Our garage has been smelling musty for a while. Recently I noticed the smell getting stronger in the house and so we decided to ask contractors to come in. It wasn't clear to me weather the smell was just old garage smell or something more serious.

We received a whole bunch of answers. Most of them said that they didn't think we had mold but suggested to remove the old insulation for replacement. Apparently exhaust fumes can get trapped in materials. Also the previous owner had the insulation installed with the paper inward, away from the ceiling, which apparently is the wrong way around. The garage ceiling which forms the floor for one of the bedrooms above also doesn't seem airtight and given there was no vapor barrier, leaked smell into the house.

Having looked at the existing fiberglass insulation which was covered with black specks we decided to remove it ourselves to see if the smell would subside. Well, after a few days of airing out post removal the smell is is nearly gone. In my opinion it was mold, but I'm no expert.

What I want to do next is make sure we can properly finish the garage to prevent smell as well as mold from reoccurring. My current thinking is that we will get the contractor to apply Enviroshiled, fill cracks and install new fiberglass which we'd have covered up with either drywall or wood paneling. I don't know if we should have all the walls insulated including the exterior facing or just do the ones adjoining the interior?If we do insulate will we create a room that's too airtight and will form new mold? Is it better to have a slightly more drafty garage? Would it make sense to install a passive vent to keep air moving? The garage is not heated and the house is in the wet Pacific Northwest.

How can we do all this the right way?

Thank you

I think it was mold, also. It doesn't look like a vapor barrier was applied, originally. Enviroshield sounds like a good idea to me. Make sure that whoever insulates the room knows the codes in your area.

The best insulation is spray foam for R value and eliminates any possibility of mold build up.

Garages walls adjoining the house is a bit dicey. Reason is, rule of thumb is the vapor barrier should be on the heated side such as the inside of the house wall. BUT when you add a garage to that and Air condition in the house the vapor barrier is for a time on the wrong side of the wall and you see the results of that now. In the old days with no Air its wasn't a big deal things balanced better.

To solve the problem spray foam that adjoining wall and no worries ever.

Use clorax with water or a Mildicide and treat area then spray foam wall cavities in garage wall against the house.

By all means use foam, but remember you will regret it for evermore, the crunch time will arrive when you want to sell your home, the Mortgage Company will send around an property inspector, and you will soon learn that roof foam gives them the heebie jeebies, and the mortgage will be refused, or if they want the business they'll order you to have it taken out, your buyers will get a whiff of the bad news and pull out, or ask for a $20 000 dollar discount off the price and, you are desperate to sell, and agree.

Spray foam and timber joist do not mix, wood needs to breathe, here's some more bad news; do a simple Google Search ask Google " Is spray foam safe to use in lofts, I took a job to remove foam from 6 houses for a Council, and there are 2 spray foam/s, ones called open foam which ruins the house loft/attic forever, the others closed foam which ruins the timberwork.