Author Topic: attic insulation  (Read 15380 times)

tfordon

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attic insulation
« on: February 29, 2012, 06:19:46 AM »
I recently read a book on insulating and would like to better insulate my attic.  There are currently fiberglass batts (R-19 I think) installed with the kraft paper facing the wrong way.  I've been meaning to correct this for a little while, and thought I would use this as an opportunity to better seal and insulate.

I've never done something like this before, so I don't know if I'm getting in over my head.  My current plan is to flip all of the existing insulation and use a foam gun to seal gaps as I go.  After flipping the existing insulation, I'd like to blow loose fill cellulose insulation on top.

In another forum, I heard that this might be overkill, and that you should just blow cellulose over the existing batts.  The idea being that with the added insulation, the vapor won't condense on the paper.

Should I go forward with my flip, seal, and fill plan?  Should I hire a handyman that I can work with and learn from?  Are there any pitfalls that some more experienced mustachians can help me avoid?

MMM

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Re: attic insulation
« Reply #1 on: February 29, 2012, 09:36:46 AM »
Hey there - glad to hear you're working on such a high-return project! An insulated attic is easy to do and saves a load of heat.

I tend to agree with the other forum - spray-in foam doesn't work very well alongside fiberglass batts.. and open-top attics are not usually vapor barriered in the first place - they depend on roof venting to release any moisture that comes through from the house into the attic. For example, in my own attic, there is ONLY blown-in insulation - this sits directly above the drywall ceilings of the second floor of my house.

So in my opinion you'd be fine just blowing a nice thick blanket of cellulose over top of everything - be sure to aim it into any cracks you see as you go to avoid air pockets.

It's a pretty easy job, and if you buy over 10-20 bags of cellulose at Lowes/Home Depot, they lend you the insulation blowing machine for the day for free. You'll just need a willing partner to stand outside and dump bags into the hopper of the machine, and a good dual-canister respirator mask, a camping headlamp, and some old clothes to be the guy standing in the attic holding the firehose that sprays out the dusty cellulose.

velocistar237

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Re: attic insulation
« Reply #2 on: February 29, 2012, 10:50:56 AM »
Here's a pdf I found helpful. It don't know how it compares to the book you have, but it's pretty good.

http://www.energystar.gov/ia/partners/publications/pubdocs/DIY_Guide_May_2008.pdf

I also like www.buildingscience.com, but you can get lost reading stuff there. Here's a document that might be worth checking out.

http://www.buildingscience.com/documents/guides-and-manuals/gm-attic-air-sealing-guide/view?topic=doctypes/guides-and-manuals

Don't spend too much time thinking about it. Sealing the big air leaks and spraying cellulose in over your fiberglass is fine. If your attic has soffit vents, be sure to put in baffles to keep the cellulose from blocking them.

tfordon

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Re: attic insulation
« Reply #3 on: February 29, 2012, 11:36:38 AM »
Thanks for the advice and the excellent resources!  It definitely looks like I could get sucked into the building science stuff.

So, the new plan is to seal any major air leaks and make insulation dams to keep the blown cellulose away from the chimney and water heater flue.  Then I'll get a buddy to help me with blowing in the cellulose.  I'll leave the existing batts in place and not bother flipping them to get the paper on the right side.

Thanks again for the advice.


ultrarunner

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Re: attic insulation
« Reply #4 on: February 29, 2012, 01:30:40 PM »
One thing worth noting:  If you have soffit vents, be sure they stay open.  They make a plastic vent channel that staples to the rafters to keep an open air channel to the soffit, and it extends above the insulation.  You could probably be more mustachian, and make something similar (1/8" or 1/4" thick MDF, etc would probably work well). 

Good attic ventilation is important to reduce heat to keep the house cooler, reduce moisture, extend shingle life, etc.   If you live in a hot day / cool night dry climate like we do in Colorado, it also lets you install a whole house fan so you can give your money sucking A/C unit the big fat FU.  :-)

BenDarDunDat

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Re: attic insulation
« Reply #5 on: March 09, 2012, 02:26:57 PM »
Ultrarunner is correct.  You have to make sure you keep good airflow in your attic. 

Blindsquirrel

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Re: attic insulation
« Reply #6 on: April 08, 2012, 05:18:56 PM »
    Insulate the heck out of your attic. It will pay massively. Recommendation in Ohio is R49 for attics. Back portion of mine is now about R90 and front is R49. We cut propane use from 1100 gallons (ouch!) to 700 gal, to 400 gal last year (not a very cold winter).


KingZ

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Re: attic insulation
« Reply #7 on: April 20, 2012, 09:18:43 PM »
Just saw this thread while surfing the forum, but thought I'd share my experience.  I had the exact same project and questions as the op.

Adding more insulation will only be slightly effective if you do not seal the "attic bypasses", or air leaks.  The real insulation pros do this, and the craigslist cheapies do not...because it takes time.  This consists of sealing all areas where air transfers from the house to the attic.  This includes interior wall top plates, fixture holes, soffit openings, electrical holes, etc.  I used up four cans of spray foam sealing these.  You can tell exactly where these leaks are and how bad they are if you have gray/dirty/discolored fiberglass insulation around the "bypasses". The dirty insulation was your filter for all the air leaking.  **Don't mistake this for attic baffles which are required and let fresh air into the attic from soffit vents.

