Mold and fire question
So I am having string of bad luck on my new home construction. Towards the end of the project it caught on fire which destroyed the roof. As part of the remediation they pulled the drywall and insulation off and I am greeted with more wonderful news, there is mold on the interior OSB.
For some information the walls were prefabbed panels that were delivered on site. From outside to inside, there is vinyl siding, tyvek drain wrap, OSB, 2×6 framing, fiberglass batts, drywall, and then paint. They did seal wiring holes in the 2×6 and used owens energy complete sealent to create the gasket effect when the drywall went on.
The hygienists are still looking into this but they believe the mold was part of the building process and not the water from putting the fire out. Their belief is that the wall panels could have gotten wet and even though it was dry to the touch when they installed the fiberglass batts once they put the drywall on mold started to grow because there was moisture. I was told they have seen mold issues with newer energy efficient homes.
My builder doesn’t believe so since there was 2 months between when the roof shingles went on and when the fiberglass batts went in so there was ample time for the panels to dry.
I am not sure what to believe at this point but am trying to stay positive and concentrate on moving forward. I am very paranoid about mold so here are some questions:
1. What should I be having my builder do to avoid the possibility of introducing mold during the rebuild? Should I have them test the walls with moisture meters before the insulation goes in? Should I make sure the HVAC system is running with the dehumidifier as soon as the drywall goes up?
2. Would it make sense to look at other products like Spray Foam or Rockwool instead of fiberglass batts to help reduce the risk of mold? Closed cell seems pretty costly so this might be overkill and not sure if I am trading one hopefully manageable mold problem with another?
3. They are still investigating but they suspect the fire started in the attic from an electrical wire that arced and it was buried under all of the cellulose which started to smolder and eventually catch on fire. I thought Cellulous was fire retardant so am surprised it smoldered. Again I am paranoid about fire now and I realize that cellulose is pretty common and ultimately you shouldn’t he having electrical issues in the attic but is there anything else I can do to reduce a fire from starting in the attic?
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Hopefully, an insurance company is involved. It seems to me that if there is some chance that the OSB got wet due to fire fighting, the insurance company should pay for all necessary work.
Q. "What should I be having my builder do to avoid the possibility of introducing mold during the rebuild? Should I have them test the walls with moisture meters before the insulation goes in? Should I make sure the HVAC system is running with the dehumidifier as soon as the drywall goes up?"
A. It would probably be a good idea to test the moisture content (MC) of the OSB before the walls are insulated. It would also be a good idea to install a hygrometer in the house to test the indoor relative humidity (RH). If the RH is high, a dehumidifier might be useful. It would be easier to give advice on these issues if we knew your location or climate zone.
Q. "Would it make sense to look at other products like Spray Foam or Rockwool instead of fiberglass batts to help reduce the risk of mold? Closed cell seems pretty costly so this might be overkill and not sure if I am trading one hopefully manageable mold problem with another?"
A. None of the insulation products you listed will encourage the development of mold, as long as it is properly installed. So the choice of insulation material is not really an issue here.
Q. "They are still investigating but they suspect the fire started in the attic from an electrical wire that arced and it was buried under all of the cellulose which started to smolder and eventually catch on fire. I thought cellulose was fire retardant so am surprised it smoldered. Again I am paranoid about fire now and I realize that cellulose is pretty common and ultimately you shouldn't he having electrical issues in the attic but is there anything else I can do to reduce a fire from starting in the attic?"
A. You might want to have a different electrical contractor involved, or have the wiring inspected before the attic is insulated. Cellulose is not associated with fires. If you had an electrical fire in your attic, the problem had to do with the wiring, not the choice of insulation.
If heated high enough for long enough the fire retardents in cellulose can eventually dissipate and cause it to smolder (locally) but those conditions are extremely unusual. If you take a propane torch and apply the ~2000F flame tip directly to the material it won't light off right away, but in a few tens of seconds it will. At lower temperatures it takes a LOT longer. At 500 F it could take weeks. (Just a WAG, never done the experiment myself.)
What was the average outdoor temperature for the 2 months prior to installing the insulation? Was the house being heated & ventilated during that period?
What is your location/climate zone?
This situation should be a reminder to all of us that any building project needs to be insured from the first day. No one having a house built should assume that the builder carries Builder's Risk insurance. Whether the homeowner or the builder insures the work is less important than that someone does.
It's also important to make sure coverage continues until the house is done and regular Homeowner's coverage takes over.
About 30 years ago, I represented a builder of a senior housing project in Massachusetts. Literally hours before the ceremony that would mark the completion of the work, the building burned down. The builder's risk policy had expired a few weeks earlier. Next stop was insolvency proceedings
You say that the panels were prefabbed but that the fiberglass went in and the drywall attached after the panels were put in place.
Isn't another cause for mold the moisture that can appear in the time between putting the insulation in and the time the drywall is placed? If there are several weeks between the two and it's cold climate wintertime and propane heaters are used during construction, then all that combustion moisture can condense on the interior of the sheathing. The OSB could have started out bone dry but ended up wet.
