temps drop where as Fiberglass does. R value stays pretty constant even after it settles. Cellulose is also available in bats. There are one or two new items out there but I have not researched them. Fiberglass allows too much air migration hence the reason the r value drops with the temps. ( before you jump on me - look it up)
The best return on investment might actually be foaming between the rafters and converting the attic to conditioned space. Depends on your circumstances though.
contractor here.... I like fiberglass option. I blew my attic to R-50 3 years ago, it settled a little the first year but now its static. I dont like what happens when t he cellulose does when it gets wet. it absorbs the water and allow it to migrate through the insulation. Fiberglass seems to only get wet in the area right under a leak. Mold likes to eat celulose, just add water.
never had a problem with mold and cellulose. had some get wet due to a chimney problem. never had a mold issue in any of 3 homes that I did with cellulose- spans the course of 40 years. current home issue with ridge vent and high winds blowing snow/ rain some areas where cellulose got wet , do not see any mold problems. heck they install cellulose as a sprayed on wet pack ( not dripping but damp, glue base) for some installations. please look up "Minnesota Sustainable Housing" they have a nice brief on the subject at hand - nut shell - fiberglass while not supporting mold does pass the moisture on to the framing components that do, where as cellulose absorbs and spreads said moisture out over a larger area to dry. Course if the moisture is a continual problem- there are other issues at hand that must be corrected first with either type.
Nothing that I saw for rebates, short of a rebate on LED light bulbs... My first thought was cellulose, but I’ve bewn reading about the blown in fiberglass (Attic Cat by Owens Corning). Still kind of torn between the two, but I’m definitely leaning towards blown in something for ease of application. No signs of mold at anywhere in the attic. Ventilation appears to be good. The roof was done in 2014 and they cut in a ridge vent. There are baffles along the soffit, so that’s a good sign. All that said, this was a seasonal home for most of its existence except for a few years in the late 90s. The only thing I know for sure is that R19 ain’t enough attic insulation in northern Michigan....
With the new roof, this idea wouldn’t work. Something I’m considering when I do a roof replacement as it will allow me to make my attic a conditioned space. bobdog2o02 id be curious to get your take on it. Unfortunately you can’t read the whole article without subscribing. How to Install Rigid Foam On Top of Roof Sheathing - GreenBuildingAdvisor
I've seen rigid on top of sheathing, no issues. It would be just as easy with a new roof to hang batts in the rafter bays.... The spray foam is just a death sentence for exterior applicions, it doesnt allow airflow(duh) and cant completely prevent condensation. The condensation gets trapped and if its on wood or steel its decay central.
We currently have blown in fiberglass, installed years ago. It had settled a bit. And, I want to add knee walls around the perimeter with another 12 to 18". We're going to add cellulose to the top of the settled fiberglass, and the knee walls will also be cellulose. Hybrid!
My understanding is that when you are going to use it to make the attic a conditioned space that it is applied directly to the underside of the roof sheeting...so where is it going to condensate? The guy I had here to do some spray foam work is well respected in this area and he said this is how they would prefer to do it in attics...said they have had excellent results with it.
yes if everything is squeaky clean so that perfect adhesion is gotten - no condensation occurs- the other thing , which is seldom mentioned, is it needs to be closed cell type. Open cell which what is mostly used acts like a sponge- hence the bad rap. Cheaper than closed cell. Similar to fiberglass mfg conveniently not mentioning the the r-value drop with temps below 30 deg, F. Then someone will bring up rodent issues cellulose vs fiberglass- little buggers don't have any problems with the glass either. cellulose is treated with a number different things regarding bugs , rodents and fire. and for the echo minded it is way greener than fiberglass. Fiberglass was actually a waste product from something else, not much different than cellulose in that respect except that close to 40% of cellulose is recycled products. bonus ya don't spend a week itching from all those tiny little glass fibers invading your skin unless using a hermetically sealed suit. to each his/her own. Ford vs Gm vs Dodge deal anyway.
Blown in anything is better than batts. Modern blown fiberglass isn’t itchy anymore, they fixed that. I blew 178 bales of cellulose into my shop and it is a very dusty job. DIY friendly to blow in and superior to the best batt job.
