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Old 04-16-2013, 12:37 PM   #1
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insulating old 1977 home attic


There's only 8-10" of rolled fiberglass up there, and up in Minnesota...I want to put it to 20". So I was going to add 10" of blown in fiberglass, unless I should do cellulose?

I am working between Home Depot's Owens Corning Atticat @ $32.75 each and Lowe's Johns Manville @ $28.47 ... i'll have enough for the free rental of either, I am just wondering which is better, if any different at all? Will these also get me to where I want to be?

Am I missing anything else either? Besides just blowing it in on top of the rolled stuff, do I need to run anything?

Also curious, will this help my heating/cooling? Just moved in, but noticed I need to keep the furnace at 76 or so otherwise it's nippy in here when it is 30-40 outside.

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Old 04-16-2013, 01:24 PM   #2
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insulating old 1977 home attic


Use cellulose, it has a better r value per inch, and is safer. Depending of the attic ventilation you may need to install baffles. What do you have for ventilation?

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Old 04-16-2013, 02:25 PM   #3
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insulating old 1977 home attic


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Originally Posted by vivithemage View Post
There's only 8-10" of rolled fiberglass up there, and up in Minnesota...I want to put it to 20". So I was going to add 10" of blown in fiberglass, unless I should do cellulose?

I am working between Home Depot's Owens Corning Atticat @ $32.75 each and Lowe's Johns Manville @ $28.47 ... i'll have enough for the free rental of either, I am just wondering which is better, if any different at all? Will these also get me to where I want to be?

Am I missing anything else either? Besides just blowing it in on top of the rolled stuff, do I need to run anything?

Also curious, will this help my heating/cooling? Just moved in, but noticed I need to keep the furnace at 76 or so otherwise it's nippy in here when it is 30-40 outside.
the great debate is on! Fiberglass pros and cons
Con it itches like a son of gun!
Pro does not settle over time
Con melts in extreme heat i.e. fire over 850 degrees
Pro not a combustable
Con after your attic reaches Minus 50 degrees f the R value drops
Pro Unless your living in Barrow Alaska not going to happen
Cellulose pros and cons
Pro cheap
Con chemicals are added to slow down flame spread to a slow smolder
Pro does not burn that fast
Pro does not itch
Con may cause skin and eye and lung irritation from fire retardant chemicals
Pro does work
Con settles must buy 25% more then needed to maintain the Rvalue.
You decide what you want to use. No matter what product you use get to at least a R49 And once it is in leave it the heck alone do not compress it either one.
Best of luck to you. Also check in with your local power company they have rebates available too.
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Old 04-16-2013, 03:03 PM   #4
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insulating old 1977 home attic


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Use cellulose, it has a better r value per inch, and is safer. Depending of the attic ventilation you may need to install baffles. What do you have for ventilation?
How do I know if I need baffles?

Thanks for the info ... how do I know what rvalue, isn't that basically saying put in 14 inches, since cellulose will settle 25% or so?

I currently have fiberglass, can I mix the two? I am leaving it in, so I can't imagine getting fiberglass will 'hurt' it any.
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Old 04-16-2013, 03:10 PM   #5
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insulating old 1977 home attic


I would put baffles in no matter what. They keep the insulation away from the roof deck so the air comming in your soffit can make its way to a ridge vent. Even if ridge isn't vented you'll be ready for a vent if you ever re-roof it.
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Old 04-16-2013, 03:29 PM   #6
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insulating old 1977 home attic


Air-sealing the attic is far more important than insulation type or ventilation, do that first. Check under the existing batts for a sign, it's a great dirt collector as air moves right through it (think furnace filter); http://www.finehomebuilding.com/PDF/Free/021105092.pdf

Yes, you can mix the two, cellulose will stop convective loops and slow an attic fire when burning rather than feed it trapped air in the f.g. If affordable, use some rigid foamboard over the exterior walls as it will prevent wind-washing of any loose-fill there, increase the R-value due to low clearance, and help air-seal the ceiling drywall/top plate joint-- so hard to reach (prevent ice dams).

Gary
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Old 04-16-2013, 08:05 PM   #7
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insulating old 1977 home attic


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Originally Posted by Gary in WA View Post
Air-sealing the attic is far more important than insulation type or ventilation, do that first. Check under the existing batts for a sign, it's a great dirt collector as air moves right through it (think furnace filter); http://www.finehomebuilding.com/PDF/Free/021105092.pdf

Yes, you can mix the two, cellulose will stop convective loops and slow an attic fire when burning rather than feed it trapped air in the f.g. If affordable, use some rigid foamboard over the exterior walls as it will prevent wind-washing of any loose-fill there, increase the R-value due to low clearance, and help air-seal the ceiling drywall/top plate joint-- so hard to reach (prevent ice dams).

Gary
What is a batt exactly? Where would the foamboard go...between the old and the new?

Quote:
Originally Posted by jsbuilders View Post
I would put baffles in no matter what. They keep the insulation away from the roof deck so the air comming in your soffit can make its way to a ridge vent. Even if ridge isn't vented you'll be ready for a vent if you ever re-roof it.
Where should I put the baffles exactly? We do have soffits from what I can tell....what would I do to for that exactly?
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Old 04-16-2013, 10:39 PM   #8
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insulating old 1977 home attic


also, which stuff is better, home depot's or lowe's?
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Old 04-17-2013, 05:19 AM   #9
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insulating old 1977 home attic


What GBR said is really important. You want to air seal before you do anything with insulation. You lose a lot of heat through the leakage of air into the attic. Get some spray foam (great stuff works) and seal around all openings, penetrations, gaps and cracks. It also helps a lot to seal around the top plates. It's so much easier to do this without 20" of insulation to work around.

How is your attic ventilated?
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Old 04-17-2013, 01:26 PM   #10
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insulating old 1977 home attic


I will grab some caulk and get around the bathroom vents before I blow the insulation ... I just got the insulation, so i'll get started caulking now, and blow later tonight while it is cold out and the attic is freezing

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