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Attic insulation questions

Post in 'DIY and General non-hearth advice' started by Rich M, Nov 29, 2007.

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  1. Rich M

    Rich M New Member

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    My single story house is cinder block on slab and the oil furnace duct goes straight up off the heat exchanger into the attic (so does the exhaust stack) and there it branches off in ducts for all the rooms. This furnace area (small utility room) has major heat loss and I want to insulate the attic with roll fiberglass thoroughly around where the duct and stack comes through the ceiling. Do I need a special type to be against these hot metal objects?

    Also my kitchen attic could use another layer but there are lots of wires from the ceiling lights (not recessed) and wall outlets. To simplify a thankless job is it safe to just lay the fiberglass roll insulation over the wires?

    Lastly, I do have one recessed light in the living room directly over the hearth. I would like to put insulation over that and tight up against the masonry chimney (with ss liner) as this is another area of heat loss. What type do I need there?

    I intentionally neglected these 3 areas when I added roll insulation a few years back for fear of fire danger. But I'm sick of the heat loss and really need to do something about it, just want to be sure I don't cause a fire and end up burning the house down! Thanks in advance.

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  2. TheSmith

    TheSmith New Member

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    Im not a electrician but I think your safe with laying insulation over the wires.The insulation installed in walls rests on anything in the walls cable,phone, and electric.When in doubt it wouldnt hurt to call your building inspector.most insulation is flame retardent to certain degree.
  3. Rich M

    Rich M New Member

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    That makes sense, that makes that part a whole lot easier.

    I also learned that I can make a hardware cloth enclosure to keep it off the recessed light so that's solved too.

    The only thing left is what will work against/near the oil furnace exhaust stack? (I'm pretty sure I'm safe putting it against and on top of the main duct?)
  4. Hogwildz

    Hogwildz Minister of Fire

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    The fibergalss isn't going to sit flat on top of wires & such. Why not just blow insulation over what you already have? The blown in will go around the wires easier and tighter.
  5. Rich M

    Rich M New Member

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    Blown in would be ideal but I was trying to avoid the expense. If I did it I'd want to do the whole house, I'm trying to just do 3 relatively small trouble spots.
  6. Highbeam

    Highbeam Minister of Fire

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    Our Home dept lets you rent or borrow the insulation blower machine to blow it yourself. It is cellulose though and maybe you don't want that.

    Your HVAC ductwork and wiring can certainly be in contact with the insulation. The chimney for the furnace should not be in contact with any insulation. My HD home improvement book shows a little box built around the stack at a 2" minimum offset and then insulation blown against that. You can air seal the chimney penetration with fireblock caulk. The air seal is more important than the insulation anyway.

    Have you gone around the tops of the walls and around the light fixtures sealing up any gaps? It would be easier to do this now than after even more insulation is in the way.
  7. eba1225

    eba1225 Feeling the Heat

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    Blown in would be good but I did not as I have read that the blown in settles more than the fiberglass and therfore looses some of its insulating capacity. If I remember correctly fiberglass settles less than 5% while the blown in stuff settles between 25% and 35%. For going over wires it is not a problem, what I have done is carefully pushed them down to be flat and laid the fiberglass right over top of them. The hardware cloth wors great for the recessed lighing protection.
  8. Hogwildz

    Hogwildz Minister of Fire

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    I have been comparing blown in vs. fiberglass here locally. And the blown in is less expensive as the fiberglass. If you buy enough bags, the blower is free for the day. If not, its a cheap rental. No hauling, only a long hose up into attic. You can blow it thick as you want/need, and blow it a bit thicker to compensate for later compression down the road. I am def going this route with my addition. And will be going very thick. At Under $9.00 a bag its much cheaper than fiberglass, no wrestling with, no messing with wires etc, and no itching. For R-19 its 2.5 bags per 100sf, R-25 is 3.5 per 100 sf, and R-30 is 4.4 bags per 100 sf. I am going to do about R-60ish in depth, then if it settles I will still have over the R-49 I want to keep as minimum. Cheaper and easier than fiberglass.
  9. Rich M

    Rich M New Member

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    Great info, thanks guys. That stack enclosure sounds easy enough and good call on how to air seal the stack itself. I think I'll try to budget for doing the whole thing with blown in. I wouldn't need much in the areas I've already done and it would sure be a heck of a lot easier in the areas I need to do. Cheaper is better too.
  10. saichele

    saichele Minister of Fire

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    I blew 60 bags into my attic a couple winters ago, and agree with most of your analysis, except I came out of the attic looking like a gray snowman. Spring for one of the tyvek painters suits.

    Steve
  11. Rich M

    Rich M New Member

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    Now that's a great idea, I wouldn't have thought of that.
  12. fbelec

    fbelec Minister of Fire

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    hey rich
    i'm a electrician here in mass. there is no problem with insulating the wires they are not air cooled. as far as your recessed light if it is a fairly new unit, take out the bulb and take down the trim. look inside and see if you can find model number. if you see one that either starts with or ends in IC then you could pack insulation around it. if you can find any numbers or the model number does not have a IC then you have to keep the insulation away from it by 3 inches around. if it is not the IC type i have seen guys build a solid type of insulation box around big enough for the 3 inch space and that works for drafts. or if your handy just replace the unit with the IC type of fixture.
    i have never heard of a fire starting from a fixture that has to big of a bulb or non IC and packed with insulation. what will happen if you insulate a non IC type fixture is when the fixture gets hot the light will go out and when it cools itself down the light will come back on and just keeps that cycle going until it fixed. if it's a lightolier fixture they mount there over heat sensor on the electrical junction box and it might not feel the heat and overheat. i'm not sure if it gets hot enough to fire but if you over heat any bulb they will blow out sooner than they are suppose to.
  13. fbelec

    fbelec Minister of Fire

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    by the way there is a type of insulation that can go around chimneys and the such. around here they make the contractors seal up and holes with either firestop caulking or around chimneys it's this very dense yellow looks almost like regular fiberglass but it is different. and man you want to talk about itchy. and if you manage to get a mouth full of dust you'll be choking for a while.
  14. Rich M

    Rich M New Member

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    Thanks fbelec, very helpful reply.
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