Attic insulation questions

[Duck tape Bill]

So here is the back sorry: I want to add some insulation to the attic space in my house that currently has fiberglass bat insulation between the 2x4 roof trusses. The upstairs gets hot in the summer, and cold in the winter, and it's obvious that there isn't enough insulation up there. My idea was to simply rent a diy machine and blow in another 6-8" of cellulose on top of the fiberglass, but after spending some time up in the attic over the last year or so I'm less sure of my plan.

Here are the problems:
1. the current insulation is old, crappy, has been moved by me and previous owners, and has lots of animal S!@# in it (mouse, and something larger).
2. it's not installed evenly, so I wouldn't get an even depth of cellulose if I put it on top.
3. much of the paper backing on the bats, especially along the center of the attic, or anywhere a wire goes through, has been ripped.

Here are my questions:
1. does it make sense to take out the old insulation (pain in the ***, but I'm more than willing to do it).
2. if I remove it, I remove the paper vapor barrier, is that a problem? (note; I plan to seal all air gaps with foam)
3. how would I replace the vapor barrier, if I needed too. (if not then obviously it's not a problem).

Thanks in advance.

 

[mg283680]

I'm pretty far south of you (DFW) but I blew in cellulose and it made a big difference. Removing fiberglass doesn't sound fun.
Might want to remove the and from the sig.

 

[gpflepsen]

I would expect a vapor barrier under the insulation, like a poly sheet.

Regardless, unless the poo was causing issues such as smell, I'd just blow cellulose over the fiberglass. Mark as many truss webs with a sharpie with the depth wanted. It's easy to make the depth uniform with ample marks.

 

[WVBrady]

Whichever way you go, I imagine that you will wear a good respirator. Important not only for fiberglass dust, but also mouse droppings which can carry hanta virus.

 

[davidw221]

Lowes has fiberglass with the blower, don't use Cellulose, I use to blow that **** in houses for a living, not my house, just fiberglass.
The ceiling needs to breath, use the egg carton blockers they sell at the home stores, you need 1.5Ft of vents for every 100sq of attic space.
NO vapor barrier for the ceiling, your garage needs to get rid of the moisture, molt will develop if you do this!

 

[Duck tape Bill]

Might want to remove the and from the sig.

Lol, it's a quote form the Simpsons, something Ralph Wiggum says.

“Me fail English? That's unpossible”

 

[Duck tape Bill]

Whichever way you go, I imagine that you will wear a good respirator. Important not only for fiberglass dust, but also mouse droppings which can carry hanta virus.

Way ahead of you on that. I hate the dust form fiberglass, even just on my skin it itches, so I figure it's worse in my lungs.

Lowes has fiberglass with the blower, don't use Cellulose, I use to blow that **** in houses for a living, not my house, just fiberglass.
The ceiling needs to breath, use the egg carton blockers they sell at the home stores, you need 1.5Ft of vents for every 100sq of attic space.
NO vapor barrier for the ceiling, your garage needs to get rid of the moisture, molt will develop if you do this!

I have plenty of venting (full length ridge, eve, and soffit). The space is above the 2nd floor, so above the bedrooms (not on top of the garage). Sorry, I guess I should have clarified that.

 

[Duck tape Bill]

I guess my thoughts are that removing the old crappy fiberglass and starting over with new blown in cellulose would be better/cleaner in the log run. My main concern isn't the extra work involved, but the fact that removing the fiberglass would remove the paper vapor barrier at the same time. There's no good way I know of to replace it once it's gone, but at the same time, it's already messed up in enough of the attic that it might as well not be there, and there are zero issues with moisture in general.

I guess my biggest questions is: can I pull out the old fiberglass, seal all the air spaces with foam, and blow in cellulose without any problems?

 

[DC73]

I guess my biggest questions is: can I pull out the old fiberglass, seal all the air spaces with foam, and blow in cellulose without any problems?

Insulation details are very climate specific. What works well in one part of the country may be disastrous in another climate. Pose your questions on the Q&A forum at GreenBuildingAdvisor.com

I think you'll be alright with your plan but best to check with the experts.

I've covered fiberglass batt insulation with blown-in cellulose (I much prefer cellulose over fiberglass) and it worked well in my climate. Personally, I wouldn't remove the existing insulation.

DC

 

[Chris705]

Paint stores sell a low permiable paint to use as a vapor retarder on your ceilings. While kraft faced or foil face insulation offer a certain level of stopping vapor transmission each joist or truss bay allows vapor to pass along the seams. There would likely be less vapor transmission if you painted ceilings below & sealed up wire & elec boxes with foam.

 

[SMKS]

Lowes has fiberglass with the blower, don't use Cellulose, I use to blow that **** in houses for a living, not my house, just fiberglass.

Can you give any specifics on why you think fiberglass is better?

I've been researching this for my house and I'm leaning towards ellulose.

 

[DC73]

Can you give any specifics on why you think fiberglass is better?

