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Old 09-01-2010, 01:18 PM   #1
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Cellulose Insulation Questions...


I am getting ready to start tackling the job of insulating my 1915 Bungalow, but I have a few questions.....I saw on another thread someone suggested "Insulate & Weatherize" by Bruce Harley, so I plan to pick that up and read it as well.

The questions I have for now are:
1) When dense packing am I correct that I should start at the bottom of a wall and blow up until it packs, then move to the middle and blow up and then down (or vise versa) and then move to the top and blow down? My understanding is one 24-30 bag will fill about three 8' high walls on 16" O.C.. My walls are 16" O.C., but 9' tall and the bags I'll likely be buying are about 19lb bags, so I'm guessing about 1 bag for every two bays. Does that sound about right? Curious, so I buy enough and so I can somewhat ensure I'm packing the wall correctly.

2) What's the best way to insulate my joist bays between the 1st and 2nd floor? On one hand I'm not crazy about drilling through the Rim Joist every 2' or so, but I'm not sure how else to really get in there. I am also not sure how I get it to fill the outer edges without filling the entire bay. I've seen where some people use a bag method, that seems to create a block of some sort to keep the insulation from filling the entire bay, but I'm not sure what kind of bag or how this works.

3) What about vaulted ceiling in attic and a small shed roof over a box out in my kitchen. Both have 2x4 framing, so I can't get much insulation in there, but I've been told dense pack will help prevent ice dams. The plan is to turn the attic into a walk-in-closet/storage area since there is a door leading to it from the master bedroom. In this area, I will be leaving the exsiting insulation between floors in place and covering with 3/4" OSB flooring. That will be dense packed as well most likely.

4) What about knee walls in the attic. The plan is to actually build the knee walls with built in drawers/shelves to help take advantage of the unused space behind the front of the wall. Since the unused area behind will be totally dead space, no way to vent, should I build a back wall which is insulated and then leave the space behind that empty or dense pack that whole area? My rough guess is the space would be about 18"-24" high x 18"-24" deep once the drawers and shelves are in place. If it matters, I have rafter tails, so no sofits to worry about.

5) I also have an area of attic space, which is above a 1st floor bedroom. It's been insulated with one layer of batting over the bedroom ceiling, so it's obvious it needs more. The problem is this attic space is basically a right triangle with the sloped part of the triangle being the roof line, the bottom the ceiling below and the verticle edge being an insulated knee wall to a 2nd floor bath. Since part of the slope of the roof is the bathroom ceiling it is insulated with batting and thus no air cavity to let air escape out of the attic space at the peak of the roof. This has me wondering, do I just add blow in on top of the batting that's in place or should I install paneling or drywall against the 2x4 roof joists and blow dense pack into there as well, install a floor and turn this into a small storage nook?

6) The attic above the 2nd floor, there really isn't much attic space up there to speak of. As I tried to explain in #5, part of the roof line is finished ceiling, there is only at most an area of 5' wide x 18"-24" tall above the ceiling. I've had to crawl through the area and it was just enough to do so. Again, not sure it has "enough" insulation above the ceiling, but any more would almost completely fill the area, if not completely fill. Maybe it's ok as is and this area does have a roof vent and a turbine.

I hope these descriptions make sense, if need be I can make some diagrams and post them as well. I plan to start on the walls in the next week or two, if not sooner, but if my equipment rental starts to run out and I have left over material, I figure I'd quickly use the left overs to top attic spaces off if possible, since they'll likely fill quicker than walls....

Thanks for any pointers

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Old 09-01-2010, 01:27 PM   #2
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Cellulose Insulation Questions...


Ok, to try to get the best answers possible and to avoid confusion, I drew up a couple of quick diagrams.

Question 4 picture shows how I plan to insulate along the roof line in my 3rd question above, then shows how I plan to build built in drawers/shelves in the 4th question. Do I just build a 2x4 wall behind the drawers/shelves and insulate that little wall or completely fill the area with the red X?

Question 5 picture relates to my 5th question regarding the attic space above my 1st floor bedroom. Do I blow in insulation on top of the batting above the 1st floor bedroom or install a panel/drywall/foam board insulation and dense pack the rest of the slope and use the area as storage? It's non-vented and non-conditioned space.

Question 6 picture relates to the 6th question regarding the attic above my 2nd floor rooms. I believe I need several more inches of insulation above the green area, but that would just about eliminate that attic space, should I leave it alone, add the insulation and then leave it alone or dense pack the entire area? It does have roof vents and a turbine, which all could be left or removed. As it is, it's just barely enough room for someone to crawl through on their belly, going only forward and backwards, no turning around....

Thanks again...
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Old 09-01-2010, 03:04 PM   #3
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Cellulose Insulation Questions...


