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Attic Insulation

Post in 'DIY and General non-hearth advice' started by vinny11950, Apr 7, 2014.

  1. vinny11950

    vinny11950 Minister of Fire

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    So, a spring project this year is putting/replacing the insulation in the attic at my parents place. And air sealing it. Maybe a radiant barrier. I want to do this before it gets too hot up there.

    However, I did a quick look on Saturday, measured the ceiling joists, they are 2 x 6, but the first three beams I measured are spaced uneven - not all are 16" on center.

    One had a gap of 14", the next 15", and then 13".

    Is this usual for the builders to space them uneven? maybe there is a reason?

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  2. semipro

    semipro Minister of Fire

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    Seems unusual.
    Are you thinking of batt insulation?
  3. gzecc

    gzecc Minister of Fire

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    Do blown in on top of the rolled. It fills the voids (which are all over the place). Its also a deterent for critters and fireproof. If you want to put another layer of rolled on top of that you can do that also. Rent the machine and buy the bags from Lowes.
  4. Highbeam

    Highbeam Minister of Fire

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    So your plan is to remove the batts and then airseal and then resinsulate with new? That's a good plan but you would be foolish to put batts back in. In so many ways batts are inferior to blown in cellulose or fiberglass. Blown in is cheaper, easier, better, and has no problem with odd sized stud cavities. Just saving yourself from handling those batts is great.

    By the way, you can just slice down a batt to fit or compress it into the cavity if you can compress the batt without the batt buckling. The R-value comes from the thickness.
  5. Clarkbug

    Clarkbug Minister of Fire

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    Wanted to piggyback this thread some, but might start my own.

    My attic has some insulation, but its blown in already. But no air sealing. Any tips for the best way to handle this situation?
  6. Highbeam

    Highbeam Minister of Fire

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    Do you want to airseal? If so, have the old removed or do it yourself. It's just about the same machine used to blow it in but in reverse so it's a huge vacuum tube. This is good since it sucks out old nasty (asbestos?) insulation and mouse turds, lets you inspect for water leaks, air seal real well, install proper soffit ventilation, maybe run some new electrical circuits, air seal like a champ, and then fill up with the latest and greatest blown in insulation.
  7. vinny11950

    vinny11950 Minister of Fire

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    thanks for the ideas, guys.

    i was thinking Roxul comfortbatt but if all the bays are uneven, cutting all those batts is not going to be easy.

    i was thinking the Roxul batts would not fall when redoing ceiling sheetrock. plus, my dad does not trust blown in cellulose not being a fire hazard (as discussed in other threads).

    the fiberglass that is there now is a mess. Squirrels had their way with it a few years back. i gotta clean up that mess and their poop too. at least one carcass that i found.

    i want to start from the farthest end and then work my way to the tiny, attic entrance hole in the closet. this way i can fix the wiring (squirrels again), seal and clean as i make my way back.

    i will take some pics next time i am up there.
  8. woodgeek

    woodgeek Minister of Fire

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    I thought along these lines re the ancient loose fill and batts (both FG) in my 50 yo attic. I thought a company could pull/vacuum them out, and I could start 'fresh'. Removal and disposal doubled the quote...so I just went blown in over. An attic does not need to be beautiful, just sealed and insulated.

    As it is, removal is not required... wear a good valved respirator (for the poo and the FG), and you can move that stuff to airseal, then move it back. Only need to move a chunk at a time. Then get a machine and blow loose over it. While cellulose doesn't burn...get him atticcat fg loosefill if he prefers.
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  9. vinny11950

    vinny11950 Minister of Fire

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    any one hear anything good or bad about Roxul Rockfill?

    http://www.roxul.com/products/residential/roxul rockfill

    sounds interesting but to get an R-25 i need 8.75" of it according to this PDF data sheet:

    http://www.roxul.com/files/RX-NA_EN/pdf/Technical Data Sheets- updated/ROCKFILL - US.pdf

    never realized how much insulation is recommended.

    http://www.energystar.gov/?c=home_sealing.hm_improvement_insulation_table

    the attic has R-15 FB at best, though after the squirrels the mess it is, it has to be lower.

    on average their pellet usage goes from 3 tons, on an regular winter, to 4.25 tons, this last winter. i figure if they could save a ton a year it would mean a savings of $250 to $300 a year in pellets. also, it would make the electric base board heating they have more viable as a backup as the house would stay warmer.