I've been researching this for my house and I'm leaning towards ellulose.

I don't agree with David that fiberglass is better. My research says otherwise. I prefer mineral wool over cellulose but it does cost more.

Check out BuildingScience.com and GreenBuildingAdvisor.com for plenty of info.

DC

 

[WoodstoveWil]

I have plenty of venting (full length ridge, eve, and soffit).

I would check to make sure that the vents you have in place are working together. When I was working construction (a while ago) we had customers that wanted maximum venting and requested gable vents, ridge, fans, you name it on the same project. The vent systems are each meant to work as a standalone and can work against each other if more than one type is installed.

 

[finn]

My experience is that fiberglass is much cleaner to blow into the attic.

The modern formulations keep the dust down compared to cellulose, and I don't notice an "itch factor." Costs more though. It's also less of a hassle to deal with in the event you have to crawl around in the attic in the future.

I've been renovating a late 60's houst that was insulated with period fiberglass batts. They are really unfriendly to handle compared to any of the brands I can get from the box stores or lumberyards now.

Not as sharp & scratchy. I assume there is technology to melt the ends of the individual strands in the production process now.

 

[Slowgsr]

I just blew r45 over r14 batts of roxul. I blew in fiberglass, should be about r60.

Very easy to do, clean, very little dust. I wore a respirator, and wasn't even itchy when done. I marked my trusses and once I got near the end I had extra so the front of the shop got a little extra.

To do my 30x30 building it took less then 2hrs - you need a helper to load the machine while you stay in the attic

 

[Milzo]

I don't agree with David that fiberglass is better. My research says otherwise. I prefer mineral wool over cellulose but it does cost more.

Check out BuildingScience.com and GreenBuildingAdvisor.com for plenty of info.

DC

X2 cellulose is better than fiberglass. more r-value per inch and restricts airflow more than fiberglass.

 

[Duck tape Bill]

Thanks for all the replies. After being up in the attic several hours last weekend, I decided the old fiberglass bats have to go. I need to move most of them to air seal the attic anyway, and I think in the log run it's better to just get rid of the old nasty stuff and start fresh, so that's what I'm going to do. Based on what I've read, and the comments here & in other threads, I'm going to go with cellulose instead of blown fiberglass. Again, thanks for all the replies.

 

[Radix2]

I think if you read the latest on insulation and vapor barriers you will find that very very little moisture moves through painted drywall - the moisture moves through air leaks and having things like plastic barriers in the mix is often more trouble than it is worth. I think your plan to seal the air gaps is the best one and the use of cellulose to limit air circulation is an added help.

 

[csp]

If you go to the trouble of removing the existing insulation it would be worth your while to seal every intrusion into the ceiling drywall. Can lights, electrical boxes. flue and vent pipes are prime sources of heat loss from air movement. There's no better time to seal them if they are all exposed.

 

[mg283680]

Regarding post #17, is a great insulator so if you blow in something over the glass, its good.
Why do the bats have to go?

 

[Duck tape Bill]

If you go to the trouble of removing the existing insulation it would be worth your while to seal every intrusion into the ceiling drywall. Can lights, electrical boxes. flue and vent pipes are prime sources of heat loss from air movement. There's no better time to seal them if they are all exposed.

This is exactly the plan

Regarding post #17, is a great insulator so if you blow in something over the glass, its good.
Why do the bats have to go?

The old bats need to go for several reasons (I already went over this, but I think more detail might be helpful):

#1 - Air Gaps: The bats were originally 4ft r30 bats laid between the roof trusses, so to start with there is an air gap every 4 feet where the paper vapor backer meets. Plus the electrical wiring was installed after the attic was insulated, so all the wires (and there are many) that run through the attic created more open air gaps wherever the electricians put a light box or ran a wire into the top of a wall. Of course, when the ran a wire, they move the insulation, tearing the vapor barrier. Also, none of the wire holes, light boxes, wall gaps, vent pipes, flue pipes, ext. were sealed, so lots of air moves between the attic and 2nd floor.

#2 - Insulation Ain't What it Used to Be: What started out in 1984 as r30 insulation has, over the years, settled to more like r20 (r30 wasn't enough anyway). Besides normal settling, the previous owners clearly had a mouse problem. So every bat I've touched has mouse droppings and mouse-houses in/on it. There was also at some point larger animals, probably a raccoon, living up there... which also left lots of poop, and made a house for itself. I don't like the idea of this, and covering it up doesn't sound right to me when I can get rid of it.

So, the plan as it stands now is:
1. Build insulated walkway down middle of attic to maintain access (75% complete)
2. Remove old insulation
3. Vacuum animal waist, residual insulation
4. Seal all air gaps (~50% done to places I could easily access)
5. Blow in cellulose to r48 (~15")
6. Enjoy watching my gas/electric bill go down, and having the upstairs bedrooms more comfortably heated/cooled.

Ps: I'm planning to work on this and have it complete by new years. I'll try to get some pictures if anyone is interested.