I’ve finally gotten around to finishing up the insulation in my own house. I’m always pretty diligent about other homes and insulation, but I was either too lazy or two broke (or both) when it came to my own home. Actually, I was making an effort to save the plaster walls. So needless to say, for a while I has a bunch of empty walls and nothing in the attic. I blew in cellulose into my walls a few weeks ago and it worked out really well and was rather inexpensive. I have a fiber optic scope so I was able to watch an make sure I got a good dense fill in the cavities so I’m pretty happy with the results. All of the plaster is now patched and painted. I’m ready to move on to the attic. Due to the fact that my daughters room has a fiber optic star field in the ceiling, insulating the floor in the attic is not really an option. If there was no floor up there, I’d be a little less reluctant, but I’m not about to snake the hose under the flooring through a web of expensive glass fibers. I have an un vented roof, so I’m planning on insulating the joist bays. I had a spray foam outfit come out and look at it and they quoted me a price that I would never recover. I calculated it would take me approximately 75 years to recover the cost. Spray foam is out since I only plan on being here for maybe two more years. The roof is a 12:12 with 2×4 rafters on 24″ centers. It has 3/4″ purlins @ 16″ on center on top of the rafters. I’ve been scouring the internet looking for insul mesh and haven’t found any rolls small enough. I probably won’t ever use it again, so I’d rather not buy a large roll of it. Is there anywhere online or maybe in the south jersey area that sells non woven insulation netting in smaller rolls? anything more than 4′ wide I’d have to cut in half anyway because of the knee wall at mid span. Is there anything else that I could use in place of the insul-mesh? Plastic, Tyvek, felt,? I’d really like to not have to buy a 9′ wide roll of the stuff. I think I’d only need about 600 square feet of the stuff. I’d appreciate any help you could give me.
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Replies
I used the heavy duty landscaping mesh from Lowes or Home Depot. This is the mesh used underneath that ugly colored mulch in order to keep the weeds from growing through. Careful though, the cheaper light duty stuff that feels like fabric is too stretchy. I think that the one that I got was made by Dupont and was super strong. It's not stretchy at all. It felt more like Tyvek than fabric.
It worked great with a dense pack method. Sheetrock went on fine afterwards.
I know exactly what stuff you are talking about. Infact, I can't believe I didn't think of it myself. I appeciate it.
The fabric filter cloth for foundation drains might work, too. $15 for 3' x 100' roll at HDhttp://www.tvwsolar.com
We'll have a kid
Or maybe we'll rent one
He's got to be straight
We don't want a bent one
He'll drink his baby brew
From a big brass cup
Someday he may be president
If things loosen up
I don't have anything to add, but please break up your paragraphs in the future. Old guys like me and Mike Smith cannot read your posts easily.
Jon Blakemore
RappahannockINC.com Fredericksburg, VA
I think it was muslin cloth I saw used on a tv show. They glued it to the studs with slightly diluted white glue. Cut a slit to blow the insulation through.
I agree with the other 'old' guys with poor eyesight hit enter occasionally and make it readable
Regal Industries sells 4 foot rolls
http://www.regalind.com/regal_wall.htm
Hi, can you tell me how this mesh/netting gets used? Is it a barrier between the plaster/lathe and the insulation?
This would be for the attic where there is no wall finish. It's to keep the insulation for just falling out. On new construction it would be applied to the studs prior to finishing the walls with sheet rock or what ever finish you are using. It's to keep the loose insulation in place.
Lumber wraps are free from behind any lumberyard, truss plant, or big box.
I have rolls of tyvek and plastic sheeting, I was just worried about trapping moisture.
My understanding is, if you're blowing cells, that moisture ganging up in one spot isn't a consideration.
You are better off with netting. Allows for faster drying to the inside. Also, the cells will blow much easier behind something more permeable.Steve
My walls were blown between sheathing and plaster, and it seemed to work easily and admirably without having to buy special material for scrim. I think that's what the OP was getting at...not spending a lot of $$ if he didn't need to.Drying to inside? Maybe i'm missing something, but i don't think the poster is talking about spraying wet cellulose in the bays, rather the DIY thing.
