I have used an Ozone machine to kill mold on a small remodel project and it worked great, you should research it , it may be an easy alternative.
Here is just one site I Googled up
Mold-Kill.com - Kill Mold with Ozone Generators
I am a professional mold remediator. I own a national franchise that does Fire, Water and Mold Remediation and I teach in Canada 4 times a year.
Whatever you do. Do not listen to the post I have quoted. Ozone will not kill mold and there is no shortcut to mold remediation. You do not kill mold you remove it. Even dead mold spores can be highly allergenic.
Having said all that. Something you might do is call a local Disaster Restoration professional to come out and give you a free estimate. They will walk you through the process. From that point you can choose to do it yourself or have them do it and you will have their scope of work.
The process for mold remediation is simple. Physically remove it.
I do not know the extent or severity of your loss but since it is a grow house you are most likely as you stated looking at a full gut to the studs. After gutting to the studs you can use dishwashing liquid mixed with water and a scrub brush to wash the stud framing. This should be what is called a "damp" scrub or wipe you do not want to over wet like you are washing a car or anything. If there is still mold growth present at that time you can sand the stud framing until you no longer see mold present. This should be done with a sander attached to a HEPA vacuum or you can simply use a wire brush to abrade off the mold. You should then wash the framing again and allow to dry or place fans on it to help dry it out. After all that you can seal it using a product such as kilz or zinser (pigmented shellac) then rebuild. The use of sodium hypochlorite is generally used at a 10:1 ratio but professionals use specific products. You might be able to find one at a local hardware store or Lowes. I know that "Gloves Off" is a popular non-toxic anti-microbial product in Canada. If you are to do it yourself make sure you have appropriate skin, eye and respiratory protection. Consult your local province for laws regarding all this.
If it were done professionally there would be engineering controls in place such as negative pressure HEPA filtrated machines running with containment barriers, etc...but if DIY that is about as good as you are going to get.
There are serious health risk when trying to remediate a grow house. My professional opinion is DO NOT attempt this yourself.
Lastly regarding the air handling units. Have a pro (HVAC contractor)look at these for sure. In 99% of the the cases I see on homes like this the duct work must be replaced. It is too risky as it is the delivery system of air to your home. If it has spores still in it (even when cleaned) they can contaminate the home all over again or leave a lingering odor.
One last thought. I would recommend having it tested. You can actually go online and order swab samples that once you think you are complete with the cleaning process you can take the samples and send them to a lab for testing. It is not the best testing that can be done but it is the most cost effective. This might give you some peace of mind.
Conditions for mold growth are as follows:
Moisture (above 60% Relative Humidity or >16% Moisture content of wood >20% for destructive growth)
Time (24-72 hrs for germination)
Temperature (most prolific growth occurs above 80F but can grow in a range of temps)
Cellulosic food source (wood, dirt, etc)
Stagnant air
