Blown in or rolled out Insulation for attic?

[fishwatcher]

Hi everybody,

I have an attic space for my house which is 2500 sq ft, that currently has an avg R value of R19 (range is anywhere from R0 to R30). There is rolled in insulation now, and I'd like to add to it, to get the R value up to R30 @ least.

I have a quote from a company, to get up to R38, by adding blown-in insulation or add'l rolled-in (both on top of what I already have). The difference in price is $100, with the rolling in being a slight bit more).

The advantage of the blown in, is it's easier to do (for the company), and also that they could get to some more of the nooks and crannies where roll-in is tougher to do.

It's also messier, in case I ever need to do anything up there (add storage, add house fan or attic fan.

Any thoughs or experiences you might share on this?

I live in the south SF Bay Area (San Jose/Cupertino).

My goal is to reduce the temp in the house during the summer, and of course increase insulation for winter as well.

A next step, might be to add a house fan, and/or attic fan, to get the heat out of the house and attic.

 

[mycroftt]

The advantage of the blown in, is it's easier to do (for the company), and also that they could get to some more of the nooks and crannies where roll-in is tougher to do.

The advantage of the rolls is that it is easier to lift up if you want to do any work up there. It is also cleaner. I currently have blown-in and I'm replacing it piece-meal bay by bay as I need to do work up there. The ceiling fan for the den required installing an electrical box so that bay now has rolled-in insulation. I have to replace the bathroom exhaust fan and vent it out the eave because the hacks that built the house just vented it into the attic - so rolled-in insulation will be going in there...

 

[Bob W]

I've used both, and there's no reason you can't do insulation yourself. I use the rolls anyplace with easy access, or where it has to be suspended like on walls. I use blow-in anywhere with difficult access.

The advantage of the blown in, is it's easier to do (for the company), and also that they could get to some more of the nooks and crannies where roll-in is tougher to do.

Even doing it yourself, the blow in is easier in some ways, more difficult in other ways. For instance, it takes two people to blow-in, one to feed the machine and one to handle the hose. The blow-in machine is ~very~ heavy. But the work itself is faster and easier. Roll insulation is time-consuming and a PITA, but you can do it alone.

It's also messier, in case I ever need to do anything up there (add storage, add house fan or attic fan.

A non-issue, IMO. Working in either is dirty.

My goal is to reduce the temp in the house during the summer...

That's the primary concern in New Mexico too. I did something that makes a lot of sense to me but isn't usually done, with incredible success - I insulated between the roof rafters! That way the attic doesn't get hot to start with. The difference is night and day; the 3rd floor used to get too hot to even go up there, and now it's only a bit warmer than the rest of the house.

A next step, might be to add a house fan, and/or attic fan, to get the heat out of the house and attic.

My mother's house in Illinois has an attic fan. It works off a thermostat. There are also un-powered roof vents. Save your electric $$ for the AC and refridgerator. Eave vents are important too, for fresh air intake. And I've seen hip vent systems that install beneath the roof shingles.

Lots of choices and options. But no single thing will make more of a difference than a large shade tree keeping the direct sun off the roof.

Good Luck!
-Bob

 

[TLM]

The best results seem to result from using the insulation in block form, rolled fiber insulation seems to be softer and more difficult to handle.

Blown insulation needs cover on top that the others don't.

TLM

 

[dttomcat]

Avoid the blown stuff like the plauge!!! What a friggin' mess that stuff is. Everytime I
went up into the attic for 20+years that blown stuff would get all over. Plus I'll bet you
and your family will end up breathing the stuff. It would be worth $1000 additional if that's what it cost. Sorry for the rant. -DT

 

[spyder10]

...Plus I'll bet you
and your family will end up breathing the stuff.

Well the blown insulation is usually cellulose, which is not especially great to breath, but is no where near as bad to breath as glass fibers are.

 

[Ken C.]

Blown-in insulation = major fire hazard.

