Paolo- the first thing to note is that you’re in Ontario Canada. You have weather considerations and you have radon considerations because of regional conditions that we must consider when inspecting.
Nothing in the pictures you posted are “significant deficiencies” in accordance with home inspection standards. However, you should be obliged to add into your inspection report these things which you would be allowed to talk about which definitely would is be beneficial to the client. Remember, your job is to observe and report not analyze.
These installation practices appear to be in an older home (if it were constructed in Tennessee). The return duct is a metal pan against the floor joist. This is not any longer a preferred method of installation. It is also observed that the pan is separated from the joist in the picture. This will pull in outdoor air which is a weatherization concern as well as a radon/indoor air quality concern.
Note: sellers are not required to upgrade construction standards to current standards.
If the round duct is in fact an HVAC ducts, it should (must around here) the insulated. This falls under weatherization and also as you observed, causes condensation in unconditioned spaces below the house.
You are correct about the missing three screws.
HVAC installation practices requires proper support of the duct, not using electrical wires and structural members. Not home inspection issue however.
The rusted wingnut is from the sheet metal screw attaching the register boot to the duct above and is a result of condensation. Insulation would correct this. The wingnut is for a damper to control air flow. This will always happen because of the duct is below the dew point temperature of the crawlspace/basement when the air conditioner is running. It becomes a problem when this condensation in the rots the floor, contributes to mold growth, and insect infestation .
The air duct that is not screwed or taped is not adequately inserted into the adjoining duct. This will cause leakage into the crawlspace which causes the inside of the house to go into a negative air pressure which will pull all kinds of bad stuff through the building envelope. This and the return duct leakage can become problematic because of weatherization and indoor air quality concerns. This could be reported as “does not operate as intended” because air duct is intended not to leak.
Now, in reference to the electric wire touching the duct; I am going to have to disagree to some extent with Robert Young’s opinion about the duct getting high enough to melt electrical insulation. Robert is in Canada and can probably help you more than I can concerning standards there, and is an excellent resource to new inspectors such as yourself.
The duct could get hot, but it would have to be a catastrophic malfunction which would probably be burning the house down before two layers of electrical insulation was compromised. Electric and gas furnaces have high temperature safety controls to prevent such a condition. These furnaces have multiple controls to protect over temperature of the supply Plenum/heat exchanger. They are electric snap action safety devices around 120 to 140°F ranges and fusible links which are one time safety devices like a fuse. These are rated at higher temperatures than the electrical safety’s. So it is near impossable for for a safety failure this catastrophic to occur. There is the potential for vibration or sharp electrical duct to cut the insulation, causing a breaker trip I guess.
So the short of it is that your observations are well made but your documentation should reflect the extent of the concern to your client. Referring further investigation by someone else cost money that no one will appreciate, so I would point out my observations and let the client follow-up as they see fit. No mention of the house may burn down because electrical wire is touching the duct etc. I advise my clients of the “potential” for conditions such as these (never that they actually are occurring).
There is an opportunity here to up sell radon testing/weatherization testing services once you become a proficient home inspector. But it is my opinion issued work on your home inspection standards before you branch out into other fields (unless you are already qualified from a previous life).