r-19 insulation in 2×4 space
KylefromKy
| Posted in Energy, Heating & Insulation on
I have an old attic I’m converting into a living space and am about to install ceiling insulation. The old rafters are a full 2″ x 4″ and I heard somewhere that r-19 insulation (5.5 “) can be compressed into that space yielding a higher r-value than r-13 (3.5″) which of course would leave 0.5” of air space. I don’t want to add wood to the underside of the rafters to make them taller because the living space is already very small and short. Any advice, or better yet experience on the subject?
Also, should I take the time and effort to bend over the 10,000 rusty nails that protrude through the sheeting boards and will therefore poke into the insulation?
Lastly, why do pirates like a lot of insulation in their homes?
Replies
Welcome new guy..hey, another Ky-ite..ok here goes, ya have a LOT of loose ends there..vented attic or not? What PART of Ky? Did you know fiberglass insul pretty much sucks?
I would hang around here awhile and watch what develops..there are many ways to insulate that can do more harm than good..about the nails? Leave em alone.
Welcome again.
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The attic is not vented, I'm in northern Ky (Cincinnati, almost), and no, I didn't know fiberglass insulation sucks but that would be a bad thing for any insulation to do now that I think about it.
Basically, what happens is that it loses performance as the temps drop. It also can have errant air currents though out it, those currents can contain moisture from the household and condense on the under side of the roof..read rot, mold, etc. That is part of why insul cavities are vented..to have fresh air from the soffit vent to the ridge..The moisture needs to be STOPPED from getting in there to begin with.I am just down 75 from you below Lex. And have a 'cold-non vented' roof..it works in our climate but so well in others.I really lean towards rigid foam..cut it to fit between the rafters, seal any gaps with foam spray..then sheetrock away.
Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
Ok, it sounds like the consensus is rigid foam. That might actually help discourage the rat snakes from living in the attic. (They love the fiberglass because they just slither right into it and disappear). Is rigid foam the same as styrofoam? How does the cost compare to fiberglass? What widths and thicknesses does it come in? How should it be cut? (I have actually cut some on the table saw once with excellent results but there must be a quicker way). How is it held in place? (Some of the spans between rafters are close to 30"!) Thanks to all who've responded.
I'm building a new house and having xylene (sp) foam put in. It supposedly gives an r-19 in a 2x4 cavity. Complete seal, even the snakes will be kept out. Costs more than blo-in batt or fiberglass. supposedly does a much better job.
yeah, rigid foam is the answer
you guys really get snakes in your attic insulation ???
you guys really get snakes in your attic insulation ???
I pulled an 10 foot black snake out of a second story wall cavity when I was demo-ing plaster once. There were lots of skins in the attic. They come in hunting mice.
I invented the trouser snake rumba.
Styrofoam is Dow's copyrighted name for their blue foam board (XPS). Owens Corning has pink board. R-5 per inch. Dow's Scoreboard goes up to 3" thickness, if you can find someone who stocks it or will special order. People tend to just put 1" and 2" boards together, but there are problems with moisture infiltrating in there through the wood. There's also polyisocyanurate, technically R-7 per inch but it stabilizes at a little over R-6; I decided to stay with XPS to keep the isocyans out of my bathroom. Dow's polyiso goes up to 2", Johns-Manville goes up to 3".I tried cutting foam board with various kinds of saws. After I finished vacuuming up the mess, I went and got a Milwaukee heat gun with the foam cutter attachment.
Down here, only HD carries 2" foam..concrete supply place has 1.5"2" at HD is about 17.00 a 4x8, 1.5 from the concrete block place is 19.00..so, I do the trek to HD. Lowes only has 1/2 an 3/4...I have had luck with a hot wire, drywall saw, bandsaw..and a cordless circ saw..each has it's place.You can 'glue' it up with dabs of greatstuff foam (use a prop to hold it till it grabs.) Or cut it tite an jam it in..friction holds, kinda.I foam any gaps with greatstuff MESSY but it helps.I have had no luck with any tape staying stuck for long,between the sheets..cuz I am not going fast enough to get my drywall up to hold it in place.Being as the roofing nails are stcking down through the sheathing you wont Slide it into place to well, aim well, and jamm it up in there on the first shot.I know ya dont want to lose head room, but I am strapping with 3/4 wood on 16 centers and filling in with more 3/4..drywall dont like rafters on 32" centers..think about that. It'll also let you get a flatter cieling if the rafters are crowned or bowed at all.
Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
I'm still waiting for someonw to answer the question in his original post about "why pirates like a lot of insulation".
I'm assuming it's got something to do with "AAARRRRRRR" values.....lol. Maybe Luka and Darcy can confirm that?
Bob
I'd say ya nailed it..you get an AAAAAAAAYYYY...
Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
Thanks to everyone for their responses and good ideas. Even though the consensus is that rigid foam is the best way to go, I'm still considering FG because nearly 3/4 of the house is already done that way, and there are so many aberrations, anomalies and irregularities in the framing of the cavities that it would be too tedious to cut and fit foam precisely whereas FG can be easily bent to my will. (That and the fact that as retired set designers for the comedy show "Hee-Haw", the previous owners and I are obliged not to build anything too well.)
If indeed I go this route I still would like to know which option would result in a higher R-value: R-13 with a 1/2" airspace above it or R-19 compressed to 4". Anyone have any spec's?
I guess that a good vapor barrier is vital. How well would 1/2" r-board do as a vapor barrier if the gaps were taped with something?Regarding the rat snakes, yes we really do get them in our attic. (pictures attached, hopefully). The house was abandoned for almost a decade and they decided to move in. Over the years we have removed dozens of them from the house and yard. We use the nifty "Marlin Perkins Memorial Snake Catcher" made from 6' of 1/2" cpvc with a thin rope running through it forming a noose on the business end. We have developed quite a routine, one he would be proud of. I carry the snake away from the house and my lucky wife gets to hold an empty feed sack while I lower the writhing creature into it and then we quickly roll down the top of the bag to close it off. What next, you ask? We jump in the truck and drive about 2 miles away and release the snake into a mostly deserted rural area (except, I think, for the local property valuation administrator's house). My wife still graciously helps me do this even after discovering a number of carefully placed snakeskins in the bathroom.
And, finally, the answer to the question "Why do pirates like a lot of insulation in their homes?" is of course, as you guessed, "They like a really high AAAAARRRRRRR-value!"
quit dumpin snakes in MY yard..ok, go with the FG..howw ya intend to hold it in?I stuff it tite like ya seem to want to do..I have no usable data, but I am also using foilfaced duct board on my place (it's free) at 4.3 R per inch.Them Hee-haw folks get around huh?
Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
Sure, foilbacked 1/2 inch with foil taped seams works but what are you going to do pressing an R-19 batt up in in there?
You planning a tight fit against your sheathing or making baffles?
me thinks he is nonvented, like my place..gonna jamm it in tite. My guess.
Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
Right. The attic is non-vented and I'm hoping the vapor barrier will prevent moisture from getting in there in the first place.
Well, I wouldn't test therory with fiberglass batts.
If you are sold on doing the nonvent I believe densepacked celluous has the recommendation of the experienced hands here. To do it right on an old house takes a good degree of technical merit to pull it off. Be attentive to detail.
IMHO Old houses need the security blanket of venting cause moisture's going to find a way in there unless exact then no way to get out.
Plenty of stories about useless wet fiberglass insulation.
be waryButWDIKnow
Edited 12/7/2004 4:53 pm ET by rez
When you say no vent you also have to consider what is happening to your roofing.It sounded like the 2x4s are the roof rafters?????? if so you will need to keep it vented up there to not burn the shingles off the roof.
If you want I think I can dig out the reduction in R by compression. Ive seen it recently, now if I can only find my pencel oh there it is- right where i left it behind my ear. Twenty minutes ago.
Yes, the 2x4's are the rafters but the roofing material is corrugated tin, so I don't know if that could be damaged by heat or not. . .and I would be interested in learning what the reduction in R-value is under compression. Thanks.
Does anyone else have problems uploading image files? I keep getting either a generic error message with my Firefox browser or a message from IE saying the web page has problems that might prevent it from funtioning properly.
http://www.celbar.com/pdf/energystudy.pdf
Here's a little info that will disswade you from using the batts, I'll keep looking for the little blurb I saw on the compression reduction.
If you use foam board you cut it like sheet rock, if it's thicker than say 1.5" to get a good clean cut use the utility knief-straight edge-score then follow it with a nice dull hand saw down the score line. Makes for perfect fits. Also for those nails use something like these for end cutting the nails.
http://www.knipex.de/addons/katalog/seite/en/schneid/schneid01.htm
Good post.
Couldn't get a price on those nippers shown.
You got an idea how much they run?
