I did my first 2 inspections this week on my own, the 2nd house which looked like a ready to move in perfect little house had some things that I question, maybe you guys can help me out. This is in Las Vegas…

1. Main water line going into the house does not have a back flow preventer. It also doesn’t look like there is a yard that would need a sprinkler system, it seems to be a community yard, so is not having a back flow preventer ok since there is no sprinkler system connected to it?

2. I went up in the attic and there is 1 furnace unit installed but I did not see any fresh air ventilation. It had cocoon insulation so I thought maybe they put the insulation over the vents, but when I looked outside again there are no attic vents or soffit vents, just some small tile vents which I am not sure what their purpose is (see pics)

I do not see why it would need a backflow device unless it is required by the AHJ.

In picture #3 it looks like there might be a coaxial termination kit going through the roof. It also looks like there is combustion air piping going to the furnace in picture #5. Is this what you are asking about or are you asking if outside air is being brought into the furnace itself? To me, it would seem odd to want to introduce that warm of air into the system.

Yes, I am asking if outside air is required in this case for the furnace.

My guess is there is not an issue in a large attic space.

Did they have a drain pan under that unit ?

Calculations
Confined vs. Unconfined Space
In new or rehab construction, the most important factor
governing the installation of gas appliances is whether or not the
room is classified as a confined or unconfined space. The only
way to determine whether or not a room is a confined or
unconfined space is to perform a room volume calculation
using:

1. The dimensions of that specific room.
2. The total Btu per hr input rating of the appliance(s) to be
installed in the room.

Space, Confined: A space in which: 1) the volume is less than
50 cubic feet (ft3) per 1,000 Btu per hour of total input for all
appliances in that space; or 2) the total input of all appliances is
greater than 20 Btu per hour per ft3 of space. (See Calculations on
Page 39.)
Space, Unconfined: A space in which: 1) the volume is equal to
or greater than 50 cubic feet (ft3) per 1,000 Btu per hour of total
input for all appliances in that space; or 2) the total input of all
appliances is equal to or less than 20 Btu per hour per ft3 of
space. Rooms communicating air directly with the space in which
the appliances are installed, through openings meeting NFGC
regulations and not furnished with doors or mounted hardware
which can accommodate a door, are considered a part of the
unconfined space.

Unless the AHJ requires it, I highly doubt it. I do enjoy how someone tried to save the homeowner some money by using an old furnace door for the roof vent.

It looks like there are two pvc pipes coming out of the furnace which would mean it is getting is combustion air from outside. It also looks like a concentric vent termination above the roof. Was that the case?

Just looked again and it looks like there is a third condensation line for the flue which really makes me think it was getting its combustion air directly from the outside.

Actually I think I see a concentric vent on the exterior shot…

That’s what I just said

OK flying through and saw the 2 pvc part.

The furnace is missing a support it should have 3. The front support is also closer than 6" to the front of the furnace.

Excerpt From the installation manual for this furnace.

SUSPENDED FURNACE / CRAWL SPACE INSTALLATION
The furnace can be hung from floor joists or installed on suitable blocks or pads. Blocks or pad installations shall provide adequate height to ensure that the unit will not be subject to water damage.

Units may also be suspended from rafters or floor joists using rods, pipe angle supports or straps. In all cases, the furnace should be supported with rods, straps, or angle supports at three locations to properly support the furnace. Place one support at the supply end of the furnace, one support located approximately in the center of the furnace near the
blower shelf, and the third support should be at the return end of the furnace. Maintain a 6” (15.2 cm) minimum clearance between the front of the furnace and the support rods or straps.

I can see three supports in the picture but only two are on the Furnace. The plenum requires additional support.

I see the 2 PVC pipes connected to the unit and they do terminate at a concentric vent on the roof. There is no drain pan, and I also see the support issue. Thank you very much; all of your comments were very helpful!