# Attic re-insulation in December?



## edge-of-the-woods (Nov 29, 2016)

So we have an attic full of vermiculite insulation, which may or may not be contaminated with asbestos, but state law says we have to treat it like it IS contaminated.  

We have the means to pay for the stuff to e removed, but then we will need to re-insulate.  Not only that, but after it is removed, I want to air-seal the attic floor, and run a few new wires for lights and a ceiling fan, and build a catwalk across the rafters so you can still move around up there.

Is it totally nuts to do this in December?  It would probably mean two days of having no insulation in the attic while I did all that work, and then blew in new fiberglass.  Would the heating bill be insane for the weekend?  I could either crank the heat and blow through propane, or keep the woodstove running the whole time.

Thanks!!


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## heat seeker (Nov 29, 2016)

I would think that your losses would be made up pretty quickly with better insulation, not to mention being more comfortable in your home. I say go for it!


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## Highbeam (Nov 29, 2016)

I'd much rather do that attic work in December than in August. Winters are the best time for attic work.

You'd be surprised how little difference the insulation makes since what you had was just vermiculite. Blowing in FG eh? There's a whole debate about cellulose vs. FG. I've done both and gotta say it's a hard choice.


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## gzecc (Nov 29, 2016)

Could be a warm weekend in December. Keep the stove going.Do the bedroom area first.


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## lml999 (Nov 30, 2016)

Have anything like Mass Save in Connecticut? I'm having about $4K of insulation work done next week - top sealing, insulation added, vent hoses replaced, etc, for about $800.


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## edge-of-the-woods (Nov 30, 2016)

lml999 said:


> Have anything like Mass Save in Connecticut? I'm having about $4K of insulation work done next week - top sealing, insulation added, vent hoses replaced, etc, for about $800.



Oh man, I would LOVE to do that, but.....the vermiculite means that no company that is "approved" by the state to do energy audits will touch out house.  They can't do a blower test with possible asbestos in the attic, since they would be pushing air all throughout the whole house.  So, we can't be audited until we remove all the asbestos, and I'm not willing to bet that the auditors could get out on the same day that the insulation is removed.


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## edge-of-the-woods (Nov 30, 2016)

Highbeam said:


> I'd much rather do that attic work in December than in August. Winters are the best time for attic work.
> 
> You'd be surprised how little difference the insulation makes since what you had was just vermiculite. Blowing in FG eh? There's a whole debate about cellulose vs. FG. I've done both and gotta say it's a hard choice.



Yeah I tried to read a lot on FG vs. cellulose, but didn't see much to recommend me one way or the other.  I'm just hoping the blown FG is less attractive to critters than the cellulose.


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## sportbikerider78 (Nov 30, 2016)

Why not just leave the current insulation and lay down some more large insulation blankets.


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## Highbeam (Nov 30, 2016)

What got me to switch to cellulose on my last job, 1800 SF of R50, was the air sealing. The FG allows warm air to rise right through it. The new loose FG is not itchy at all so it makes a pretty good animal house.


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## edge-of-the-woods (Nov 30, 2016)

sportbikerider78 said:


> Why not just leave the current insulation and lay down some more large insulation blankets.



We want to be able to do some electrical work and duct work up there, and air sealing.  The vermiculite needs to go for that.


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## semipro (Nov 30, 2016)

Highbeam said:


> You'd be surprised how little difference the insulation makes since what you had was just vermiculite. Blowing in FG eh? There's a whole debate about cellulose vs. FG. I've done both and gotta say it's a hard choice.



Having worked with both I still strongly prefer the cellulose.


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## edge-of-the-woods (Nov 30, 2016)

I think I might go with the cellulose.  I like the idea of the borate/boric acid treatment on the cellulose in terms of being less inviting for critters that might get into the attic.  

It looks like I need 150 of the 19 pound bags you can get from Home Depot or Lowes!  They recommend insulating to R60 for here in Connecticut, which is 18" of blown-in cellulose.  For our modest 1500 square foot house, that comes out to 150 bags.  Holy crap.