Edited 12/8/2004 1:54 pm ET by rez
I use a channel lock of a simular type cost about 20$ but with a little hunting I found this.http://www.knipextools.com/steelcutters.html from this page http://www.knipextools.com/steelcutters.html scroll down to the 6101-8 Looks like 42$ plus a little shipping.
I own http://www.knipextools.com as mentioned above. The tool listed for $42 is actually a high leverage bolt cutter, much cheaper standard end nippers are available from knipex. Check it out, knipex is by far the best brand of pliers. and my site is the cheapest place in the USA to buy them all..... guaranteed.
these are the type that I've been using.
View Image
148-10
Cutting Pliers - 10"
End cutting nippers
$16.25
148-14
Cutting Pliers - 14"
End cutting nippers
$19.95
Ya, a quality tool. I have a couple oldies that are similar.
One time I was at one of those taiwan quickie tool places and saw some nippers for several bucks.
Thinking to get a spare for one of the odd tool boxes, I bought it.
First time I tried to pull a nail it notched the teeth.
cheep tools bite
Owens Corning used to make a high density fiberglass batt. I got the stuff for fitting into 2x4 and I believe it was an R-13 (?) (it was 2 higher than what a regular 4" batt would perform)
They also made a higher density one for 2x6 as well.
Kyle,I recall that the reduction in r-value for a R-19 batt fit into a modern 2x4 wall yields R-15. Compressing the FG gives higher R per inch of thickness, up to a point. You might get R-15.5+ in your 4" cavity.I still use FG on little jobs, because convenient. However, most everything else is better one way or another. FG is transparent to IR radiation, so it is poor in roofs and attics, especially in summer. The hot sheathing radiates and the IR goes thru the FG and is absorbed by the drywall, heating the room contents by re-radiation. Cellulose is much better in this regard, as well as in response to airborne moisture content. Foam is better, too.Bill
(Edited to mention the 4" cavity.)
Edited 12/17/2004 3:49 am ET by Bill
Why not just use R-15 dense in 3 1/2" insulation?
It is made for 2x4 studs. HD carry's it is about the same price as R13
hi, jim....
we don't use no stinkin fiberglass 'round heahMike Smith Rhode Island : Design / Build / Repair / Restore
snork....heheheheeh
Spheramid Enterprises Architectural Woodworks
I'll just do it>
OK I'm a little late in the game posting here but... You say there are alot of nails poking thru but you also say its corrugated tin. How is that possible?
I would personaly insulate the roof like a hot roof desighn. Lots of disscusion here abought insulating cathedral ceilings, which is basicly what you have but lower. This just means no venting. The thinking goes that if you insul the ceiling really well, then moisture cant collect and condensate.
Because its a metal roof I would recomend that you get foilfaced foamboard pushed up aginst the underside of the roofing. This will really help the attic space from getting hot in the summer from IR heat. There are products now being sold for roofs that are basicly reflective mylar applied to the roof deck before the shingles go down. It really cuts down on how warm an attic gets in the summer.
I would cut the foam bord an inch narrower than the width of the rafter bays. Then fill in the 1/2" gaps with cans of expanding foam.This will give you a good vapor barier. Repeat untill you have reached the stud depth. Using the foam board will give the maximum amount of R value for the small amount of space you have to work with.
The house dates back to around 1850 and started out life as a one room 1 & 1/4 story log cabin, probably with wood shingles. The roof has multiple layers now, from the bottom up as follows: 1" random width rough sawn sheeting boards with protruding nails, (from wood shingles, presumably) 1/2" cdx, builder's paper, and corrugated tin held down with neoprene gasketed wood screws. The foil board seems like a good idea to deflect heat. Thanks.
Special Christmas card attached!
wanna trade?looky here, sorry it's a long thread, but the pics will get your attn. for sure.http://forums.taunton.com/tp-breaktime/messages/?msg=38593.269
Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
Interesting, but I'm not sure which photos you wanted me to see. The copper chase?
that thread is long, ya'd have to scroll back to the start and pick and choose. My insulating is in there somewhere, among other oddities and obsfucations.This house is in Madison Co. approx 175 yrs old , no one knows for sure. Consensus is that it is the oldest in the county.The metal roof was added around 1910, has split ash rafters on one half, and cedar poles on the other, strapped for wood shakes. A real pain to insulate.Using foilfaced duct board and EXP foam was really my only option, other than spraying the whole thing with foam, which would have cost more than i paid for the house.Peruse it if ya want, the copper chimney support is about the last of the pictures posted.
Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
Wow! I just perused the thread and it looks like we're rehabbing the same house, in a lot of ways. I have a hundred or more pictures from our last 14 years of work, but to save you the agony of viewing them all I included just a few.