3.5" is very little room to insulate in.

Where in the country are you located?

Are you planning on re-roofing any time soon?
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Old 09-01-2010, 03:41 PM   #4
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Originally Posted by xxPaulCPxx View Post
3.5" is very little room to insulate in.

Where in the country are you located?

Are you planning on re-roofing any time soon?
I am in central Kansas. Extreme highs for summer are about 110*F, usually 90's - 100. Winters are generally 20-30*F with Extremes down to about 0*. I'd say the extremes are usually only a few weeks.

I know 3-1/2" isn't very much, which is why I want to dense pack the slopes that would only be that. At this point the budget just isn't there for foam and something has to be done. Maybe by the time I actually get to the attic spaces, I'll be able to budget someone to come spray foam. Like I said, I'm starting with the walls and the shed roof over a box out in the kitchen.

The shed roof is 3-1/2" near the edge, but actually increases to near 6" against the wall. I am planning on installing a tounge and goove bead board planks for the ceiling in that area, as I think it'll fit the look of the old house, especially since this area used to be a covered side entry. What about using the thickest rigid foam panels I can tuck up there instead of drywall and installing the planks to that. Plus if I use the 3/4" planks instead of 3/8" planks surely that'd give me some added R-value.

No....a new roof isn't in the immediate future, but hail storms are common, so anything is possible. Why do you ask?
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Old 09-01-2010, 05:27 PM   #5
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Cellulose Insulation Questions...


If you were doing a new roof, you could add a layer of foam over your existing deck, then add sleepers for vent channels to a ridge vent, then sheath over that.
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Old 09-04-2010, 01:51 AM   #6
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you need air on top of your roof insulation, between it and the roof sheathing. if you don't vent it, you are very likely to get condensation on your sheathing, then rot. any way to insulate inside the 2x4's?
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Old 09-07-2010, 12:46 PM   #7
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Originally Posted by jklingel View Post
you need air on top of your roof insulation, between it and the roof sheathing. if you don't vent it, you are very likely to get condensation on your sheathing, then rot. any way to insulate inside the 2x4's?
I was under the impression for vaulted ceilings as long as the entire area was insulated you didn't need the gap. Am I wrong to believe this?

Insulating inside the 2x4's isn't very favorable as the ceiling height is already pretty low in these areas.
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Old 09-07-2010, 01:07 PM   #8
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MB: I'd check into this further, but I am 100% sure of the ventilation. That said, I could be wrong for your geographic area. Regardless of how perfect your air barrier (or vapor barrier, if needed) is, you are going to get some moisture sneaking out. When it hits the cold sheathing, condensation will occur. You might get by if your roofing material is breathable, but I would never build a hot roof. I know of 3 (2 in AK and one in OH) that had exactly this problem, and everywhere I read says "air over insulation". Even in walls, the exterior is supposed to by 5 times more permeable than the interior. You may want to read on buildingscience.com, greenbuildingadvisor.com, etc. Apparently, closed cell spray foam is its own vapor/air barrier and does not need an air gap; dunno, never will use the stuff as it is prohibitively expensive for my situation. Let me know if you ever learn otherwise about the air over insul. Thanks. j
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Old 09-07-2010, 01:17 PM   #9
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Originally Posted by jklingel View Post
MB: I'd check into this further, but I am 100% sure of the ventilation. That said, I could be wrong for your geographic area. Regardless of how perfect your air barrier (or vapor barrier, if needed) is, you are going to get some moisture sneaking out. When it hits the cold sheathing, condensation will occur. You might get by if your roofing material is breathable, but I would never build a hot roof. I know of 3 (2 in AK and one in OH) that had exactly this problem, and everywhere I read says "air over insulation". Even in walls, the exterior is supposed to by 5 times more permeable than the interior. You may want to read on buildingscience.com, greenbuildingadvisor.com, etc. Apparently, closed cell spray foam is its own vapor/air barrier and does not need an air gap; dunno, never will use the stuff as it is prohibitively expensive for my situation. Let me know if you ever learn otherwise about the air over insul. Thanks. j
Hmmm......I know as far as my walls, I didn't think I had any sheathing or vapor barrier and I called and spoke with the supervisor of inspection and asked him about using the cellulose in my walls. He said in his 30 some years as an inspector he's never seen a problem with an application like I plan or my walls. I didn't ask about my roofline, but part of my current roof has fiberglass installed directly between the sheetrock and the sheathing with no air barrier and so far I haven't seen any problems on the drywall which has been up since the 80's judging by the remodel work done in this area. Looking at the roof sheathing may not tell much either if I can get up there as it was replaced within the last 5yrs. I've lived here two years now and it was a foreclosurer prior to my purchasing the home.

