Getting max R’s out of Cellulose
cameraman
| Posted in Energy, Heating & Insulation on
Blowing cellulose in attic, Michigan, is there such a thing as to much cellulose?
My area I beleive reccommended is 52 R, can I achive this will Cellulose?
Will I reach a point that I will not gain any more R’s?
Can this be done all in one instalation or should the cellolouse be blown in layers or lifts?
I have plente of head room and I am in the process of foaming any air infiltrations and protecting proper soffet venting.
Replies
you'd need 16 or 17 inches of cellulose to get an R-52.
every time you double the R, you cut the heat loss in half. So R-2 cuts your load in half. R4 cuts it to 25%. R8 cuts it to 12.5%. R16, 6.25%... notice how the R number increase doubles, and your heat savings halves every time you double again.
R50 is very high unless you're going for something like passive house standards. R30 to R40 are typical points where you would hit the wall of "diminishing returns" unless you're prepared to go "all the way" to downsizing your heating system to basically not much, so all that extra money can go to insulation.
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
thanks for that post... I didn't know that... don't know how i missed knowing it... thought i'd read everything i could find on r-values and ways to "seal & save"maybe I have read it and just didn't "get it" until your postthanks
P
It's called the law of diminishing returns. Graph the heat loss against the R-value and you see what happens to the line. It's not a straight line.
The other poster is right, though ... installing R50 vs R38 is costing very little in labor. And energy costs WILL NOT (over time) go down. To add the additional R12 later would be cost prohibitive ... OK very expensive ... relatively speaking. Do it once, go the extra mile I always say. The cost compared to a whole house is tiny. In Michigan, you can use all the help you can get, too.
If you do the R50 ... time to find the next energy hole and see what you can do to 'plug' it. :)
I have seen people talk about R60 in the ceiling. There is not much more labor to go from R30 to R52. Energy prices are never going to go down only up. As you indicated air sealing is extremely important on the ceiling in colder climates. The attic access hole needs to be sealed also. There are some good details on this site on how to do that.
but you're only cutting about 1.56% more of your heat load through the ceiling out with the jump from R-32 to R-64 (to use nice, geometric friendly numbers).the money you spend doing that could undoubtedly be spent better elsewhere in the envelope to save more energy. That's, quite simply, a waste of money unless all your other envelope components are already at ideal levels.THAT is the question when buying insulation. You don't win by increasing your R to 60 if you, say, miss an opportunity to upgrade your windows or buy some spray foam to seal up cracks or whatever. Doubling your material cost for the insulation to save 1.56%... which is something, don't let the small number fool you, but it's not huge... is possibly a mismanagement of your envelope dollars.That said, there is a tipping point as the passive house people have been demonstrating. Go far enough, and you save elsewhere.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
1.5% over what? Nothing. R60 does cut heat loss over R-32 by like 46% ... although 46% of an already small number ... is still admitedly a small number. R-32 is way too little IMO for Michigan winter standards. Even in the NW, the minimum is more like R-38 by codes. The additional cost of the additional insulation will not really be enough to pay for other options ... particularly better windows. The cost to add additional insulation at some later point in time could be [relatively speaking] enormous. He's going to put in a few more bags of insulation over the minimum ... maybe a hundred bucks or so.
Your point is well taken, though and it's a reasonable perspective. With the brick walls, he'll have such a disparity of thermal load on the house. Replace the windows with something that might be half the load of his walls!! Now THAT would be strange.
I was just using geometric friendly numbers. most people insulate to near an R40 in the ceiling in cold climates. that's fine. and if you're DIY'ing your own insulation and it's cheap material, great, your "tipping point" is going to be very different then someone paying for insulation. But whatever it cost to get to R30 it will cost almost double to get to R60, and your heat reduction will be very small at that point.if he has brick walls, he'd be much better off trying to figure out how to insulate those walls than how to get a very high R in the ceiling. but if the very high R in the ceiling is cheap, it's not preventing any other upgrades from being done and I have no problem with it.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
points well taken. Pay your money, take your choice. Everything follows the laws of thermo ... there ain't NO free lunch.
When I built my house 1972 Cincinnati Ohio area R19 was considered a lot. Today R42 is considered a minimum here and the code requires R38. Yes I have seen the charts that the highest return occurs to about R5. From there the curve starts to dramatically flatten. So what. Someday the Code will require something well above R38. In fact with Cap and Trade looming the extra cost to go to R60 will be money well spent.
