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Let’s talk attic insulation

Discussion in 'The DIY Room' started by Warner, Oct 4, 2020.

  1. Warner

    Warner

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    We live in a cape style home with a full dormer on the back side of the house. The attic is roughly 760 square foot. The insulation that is up there currently is r19 fiberglass batts. There are proper vents installed but there are no soffit vents so I’m not sure what there function is (my parents had the house built by crackheads unfortunately they didn’t find out till it was to late). There are 14”x16” gable vents on either side.
    My plan is to seal all The recessed lights and other electrical boxes and lay r49 fiberglass batts in the opposing direction to the current insulation. We have a central chimney that I’ll stuff roxul insulation around.
    I’m open to any suggestions as I’m not an insulation installer. I did have a guy come out and give me a quote his suggestion was to foam the roof and blow in the floor area 4K$. Not happening.
    Wife has requested that a light fixture be replaced that requires me to go into the attic. While I’m up there I figure I need to tackle this project.
     
  2. BDF

    BDF

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    For whatever this is worth..... I just put a second floor on my house and so <effectively> had a new construction attic. Looked into all the methods of insulation. The 'hot thing' now is what is called warm attic insulation where they blow liquid foam insulation up against the inside of the roof, sheathing and rafters (or the top of the trusses). Excellent R rating but it has some caveats IMO: if they mess up the mix, it generates some nasty chemicals such as formaldehyde and can effectively poison the house. But assuming it goes on correctly, there are still some problems, again IMO. First, if there is ever a roof leak, you will not know it because the water will flow down the inside of the insulation foam and into the walls. Nasty. And if or when the insulation or roof needs repair, you cannot get the insulation off the trusses and sheathing making a new sheathing job into something really nasty (read: expensive).

    That leave the usual suspects for ceiling insulation, the common fiberglass batts and loose mineral insulation that is blown in. I choose the mineral insulation because it can be moved around to expose (Easy Boys!) any part of the attic floor that might be needed, it is easy to install (they blow it in), it is non- toxic and not a fire hazard and is quite reasonable in price (I think $1,300 all in for a 24 X 40 ceiling to 12" deep, about $200 more for 16" deep). The downside of this is that it leaves a field of insulation that one has to walk 'through' and find the truss bottoms underneath and that is a long way from being slick. But I do not plan on using the attic for anything including storage so the only time I need to get up there is to add new wiring or similar, or correct some type of problem such as existing wiring, plumbing, etc.

    As I said, for whatever it is worth, that is what I choose and why I choose it. Not knocking any other methods, and clearly all methods work.

    Brian

     
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  3. Warner

    Warner

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    Thanks for your input. I’m leaning away from blown in mostly because it will be an over an extend period project and I don’t have to rent equipment to put the batts down. I could be swayed tho.
     
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  4. Warner

    Warner

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    Also we have a standing seam metal roof so possible leaks should be minimal.
     
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  5. brenndatomu

    brenndatomu

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    We have a cape cod with the typical long narrow room upstairs with an attic on both sides and above...I am about 3/4 the way through doing "cut n cobble" foam insulation...basically surround everything with foam insulation board then seal it all up with cans of spray foam...ton of work, but effective and affordable.
    Almost done with the side attics and the part of the upper room ceiling that runs parallel with the roof (think cathedral ceiling) then just going to blow loose fill fiberglass into the upper attic.
    Wouldn't worry about it all all but it gets hot up there in the summer and cool in the winter since the HVAC ducts going up there are inadequate, and no good way of making it right...I think things will be fine once properly insulated though.
    Sure wish I would have thought to deal with the upper attic/ceiling insulation when I replaced the roof a few years back...would have pulled the sheeting up and taken care of things...a lot easier than army crawling around in insulation and mouse poo!! :hair:
     
    Last edited: Oct 4, 2020
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  6. TurboDiesel

    TurboDiesel

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    I hate my cape cod house!!! because of the insulation problems...
    Ugh.
     
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  7. brenndatomu

    brenndatomu

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    Oh, and I just added a power vent to the attic this summer too...the house does have gable vents on all 4 sides...but that just doesn't flow like a properly done soffit and ridge vent system...we don't have soffits, so that was out for us...the cost of running the fan seemed to be more than offset by the AC running less.
     
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  8. Warner

    Warner

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    We have the knee wall on one side. The attic I can stand up and walk around no problem.
     
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  9. Warner

    Warner

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  10. Warner

    Warner

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    Disregard the mini split lines hanging out. Lol
     
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  11. brenndatomu

    brenndatomu

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    I can't quite stand up straight, even if I'm right against the wall...one of the disadvantages of being tall...I'm super ready to be done with this job!
     
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  12. Nitrodave

    Nitrodave

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    We blew in 64 bags of cellulose this summer... 28x50’ ranch style house with cathedral ceilings... HOLY CRAP what a difference so far. The wife cooked some pizzas last night... temp in the house went up 2 degrees
     
  13. BDF

    BDF

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    Places such as Home Depot will give you the blower at no cost if you buy enough insulation from them. And even if you need to leave an area bare, you can blow all the insulation around the attic and later spread it with a leaf rake.

    Again, not trying to talk you into or out of anything, merely my thought process and how I got to using cellulose instead of fiberglass batts and blown- in rigid foam.

     
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  14. Warner

    Warner

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    My only issue with blown in is I’d have to build a dam around the access hatch.
     
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  15. brenndatomu

    brenndatomu

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    I saw an interesting idea on how to beef up insulation and still have storage space...install insulation enough to fill in floor joists, then frame up an area the size you want running the joists perpendicular to the floor joists...fill with insulation, install plywood over it...move in "stuff"
    Probably not a new idea, I just never seen it before...
     
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  16. brenndatomu

    brenndatomu

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    Easy enough to do...
     
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  17. Warner

    Warner

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    Good idea, I have no plans to use this space for storage. It’s a PIA to get in and out of.
     
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  18. Warner

    Warner

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    Yes not a problem. If blown in is superior.
     
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  19. BDF

    BDF

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    Yep, and I am going to cut a block of rigid insulation to fit into the scuttle to insulate that a bit. A bit of a pain to move in / out of the way but again, I do not expect to be going into my attic very often and certainly not weekly, for example.

    Rigid foam on the inside of the roof ends all those situations and makes it really easy to walk around in the attic, as well as providing a warm (and cool in the summer) attic for storage, etc. There are advantages to all ways of doing this and in the end, we each have to pick which one works best for us. That said, I would be wary of buying a house with rigid insulation in the attic for the reasons specified in the earlier post.

     
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  20. Warner

    Warner

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    I
    Yeah, I put three layers of 3 inch foam. I really hate having to go up there. Pulling the foam out isn’t fun. I’m thinking I’ll glue or bolt the hatch cover and layers of foam so I don’t have to pick it out piece by piece.
     
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