Seal these bypasses first, then blow in cellulose on top of your fiberglass.  I live in MN, code for new construction attic insulation is R-38, I put in enough for R-60, which is recommended for green building in our region (my townhome built in 1978 had R-19). My gas bill/usage went down 45% in the winter, and the electric was down 30% during summer.  This is definately a DIY, with the help of 1 buddy during the spray phase. Be sure you seal the bypasses before you buy the cellolose w/ 1 free day of rental...it may take you longer than you think to fill the bypasses:)   

Here is a nice pictured DIY for "attic bypasses".
http://www.familyhandyman.com/DIY-Projects/Saving-Money/Energy-Efficiency/how-to-seal-attic-air-leaks/View-All

reverend

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Re: attic insulation
« Reply #8 on: May 03, 2012, 10:21:59 PM »
I found that my house in Denver didn't have any insulation over the master bedroom. APparently it was a pain to put in because they basically sealed off that part of the attic in building the house. I complained to the builder when I found out (I found out by putting a ceiling fan in the master bedroom and saw no insulation!) and they sent someone out to cut in an access and then another company came out and blew in a LOT of insulation over the entire attic.

Ideally the entire attic and ceiling would be sealed tight with open cell foam, but my house is cheap and I wasn't about pay for that. :)

If you want to see how houses SHOULD be built, read up on how these guys build their houses: imaginehomessa.com

markstache

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Re: attic insulation
« Reply #9 on: May 23, 2012, 12:48:27 PM »
I put in "shake 'n' rake" fiber glass insulation my attic. Very easy. The only equipment you need is a garden rake. Cut open the bag and fiberglass expands. Then use the rake to puff it up and spread it out. Couldn't be easier. I'm sure cellulose is good too. This seemed like the best value when I decided to add a few inches of insulation to my attic.

gillstone

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Re: attic insulation
« Reply #10 on: June 02, 2014, 10:46:37 AM »
OK so the more I research this the more confused I am.  We have a 1956 tri-level.  The top level has a living room with a vaulted ceiling and a dining and kitchen with an attic above.  Total attic square footage is around 325 sqft.  The insulation is clearly not up to par.  The kitchen and dining can never get cool enough in summer and in winter we can see patches on our roof where is snow melts a lot faster than it does on other neighborhood houses which have the same floor plan.
Also in the attic is a 92% efficient gas furnace next to the ductwork and the venting for the gas water heater.  I plan on sealing that area off from the rest of the attic in consultation with an HVAC guy to make sure I don’t accidently screw up a perfectly good furnace or make something go boom etc…

Access to the attic is only enough space to change furnace filters, in order to get in the rest of the space I will have to cut a hatch in our dining room ceiling.  From looking at what is visible I have approximately 12in of blown in cellulose over a batt of fiberglass on the floor of the attic.  In the rafters are pink fiberglass batts - three of which are starting to fall from the rafters.  There is no additional vapor barrier in front or behind the batts. There is no asbestos.
The attic has soffit vents and a single static roof vent at the peak of the roof.  I’ve been on the roof so I know we don’t have a ridgeline vent.

I want this done right and with sealing off the furnace from the attic (but not the rest of the house or its combustion air sources) as well as general can of foam air sealing around fixtures I can get the first steps done.  What I’m flummoxed on is the next step.  Do I focus my energy on adding more cellulose, making sure the soffits are clear and not sweating the rafters? Do I work on the rafters, putting in the right materials the right way and not worry about how thick the cellulose is? Or do I do both? What would that even look like?

Also, should I change up my roof venting? And if I do, with what? 

Last note, I live in Montana so we get some wide temperature swings between night and day and a dry climate.

Greg

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Re: attic insulation
« Reply #11 on: June 02, 2014, 12:23:57 PM »
Let me understand, you have blown-in insulation at the ceiling joist level and batts at the roof rafters?  That doesn't make a whole lot of sense, usually it's one or the other.  The batts may be interfering with attic ventilation, partly because one of the jobs of attic ventilation is too keep the underside of the roofing cool.

Unless you want to condition the space, remove the batts and up the blow-in insulation.

phred

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Re: attic insulation
« Reply #12 on: June 02, 2014, 12:48:01 PM »
agree that batts up in the rafters sounds strange

is the vaulted ceiling insulated?

gillstone

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Re: attic insulation
« Reply #13 on: June 02, 2014, 01:20:28 PM »
Let me understand, you have blown-in insulation at the ceiling joist level and batts at the roof rafters?  That doesn't make a whole lot of sense, usually it's one or the other.  The batts may be interfering with attic ventilation, partly because one of the jobs of attic ventilation is too keep the underside of the roofing cool.

Unless you want to condition the space, remove the batts and up the blow-in insulation.


Yeah, the previous owners did a lot of DIY work of varying research and quality.  It's likely they looked up there and decided to blow in some insulation and call it good without paying attention to what was there. 

Before purchase we went through with the home inspector with an IR camera, it showed the vaulted ceiling was insulated.  Also temperatures were consistent and showed no areas where water had built up or small leaks.

phred

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Re: attic insulation
« Reply #14 on: June 04, 2014, 08:23:55 PM »
you need a second roof vent at the peak - other side - for some cross ventilation.  Keep the soffit vents clear. Take down the insulation stuck up in the rafters, and lay it on the attic floor on top of what you already have.  If those batts have a vapor barrier, you will need to slash the barrier in several places so moisture can't accumulate.