First off, it's not about "maximum return". If something gives you a 200% return per year that's great, but that doesn't mean the next step, 100% return per year say, is a bad deal. you don't stop at a maximum return, that's ridiculous. It's just about some return. IF the money you spend going from R40 to R60 could have done more good elsewhere, such as an upgrade in insulation type, more detail to sealing, better windows, better mechanicals, etc, then it was money poorly spent. Note the big IF there; it's a very big IF, and determining IF that is the case you are in in a particular project takes some time and effort to figure out. And lots of math.that is all. it's about maximizing the power of your energy saving dollar, not just throwing it at R-value like that is the only thing in the world.That said, I'm a fan of passive house goals, which does stress very high R-values, but it does a lot more than that as well. But unless you're prepared to go "all the way", there is a point where adding R-value does not make good sense anymore. that point is different for each building, budget, and climate. and PassiveHouse promotes high R-values, but it too is an exercise in managing the building construction resources as tightly as any I have ever seen. Otherwise you wouldn't even bother, since a major goal is to engineer a house in which mechanical system savings can pay for most of your upgrades.so the answer to the question, "is there such a thing as too much R-value", then answer is, quite simply, yes, if money matters at all. and for most of us, it does. That is the question that was asked, that was the question I answered, and frankly, I'm correct.If you want to argue about PARTICULAR levels of R-value, don't bother unless you're ready willing and able to do the math on a particular building. You simply can't say that R40 makes sense for every home in america, or even every building in your area. Maybe in most cases, maybe even nearly all, but not all.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
Rob, good discussion.... along the lines of "picking the low-hanging fruit"
our standard is R-60 cellulose attics... here's some numbers:
a 1000 sf attic at R-40 ( let's use R 3.6/ inch ) that would be 11"
a 1000 sf attic at R-60 ..... that would be 17"
the difference is 6" ...... cells have a settled density of 2 lb/ cf
so 1000 sf @ 6" would be 500 cf x 2 lb/cf = 1000 lb
we buy 25 lb bales of Cell-Pac so 1000/25 = 40
40 extra bales to go from R40 to R60... at say $9/bale = $360 for additional material the labor is what an extra 4 hours ?
we're already there, we've already prepped, we still have to break down
this seems like a no-brainer to go from R40 to R60
are my numbers wrong ? ( wouldn't be the first time )Mike Hussein Smith Rhode Island : Design / Build / Repair / Restore
wouldn't take very long to save $360 in fuel costs even if you didn't save much, that sounds like pretty good figuring to me, for your homes, in your climate.I assume you are not doing finish attic spaces or anything with limited space in your roof system? that is, that you have no extra cost for the space required for 6" more insulation?-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
I quickly ran through the responses to your question and there was something that I think wasn't mentioned.The thing about R values is that they are often quoted without the qualifier that the quoted value is for ideal conditions. Unfortunately, installing/retroffitting insulation properly in an old home will never be an ideal condition. It's not much better in most new homes either,as they usually aren't designed with a goal of being energy efficient.There are many things that are going to make the R 50 ceiling that you hope to achieve into one with an a much lower overall R value. Thermal bridging and air leakage being the two immediate concerns. You are doing your best to address the air leakage but in a old house not designed to have a well sealed envelope it won't be perfect.So, if I recall a graph I once saw, in an ideal world after R 40 you pretty much don't have any more heat loss. But your house is not ideal conditions, that's why you'll see guys like Joe Lstirburek saying you should be putting R 60 in your attic. To make up for all the thermal bridging and air leaks. R 60 's worth of cellulose does also seem to help a bit with air leakage, I think : )As Mike Smith, and others, pointed out the extra cost for the cellulose is pretty tiny especially when you factor in the long term savings, and also the unquantifiable benefits in making your home more comfortable in the winter. (Your house will be cooler in summer too!)
yes.... sloped ceilings and cathedrals always screw things up
the other things that are difficult are unfinished areas that "might" get finished in the future...
have to create barriers that are that are usually not up to our standardsMike Hussein Smith Rhode Island : Design / Build / Repair / Restore
You are right about the curve 'falling off' at around R-5 ... dramatically. I graphed it, but don't know how to show that graph here.
However, R-19 loses about 1/4 the heat of R-5. R-19 is economically reachable in walls due to commonly used construction techniques. R-38+ is usually economically reachable in ceilings/attics.
Codes normally require what is already common in construction practice using readily available materials and common construction techniques. As such, we have to remember ... the codes are MINIMUM standards for those who choose to do no more than the minimum level of effort and expense to meet that aspect of the code. We frequently see people that exceed the code for a variety of reasons (e.g. stair width for more comfort, aesthetics, and/or accessibility).