With that said, I pulled several rows of siding off to gain access to blow sometime soon and I do have 1x sheathing on the house and there was at one point a wrap of some sort, but it's pretty much worthless at this point and other than placing tar paper over the areas I will replace the siding, I won't be going back with anything else as I can't afford to replace 50% of this clapboard siding, if I were to pull it all off.... I figure the inspector said it was ok to blow cellulose in my walls without sheathing or wrap, it should be ok now........

Not sure how that relates to my roof, but figured I'd mention it. I'll keep reading up on the subject!! Thanks!
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Old 09-07-2010, 01:37 PM   #10
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"Looking at the roof sheathing may not tell much either if I can get up there as it was replaced within the last 5yrs." Red flag. WHY was it replaced? A house built in the 80's should not need new roof sheathing; maybe it was a "just for stink and giggles" deal?? If it HAD to be replaced, then I think we know why, and we know what you'll be doing down the road. The house in OH that I referred to looked fine for many, many years, until one day a guy got on the roof to replace a few blown-off shingles and stepped through the sheathing. If a house is leaky, then walls are more forgiving because of all the air movement through "easier" spots. Many houses built in the 80's were not real tight; oil was cheap, and few folks took the time to detail.
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Old 09-07-2010, 02:19 PM   #11
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"Looking at the roof sheathing may not tell much either if I can get up there as it was replaced within the last 5yrs." Red flag. WHY was it replaced? A house built in the 80's should not need new roof sheathing; maybe it was a "just for stink and giggles" deal??
The house was built in 1915, not the 80's. The sheathing was replaced because of a code change right before a hail storm about 5yrs ago. Basically, every house in probably a 30-50sq mile radius got new roofs including the sheathing. If they didn't, they should have, it was that bad of a storm and the new code said something to the effect that any roof with more than 2 layers needed completely stripped and the old cedar shingles and/or 1x material that constituted the old decking wouldn't suffice.

Two of the oldest neighborhoods in town were hit, most of them had 1x sheathing and/or cedar shingles underneath and multiple layers of ashpalt on top, so pretty much everyone ended up with new OSB sheathing and one layer of asphault. Good for the home owners, but very, very bad for the insurance industry in our area.

Basically, the roofers were allowed to leave every other 1x board in place, but then they put new OSB on top of that. That's why I can't tell....
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Old 09-07-2010, 02:49 PM   #12
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1915? It has done well, then. Maybe a little more tlc and it will make it to 2050. I'm glad we don't get big winds; cold I can deal w/. Good luck w/ your project. j
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Old 09-07-2010, 03:33 PM   #13
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I just found a link discussing my vaulted ceilings. Here is that link if you care to read it and yes, it'll easilly make it another 95yrs. These houses were very well built and I'm doing what I can to make it better yet!

Need advice on vaulted ceiling insulation There is another link that article talking about some of the very problems I have and it's from Energy Trust of Oregon. Part of me feels if it'll work in Oregon, it should work for me in Kansas, but maybe I'm wrong.

For now what I think I'll do is try eventually install baffles from the area above the bedroom and give that area space to vent up to attic above the 2nd floor bath. I guess that's called a rake and crown ceiling. Then for the attic space I'm converting into a "closet", I think I'll try to use 1/2" rigid foam to create baffles so I can get 1" air gap between it and the sheathing, then fir the 2x4 joists down another 1-1/2" and isntall up to 1" foam on the bottom of that. I'll then dense blow cellulose into the space between the 1/2" and 1" rigid foam and then cover the 1" foam with some sort of cedar panel. Though this won't give me a perfect R-30 - R-38 some say I need on a ceiling, it should get me close to R21 or R22, maybe even as high as R25 if I use foil faced rigid foam.

Dow says their rigid foam is R2.5 per 1/2" = R 7.5 if I do as I'm thinking. From what I find Dense-pack Cellulose is R4 per Inch based on HUD housing, giving me R14 from that. I see that foil faced is up to R7 per inch, so maybe I'll use that instead of the 1/2" foam to create the air gap. Actually wonder, if I could just use that for the entire fill, which would get me very close to R-30. Hmmm.....
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Old 09-07-2010, 08:09 PM   #14
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It's your call, but I still don't like a hot roof. (1) You CAN'T stop every bit of moisture from sneaking in. (2) If you pack cellulose (which is good stuff) so tight that it is an air barrier, I'd suspect the R value will drop to "Jack Stink"; just my hunch. (3) The sun is going to heat the roofing, and then the wood underneath. I am not sure that is in the best interest of the wood. This is likely a good place for good air sealing, but no vapor barrier (ie, visqueen, TuffNuff, etc).

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