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## lml999 (Nov 30, 2016)

edge-of-the-woods said:


> For our modest 1500 square foot house, that comes out to 150 bags.  Holy crap.



This is why I hire a guy with a truck. 

I had some prep done for building a shed. The guy doing the work said "you should put down some gravel". I figured that would be about 50-100 bags of gravel to shlep from Home Depot in my wagon. I asked "what are my options?"

Literally 30 minutes later, on a Saturday, a truck dumped 2 tons of gravel on my property. Probably cost less that way too! And the guy doing the work clearing the space used his Dingo to spread the gravel.


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## Dobish (Nov 30, 2016)

do it in the winter for a couple of reasons.... if it is too cold, you can go somewhere else....

Being in the attic in the summer is terrible, but being in the attic in the winter isn't all that bad, especially on a sunny day. there is so much less humidity, and you can get up there without sweat pouring into your eyes and your clothes ringing wet. You probably want to have long sleeves on anyway, so why not have it be a little chillier.

Also, with a good thermometer or infared camera, you can really see where the holes are that need to be sealed up.  In the summer it is less noticeable, but in the winter, those spots really show up as different temps!

You will also notice the difference a lot more when you seal everything up and get it all nice and cozy. what you spend on running the furnace a little hot or keeping the stove loaded will surely be made back in what you will save over the course of the next few weeks. The longer you wait, the longer you are just pumping warm air out of the house.


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## lml999 (Nov 30, 2016)

Dobish said:


> Also, with a good thermometer or infared camera, you can really see where the holes are that need to be sealed up.  In the summer it is less noticeable, but in the winter, those spots really show up as different temps!




Second that...the little infrared thermometer is very useful. They run less than $50 on Amazon and can really help identify where you've got infiltration.


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## semipro (Nov 30, 2016)

edge-of-the-woods said:


> I think I might go with the cellulose.  I like the idea of the borate/boric acid treatment on the cellulose in terms of being less inviting for critters that might get into the attic.
> 
> It looks like I need 150 of the 19 pound bags you can get from Home Depot or Lowes!  They recommend insulating to R60 for here in Connecticut, which is 18" of blown-in cellulose.  For our modest 1500 square foot house, that comes out to 150 bags.  Holy crap.


The cellulose in the bags is highly compacted.  It will expand immensely when you blow it in. Read this: http://www.homedepot.com/catalog/pdfImages/cb/cb921ee2-35b7-4fc2-a8c1-0a7eb8cc240c.pdf

Edit: Despite this I think your calculation is right.  It goes pretty fast though as long as you have someone dedicated to loading the blower hopper.

Voice of experience here: wear some good respiratory protection.  The stuff really flies!
When I did one attic I had a few days beard growth and I came out of the attic looking like Santa (or Jerry Garcia if you prefer).


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## FTG-05 (Nov 30, 2016)

edge-of-the-woods said:


> Yeah I tried to read a lot on FG vs. cellulose, but didn't see much to recommend me one way or the other.  I'm just hoping the blown FG is less attractive to critters than the cellulose.



I don't understand either comment - at all.

Cellulose blows FG away, let's count the ways:

- Cellulose seals some air infiltration, FG doesn't.  One reason they call it "filterglas".
- Cellulose is a much better fire retardant.  Search youtube for the video of the guy melting a penny in his hand with cellulose and the video of the three "houses" set on fire.  Cellulose wins hands down
- Cellulose has an intrinsic insulation value, even compressed; FG doesn't.  It's only claim to fame is holding air, which does insulate.  Compress FG, there goes your insulation value.
- Cellulose repels rats and mice, FG doesn't.  This is opposite of your last statement.  Install FG, get ready for the mice and rats in winter.

I'm getting ready to install about 50 bags of cellulose this winter; no way I'm waiting on summer or even spring, way to hot.  And they don't even sell blown FG around here, I already checked before I did my research.

Good luck!


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## iamlucky13 (Nov 30, 2016)

I put ~30 bales of cellulose in my somewhat small attic a couple years ago to increase it from ~R10 to ~R38. Cost wasn't bad, but it was a dusty job.

