Insulation, Radiant and Vapor Barriers - attic insulation
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firsthome
03-27-05, 03:26 PM
:confused: I want to add insulation to my attic. After reading some of the threads here I am unsure about how to go about it. I will be using the pink fiberglass roll out kind. Do I just roll it out and cut it to fit? I was told it would be better to use the faced, can I use the unfaced? One more question, Can I lay it directly on the floor or do I have to put something else down first? Thank for any replies.
michiganguy
03-27-05, 07:26 PM
You mentioned "adding insulation ", which implies you already have some
insulation up there now. If you are adding insul. to existing insul., it is
important tnat you use only unfaced insul. The rolls of insul. will come in
2 different widths, it depends on whether you have trusses or rafters.
Trusses require 22 1/2 '' wide insul. and rafter framed attics need 14 1/2 ''
wide insulation. If you have a 5/12 or less roof slope , you might want to
consider blowing insul. into your attic , due to very restricted working space.
insulation up there now. If you are adding insul. to existing insul., it is
important tnat you use only unfaced insul. The rolls of insul. will come in
2 different widths, it depends on whether you have trusses or rafters.
Trusses require 22 1/2 '' wide insul. and rafter framed attics need 14 1/2 ''
wide insulation. If you have a 5/12 or less roof slope , you might want to
consider blowing insul. into your attic , due to very restricted working space.
firsthome
03-28-05, 06:08 AM
How can you tell if you have trusses or rafters, other than the size? I am adding insulation because they did not finish the attic. They only placed it over two of the rooms. The back room and one of the rooms in front of the house. Also, does it matter which "R" number I use? I was told by a store clerk the higher the number the better the insulation. Thanks again for all your help.
jmazur
03-28-05, 08:48 AM
How can you tell if you have trusses or rafters, other than the size?
here's a pretty good image of what a common truss looks like:
http://www.nachi.org/tips/0354.gif
here's a pretty good image of what a common truss looks like:
http://www.nachi.org/tips/0354.gif
michiganguy
03-29-05, 07:59 PM
The guy was right about more is better, but it's important to determine the
highest R-value that's practical for your particular house. Generally, houses
with steeper roofs can stand more insul. depth ( R-value) than houses with
5/12 roofs or less. The more insul. crammed into an attic diminishes the air
space above the insul. to the roofboards making adequate ventilation very
difficult to achieve. I don't know of any specific rule to determine how much
is too much insul. in a given house, but if in doubt, guess on the conservative
side, you don't want ventilation problems.
highest R-value that's practical for your particular house. Generally, houses
with steeper roofs can stand more insul. depth ( R-value) than houses with
5/12 roofs or less. The more insul. crammed into an attic diminishes the air
space above the insul. to the roofboards making adequate ventilation very
difficult to achieve. I don't know of any specific rule to determine how much
is too much insul. in a given house, but if in doubt, guess on the conservative
side, you don't want ventilation problems.