If you want your house to burn to the ground in a matter of minutes then get the blown-in stuff. I've seen a fire go from a small flame to a raging inferno in 4 minutes...tops. Once the flame gets into the walls it's all over.

 

[JatMat]

Blown-in insulation = major fire hazard.

Ken, are you referring to blown in cellulose or fiberglass or both. I have 14" of fiberglass ( me thinks) blown in. Once had a fire that started in the wall behind a faulty fireplace, it was stopped at the top of the wall because of the insulation allowed it no air, I was able to rip off the sheetrock and put out the charred and smoldering studs with wife and kids bringing buckets of water in, I had the water ready before I ripped it off because I felt how hot it was. But what you said has given me pause. Should I have it taken out and rolls put in? You know what you are talking about and I respect that and would appreciate your input.

Jim

 

[Ken C.]

If you suspect that you have a smoldering fire in a wall that has blown-in cellulose insulation you should never, ever try to put it out yourself. Once you pull the sheetrock you'll feed the fire the oxygen it needs. Once that happens it's all over. Fiberglass smolders and it doesn't burn as quickly as the cellulose but it does burn. It generates a lot of heat if left sitting. You were lucky. Always call the fire department is you suspect a fire in your walls.

 

[spyder10]

Cellulose insulation is treated with fire-retardants to help prevent smoldering which IIRC is more dangerous than a flash-over type flame.

 

[JatMat]

We live on top of a mountain, and it was during an ice storm, the first two trucks sent out slid off the side of the road. The third came from a different direction and station, I had the fire out, smoldering 2x4's torn out and taken outside before any one showed. The fire inspector that finally showed up, said God was with us, had the fire reached the attic, and gotten the rafters on fire, we would have been gone in that 4 minutes you talked about. Our family was safe and we had insurance to cover the smoke damages to carpet, walls and ceiling. You are right, call for help, but if I had gone outside and waited, we would have been building a new house rather than painting and putting new carpet down.

 

[555]

Blown-in insulation = major fire hazard.

If you want your house to burn to the ground in a matter of minutes then get the blown-in stuff. I've seen a fire go from a small flame to a raging inferno in 4 minutes...tops. Once the flame gets into the walls it's all over.

Wow you've got me thinking.

I just had a house built the only place they used blown in Cellulose insulation was in the attic.

everything else is fiberglass.

so do you think one should vacuum out the cellulose in the attic and replace it with blown in fiber glass?

 

[TLM]

Hereabouts most blown insulation is mineral fiber, glass and cellulose being in the minority.

Fiberglass smolders and it doesn't burn as quickly as the cellulose but it does burn.

I would like to know where this is from, I have done some fire tests with fiberglass and it did not burn or even smolder. It crumbles when exposed to too high temp but as I understand it, it is difficult to burn something that basically is already burned.

TLM

 

[Ken C.]

I'll get that info for you when I locate the source. I seem to have lost the link.

This is what I do know as given to me by our resident fire inspector in house....fiberglass blown-in is designed to smolder and not burn. Cellulose smolders but free burns when exposed to O2 in some cases where firestops are not present.

Fiberglass blown-in insulation is mean to be used in attics, not in walls. The fiberglass compresses itself after time resulting in heat loss throughout the home. Cellulose in walls is preferred as it doesn't compress.

 

[Deerslayer71]

Sorry all you Fiberglass fans, The cellulose is a better product when it comes to R value.
Ken there is flame retardant in the cellulose. I did my own study on this and could not get the stuff to burn. little bits or handfuls on an open fire, even a torch. I was able to get fire when I soaked it in Kerosene . I guess it would make a good wick.

I Built Homes for 13 years. The fact that fiberglass batts come in a defined shape means that the nooks and crannies are going to be left exposed. (less insulating going on here)
I put Celulose in my own home.
Generally attics are not rated to carry any more weight than the drywall and insulation. Excepting for attics that are designed for storage. So, Build a bigger garage and put stuff in there, Blow in cullulose and stay out of the attic.