You play the guitar? I play the banjo and hammered dulcimer. (http://www.kylemeadows.com). Are you from NC? I was born in Concord, NC but raised mostly in SC.
My wife and I sometimes take her father to Nicholasville (near Lexington) to visit his sister. Maybe we can see your place someday?
ROTFLMAO!!!! yep ...we are in the same mess. Too funny. I am an hour from N-ville, give a shout anytime.You seem to have a better sense of humor about it than I have had.I was in far western NC, Macon, Jackson, and Swain Counties...for about 10 yrs. The Smokies just got outta hand with tourists and bad air.We gotta talk, bro. This is crazy.
Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
ROTFLMAO!!!! What does that (and all the other abbreviations) mean? LOL, BTW, IMHO ? Where's the codebook? I'll contact you when we're heading that way.
Goooooood Lord, there must be something in the water down there! Another Sphere...
You know, they've got these machines called front-end loaders that could take care of your housing woes all in one day :) I DO like the property though. Assuming the property extends a nice distance BEHIND the house (nothing worse than having a 1/4mile long driveway, but some yahoo puts a house 50 feet BEHIND yours). Nice long driveway.. did the dawg come with the property? (beagle?).
And btw:
BTW -by the way
LOL - laugh out loud
ROTFLMAO - rolling on the floor laughing my a$$ off
dw - varies, typically refers to (dear, da, dang, etc) wife or dishwasher or dewalt, look for context...
PITA - pain in the a$$
IMO - in my opinion
IMHO - in my honest opinion
jt8
Our front end loader hasn't run in about ten years and so we must continue. Patsy, the beagle, (as in Cline, because she sang so well) didn't come with the property but visited and liked it well enough to stay. Alas she has gone to Beagle heaven, where there are unlimited rabbits and no cars or fences.
The property (about 100 acres) is far nicer than the house, which sits (somewhat crookedly) almost right in the middle, so the only yahoos we have to lookout for are ourselves. (We have met the enemy...) My wife's father bought it in 1960 for the grand total of 17K! We are very lucky to have it now.
ROTFLMAO
LOL,
BTW,
IMHO
Where's the codebook
Rolloing on the floor laughing my ace off
Laughing out loud
or Lots of luck
by the way
in my humble Opinion
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
KylefromKy: Is the picture of the window a commentary of your opinion of Marvin windows?
No, I like Marvin windows just fine. Especially when you get them out of the bargain bin! That was just a sticker off of a new one and I liked the way it looked on the old french door.
I would definitely NOT use R-19 in a 3.5" space. You will lose R-value and waste money, deny the ventilation space, and cause yourself grief trying to stuff it in and keep it in.Wasted time
Wasted money
loss of ventNow adding the 1/2" Thermax across framing facers to add R-value and stop thermal bridging while adding VB is a good thing!
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Absolutely right Piffin. Forget the 2x6 insulation.As far as cutting foam insulation, someone said a bunch of power tools would work. forget that. use one of those break off razor knives, they stick out long enough to cut through or at least score deeply insulation up to 2 1/2" thick, just snap it off.
I'm surprised no one has mentioned snow melt issues. In Minnesota we vent for the reason of icicle that reach the ground and ice damns that ruin your plaster in the spring.
I had the same insulation questions many years back in my first 1.5 story house. I went with R-13 insulation, with a true 2X4 and got 1/2" venting. use the Kraftfaced insulation to hold it in place and still add a poly vapor barrier. (6-mil. poly) I also added a .75" sheet of polystyrene under the rock and over the rafters. Just take off your shoes when going upstairs you won't notice the difference.
Make sure the eve vents and ridge venting is adequate or nothing works.
Edited 12/7/2004 7:41 pm ET by hammer-n
mad dog... did you see the bit about Calvin's wife , Joyce , hosting a BreakFest ?
where the he*l you been ?Mike Smith Rhode Island : Design / Build / Repair / Restore
Nope.When?
this comming summer in the glass city... wherever that is
so , dude, whassup ?Mike Smith Rhode Island : Design / Build / Repair / Restore
Mike,Sounds real good. I'd be up for a "close" fest, since I can get from here to Cal and Joyce's house in about 6 hours, maybe less. Cool place, would love to see it again, and if Karin didn't want to come along, I'm sure there will be lots of hotties around, hehheh!How'd yours go? I suppose there are pics all over this site? Wish I could of made it, but what with working for the man, and I got a whopping 17.5 hours of vacation last year, plus some unpaid time helping the mother in law in Florida with her house, well...Other than that we'll have to catch up later.