Yeah, I did my walls. 2x4 walls with 3/8" rock over plaster & lath on the inside and asbestos siding over wood claps directly on the studs. The sheetrock made patching easy. I'm talking about between the rafters in the attic. And no wet spray. I was concerned with using something like tyvek or plastic and having it trap moisture on the inside
>>I was concerned with using something like tyvek or plastic and having it trap moisture on the inside<<That's what I was talking about when I said the netting would facilitate drying to the inside. During periods of high moisture load (high humidity) the cellulose will pick up moisture content. During periods where the interior humidity is lower, it is good for the cellulose to be able to diffuse moisture to the inside air. I wouldn't use plastic or tyvek.As a previous poster mentioned, you can get the mesh in 4' rolls from regal industries. It's not particularly expensive.http://www.regalind.com/regal_wall.htmSteve
I understand the aversion to vapor *barriers*, but housewrap (lumber wrap looks to be the same woven material) is classed as more permeable (>10 perms) than vinyl wall coverings (0.1-1.0 perms), according to a summary i found. It's in the same range as....cellulose. In fact, a person could do a lot more damage to the permeability of a wall with latex paint than with lumber/house wrap. So...seems like a good solution to me, still, but perhaps my frugality is coloring my judgment. I'm willing to be shown the flaw in my thinking and i suspect i'm about to learn something. <G>Won't it have to be covered with something inflammable anyway? There's goes your mesh-breathability.
I don't think the housewrap is any cheaper than the mesh. Actually I'm pretty sure the mesh is substantially cheaper. Actuallly I think the mesh is just housewrap minus a few ingredients. Feels like spun polyolefin to me.Also, having blown way too much of the stuff, it's really easier to blow behind the mesh. It lets the air pass through it as you are blowing, letting you get a really good pack. Takes more fussing with something that lets the air get all bottled up behind it.In theory it'll have to be covered with something, but you know the gap between theory and reality...
Edited 8/31/2009 6:20 am by mmoogie
Way-ulll...i was suggesting a FREE alternative, locally available, that keeps waste out of the landfill. But the more you pay, the more it's worth. ;^)
I had virtually the same situation as you and I blew into the ceiling joist bays much the same way you would blow into finished walls. Drill holes from above blow cellulose and then plug holes. The one thing you might try to check out is to see if you have the same issue I had. My second floor joist bays had FG bats installed as far as the knee walls in the upper floor and no farther. So I had bat___Floor/Ceiling_____bat. Well the air would just travel above the bats across the joist bay and out the other soffit because the builder didn't put any blocking into each joist bay to stop it. So I blew Cellulose from above to fill the rest of the joist bay and it fixed the problem. Yeah it was overkill because now I have insulation between two heated spaces but the side benefit is it helps deaden the sound from the second floor. There were some spots where I could get behind the knee wall and in those spots I was able to insulate over the bats and stop the air from that way too.
I'm going to do in between the rafters in the attic. My intentions are to staple up the netting across the rafters. Roll the white glue down the rafters to seal the netting, and blow in from a hole in the middle, and then from a second hole at the top. Filling all the way down into the soffit. My soffits are solid with no vents, so I don't see a need to keep the insulation from falling into the soffits. I can't insulate the attic floor like I normally would because I have the fiber optics running in the floor that I can't disturb. Between the rafters is the only option. Unfortunately, the rafters are only 2x4 @ 24" o.c. I know I won't get much in there, but anything is better than nothing.
You still have options, even with those shallow rafters.Take some OSB an make 3" x 9" rectangles. Nail or screw these onto the face of some 2x3 lumber every 3 or 4 feet. Now nail or screw the other side of that OSB to your rafters. You've created a spacer that you can glue the netting to that will be deep enough to give you really good insulation values. Adjust the depth for the R value you are looking for.For the floor, roll the netting on top of the joists, then lay up some 2x6 or 2x8 perpendicular at 24" OC. Cover with OSB so you don't put yer foot through it, then drill holes and fill with cellulose.
Tu stultus esRebuilding my home in Cypress, CAAlso a CRX fanatic!
Look, just send me to my drawer. This whole talking-to-you thing is like double punishment.
I think I might use the idea of packing out the rafters to get more depth. I can't build up the floor though because it's a walk up attic.
Just walk it up one more step then!
Tu stultus esRebuilding my home in Cypress, CAAlso a CRX fanatic!
Look, just send me to my drawer. This whole talking-to-you thing is like double punishment.
well... It sounds so simple. If I did that, I'd have to add 9" to keep the risers consistent. If I add 9", I'd only have about 6' of head room left. I'll stick with packing out the rafters.
As I have about 40" of attic headroom at the peak... I'm officially jealous!
Tu stultus esRebuilding my home in Cypress, CAAlso a CRX fanatic!
Look, just send me to my drawer. This whole talking-to-you thing is like double punishment.
My house isn't that big. 1180 sf which is really small for the neighborhood. The walk up attic is one of the nice things about the house.
