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Discussion Starter #1 (Edited)
I have a question about insulating my attic + air-sealing and attic maintenance after finding elevated mold spores in the attic.

First, some background info: the house is in Michigan (near Detroit), built in 1964. This year (2019) I've done a mold test using an air sample, and results came back as such:

Spore estimate count per cubic meter:
chaetomium 200
stachybotrys 50
penicillium/aspergillus 1500

Looking at the mold test results I wondered if I need to clean out my attic, remove old insulation, and reinsulate the attic.

When I went up into the attic I've discovered that it is very dusty and poorly insulated. I am currently at R11-13 (estimated). I am also concerned about mold.

I saw signs of water damage stains on some walls and attic drywall flooring. At one time several years ago the pump on the SpacePak blower coil unit failed, leaking through the drywall ceiling. That has been repaired.

Attic is vented with vent caps, but there are no soffit vents and no baffles.

I have a few questions in no particular order:
  • Do I need to remove my old insulation (due to mold)?
  • Do I need to remove my old insulation (due to all the dust & debris in my attic)
  • What is my current insulation?
  • Do I need to add more insulation? What kind?
  • Do I need to add baffles? Do I need soffit vents?
  • Do I need a radiant barrier?
 

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Discussion Starter #3
Yes, outdoor test only had 820 the of Penicillium/Aspergillus Group spores, and none of the other kind.

I haven't seen any actual mold growing in the attic but I haven't looked everywhere. I could probably add soffit vents although I never have done that before and will need to do some research.
 

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The problems are from moisture coming in through the roof and apparently not enough ventilation in the attic space. Soffit vents would improve ventilation but need to have baffles so that they are not blocked by the insulation.

As the mechanicals are in the attic space the mold risk is a concern as any leaks in the ducting could conceivably take mold spores from the attic to the living space. Another concern is trying to sell the house in the future with any evidence of mold having been present.

If it was my house I would want to remove the old insulation and air seal everything including the duct connections. Most houses have poor air sealing and inadequate insulation and so benefit from an upgrade regardless

At my house in Dallas the builder put a hot water heater in the attic space and when it leaked it damaged the ceiling. Surprised me to see this as in California there would have been a metal drain pan and an overflow drain pipe to the outside. Not unusual to have washers on the second floor of houses and condos and any leaks should be contained.
 

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I do believe the insulation is the problem. If you did not leave any airspace between the insulation and the underside of the roof sheathing then you will move the dew point inside the building and create the very problem you are having.

I would make sure all the ventilation is set up correctly (add soffit vents, if possible and do your research), and possibly get a dehumidifier if there's dampness due to leaks.

Yes, you'll need to remove the old insulation as with moisture it makes perfect conditions for mold to grow. To clean mold I used a bleach and water solution. It's better to take action now before you have to call someone over to professionally do it.
 

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Just curious but after a fresh snowfall is the snow on your roof mostly melted after a few hours? The reason I ask is that when I bought my house new, there was minimal insulation in the attics (tri-level) and it was probably about R13 or so, similar to yours. The roof was always melting the snow and my heating bill was crazy high. The following year I added R19 rolls on top of the existing R13 blown in insulation and cut the heating bills in half.
 
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