Several coworkers have hired insulating work out and said because the insulation companies get their insulation at wholesale prices and work so fast, for simple jobs it's barely any higher cost to hire the work out. If there is much prep work, however, that can change radically.

Also, R60 cellulose might be at or near the limit for what drywall can support in a ceiling. There are pounds per square foot specs for drywall that might be worth looking up.

A couple days with an uninsulated attic shouldn't make much of a spike in your power bill. When I was in a rental with uninsulated ceilings, inconsistently insulated walls, and bad infiltration, before the recession when gas prices were skyrocketing, I think our worst natural gas bill ever was about $150 (moderate, 4300 heating degree day climate, about 10% of that was water heating). It probably would have been around $300 if we had electric heat or propane.

That's $5-10 a day spent on heating. Granted, we were fairly conservative about the thermostat setting, and the upstairs was naturally much cooler than the downstairs, but I think this is a reasonable ballpark to expect, adjusting proportionately for climate.


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## mcdougy (Dec 1, 2016)

R50 is lots of insulation, the gains going to r60 are very minimal. You can never stop heat being attracted to cold, you can only slow it down. From r10 to r20 is significant in slowing the process,but by the time you go from r50 to 60 the difference is minut. They are your pennies but be careful of good sales pitches. If you want the ultimate air seal lay down some poly and spray foam then install cellulose. Fiberglass is the lowest performing of the 3 insulators I have mentioned. Significantly lower by simple tests. Cellulose outperforms roxul as well. I also recommend contacting a insulating company, quotes are free and you may be surprised. Here, I can get it installed cheaper than buying cellulose from HD with the free blower rental offer. Prolly be a faster install as well, since you are showing concerns of non insulated time. It's not a glorious job by any means.


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## Dougsey (Dec 1, 2016)

I second the idea of an air sealing application of spray foam. 

mcdougy- Curious, why do you suggest the poly? Wouldn't it be best just spray foam the sheetrock so the joints and any holes in the top plates get sealed?


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## Highbeam (Dec 1, 2016)

I couldn't get a contractor to come close to the DIY price so I blew over 160 bales into my 1800 SF shop attic. Used the Home Depot blower and had the wife feed from below while I ran the hose. We stopped a couple of times. Ran out of bales and needed more. When you're in the attic you can't communicate with the blower operator.

The hard part will be finding a store with 160 bales in stock (I bought out two stores) and then bringing those bales home. It's like bales of hay. You aren't going to fit many in your prius!


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## mcdougy (Dec 2, 2016)

Dougsey said:


> I second the idea of an air sealing application of spray foam.
> 
> mcdougy- Curious, why do you suggest the poly? Wouldn't it be best just spray foam the sheetrock so the joints and any holes in the top plates get sealed?




I'm not familiar with u.s.a. Building practices, but here a new home does require 6 mil vapor barrier on the warm side of the envelope. This is up for debate. But nonetheless, imo spraying the hole ceiling is the ultimate, but in reality prolly not needed. I like to have the insulators spray the top of the walls and seal in the vapor barrier that they lay across the attic side of the ceiling. This is only practical if it is a stick frame roof with ceiling joists. If it's trusses poly isn't practical, but often here if the construction is new enough for trusses, the poly is most likely present. 
Spraying the entire ceiling is not going to gain much as far as the seal goes due to the taping of the drywall. Plates and electrical devices yes. If it's a pot light wrap it in poly and foam it in if necessary.


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## edge-of-the-woods (Dec 3, 2016)

Highbeam said:


> I couldn't get a contractor to come close to the DIY price so I blew over 160 bales into my 1800 SF shop attic. Used the Home Depot blower and had the wife feed from below while I ran the hose. We stopped a couple of times. Ran out of bales and needed more. When you're in the attic you can't communicate with the blower operator.
> 
> The hard part will be finding a store with 160 bales in stock (I bought out two stores) and then bringing those bales home. It's like bales of hay. You aren't going to fit many in your prius!



Yeah that's gonna be me, I think!! Lol. That and the cellulose Santa beard. 

