# Thread: Not sure you can help. Hope you can.

1. Regular Guest
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## Not sure you can help. Hope you can.

As many of you have read I will be getting a new unit/furnace installed. In looking at my attic I noticed I did not have much insulation and in doing research I am currently at a R13 but should be at a R38.

My question to all of you if can help of course is, how many bags of cellulose insulation do I need for a 1500 sg ft attic to get to this level? Also I have been told that since this is not a new construction I can put however much insulation I want.(Of course not exceeding the R38) Is this a true statement?
I have no concept of R-value and no matter how much one explains to me and looking at the cellulose bag to see what they recommend I still get lost.(Was not very good at math ) I have asked for help and even they don't know.By the calculations that I come up with I am supposed to get 90 bags!!

I figured I want to save money on energy cost so this was another thing I was looking at. And I know many of you have seen plenty of insulation since you guys go up in the attic too. I just don't know who or where to ask. Thanks for all of your help.

2. i would say start with 5 or so bags at a time and see where you get. This way you only use what you need and can but in at each trip up into the attic

3. Professional Member*
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Length X Width of attic = Sq. Ft

Desired R value - Existing R value = R needed to add

You need to add R25 worth of cellulose.

Take your attic Sq Ft and divide by the manufactures maximum coverage Sq Ft at R25 (Chart should be on bag) and you have the number of bags.

I have a chart that says R24, 7" deep needs 34 bags per 1000 Sq Ft

I would advise you to air seal your attic first. Adding insulation to a leaky attic can cause more harm than good.

You could buy 10 bags at a time and start to the required depth and continue until it's done. They have rental machines that chop and blow the cellulose nicely but this can be done by hand.

4. Big
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## Have

you used the blower HD has . Just added in insulation and it blow it in the walls & ceiling .

5. Could be different in your area. But Insulation is allowed to be more then R38.
The value given for an area, is the min, not the max.

6. Make sure there is minimal air leakage into the attic before you add instulation. Cellulose, fiberglass and similar are all good air filters but of zero use against moving air. Those types of insulation are useful to stop CONDUCTION HEAT losses/gains but NOT convection losses/gains. So if your ceilings and wall partitions leak air into the attic, adding insualtion won't be anywhere near as advantageous as it would if you first seal the leaks. Top floor ceiling lights, exhaust fans, recessed lights, electrical wires, refrigerant or gas lines, all are sources of air leaks directly into the attic. And even first floor recessed lights and similar ceiling penetrations will allow air to move from the first floor, up through wall partitions and into the attic in what's known as 'Stack Effect'. So spend some time and money sealing the envelope (the living space) before you add insulation. Once it's sealed, then add the insulation so you get maximum benefit for the money and time you're investing.

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