Attic Insulation Requirements?

[cjherren]

Hey I have a question that's had a few people and I debating about. I am preparing to add insulation to the attic in my house. I've checked several insulation requirement fact sheets for my area and they seem to be coming out to R-49. I have considered getting the R-38 - R-49 for my attic but I've also read that it's not good to smash insulation down. My house is house old (100 years?) and the joists that run across the floor of the attic are old 2x4's (as opposed to the 2x4's now that are actually 1.5x3.5). Therefore there really isn't a lot of space for insulation. I definitely want to add as much as I can though because this house loses heat through the attic most of all.

I don't want to use spray in insulation, and I hope to refinish the attic, therefore, I would need to push the insulation down a bit at one point.

My question might be obvious already, but what should I do? Should I add extra insulation or only put in something like R-19 which is not even close to the requirements for my area? Thanks for any help.

[Dan Auito]

Unless you're going to try and create living space up there in the future I would blow in the additional amount necessary to achieve R49.

[cjherren]

When I said refinish, I meant I would be fixing it up so it's fully accessible. There are stairs leading directly from my bedroom into the attic, which would make it convenient as a extension to my room.

So yes it will become living space eventually.

[Dan Auito]

Personally then I would see what I could feasibly add which could get scrunched a bit, then go forward with the decking/plywood and get the carpet and padding in to create the barrier now!

[cjherren]

Does R-19 at this point seem to little? My mother has been trying to help out and get insulation but she's stubborn and uninformed about insulation. She insists that we get R-13 to R-19 because she doesn't want to spend a lot of money.

[Dan Auito]

Pay now or pay substantially more later over the long-haul in heating bills. Mom is thinking penny-wise pound foolish as the saying goes!

I'm thinking you may be able to use the blue insulation board which is only one inch or so thick as a sub-insulating base beneath the plywood but I am not an insulation expert so let's let a few more posters chime in before you make the next move.

[haynesm]

My question would be if you are going to finsh the attic then would not the attic "floor" (cieling joist) just be another story to the house. perhaps then you need to insulate the rafters more than the joist. The joist isulation would be more of a sound barrier, would it not. However, don't trap heat next to the decking and melt the shigles.

[Dan Auito]

Good point!

[cjherren]

My question would be if you are going to finsh the attic then would not the attic "floor" (cieling joist) just be another story to the house.

Yes, it would be considered just another floor, but the room wont be finished for some time so I've been trying to just consider it the attic still, and insulate it like so.

However, don't trap heat next to the decking and melt the shigles.

Should I not use fiberglass insulation for the rafters? I think I heard it could cause some kind of moisture problems, but I don't know why it would be much different than anything else. Rather maybe it's just especially important to make sure the vapor side is directed the correct way. Any insight on this?

[cjherren]

I'm thinking you may be able to use the blue insulation board which is only one inch or so thick as a sub-insulating base beneath the plywood but I am not an insulation expert so let's let a few more posters chime in before you make the next move.

I would have considered but I was stuck on the idea that the board insulation is generally used for walls/basements. Perhaps this would be a good idea, that way I could probably get between 2-4 sheets between each joist.

Between haynesm and yours, I am looking to insulate it like an attic but also make sure it's effectively sound proofed in the future. I don't want to waste materials in places where they won't be needed. Perhaps I can insulate enough temporarily with batts/boards and then reuse them for the rafters eventually.

[brianb_cobbres]

Gah, how to explain this.

Blowing in enough insulation if probably better for now unless you plan on finishing the space in the very near future.

Because...

Properly insulating to finish the space is a totally different animal as you have to allow for properly ventilation between from the eaves, along the roof, and up to the peak while sealing the new space off from the elements. You need airflow between those points or you will have moisture problems and you will shorten the lifespan of your roof.

Most people dont realize that most modern unfinished attics are open to the weather along the eaves and at the peak and outside air is allowed to freely flow through the attic. As your house is old you may not have the peak vents and probably just have open venting at ends of the house on the side walls which just complicates the issue. You need airflow.

In your case I would strongly recommend bringing in an insulation contractor when you are getting ready to finish the space. Insulation is a system that only works if it is installed properly and not something you want to mess with unless know what you are doing or are willing to take the risk.