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gordom
join:2006-06-14
Bakersfield, CA

gordom

Member

attic insulation question

guess i'm looking for a second opinion on my line of thinking.

here are the facts about the house. it was built in 1982, and is 2k square feet single story. it's prob a combination of the blown insulation having settled over time or not enough was put up there in the first place, either way it needs more. the hv/ac ducting is in the attic. and it only has soffit venting with nothing up top to let the hot air out.

so what i'm wondering is what kind of insulation to throw up there?

blowing more insulation would help but i'd still have to fix the venting. and unless i piled up more around the ducting would it really help with the heating/cooling issue of having the ducts in the attic. i'm estimating this will cost for blown to be about $2k not including the venting and/or/if anything needs to be done to the ducts

my other thought is spray foam. the very little bit of reading i've done so far is it'll cost 2-3 times more then blown. but by raising the insulation layer to the underside of the roof wouldn't that basically take care of the temperature difference problem of the ducts in the attic? and one forum post i read somewhere mentioned the need to seal the attic from the outside world so it becomes part of the house environment. with my only having soffit vents, it wouldn't take much to pull that off.

would the extra cost of foam kind of wash out when put up against the cost of blown, venting the attic, some how adding more insulation to the ducting, or any other problem i may not even know of yet?

pende_tim
Premium Member
join:2004-01-04
Selbyville, DE

pende_tim

Premium Member

Instead of adding ridge vents, have you considered gable vents? Easy to install and not too expensive.

cowboyro
Premium Member
join:2000-10-11
CT

cowboyro to gordom

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to gordom
You don't want to seal the roof - let it breathe or it may rot.
2k seems way too much - what would be your break-even with this cost? Calculate it before spending the money, you may have a surprise.

Msradell
Premium Member
join:2008-12-25
Louisville, KY

Msradell to gordom

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to gordom
You definitely need to add venting if you're going to put in additional blown in insulation, ridge vents are certainly the best choice and barely visible but gable vents are acceptable. You also need to ensure that you have sufficient soffit vents for the area of your home, there are many tables available online to show you the required total venting area. Spray foam on the bottom of the roof is definitely a very good choice but as you mentioned considerably more expensive. As you mentioned the advantage is that now your entire HVAC system including ductwork is inside of the condition envelope. If you do this use close to cell foam filled it also becomes the vapor barrier. You also have to remove all of the blown in insulation if you go this rout. E
gordom
join:2006-06-14
Bakersfield, CA

gordom to pende_tim

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to pende_tim
said by pende_tim:

have you considered gable vents?

unfortunately i do not have any gables. the roof slopes down on all four sides.
said by cowboyro:

You don't want to seal the roof - let it breathe or it may rot.

that is what i thought. seemed odd what i was reading about sealing the roof. and the 2k came from a home depot add i saw offering 99 cents a square foot
gordom

gordom to cowboyro

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to cowboyro
said by cowboyro:

what would be your break-even with this cost?

forgot to follow up on this point.
based on last years energy usage (i've only had the house for a year) i think my highest summer and winter bills where in the 250-300 range. but that is also sweating it out with the ac at 85 day and 80 at night. and i broke down with the heater when it reached 60 inside.

the house has other insulation issues, this seems like it'd be the biggest improvement for now.

cowboyro
Premium Member
join:2000-10-11
CT

cowboyro

Premium Member

said by gordom:

the house has other insulation issues, this seems like it'd be the biggest improvement for now.

Is the attic the biggest insulation issue? How much do you have now? How are the windows? Depending on the answers you may be throwing away money.
gordom
join:2006-06-14
Bakersfield, CA

gordom

Member

said by cowboyro:

said by gordom:

the house has other insulation issues, this seems like it'd be the biggest improvement for now.

Is the attic the biggest insulation issue? How much do you have now? How are the windows? Depending on the answers you may be throwing away money.

the windows are all double pane. they are old, one or two will not open. and one has something between the panes (dirt, dust, not sure)

the only other big notable item is the single pane french door going to the back yard. i'm still working with the wife on what to replace the door with and what style (another french door or a slider)

and i know some is lost through the hardwood and tile floors that i've grown to like the look of. we may try some small throw rugs

robbin
Mod
join:2000-09-21
Leander, TX

robbin to cowboyro

Mod

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said by cowboyro:

You don't want to seal the roof - let it breathe or it may rot.

Unvented, conditioned attics are more energy efficient and have become more popular in recent years. This Department of Energy document provides some good information along with references.

»www.google.com/url?sa=t& ··· &cad=rja
MaynardKrebs
We did it. We heaved Steve. Yipee.
Premium Member
join:2009-06-17

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With a 2k sq. ft. single floor footprint your worst heating loss/gain is going to be the roof. What's the depth of the blown insulation now?

Best thing for you to do is to blow more cellulose insulation into the attic. Not sure what the building code called for in CA in 1982 but I'd guess it was around R20. Check the current building code and bring it up to at least current code. Blow extra insulation over and above code over the ducts.

Ridge venting may/may not have to be done depending on local code and other factors. Also see my buddy's web site »www.buildingscience.com
scross
join:2002-09-13
USA

scross to gordom

Member

to gordom
I was in Home Depot today myself, looking at insulation products. IIRC, their DYI deal was buy at least ten bags of blow-in insulation at $30 each and they give you the blow-in machine rent-free for several hours or a day or whatever. So $300 and up, depending on how much blow-in you need.

cowboyro
Premium Member
join:2000-10-11
CT

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said by robbin:

Unvented, conditioned attics are more energy efficient and have become more popular in recent years. This Department of Energy document provides some good information along with references.

Not bringing in fresh air and not installing bathroom fans also saves energy...
Ending up with dry rot because of no ventilation will offset a lifetime of potential savings.
averagedude
join:2002-01-30
San Diego, CA

averagedude to gordom

Member

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See the attached PDF for california requirements.

cec-400-2012-004-cmf-rev
page 244 shows what insulation you need for your climate zone.
A quick check shows that at minimum you will need R-30 and max R-38.

CEC-400-2012-005-CMF-REV
page 56 and going forward lists cities and their climate zones.

more information can be found at
»www.energy.ca.gov/title24/