As energy economics and product development and construction techniques change, so will the code. I would surmise that codes rarely (if ever) would push any cutting edge technology or techniques or products (although they do allow them).
Edited 9/30/2009 8:45 am ET by Clewless1
I like your analysis. Some thoughts ! Codes are retrospective. They are based on what has worked in the past. As earlier indicated in this thread calculating where to spend energy related dollars based upon today's cost will yield one set of numbers that leads to one strategy. If energy costs are projected 10 years ahead and those same calculations are made an other strategy would be arrived at. The unknown is what the costs of materials we use to slow down energy loss or gain down the road will be. Looking backward it would have been cheaper to insulate the attic in my house to R60 in 1972 than what R19 would cost today. Energy consciousness is in its infancy. Hopefully the industry will become smarter and to achieve a reasonable energy efficient envelope at least on a new home and hopefully retrofit situations will become more reasonable. I have done a number of improvements on my house based upon an energy audit. Early on I realized I would have to do these improvements myself because to hire someone to do them would never equal the money saved. Lucky for me I was able to make those changes. There is one large area of the attic that is unaccessible. In 10 years when that area needs to be reroofed I will pull some plywood then and seal and add insulation to that area. The low hanging fruit and the area that seems to be struggling for improvements are windows. My 37 year old windows have an R value just over 2. The best American window manufacturers today are struggling to produce a product with an R value over 4.
Good thoughts. FYI you can get windows w/ R-values that approach R-10. I am not talking cutting edge/emerging technology here, either. The technology has been avalailable for about 30 years now and some window manufacturers use it regularly. I refer to Heat Mirror low-e mylar film technology. The 'standard' glazing has U-values in the 0.20 - 0.25 range. If you do multiple films, you can drive that down much further. A colleague of mine installed a triple film window in a new house he built. Don't recall the declared value ... I think it was like R-11 or around there.
Thanks
Jay,
The acess hole is a 32" door and steps off from our bedroom.
I have attached 1" foam to the backside of the door and weather sealed just as if it were an entieror door.
as i understand it always seal the ceiling/roof first... if you can stop the "suck" smoke stack effect first... then alot of smaller air leaks down low don't have enough "suck" for them to be as much of an issueI deal alot with all brick structures... what you do not want to do is seal up your bricks too much... you have no expansion joints... your brick structure was designed to move... expand & contract... and to breath... the gaps between yur bricks are there for a reason... second line of defense to keep moisture out... and to be able to dry out...good luck
p
That's exactly my plan, start at the top and work down.
I have a lot of sealing to do, I have been in the basement, placed my had by a chase to the attic and feel the draft.
That is how I interpted the air space between layers of brick, traps moisture.
Another good use of the airspace between layers of the brick....
we used it as a chase to run romex during rewiring the house.
Not to mention a good place for the squirrels to store walnut shells!!
as i understand it always seal the ceiling/roof first... if you can stop the "suck" smoke stack effect first... then alot of smaller air leaks down low don't have enough "suck" for them to be as much of an issue
Yep I agree. IIRC there was a discussion years ago (might even be the forum before BreakTime was BreakTime) about this. The gist was, that if the ceiling plane was air sealed correctly, you could open a window on a zero degree day and not feel any draft.
Quantum materiae materietur marmota monax si marmota monax materiam possit materiari?
Yep I agree. IIRC there was a discussion years ago (might even be the forum before BreakTime was BreakTime) about this.
Yup, Freddy Lu & Gene Leger vs the Deniers. Many threads about that.
The gist was, that if the ceiling plane was air sealed correctly, you could open a window on a zero degree day and not feel any draft.
Yup, built one like that. Open the front door at below freezing temps and not feel it until you step outside.
Joe H
The only time there's "too much" insulation is when it blocks needed airflow or simply gets so heavy that it causes structural problems. But, as others have indicated, there's a diminishing return the thicker you go -- that is, the second 10" don't save as much as the first ten, etc.
Yes, absolutely, you can do it. Don't have to worry about 'lifts'. See the other notes about the diminishing returns ... but the cost is small and if you have the room, go for it. My first house ... 1979 I installed R-49 in the ceiling ... that was WOW, back then, but really it's no big deal.
What are you putting in the walls?
Thanks for all the replies, so here’s my plans.
1919 2 ½ story brick home, attic floor is sheeted with 1x12 rough sawn on 2x6 joist.
