dj_figgy
Premium
join:2002-08-14
Eagle Point, OR
| Insulation Question
I have a question regarding ADDING insulation to an attic, and request any input on people who have done it.
House was built in 1999, approx 1300 sq feet, 3 bedroom, 2 bath in Southern Oregon.
We have very hot summers and very cold winters for the most part. Current system of central air A/C and gas furnace both do an ok job, but run a lot...so I would like to make the house more efficient if possible.
I would like to do this project myself, with the help of my wife. I have never been up to our attic, but found our home inspection report to reference what our current insulation was...it indicates there is approx 14 inches of blown in fiberglass R-38 insulation...in addition to fiberglass Batts. He was uncertain of R value on the batts.
I wanted to go up in the attic anyway, as the inspector also stated the vent in one of our bathrooms goes up in the attic but then ends prematurely..??? NOT good.
Anyway, we were at Home Depot and noticed that if you buy 20 cubes of their blown in insulation, you get the machine rental for free. It was $11 a cube. It's called Greenfiber "Cocoon" (www.us-gf.com) Has anyone done this?
The US Dept Of Energy says I should have R-49 in my attic...not R-38...which is why I'm concerned also. Any input would be great, thanks! |
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SparkChaser
BURY BECK
Premium
join:2000-06-06
Downingtown, PA
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| I'd be more concerned about the vent. Moisture in the attic is going to cause many problems beside lower the insulation R factor.
If you have R-38 blown in and batts on top of it, it is probably already R-49. I don't know the weight of cellulose insulation. It's been 20 years since I looked at it but if it's heavy it could compress your other insulation and decrease the effectiveness of it.
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cdru
Go Colts
Premium,MVM
join:2003-05-14
Fort Wayne, IN
| reply to dj_figgy
Fiberglass has a R-value of about 3 per inch. If you have 14 inches of blown in insulation plus batting (figure 4"-6" for a truss or 8"-10" for stick built attics) you are looking at a minimum of 18"-20" of insulation which would give you beyond your R-49 rating. I would agree with SparkChaser  that you probably don't need to add insulation.
If your attic is quite hot in the summer, you may be much better off checking into the attic ventilation. Home builders often put only enough venting in to pass code, but then the blown in insulation subsequently covers up the vents or otherwise blocks the airflow. There are multiple different types of vents available from passive to active that can help. It's recommended to have ventilation in a 1:150 ratio, meaning 1 sq ft of vents for every 150 sq ft of attic space (not roof surface). If you go with a powered vent, each cubic foot/minute is sufficient to maintain the 1:150 ratio. You can also use a combination of the two and set the powered vent on a thermostat/humidistat to only kick on for additional help when needed.
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SandShark
So it goes
Premium,MVM
join:2000-05-23
Santa Fe, TX
clubs:
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| reply to dj_figgy
said by dj_figgy :Current system of central air A/C and gas furnace both do an ok job, but run a lot...so I would like to make the house more efficient if possible. With the heat you've had and are now having, it would not be unusual for your A/C to run a lot if it's sized properly.
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mvpulsts
join:2001-11-14
Atlanta, GA
1 edit | reply to dj_figgy
The minimum sized batts of insulation you can get typically are r-13. those on top of your existing r-38 give you r-51. There is a point of diminishing returns as you add insulation. There becomes a point where more insulation doesnt do anything except drain your wallet. Im not sure how the winters are in Eagle Point but you may want to look into this.
Something to concentrate a bit more on would be penetrations. Do you have recessed lighting in the ceilings anywhere? Is it a full atic with stairs? Or just a scuttle hole with pull down ladder/stair? You should make sure all these areas are well sealed. You can get/build a large clamshell type cover for your attic access which would sit on top of the opening and cut down on a lot of loss.
check all widows and doors and outlet/switch covers etc.. for proper weather stripping.
A lot of local utilities have energy auditing programs set up where they can send out an inspector and help you determine where the losses are and how to fix them. This is sometimes a free service.
OH and yes, the AC, properly sized, should be coming on for a few minutes several times an hour. This is primarily to keep the humidity down. An oversized AC unit will cool the house too quickly and not be able to dry it out. This will lead to moisture in/on the walls and lead to mold issues. |
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