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attic insulation


Dana_D's Avatar
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10-06-01, 02:48 PM   #1  
Dana_D
Hi! We purchased our home two years ago. The home inspector said that one of the biggest problems with the home was a total lack of insulation in the attic. 2 1/2 inch bats in some places, nothing in others. We live in Central New York (192" of snow last winter). Over the past two winters we have has horrible icing on the roof and dripping on the walls of our master bedroom. So this fall we will finally insulate. We have had two different contractors come to give us estimates. The prices were similar, but the advice differed. I hope that someone can give us advice of what path to follow.

Both advised sealing of the attic and 10" of blown in cellulose insulation over the existing bats. The two main differences came in soffit ventilation (we have none) and roof ventilation. One person said we needed to add 5 roof vents. We currently have 3 roof vents and 2 gable end vents. (our roof is about 1400SF) One said the attic ventilation was sufficient. One suggested cutting 3" soffit vents along the entire roof overhang on both sides of the house. The other suggested 15 rectangular openings spaced evenly around the house. Both were knowledgeable men, affiliated with New York's energy star program. WHO TO BELIEVE???

Any advice would be most appreciated! Thanks in advance.

[Edited by Dana_D on 10-07-01 at 05:17]

 
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twelvepole's Avatar
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10-07-01, 07:59 AM   #2  
Attic insulation

Go to http://www.owenscorning.com to learn more about insulation and R values. Our expert rbisys should be along soon to shed some light on your attic.

 
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10-08-01, 01:56 AM   #3  
Insulman
How much R-value are you getting from the 10" of cellulose, If it is at least R-38 then that is good ... as for the ventilation either method of venting the soffits is more than sufficient.. I prefer the continuos vent idea but would not be against having 15 individual vents installed either... Seems to me you made need an additional 2 roof vents to equal the 1 foot of venting per 300 foot of attic ceiling.. (Most builders today prefer ridge vents over the caps, but I wouldn't change that until it time to change your shingles. However if your gable end vents are at the top of your peak they will likely carry warm air out of the attic once the soffit venting is installed..

The following is a paragraph I copied from The US Department of Energy web site

http://www.ornl.gov/roofs+walls/insulation/ins_01.html

*** this is a very informative site on insulation**

A well-insulated attic should be adequately ventilated to prevent moisture accumulation. Attics may be ventilated with a combination of soffit vents at eaves and continuous ridge vents. Attic vents may also be installed in gable faces. Many codes and standards require one square foot of unobstructed ventilation opening for each 300 square feet of attic floor area if a vapor retarder is included in the top floor ceiling. Twice as much ventilation is recommended if there is no vapor retarder. The net free area of a vent is smaller than its overall dimension because part of the vent opening is blocked by meshes or louvers. The openings should be equally distributed between the soffit and ridge vents or between each gable face. Never cover or block vents with insulation. Take care to prevent loose-fill insulation from clogging vents by using baffles.

So seems to me they are both giving you good advice.. So I would suggest you go with the best price, assuming you don't feel one contractor is going to perform a better job over the other..


Good Luck

Jim




 
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10-08-01, 02:29 PM   #4  
Dana_D
Hi again. The R-value that was quoted to me was the existed 2 1/2 inch bats have R11 and adding 10" of blown in will add 38, totalling R49.

They will also install styrofoam baffles. And the guy who wanted to install the continuos soffit vent, said they would be 8" wide, not 3" as I stated before. Thanks again! Dana D

 
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10-09-01, 06:15 PM   #5  
rbisys
Greetings Dana D,

I'm an insualtion contractor and I run into your type of vent problems all the time. The purpose of the attic vents is to remove MOISTURE from the attic. Cap and gable vents are about useless. The only way to get proper venting is with a ridge vent and continious soffit vent.

You can have problems with too much soffit venting and no ridge vent or with cap vents because the air will flow over the insulation. I have seen the air move insulation up to 3' from the edge of the building, leaving the ceiling drywall bare. try; http://www.cor-a-vent.com. They have the best system and will tell you the proper methods.

Next. Installing "R" 38 is a waste of money, despite what you have been told. The maximun energy savings vs costs is about "R" 19. The additional "R" 19 will probably never pay for it self in your life time. If you are having above average moisture in your area it could be detrimental to the cellulose because paper absorbs a lot of moisture which greatly increases heat flow, both ways.

If you can find some one who installs radiant barriers in your area, that would cost less and save you more in energy costs. Sorry, radiant barriers do not have "R" values because they reflect heat energy, at 97%, cellulose less than 10% efficiency, both ways. You can also DIY.

For more radiant barrier info, enter your search engine, "radiant barriers" or "reflective insulation".

Thank you for considering my opinion.

 
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