You won't lose R value (as compared to standard 3.5" fiberglass) stuffing 5.5" glass into a 3.5" cavity. You'll gain something, but will not get the full R-19.Standard fiberglass insulation is not "optimal" -- making it denser (more compressed) would increase the R value (and also decrease infiltration losses). In fact, you'd probably have to get the glass near solid to see the R value peak and begin to go down. It's just that there's a diminishing return (and price points, code minimums, etc) that causes manufacturers to sell it at the standard density.However, a better choice, if you're determined to go fiberglass, is to buy "high density" insulation -- about twice as dense as regular.
I was told by a rep that you lost 1r per inch it was compressed.(pink stuff).
He was blowing smoke. No way to make a rule like that work in any sort of general fashion.
That's what I thought, a 3 12" wall would be r16 ...
I can hear that.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Have you considered spraying urethane foam? I don't have to deal with snakes but I know that FG is a great place of mice/rats to nest. With foam you elimate the space, get great R value and it is tight. Cost more but in the end it will pay for itself.
No we haven't really considered urethane because the area is small. It's basically one room we're talking about.
how about ridged foam insulation ?
When you compress FG to less tjhan its design application, it loses R-value. Your best bet is foam or denspack cellulose instalation
Welcome to the
Taunton University of Knowledge FHB Campus at Breaktime.
where ...
Excellence is its own reward!
Remember if you insulate with anything other than sprayed in place foam or dense packed cellulose you need to vent. It is a lot of work to cut foam and seal all the gaps.
Have you considered sprayed in foam? I have 2x4 rafters in my house too and have a cathedral ceiling on the second floor. The only option I decided would work well was sprayed in urethane foam. R7 per inch. Since the foam adheres to the the underside of the sheathing there is no opportunity for condensation. Also there is no air (or moisture for that matter) transfer also reducing the transfer. I am putting up firing strips with some foam between the firing strips and the rafters to create a thermal break between the rafters and the drywall. The extra air gap should add at least a little more insulation as well.
In my opinion, the sprayed in foam is great and the only thing I would consider in a situation like yours. It's expensive but it is great.
Tim
Having at different times read of concerns of moisture migration found between the layers of foamboard when multistacking tight against roof sheathing in a nonvent roof insulation scenario, is this really a valid concern?
It would seem difficult that enough vapor is ever going to be present in the wood rafters to find it's way between those pressure fit sheets without also finding it's way out as with the rafters.
Is this a possible mold concern as to why it is ever bought up in the first place?
It would seem that attentiveness to detail could give a high caliber enough of an installation with foamboard as opposed to the view of only spray foam or densepacked cellulose when not venting.
Well, time will tell if I'm doing the right thing or not, I'm sure, but I'm compromising (first time THAT'S ever happened!). I'm going with foamboard in the almost flat shed dormer roof (about 10x10) and FG in the steeper (and older, more irregular) pitches. All non-vented. I'll put 1/2" foilboard with taped seams over (under, actually) everything and hold my breath. (That should stop the moisture!) The whole room is only about 16x16, so if all else fails and we're still alive we'll just redo it in a couple of decades. I do appreciate everyone's input.
Kyle- Please don't put tightly compacted fiberglass batts up against the roof sheathing in your steeper pitched area without at least baffling it with the foam pop-in vents for soffit to ridge venting.
be a big difference between two decades and two years
Edited 12/27/2004 11:33 am ET by rez
Edited 12/27/2004 11:34 am ET by rez
Edited 12/28/2004 11:30 am ET by rez
We're actually putting r-13 into the steeper roof areas and leaving 1/2" airspace. (3.5" batt and 4" rafter). We haven't figured out yet how to open up the ridge for circulation. As I said it's a corrugated tin roof and so has a metal ridge cap. Underneath that we installed adhesive self-sealing membrane thereby connecting the two halves of the roof and we're afraid to cut into it and risk creating a leak. The metal ridge cap doesn't extend very far down the slope of the roof and we don't want wind driven rain to travel uphill and find the holes in the membrane, which might be especially easy adjacent to the nearly flat shed dormer roof. This would be a lot easier to understand in a picture but uploads aren't working right now.
Just questioning the density needed for a hot roof with the FG seeing the idea of tight compaction to prevent moisture migration is all.
I'd want to check with someone experienced before actually doing it with FG.
Cheers