How long did it take you to blow in 160 bales? Did your wife get dusty when feeding the machine?


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## FTG-05 (Dec 3, 2016)

According to the calculators, I'm going to need 140 bags of cellulose to get to R38, about one foot thick.

I plan to order mine and see if they will deliver it.  Failing that, I wonder if they will load them up on my trailer on pallets.

This assumes, of course, that it's substantially cheaper to DIY vs. paid professionals.


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## Highbeam (Dec 3, 2016)

edge-of-the-woods said:


> Yeah that's gonna be me, I think!! Lol. That and the cellulose Santa beard.
> 
> How long did it take you to blow in 160 bales? Did your wife get dusty when feeding the machine?



The machine loader got almost as Dusty as the blower. After the first few bales we stopped, ran to the store and bought a second set of goggles (the high school chemistry type) and the dust mask that has cartridges. Those two pieces of safety gear plus a good led head lamp are critical.


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## greg13 (Dec 3, 2016)

How do you plan on removing the vermiculite? IF it contains asbestos you will need an approved and licensed asbestos contractor and hauler to dispose of it. 
I would have it tested first to find out for sure what you are dealing with. The cost difference could more than pay for the new insulation.


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## lml999 (Dec 5, 2016)

Highbeam said:


> The machine loader got almost as Dusty as the blower. After the first few bales we stopped, ran to the store and bought a second set of goggles (the high school chemistry type) and the dust mask that has cartridges. Those two pieces of safety gear plus a good led head lamp are critical.



Post pics or it didn't happen.


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## lml999 (Dec 5, 2016)

FTG-05 said:


> I don't understand either comment - at all.
> 
> Cellulose blows FG away, let's count the ways:
> 
> ...




I've got fiberglass bats installed between the joists in my attic, Not sure the width, maybe 10" rafters.  I'm having the attic top-sealed and then new insulation blown in. Would you spray cellulose *over* the existing FG? Or would you pull up the FG bats and discard them, then fill the space (and more) with cellulose? The workers are going to have to move some of that batting to do the sealing...

Thanks!


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## mcdougy (Dec 7, 2016)

lml999 said:


> I've got fiberglass bats installed between the joists in my attic, Not sure the width, maybe 10" rafters.  I'm having the attic top-sealed and then new insulation blown in. Would you spray cellulose *over* the existing FG? Or would you pull up the FG bats and discard them, then fill the space (and more) with cellulose? The workers are going to have to move some of that batting to do the sealing...
> 
> Thanks!


Toss it , pretty much useless


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## lml999 (Dec 7, 2016)

mcdougy said:


> Toss it , pretty much useless



I'll explore that option. Mass Save quoted "adding 6" of cellulose over existing FG" on the attic floor. Pulling all of the FG, disposing of it, and then supplying the additional cellulose may run into some $. $1200 for 1000 sq ft. of attic was retail cost cited. I'll talk with service provider about the additional work, wonder if it's worth the cost...

By the way, they cannot start the work until a HRV is installed. I'm hanging it now, in my utility room, and the service provider will install the ducts and vents.

I have a feeling that this $800 (net) job is going to run me $3K+ (HRV cost $900, wall control another $100, rebate of $500 to be received...)


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## FTG-05 (Dec 7, 2016)

lml999 said:


> I've got fiberglass bats installed between the joists in my attic, Not sure the width, maybe 10" rafters.  I'm having the attic top-sealed and then new insulation blown in. Would you spray cellulose *over* the existing FG? Or would you pull up the FG bats and discard them, then fill the space (and more) with cellulose? The workers are going to have to move some of that batting to do the sealing...
> 
> Thanks!



I'm going to seal what I can (bathroom vents and fans, lights that easy to get to etc.) but for the most part, I'm gong to leave the R-19 FG in place.  Way too much work take out and then dispose of.  As it is, I'm going to need about 140 bags to get to 12" cellulose depth i.e. an added R-38.


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## lml999 (Dec 7, 2016)

FTG-05 said:


> I'm going to seal what I can (bathroom vents and fans, lights that easy to get to etc.) but for the most part, I'm gong to leave the R-19 FG in place.  Way too much work take out and then dispose of.  As it is, I'm going to need about 140 bags to get to 12" cellulose depth i.e. an added R-38.



