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Justluckey 11-23-2008 09:49 AM

Time to replace attic insulation?
Hi all, I'm new to this forum and appreciate any advice on the topic of insulation.

I have a 24-25 year old house. It's a modular (24'x48') with an addition. My question is about the (original) insulation in my attic.

Looking at the pink fiberglass roll-out style of insulation, it's appears that there's 2 layers of approx 6" each, making ~12" of thickness. But there's not 'paper' on either side to note the make/model/R value of it. I'm assuming it will compress over time, so it may have been thicker when new.

In my opinion, my house is relatively well insulated, as we don't feel any drafts nor does the heat (1.5 year old natural efficient gas fired furnace w/hot water baseboard). When the addition was being added 2 years ago, I took off all the trim around windows & doors and used the spray foam (Great Stuff) insulation.

I've kept track of the heating bills for the past 5 years and with the new furnace, keeping our heat between 62-65 degrees (previous years 66-69), and foam insulation in windows & doors, we've cut our amount of natural gas usage by ~50% (which included adding 50% more living area to heat).

I'm concerned with the old original attic insulation. I'm not sure of the life of fiberglass and how much it deteriorates. If there's a benefit, I'd like to replace it with better (blow-in?) insulation, but I want to get decent bang for the buck. I know the spray-in foam is pretty good (tight seals & high r-value), but I don't want to pay an arm/leg for it and my return on investment may take 10+ years. (I may be moving in ~5 or so).

For those of you wondering, my highest monthly gas bill in the winter has been $215 (for 172 ccf's) since the new furnace was installed. That usage includes the clothes dryer & oven (both powered by gas).

My questions:
Is my current attic insulation old enough to replace?
What would be a cost effective option to replace with (higher r-value fiberglass, spray in cellulose, spray in foam)?


travelover 11-23-2008 11:10 AM

I don't think you have a problem. Fiberglass insulation doesn't really settle much unless you compress it by walking on it or something similar. If you feel you need more insulation, I'd add more over the top - either blow in or roll type.

If you have not looked for air leaks from lighting fixtures, chimney, etc, this might be a more cost effective next step. Look for dirty spots in the insulation where the incoming air drops dust into the fiberglass. If you have a basement, also look at the top of the rim joist for leaks / proper insulation.

EERE Energy Savers: Sealing Air Leaks

inspectorD 11-24-2008 05:28 AM

I agree
Travelover gave you some great advice.:)
Fiberglass insulation needs trapped air to do it's job. Any compressed areas need to be fluffed out so to speak.
I would concentrate on the air leaks from below the ceiling levels as suggested.
Your rim joists and sill areas are the biggest losers.
Good luck.:D

joecaption 01-11-2011 06:26 PM

Fiberglass insulation does not ever go bad and I've never seen it settle as you suggest.
It's glass so should last forever unless it gets wet.

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