The other thing you could do is sheath the underside of the rafters with 2" sheets of polyiso foam board and blow cells behind that. Gives you another R14 plus breaks the thermal bridging of the rafters.Steve
I considered that, but wouldn't that cause the same problems with trapping moisture?
And y'all think I'M the blonde one! ;^)
How's that for skirting all sides of the issue, splintie?
LOL...when i saw how little space he had to blow cells, i was going to suggest foamboard, too, but figured i'd get howled at for it!Foamboard and spray foam aren't cheap, though. How's about a "Mooney roof"?
That'll get ya about 5 more R and a partial thermal break. The foam board IS pretty spendy. If he's got the head room I like the earlier suggesting for deepening the rafters.
It is somewhat of a "mooney" roof already. it's 2x4 rafters with 1x purlins on top. The house had a cedar roof, and the cornice was applied up to the shakes. Once I had stripped the shakes, I had to put the purlins back on to keep the shingles up above the cornice. So I do have that extra 3/4", but i think I'll add a 2x3 to the bottom of each rafter to get a little extra r value. I considered the foam board, but I don't think I want to spend the extra money. I don't plan on being in the house more than one more winter, and it can always be applied afterwards.
I've insulated my ceilings, but i'm also planning to insulate my rafter bays, though the project's low on the priority list. I'm hoping for a buffered area in the attic - not quite as cool in winter, not quite as hot in summer, but with no loss of storage/head space. Why not insulate your ceilings, other than the one with the LEDs (very cool of you, Dad!), and your rafters, too? It'd be interesting to run the heat calcs on that and see if it isn't a better bang for the buck. In this case, with such small rafters, i'd also consider what adding the extra weight might do to their deflection....not to mention if the cells, heaven forbid, got soggy. You don't say what the length is (or i missed it), but 2x4 rafters 24" o.c., even at 12:12, would make me at least scratch my noggin first.
Edited 9/1/2009 3:40 pm by splintergroupie
Thanks, my daughter loves it. When I first did it, my wife and I laid on the floor for about an hour and just looked at it. I'd post some pictures, but they just look black with a few white dots. Not very exciting. I did paint it blue with some clouds so that it's fund during the day too though. I would prefer to do the floor in the attic. I think I could do alot better at keeping the heat in that way, but I don't know if it would be worth it to leave that large void over my daughters bedroom. I haven't done heat loss calc's since I was in college so I don't even know where to start with that. I'm also not sure if they would yield any really useful information in regards to insulating only part of the ceiling. The house was built in 1895, and the roof is 12:12. The rafters are supported mid span. The attic is only a total of 14' wide, so the span on the rafters is only just over 11'Here is what it looked like before I bought it. This is the only shot of the attic have.
That's some nasty-looking FG you have. Now, don't take this personally, but those rafters look like 6s to me, not 2x4a.
Yeah, the fiberglass is ugly. It's covered by a sheet of plastic for what ever reason. Like i said, this was before I bought the house. The rafters are full 2x4's. Not dimensional. I'm 100% positive of that.
In theory, yes. But I don't really think trapped moisture would be a problem in any scenario save for a physical leak in the roof, in which case you are going to have a problem no matter what.It's a risk/benefit consideration. Some say you must have a vapor barrier on the attic side of the cells, some say it's a bad idea. I don't think it really matters much one way or the other, but if there is a "better" practice it's to allow drying to the inside. I think the risk of moisture overload is minimal no matter what with cellulose, as you pretty much eliminate the main cause of moisture movement into the cavity by the simple act of dens-packing the cells. Get them over 3.5 lbs. a cubic foot and you will stop virtually all air movement through the cavity, and thereby nearly eliminate the transport of most of the moisture as well. If I was just going to net it off, to be on the safe side I would use breathable netting, simply because it's pretty cheap and why not, particularly since it makes blowing much smoother sailing. If I was looking for maximum R in minimum space, I would risk using the foam, since it isn't much of a risk really. I would, however, space the foam 1/4 apart, gun-foam the spaces between them, and tape the joints. If you have the head room to drop the rafter plane five inches, then the safest moisture control strategy would be to drop it the 5 inches and go with netting and cells. If it's going to be inspected, you might need to cover it with a fire-rated material. I can't leave foam exposed where I work. It must be covered with sheetrock or plywood.Steve
I have been considering the same method of increasing the rafter depth in my 3rd floor/attic. One thought I had was attach 2x6 steel studs to the interior 2x4 rafter face. This seems like it would go faster than the OSB and furring method. I wold then either sheetrock the whole interior space (thermoply in the knee wall) then blow it full of cells. My roof is a modified hip so there will be more to it. I can then add some storage built-ins to the knee wall.
Any thoughts or experience on this method?