Makes sense to me.

A related question...we have a couple of exposed cathedral ceilings (ie, I can get to the topside of the ceiling in the attic). They have the FG batts installed...what's the best way to add additional insulation to these areas? Am I limited to running batts perpendicular to the celing joists? If so, should I just go with FG batting? Will blown in cellulose "stick" to the sloping section? Is there another strategy to keep cellulose in place?

Thanks1


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## FTG-05 (Dec 7, 2016)

Lml, I too have cathedral ceilings.  I plan to add plywood "dams" to mine that will hold back some cellulose.  The good news about the "dam" material is that was all leftover boards from my new neighbors house building a couple months ago, all  of it was free from his burn pile.

Having said that:  I don't see why a combination of FG batts set perpendicular to the ceiling joists and current FG batts, then blow cellulose on top and in between; in other words, use the FG batts as a "dam".  I don't see why it wouldn't work. 

You do want the cellulose blown everywhere you can:  Cellulose will seal far better than FG, especially batts.


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## lml999 (Dec 7, 2016)

FTG-05 said:


> You do want the cellulose blown everywhere you can:  Cellulose will seal far better than FG, especially batts.



Agreed. I'm going to ask the insulation company if they would pull the FG batts out on the opposing side (where the cathedral ceiling meets the roof, then blow cellulose in, upgrading the insulation in that section.

With regard to the accessible side, I'm reluctant to add fiberglass batts or dams as I think the cellulose top layer would be uneven, and might still move.

What we need is a fabric retaining sheet (something heat/age/moisture resistant) that would attach to each of the joists, or perhaps every other joist, and float at an even height above the surface. (ie, not attaching the sheet directly to the joist, but using an intermediate attachment.  The cellulose would be held against the sloping surface and would not tend to move.

Or I could build a lightweight box structure with 2" semirigid 4x8 insulating panels and fill that...

The two rooms in question are the most important in the house -- our great room, where we spend much of the day (and where our wood stove will be installed) and the master bedroom, where we spend most of the night. 

Or I could just build a passivhaus with a flat grass roof and be done with it!


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## lml999 (Dec 7, 2016)

FTG-05 said:


> Lml, I too have cathedral ceilings.  I plan to add plywood "dams" to mine that will hold back some cellulose.  The good news about the "dam" material is that was all leftover boards from my new neighbors house building a couple months ago, all  of it was free from his burn pile.



Service provider said they'll just slap 2" semi rigid board on the slopes, will pick up R10 plus be more airtight. Quick and easy.

I think the stuff (the semi-rigid insulation panels) loses efficacy when it gets really cold.

We intend to be in this house 25 years, then leave it to the kids, so I want to do it right. Once.


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## DickRussell (Dec 7, 2016)

A good read on insulating a cathedral ceiling is here: http://www.greenbuildingadvisor.com/blogs/dept/musings/how-build-insulated-cathedral-ceiling


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## lml999 (Dec 7, 2016)

DickRussell said:


> A good read on insulating a cathedral ceiling is here: http://www.greenbuildingadvisor.com/blogs/dept/musings/how-build-insulated-cathedral-ceiling



Thanks, that's useful. I'm talking with the service provider about how to do this...looks like I need vent chutes and then I can blow in cellulose. I may already have the vent chutes over FG batts. A question is whether Mass Save will underwrite part of the cost of pulling the FG and then blowing cellulose.

My prior posts focus on the portion of the cathedral ceiling that is lower than the roofline. I have two ceilings where, on one side, I have access to the top portion of the cathedral, in the unheated attic...so I can add an insulation layer without concern about ventilation...


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## FTG-05 (Dec 8, 2016)

lml999 said:


> Service provider said they'll just slap 2" semi rigid board on the slopes, will pick up R10 plus be more airtight. Quick and easy.
> 
> *I think the stuff loses efficacy when it gets really cold.*
> 
> We intend to be in this house 25 years, then leave it to the kids, so I want to do it right. Once.