Stephen makes a very good point. I'd add: the first contact you have with any sub or supplier on accepting their bid should be to have them give you confirmation of their insurance and workers compensation coverage.
We seem to have had a similar experience. Our home caught fire 2 days before moving in. I really am sorry for your loss as I know what you are going through. We spoke to a public adjuster who reviewed our policy and was very helpful in discussing our rights and options. Our insurance company actually was good to work with and we didn't end up having to use the public adjuster but you may want to gather all the facts you can so you maximize the settlement in your favor.
I can't imagine that anyone can even guess how mold was introduced after an experience like that. There are too many variables. If you worked well with your builder and he is experienced then, personally, I would trust him over anyone else. I researched spray foam and our first house actually had closed cell foam throughout. Our new house has fiberglass batts. Why? Because our 2nd builder preferred batts. It wasn't a money issue for us, rather, we just went with what our builder preferred and was comfortable working with. He had built a lot of homes and had a solid reputation so I went with his recommendation. We also have a whole house ERV to mechanically introduce fresh air in the house.
Good luck with your new rebuild. Again, I just went through it myself and know it's tough to do it again but try to keep your sense of humor up and don't get too discouraged. It will go by quicker than you think once you get that insurance company focused and moving towards settlement.
Hi all, sorry for the late response but as you can imagine I've been dealing with all the issues with my home and it is really difficult process. Thanks to all of those that answered some of my questions and sharing your stories.
To answer some of the previous questions yes I do have builders risk insurance which is the process I am going through now.
I did have some additional questions on the Mold problem, the insurance company is telling me the Mold is growth from condensation and telling me this is common in newer home construction. I am in Zone 4 and am trying to understand how this happened to my new energy star home. I did read the GBA article: https://www.greenbuildingadvisor.com/blogs/dept/musings/how-risky-cold-osb-wall-sheathing but I am unsure what the builder should do different during the rebuild.
I guess my main questions are:
Is this truly common? If so should it be something I should worry about happening again?
What are people doing to mitigate condensation on the OSB and ultimately the mold growth?
If you have mold growth on your OSB, you should insist that the insurance settlement pay for mitigation of this problem.
If your OSB is clean, and you are worried about future moisture accumulation in your OSB, then the usual advice applies: exterior insulation (a continuous layer of rigid foam or mineral wool) can help keep your OSB warm and dry during the winter. If you can't afford exterior insulation, at least include a ventilated rainscreen gap between your siding and your OSB.
Personally I think it's insane that we build with highly-engineered processed wood mold factory materials that demand perfect detailing and insulating to prevent them from falling to pieces (or catching fire, or being eaten by termites, or…).
Assuming that tearing the entire thing down and restarting using masonry for the walls is not an option, if the studs are intact you could replace the OSB with asphalted fiberboard, which is water-resistant, does not get condensation as easily, and insulates slightly better than OSB. Another option is DensGlas sheathing, which is basically fiberglass-faced drywall and is common in commercial construction. Also mold-resistant, since there's no actual organic material there for the mold to eat. Or you can replace the moldy OSB with more mold-prone OSB (or plywood) but immediately cover it with exterior rigid insulation board, preferably mineral wool, and then run temporary heat inside to dry out the materials. Or even better, combine these and sheathe with DensGlass, cover with rigid mineral wool, and you can even skip the temporary heaters. That'll give you a nice mineral-based wall covering that won't mind water and won't burn, rot, or get eaten by termites, ants, or beetles, either. You can also use DensArmor instead of regular paper-faced drywall to add a huge amount of moisture and mold resistance and durability on the interior, too. That's what I'd do were I in your situation and starting from scratch with pure masonry wasn't an option.
The more I think about it, the more it seems that switching from engineered wood sheet goods to fiberglass-faced gypsum makes a huge amount of sense for a lot of applications, and they're a drop-in replacement, with no retraining required.
Nate G., doesn't drywall sheathing seriously limit your siding options? And if I were close to the coast or in another high-wind zones, I'd want something a little more substantial than Sheetrock between me and flying debris moving at 70 or 100 mph..
I don't think it limits your choices much. Most claddings should be attached to rainscreen furring strips which are themselves fastened through to the studs below. On the question of durability vs physical damage, it's not quite as bad as drywall--the facers are reinforced fiberglass, not paper. But I do largely agree with you. In such regions, I'd prefer solid masonry walls. That's what they largely do in Florida, in fact.
Kraft faced fiberglass is rather prone to mold issues - Mold just loves paper.
They do make mold and fire resistant plywood and I believe the coatings are available for retrofit.
(blue and pink wood...) They cost a bit more to install but replacement is much less likely.
Drywall also comes in mold and fire resistant varieties as well.
On the surface using a moisture tester may seem like overkill but documenting such things can in fact protect you when events like this happen. You can at the very least claim you did your best to prevent issues like this.
I would strongly advise bringing in a different electrician and have all of your wiring inspected and replaced. Where there is one bad connection there is bound to be another There is also the issue of water getting into the inside of the wire and causing problems as well.
Additionally if this was caused by a misplaced nail through the wiring then the assumption that they did it more then once is equally valid and you should inspect your plumbing as well.