All I have in the ceiling for insulation is about 2†of old Rockwool, news paper, and about a century supply of walnut shells left from the squirrels. Even this is a dirty job; I am removing all of this.
Upgrading electrical to rooms below as needed and foaming all holes, plumbing, electrical, ect…..
Running fanfold foam on the underside of the roof rafters along the perimeter down to where the roof meets the floor. Notch the fanfold over the ceiling joist to hold back the cellulose from blocking overhang venting, if fanfold foam is not strong enough I will run ½†foam.
Then run a bead of foam along the fanfold were it touches the floor to seal and hold it in place.
With the old insulation and walnut shells gone I can get a good look at sealing all penetrations.
Then filler er’ up!!
I have explored all options from fiberglass batts to spray foam the underside of the roof, including the same as above but squirt 1†of spray foam then blow cellulose on top of that to finish.
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I figured this to be my best bang for the buck, and the buck is harder to come by now!
Sounds like a reasonable game plan to me.
Walls!!!!!!
This is a solid brick`construction.
I have one coarse of extieror brick, a couple inch air space, then 2 coarses of an intieror brick, and plastered over that.
That's it, not much I can do with that except seal up the house the best I can!!!
Edited 9/23/2009 12:08 pm ET by cameraman
rigid on the inside and new drywall. Wow, that's a tough one.
After foaming all possible air leaks in my attic, I had R49 insulation blown in. It was relatively cheap.
A decent foam gun and one of the LED headlamps made the foam process reasonably painless. I went through about three of the cans of gun foam in the process. I sealed up all the drywall to header cracks, all light fixtures, all the wiring penetrations, etc... Plan on spending at least two or three hours in the attic with the foam gun.
I spent days crawling around in our attic, and was only able to seal maybe 80-90% of the leaks. A 240lb guy crawling around in a 4/12 trussed attic is going to have a lot of trouble getting into the corners where the worst leaks are.
As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz
Dan--Sounds very familiar. I never found those fan folds to shield the eve vents from getting plugged by blown in insulation. Ended up using batts of R-20 FG over the existing blown in (not much about 6-8").
Always had to slide a piece of plywood (that I could get through the access) around so it was like using a creeper under the truck. Cellulose needs to be fireproofed.
Anybody know the real value of insulation in walls fully sheathed with CDX outside then covered with building paper, then bricked? Interior covered with 1/2" gypboard.
Hot air rises and if the walls and windows are tight their isn't wind making it through to the conditioned space. Always wondered. TyrThings are not always what they seem; the first appearance deceives many; the intelligence of a few perceives what has been carefully hidden.... Roman Poet Phaedrus 15BC–50AD
Cellulose needs to be fireproofed.
Wrong.
Treated cellulose is fireproof.
Wrong wrong wrong.
Joe H
As you said Joe. Treated cellulose is fireproof. That is the fireproofing of which I spoke. Having owned a cellulose plant I can tell you that I could produce cellulose and sell it as is. However, once the cellulose is made I treated it with a fire retardant (I just used "fireproof" for short)--very few things are "proof"--watches are water retardant usually to a certain number of feet, fabric used in bedding is also "retardant". The message was just a "headsup" to make sure any cellulose was treated to be fire retardant. It is POSSIBLE to get it untreated. Being paper (less fancy name than cellulose) it burns quite well if not treated. Now you know. TyrThings are not always what they seem; the first appearance deceives many; the intelligence of a few perceives what has been carefully hidden.... Roman Poet Phaedrus 15BC–50AD
Who makes it & sells it without treating it?
Never seen any that wasn't, if it's made by a CIMA member I'm guessing it's treated?
When you owned a cell co, how much junk collected in the metal seperator?
I miss the blue wally bags, but I've heard a lot of wedding rings or whatever go through.
Joe H
I'm guessing that getting the plastic out is the bigger challenge.
As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz
I found something once, little plastic/rubbery toy.
Pretty well chewed up but mostly intact.
Always wondering what's gonna blow a vane off my fan, sure makes a racket when junk goes through.
Joe H
Hey, we don't use the R word anymore. Cellulose is made "flammability deficient".
As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz
I have already built rigid foam boxes around the bath fans and recessed light cans.
Now foaming around the vents and wire holes, ect......
I have a very steep roof and can get to the edges fine. I have the attic all wired for lights & music, 2 windows to open and exhast fan, I even take a cooler of beer.