    not to mention in the summer that attic collect lots of heat that is passed on into the house.
    Last edited: Apr 7, 2014
  10. woodgeek

    woodgeek Minister of Fire

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    Looks like the rockwool is more expensive than the blown in products, and with a small opening, I would think a blower hose would be better than hauling 60 bags through the opening. Reading the instructions, each bag has to be 'flufffed' manually after opening...how long does that take? The blown products are fluffed by the blowing machine.
    Swedishchef likes this.
  11. woodgeek

    woodgeek Minister of Fire

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    I did 80% of my attic airsealing DIY, a 'few weekend' project (that I spread over a couple years), and then had the airsealing completed and blower job done by pros. If there are any good incentives in your area, the pro route might be more attractive.
    vinny11950 likes this.
  12. semipro

    semipro Minister of Fire

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    Although I recommend blown-in cellulose overall, I can tell you that Roxul Comfortbatts are very easy to cut and work with. They are also relatively stiff. Only problem is they are friable in that they tend to fall apart too easily. I compare it to a somewhat crumbly loaf of bread.

    Cellulose has been used for a long time. Its evident that some was sold without good fire retardant treatment. I think you'll find the stuff available nowadays from the big box stores to be very fire resistant. Heck, I bet the folks at the store would give you a handful to do your own fire test with.
    vinny11950 likes this.
  13. Highbeam

    Highbeam Minister of Fire

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    Roxul is a fine product but not competitive due to being overpriced. Fiberglass will do anything that roxul can, it is made of sand and roxul from rocks. Kind of similar don't you think?

    You can remove all of those batts yourself, just drag them out the hatch and take to the dump. If you want to leave them there they won't hurt anything but if you lift each one to air seal and clean then I wouldn't waste time trying to put them back in. What a pain, you would have to weave under the wires and fight those silly thin R-15 batts. This is low skill work, just don't step through the ceiling. You can sweep or vacuum debris up, fix your wiring, and airseal.

    Nothing wrong with blown in FG. It doesn't itch anymore and is lightweight.

    You mention new ceiling sheetrock. Do that while the insulation is out. You can do some work in the ceiling by sweeping the insulation away from an area (like adding can lights) but a whole new ceiling? Do that before reinsulating.

    Oh and you can price out the material to DIY with the machine and product from home depot but then call a professional for a bid. They can often do it for less than you can buy the materials.
    vinny11950 likes this.
  14. Lake Girl

    Lake Girl Minister of Fire

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    If you are replacing ceiling, you will be able to refresh the vapour barrier too. Do this before tackling the insulation and seal it well.

    The Roxul is purportedly additional fire protection but have never had the chance to work with it.

    Find out where those squirrels have come through and seal it up well ... Squirrels were responsible for a fire at my Grandparents house in the 50s ... chewed an opening by the electric service penetration in the attic and nicked the wiring.

    If you are looking at professional install, have you checked out spray foam?
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  15. semipro

    semipro Minister of Fire

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    vinny11950 likes this.
  16. vinny11950

    vinny11950 Minister of Fire

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    My best guess was the squirrels came from an old, unused dryer vent hole left open in the basement. I have found big squirrel style droppings in the basement ceiling making me think they then moved up to the attic. The house was abandoned until my parent bought it. It would explain those funky smells coming from different closets that then vanished when I sealed that vent.

    As for the vapor barrier, the house doesn't have one and I don't think it needs it in Eastern Long Island, NY. At first I thought I needed one but have changed my mind. And going around the house, I have found mold only in the basement where it is very humid in the summer.

    http://www.greenbuildingadvisor.com/blogs/dept/musings/do-i-need-vapor-retarder

    http://www.buildingscience.com/documents/digests/bsd-106-understanding-vapor-barriers
  17. vinny11950

    vinny11950 Minister of Fire

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    I am thinking Roxul Comfort Batts this spring, after sealing and fixing electrical, then blown in cellulose or fb in the autumn.

    I want something to hold up the blown in stuff if ever I take down sheetrock.

    Thanks again to every one for the comments.
  18. woodgeek

    woodgeek Minister of Fire

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    sounds like a plan. I have crummy ceiling sheetrock, and I have always figured I would just do a second layer of sheetrock under. Ceiling might be 5/8" lower, not a lot of trim details in a ceiling.....mabe weight is an issue?
  19. Lake Girl

    Lake Girl Minister of Fire

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    Thanks for the article. I have often wondered about the differences between insulation in the US vs Canada having lived in both countries and been involved in remodels in both. I have never seen the paper/foil backed insulation in Canada. Interior vapor barrier is standard practice here.

    Roxul seems to be a superior insulating material. Will have to reconsider what insulation is to be used for further remodels...

    Second layer of drywall should not be a problem as long as proper fasteners that secure into original framing members are used. I know that 2 layers of drywall both taped are used in integrated garages to help prevent vapor transfer to the dwelling space in Canada.
  20. Highbeam

    Highbeam Minister of Fire

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    I read that article and am not impressed. The guy obviously prefers roxul vs. FG but his reasons are pretty stupid. Usually the articles on that site are far more professional.

