i bought my house knowing that the insulation in the floor and ceiling was sub-standard (but it was exempt from the standard because it was built in 1962)...now that lowe's has a $100 rebate on $400 insulation purchases, i decided i'd go ahead and update it

i've installed insulation before, but it was the standard pink stuff...R-30 for attics and floors, i think

anyway, my attic currently has this light green lumpy stuff that doesn't feel like fiberglass...it's about 6 inches deep...i'm not aware of what this is...the roof was replaced in 2000, so i ASSUME it was put in then, but i don't know for sure

my question is this - what's the R-rating for this stuff? any ideas? i'm looking to purchase some more this weekend, but i don't want to purchase anything but what i really need (i was thinking probably 15 or 19, but i don't know for sure)

also, does facing really matter? i mean, it's in my attic, and sure, it's nice to be able to push down and cut through something that isn't fiberglass, but there's plenty of plywood for myself and my brothers to move around while we install it, so i'd rather save the ~$14/roll for the non-faced stuff

2/27/2009 3:17:34 PM

If I was at work I could get one of the older engineers to answer this in a heartbeat. So I cant help much with what is currently there :/

What I can ask is what kind of heating system do you have and where do you live? (as in "NC" would be just fine, I just don't remember where you live).

2/27/2009 4:30:31 PM

If it's what I think it is (cellulose insulation), the stuff currently in your attic has a total R-value of ~22 assuming that depth is 6 inches. 11+ inches is the desired depth for that type of blow-in insulation.

2/27/2009 5:12:23 PM

6" will give you about an r-19, you can lay batts of unfaced fiberglass over it, if you use faced over existing insulation, it will trap moisture and cause mold

under the house you should use faced, with the facing towards the living area

[Edited on February 27, 2009 at 6:32 PM. Reason : make sure it doesnt get packed into the eaves and block off the ventilation]

2/27/2009 6:31:21 PM

^ yep

you can stack more pink fiberglass over that as long as you dont trap moisture

2/27/2009 11:23:10 PM

i remember hearing the recommended depth of blow in insulation is 15". i had my attic reinsulated 2 years ago to this depth. my house was built in 1964 and reroofed about 8 years ago. it's made a significant difference in the overall stability of temperature in the house. i have yet to insulate the floors (they have none, never have had any). the insulation man said he didnt recommend it unless you are going to seal off the foundation and install a dehumidifier. haven't found the money for that yet (about $5000 for my 1604 sf house).

2/28/2009 7:04:18 AM

^ why did he say to seal it off? Do you have hard wood floors throughout or something?

Reason I ask is because I have a house that is a little older than yours with the same deal - no insulation ever in the floor. I am having it put in but neither the builder nor the insulation guy said it was a big deal to seal off the basement. The hardwood guy did mention that it may cause some separation of the floor since it will starve the moisture out. Just wondering.

2/28/2009 8:45:49 AM

yeah, i have hardwoods throughout (except kitchen & bathrooms = tile). i also have mold problems in a couple of closets and the master bathroom.

2/28/2009 9:34:52 AM

okay, so the folks at home depot and lowes seem to think that my blow-in has settled...they also said that i should lay the new unfaced insulation across the joists instead of between them, so as not to further compress the blow-in (which, apparently, would reduce its ability to insulate efficiently)...does all this sound right? i mean, it does in my head, but i don't want to take the word of HD/lowe's employees when i could take the word of the rest of you

thxu

3/2/2009 9:48:27 AM

Quote :

"i should lay the new unfaced insulation across the joists instead of between them, so as not to further compress the blow-in "

i've never heard of this. it sounds wrong. when my attic was reinsulated they just added more blown-in insulation on top of what was there. i would think you either have to fully remove the previous insulation and install batts or just blow more in.

i would call an insulation company. the guys at our home improvement places are clueless 99% of the time.

[Edited on March 2, 2009 at 9:53 AM. Reason : wat]

3/2/2009 9:50:00 AM

There is a nugget of truth - compressing blown insulation does reduce its R rating because there is less room for air. Insulation works a lot like wet suits do (just with air and not water). However, if you are not to your joist level now, then lay it between the joists because the limited compression won't mean much to all compared to the new stuff being added. If you are at the joists, go across them to have the joist support some of the weight.

However, check with a local insulator. In many cases, they can install it for you at a very small premium above what you could buy it for (due to their contractor discounts).

I have a 2150sq ft house and I had an insulator put another R30 bat in the attic and an R30 bat in the crawl space (non-standard 19" floor joist spacing) for ~$1600. At the time that came about to the same cost as buying the stuff and I didn't have to mess with hauling it, cutting it down or getting itchy from the fibers getting stuck in my skin.

3/6/2009 6:01:17 PM

i ended up buying 1000 sqft of R19 for $500 with a $100 gift card from lowe's (which was fine since i'm planning on buying some more stuff in the near future)...rented their truck for $20 to get it home and paid my younger brothers $50/each for the 3 hours it took for us to put it in

it fit between the joists, though it was definitely sticking up by 2-3 inches...not a huge deal, as the attic has very little flooring (and what plywood was there we unscrewed/pried up and then just left floating on top of the insulation where i want it for some storage)

now, at least, i should have about R38 up there for $520 and 3 hours of my time...the "master" bedroom (which was an add-on and is currently not in use) still needs to be done, but i'll do that later...the living space is finished, which is what i really cared about

^ that seems like a pretty good deal right there, especially when you consider that you don't have to do the work yourself

thanks for all of the advice...i HATE putting in insulation (i've done it a number of times, but always under the direction of someone else), but it's good to be finished for now

[Edited on March 8, 2009 at 7:59 PM. Reason : .]

3/8/2009 7:57:43 PM

I don't know, but loading/compressing the insulation under that plywood might be bad for the ceiling.

3/8/2009 8:34:33 PM

it won't weigh enough to really compress it much, but they are right, you will see a greater benefit if it's laid crossways. every little bit helps.

3/9/2009 10:51:47 AM

I was told when having mine done that compressing the insulation is ok as long as it was the bats and not the blown.

3/9/2009 12:21:02 PM