It's FG that has the upside down U-shaped temp vs. efficiency curve.  In other words, as it gets colder, it gets less effective.  The worse numbers are below zero so probably don't affect a lot of people here unless you live where it stays well below zero for days on end.  Cellulose has a flat to slightly upright U-shaped temp/efficiency curve.  Another reason to stick with cellulose.


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## FTG-05 (Dec 8, 2016)

DickRussell said:


> A good read on insulating a cathedral ceiling is here: http://www.greenbuildingadvisor.com/blogs/dept/musings/how-build-insulated-cathedral-ceiling



My cathedral ceiling is interior to my attic.  In other words, it's no different than the rest of the attic other than it has a pretty good slope to it.  Maybe it's not a real cathedral ceiling then, don't know.


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## DickRussell (Dec 8, 2016)

FTG-05 said:


> It's FG that has the upside down U-shaped temp vs. efficiency curve.  In other words, as it gets colder, it gets less effective.  The worse numbers are below zero so probably don't affect a lot of people here unless you live where it stays well below zero for days on end.  Cellulose has a flat to slightly upright U-shaped temp/efficiency curve.  Another reason to stick with cellulose.



Loose blown chunks of FG can suffer from thermal looping, especially on an attic floor, as cold air above it sinks downward and warmer air above the ceiling below rises into the attic space. More dense FG batts don't suffer as much from this, and even a covering of a few inches or more of cellulose over loose blown FG pretty much eliminates thermal looping. The R value of loose blown FG is not as high as that of cellulose for the same thickness.

But I suspect the comment about insulation that suffers a small loss of R value as temperature drops was referring to polyisocyanurate foam board (polyiso). That discussion can be found here: http://www.greenbuildingadvisor.com/articles/dept/musings/cold-weather-performance-polyisocyanurate. If that type of foam board is added to the warm side of a wall or ceiling below an attic, its average temperature won't be low enough to be affected. It's when it is added to the exterior that the thermal degradation is seen.



FTG-05 said:


> My cathedral ceiling is interior to my attic.  In other words, it's no different than the rest of the attic other than it has a pretty good slope to it.  Maybe it's not a real cathedral ceiling then, don't know.



Well, yes, if there is venting above the insulation, then it's just like a horizontal ceiling, as long as there isn't "wind washing" of the insulation, as soffit vent air flows through it enroute to the ridge vent.


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## Highbeam (Dec 9, 2016)

FTG-05 said:


> My cathedral ceiling is interior to my attic.  In other words, it's no different than the rest of the attic other than it has a pretty good slope to it.  Maybe it's not a real cathedral ceiling then, don't know.



Those are typically called scissor trusses. The bottom chord is just not flat.

Cellulose will hold on with quite a slope. Worse case, it slides down some over time and you need to put more on top. That just means a really well insulated toe of slope!

There is no reason to remove the old FG. Simply blow on top of it with cellulose and you will soon forget that it is even down there. I left the old batts in my attic when I had loose FG blown in. I sometimes wonder if I should go back in and dust a few inches of cellulose over the top to air seal it better. That would be three different types of insulation! It's additive. No reason to remove it.


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## semipro (Dec 9, 2016)

Highbeam said:


> There is no reason to remove the old FG. Simply blow on top of it with cellulose and you will soon forget that it is even down there. I left the old batts in my attic when I had loose FG blown in. I sometimes wonder if I should go back in and dust a few inches of cellulose over the top to air seal it better. That would be three different types of insulation! It's additive. No reason to remove it.



2nd this!


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## iron (Dec 14, 2016)

i agree with HB. i blew in about 40 bags of cellulose over the existing FG. worked great. i seem to recall that 15" was the max depth for 1/2" gypsum, so heads up. 

and, if you're worried about heat, i would just crank up the stove. while i was remodeling my kitchen in the middle of winter (30-40 degree temps), i had a hole in the ceiling for about a week. the hole was 16'x10'. kept loading the fireplace and kept the inside of the house around 58 degrees. not the most efficient thing in the world, but better than 30 degrees.


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