Insulation, Radiant and Vapor Barriers - Can I put R11 on top of R19 to equal R30?
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01-31-01, 10:46 AM
Okay, I just bought my first house. While I grew up helping my parents rehab old houses I don't recall insulation being one of the things I learned. There is R11 on the unfinished attic walls. I want to finish this room. I know that I need R30. So, do I just add R19 or do I strip it all and start over with R30?
Thanks for all input!
Eos.
Thanks for all input!
Eos.
Mikey C
01-31-01, 03:30 PM
Ok... This is pretty straight forward, First you need to determine if the existing insulation (R11) has a vapor barrier? To determine that: Look at the insulation, if it has a paper type of backing on the one side, then you have a vapor barrier. They call this type of insulation "Kraft Face" The other type of insulation which would not have any type of paper backing is called "Unfaced" - basically just fiber insulation.
Please determine first what type of insulation exists. Also, if it is a Kraft Face insulation is that towards the room(inside) area of the attic or is it up against the outside wall. Reply to this message with the answers. We'll continue from there later.
Please determine first what type of insulation exists. Also, if it is a Kraft Face insulation is that towards the room(inside) area of the attic or is it up against the outside wall. Reply to this message with the answers. We'll continue from there later.
01-31-01, 04:29 PM
Hi, thanks for responding.
It is the paper kind and it's facing into the attic (not the wall/roof) :)
Eos.
It is the paper kind and it's facing into the attic (not the wall/roof) :)
Eos.
arkayassoc
01-31-01, 10:01 PM
The vapor barrier may be installed wrong. I am not sure I understand your description, but, it should go against the ceiling of your home, with the insulation on top of it towards the roof. In other words, the paper side goes down, when viewed from above, and should be the closest to the ceiling, and the farthest from the roof.
R-values are additive. So, assuming you put the vapor barrier against the ceiling, you can add unfaced insulation on top of it to achieve a greater R-value. You only want one vapor barrier.
R-values are additive. So, assuming you put the vapor barrier against the ceiling, you can add unfaced insulation on top of it to achieve a greater R-value. You only want one vapor barrier.
Mikey C
02-01-01, 07:28 AM
Eosgraces: Let's be very clear hear to assure I give the right response.
On the attic walls, not the ceiling and not the floor - the walls have Kraft Face insulation facing the inside of the room. "OK" To upgrade this to an R-30 rating you will unfortunately need to place an "Unfaced" R-19 behind the existing insulation. It's a bit of work. If the wall areas aren't so large, you may just want to replace with new R-30. Toss out the old R-11. Rule: The Vapor Barrier(Kraft Face) needs to be towards the warm part of your home. In this case your attic room. Next, if the ceiling is to be insulated, then the "Kraft Face" insulation needs to be facing you. Basically, pointing to the warm side of the attic room. If the attic floor needs to be insulated, the "Kraft Face" insulation will need to go towards the rooms below. (ie... facing down, not facing the attic room you are finishing.
Let me know if this makes sense.
Mikey C.
On the attic walls, not the ceiling and not the floor - the walls have Kraft Face insulation facing the inside of the room. "OK" To upgrade this to an R-30 rating you will unfortunately need to place an "Unfaced" R-19 behind the existing insulation. It's a bit of work. If the wall areas aren't so large, you may just want to replace with new R-30. Toss out the old R-11. Rule: The Vapor Barrier(Kraft Face) needs to be towards the warm part of your home. In this case your attic room. Next, if the ceiling is to be insulated, then the "Kraft Face" insulation needs to be facing you. Basically, pointing to the warm side of the attic room. If the attic floor needs to be insulated, the "Kraft Face" insulation will need to go towards the rooms below. (ie... facing down, not facing the attic room you are finishing.
Let me know if this makes sense.
Mikey C.