Sort of my man cave
why is it when anybody ask a question about insulation they start an argument about payback and dimension return?yes I save $3000 by placing my own concrete so I want to take that money and buy insulation so I be comfortable. 'well you never get payback" who cares, i use less energy my equipment doesnt wear out, and I,m comfortable. "well if your equipment doesnt wear out it will cost more to replace and not be as efficent"I am the most conservative when it comes to energy, I'm cheap. I think everybody needs a concrete bunker hurricane proof house and insulate it to r100 living on the coast" well if I buy insulation, I cant buy beer and hoho's" this whole post was about paybacks, but the guy did not ask a question about payback, he wanted to know how much papaer to get r52
why is it when anybody ask a question about insulation they start an argument about payback and dimension return?
Yeah it does happen, but the OP kinda started the ball rolling unintentionally.
FROM CAMERAMAN: Will I reach a point that I will not gain any more R's?
caused a Pavlov's Dogs situation! lol :-)
Quantum materiae materietur marmota monax si marmota monax materiam possit materiari?
Phil,
Hate to disagree with ya, but I really didn’t ask or was concerned about payback, intentionally or unintentionally,
My main concern was will I reach a point that adding more cellulose would reach my goal of adding more R’s or would the level of obtaining R values dwindle off.
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Let me put it this way, when I was a teenager working on my old cars I would add antifreeze to the car at a 50/50 mix as said in the directions. Well I started to think that if a 50/50 mix was good then running straight antifreeze would even be better. Well I was told then by many that after you get to a 50/50 mix you didn’t get any better freeze protection.
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Well in terms of antifreeze to cellulose, if 20†gave me a R-52 then would 40†give me a R-104 that was the question.
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I am insulation because it is needed and the right thing to do, will I get a return on my investment??????
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If I can save money for more beer and Ho Ho’s, now that is one of the important things of life!!
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I have learned a lot for all the post, thanks to all!! Fire up that Blower!!! Let the insulation begin.
You missed my point, but it's of no matter.Nothing personal.
Quantum materiae materietur marmota monax si marmota monax materiam possit materiari?
At least until you're greatly compressing the insulation because there's simply no room for more, you don't reach a point where adding insulation actually REDUCES the R value. It's just an exponential curve, where the heat-saving value of each additional inch starts out high but reduces fairly rapidly until the ADDITIONAL value (in terms of dollars saved) of each inch is VERY CLOSE to zero.This in not because the R value itself stops going up, mind you (10 inches have twice the R of 5 inches, 20 twice the R of 10, etc) but because the first amount of R value might, say, cut the heat loss (fuel cost) through the ceiling by a factor of 10 -- saving 9/10ths of your fuel cost -- so that any additional savings has got to come out of that remaining 1/10th. Even if you could reduce the 1/10th to zero (which you can't, quite), the you'd only save an additional 10%, relative to your original (before insulation) heat loss.But an interesting quirk of the way the numbers work out is this. If you put in an amount of insulation that reduces your heat loss through the ceiling by a factor of four (or any other factor), saving 75% of the $$ loss through the ceiling, DOUBLING that amount of insulation will save (roughly) 75% of the REMAINING $$ loss through the ceiling (though only 3/16ths of the original $$ loss).(And, of course, very quickly some other factor -- walls, windows, doors, heating system -- becomes the "biggest loser", so in terms of your TOTAL % heat savings, the value of additional ceiling insulation diminishes far more rapidly.)
As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz
Got it, so it reaches a point that I would be better off putting my efforts to windows, walls, sill plates,ect.
I understand that the attic insulation is not the answer to every thing but a good place to start.
Here's some photos of the monster that I am working on.
Thanks all for the info!
Yeah, with one like that, in Michigan, you want to insulate everything you can. Attic insulation is "attractive", since it can often be installed with minimal effort, and minimal disruption/damage to the structure. Plus, since heat rises, an inch in the ceiling is pretty much the equivalent of 2 inches anywhere else (in very rough numbers).So in terms of insulation, it IS sometimes smart to be like the drunk looking for his car keys under the street light (since it's light there), even though he lost them in the dark spot 20 feet away.The other thing to look at, of course, is SEALING. Even an empty, uninsulated wall cavity will have a much better R value if air can't easily leak in and out, plus air leakage into the house creates drafts that make the home less comfortable than would be the case based on inside temperature alone. And (as has been mentioned) leaks in the ceiling create a "chimney" effect that draws in air elsewhere.
As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz
"Plus, since heat rises, an inch in the ceiling is pretty much the equivalent of 2 inches anywhere else (in very rough numbers)."
For that to be true, the DeltaT at the ceiling would have to be twice as much as at floor level.
Jon Blakemore RappahannockINC.com Fredericksburg, VA