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Hi,
I bought an old farmhouse that has what I believe is “rock wool” insulation in the walls and attic. I’m trying to decide if I should re-insulate. The attic has four full inches of the stuff – its flush with the joist tops. I assume that the wall cavities are blown full as well.
Anyone know what the R rating is? If I wanted to add insulation to the attic, how should I go about it. Should I expect that the walls have settled a lot and need to be re-filled, or reinsulated with fiberglass batts? I’m in way-northern Michigan, so its colder than you know what.
Thanks for the help.
Frank
Replies
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Frank,
Architectural Graphic Standard's lists Rock or Slag Wool insulation at 3.2-3.7 R.
Fiberglass is listed as 3.16 R.
4" of your Rock Wool would seem to be R=14.8, best case. Northern Michigan is listed as Zone 6, and the recommended insulation values are:
Ceiling-R=38.0
Walls-R=19.0
Per A.G.S.'s
I'd start with the attic insulation first, don't know how to approach the walls, would depend on type of construction, and condition of what is there.
Good Luck,
J.R.
*Actually since none of us can see the house and none of us have either our money or our lives at risk here the smartest thing you can do is find a local COMPETENT person to evaluate the house and make some recommendations to you. Each region of the continent has its' own favorite ways to do the job. You are best off finding out what they are and following them. Info you get here is good to get your mind working about what questions to ask but not for designing the actual project.Some places you can look are: The local Coop Extension Service: Many communities have Weatherization Services that focus on low income folks but who can put you onto someone who can do a blower door test and an energy survey: Try your local electric utility also; many of them have energy upgrade offices and financial subsidies for folks upgrading their homes.It is not at all unusual to find that the payback time for some "fixes" is so long as to make your grandkids the beneficiaries.So find someone local who at least has their own reputation at stake before you spend any money on weatherization.
*I just wanted to point out that there is alot more than "payback" involved here. The issue is comfort. If you are comfortable living all winter in socks, slippers, sweats, and hat. Then turn down the stat and don't spend a penny - no payback.If you want the place hot and wear shorts, then spend whatever it takes to get there. It might not payback, but the fact is that you are the one who will have to live with it until your grandkids get it.-Rob
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Fred,
Thanks for the input. How do I go about air-sealing the attic plane? The current ceilings are plaster / lath and have a fair amount of cracking. I anticipate putting drywall up to cover the cracks, which would seem to provide a good air seal. Is there a better way?
Also, once I decide to increase the insulation in the attic, how should I proceed. With the rock wool already at the level of the top of the joists, I don't have a good way to install batts. I guess I could build 'dams' along the edges and around the attic access hole and blow in another 5 or 6 inches. This would make it mighty hard to ever move around in the attic, since you couldn't see where to put your feet. Am I missing something obvious?
Thanks,
Frank
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Sure there are several factors involved. Among them are economics, comfort, and structural integrity. All I was trying to point out is that rather than jump in with proposed fixes it is better to point a person to a local source who can evaluate the house and provide the range of options. In my experience too often house modifications are jumped into in an already comfortable house without actually considering the payback. Since it is his house he will make the decisions. I'm just putting in some grist for the decision mill.
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Hi,
I bought an old farmhouse that has what I believe is "rock wool" insulation in the walls and attic. I'm trying to decide if I should re-insulate. The attic has four full inches of the stuff - its flush with the joist tops. I assume that the wall cavities are blown full as well.
Anyone know what the R rating is? If I wanted to add insulation to the attic, how should I go about it. Should I expect that the walls have settled a lot and need to be re-filled, or reinsulated with fiberglass batts? I'm in way-northern Michigan, so its colder than you know what.
Thanks for the help.
Frank