    R-21 vs. R-23 in the same cavity. BFD. Anybody that done some heat loss calcs knows that this small of a difference means nothing.

    Then his whole point that the roxul can be cut more accurately assumes a couple of things. One, that the FG was cut poorly and the roxul will be cut precisely. Either batt can be cut to the exact same shape, they are both batts. Then he assumes that the installer will want to take the time to cut roxul perfectly. He seems to be trying to make a material problem out of a skill problem.

    Cost is much higher for roxul. The home stores currently only sell a couple of batt options. No rolls and very limited selection. They had nothing at my home depot other than precut batt lengths for 2x4 and 2x6 walls.

    What a stupid article.
  21. vinny11950

    vinny11950 Minister of Fire

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    I think the article was trying too hard to pull for Roxul. FB seems to match it closely and has a longer track record. I think it comes down to preferences. I just like the feel of Roxul. I redid a corner wall where the pellet stove is installed and put some Roxul in the 2 x 4 cavity. It turned out very tight and I think cut down some of the draft on that side of the window frame seam. Though I suspect the original install was bad and was the cause of the draft there.

    I haven't researched it much, so I don't know if FB has some horrible environmental impact that makes Greenbuilders say negative things about it.
  22. vinny11950

    vinny11950 Minister of Fire

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    Before I do any work in the attic, is there a way to get a baseline measurement of how the attic performs now so I can compare when I have it finished?

    I was thinking using the thermal temperature gun taking different heat readings from the ceiling at different points, noting the current inside/outside temperature, stove setting. Then doing the same after the improvements when all the variables are the best.

    Still, it seems fraught with misleading conditions I will never understand fully.
  23. woodgeek

    woodgeek Minister of Fire

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    Ok Pilot, but be warned this way leads to measurement madness....

    For vertical walls/windows, I estimate the R-value this way:

    I want to measure the temperature difference between the surface of the wall, and the air about an inch in front of it (outside the convective boundary layer). I do this by making a loop (shaped like a capital Omega) of blue masking tape that is 1" tall and sticking it to the wall, and then putting another small piece of tape flush on the wall right next to it. I then measure the temp of both the loop and flush tapes using my IR thermo and take the difference. (the differencing makes the calibration of the IR irrelevant, and comparing tape to tape ensures no errors from emissivity/roughness corrections. Most rooms also show vertical gradients in air temp that this method avoids if the two tapes are at the same height) I then assume that the boundary layer has an effective R-value of about 0.5, and assume DT_tape/0.5 = DT_outdoor/(R_wall+0.5), where R_wall is what you want to measure, the R-value of the wall in question (at one point). And DT_outdoor is the difference between the indoor air (loop temp if IR is calibrated) and outdoor air temps.

    With this method I can see that my wooden panel doors with (leaky storms) are ~R-1.5, my old single pane windows with old storms were R-2, Windows with new low-E storms are R-3, and that my 2x4 framed walls are around R-10 or so (lower if measured on a stud).

    On a ceiling, the boundary layer will be higher than R-0.5, but a similar method should work for comparing before and after.

    Edit: and (of course) you do this when the indoor and outdoor temps have been constant for a while, there is no wind, usually before the sun comes up. :)
    Last edited: Apr 10, 2014
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  24. vinny11950

    vinny11950 Minister of Fire

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    Wow, Geek, I will have to reread this a few times to understand and try but I will definitely try. I guess this way it doesn't matter what the temperature is outside or the time of day, as it is just taking the difference of the two points. So an improvement would mean a lower difference between the two points?

    PS Pilot would have figured this out in a second.
  25. woodgeek

    woodgeek Minister of Fire

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    Yeah. The bad news is that as the R-value increases, the DT you are measuring gets smaller and smaller. At R-15, it would only be 1/30th of DT_outdoor, or a couple degrees if it was really cold out. With a ceiling it would likely be smaller still.

    I now recall that I did try something similar with my ceilings, before and after an insulation job, and was not really satisfied with the data that came out. :confused:

    And of course, R-value tells you nothing about air leakage.

    When the attic was cold I could 'see' warm areas on the tops of the FG batts corresponding to the top plate locations, by scanning side to side with the IR thermo.

    All this measurement geekery is pretty unnecessary, I think....you know where the top plates are (above the interior walls) and you can hunt for all the big penetrations and seal them. I got a huge benefit from the DIY airsealing, like 250 gallons oil/year, or >25% improvement in bills. The benefit from going R-15 to R-50 was more like 10% (I estimate), and cost a lot more.

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