Perhaps the worst HVAC duct idea ever, according to Dr. Bailes. And your second pic looks like something out of an InterNACHI file.

Sorry to say, I paid for such systems in the '80s as HVAC tends to be an area builders left to the cheapest HVAC guys out there. Still allowed where we are, but I spec real all metal ducts only.

If panned returns are allowed in your jurisdiction and this is not a true custom home and this is your first mention of it to the contractor....

I don't see that this is that big of a deal. From what I can see, the cavity is completely sealed. It is also in a totally enclosed area. I realize the practice was used in a totally unacceptable way in the past but I just don't buy that it can't be done correctly. I could be convinced that it is terrible but this just doesn't look all that bad.

Builds are compromises. In the US, we don't build to perfection - not even close. I personally think flex duct is fine. My own house even has duct work and a unit in unconditioned space (gasp!). My house is net zero energy so remind me what the problem is?

To be fair Worthy, you build in a climate few of us would choose and build houses that few of us could afford. At some point our comps in the US are built like total crap so it doesn't pay to build perfection.

OP - do they have to meet static pressure testing requirements and leak tests? Just cause all those 90 degree turns and relatively small size maybe challenging. My real question is does anyone make a furnace small enough to use in a 1000 sqft new basement. The heat requirement should be off the charts tiny. And it looks like an old school water heater in the background. Best design would usually be tankless or heat pump.

Using wall cavities as returns is a terrible practice. Unfortunately it is allowed in some parts of the country. Over time dirt and debris collect within the cavity and pulling into the furnace. If your filter is at the furnace then it means more frequent filter changes. If your filter is at the return opening it means a lot of dirt being collected on the coil.

Tell the project manager this is unacceptable you want it replaced with metal duct work.

Is this wall the only structure between the middle of the floor and the joists above? This span of the joists seem long and would need support somewhere in the middle. I am not a structural engineer, but this wall even without the cuts does not seems sufficient to support the weight of the house above. You need to have this explained to you.

Thanks to both of you for confirming what I feared. Time to have a difficult talk with my project manager.

I’m actually surprised that they’re cutting corners here, since our specifications call for a 95% efficiency furnace (and we paid extra for a dual zone variable speed system). Seems like we’d be throwing away some of that efficiency as well.

As for the span of the floor trusses, I am thinking both walls highlighted are probably bearing, since they are in line with the lvl beams in the unfinished area, and are over thickened slab. But I really have no idea what I’m talking about :). The highlighted area on the second drawing is where the joist/wall return in question is located. I don’t know anything about hvac either, but it sure seems like they could figure out a way to make a solid return.

Someone explain to me how dirt gets in a wall cavity? Are you saying the wood gets dirty? Leaky ducts can draw in dirt - sure. Most wall cavity returns probably leak. But wood framing doesn't create dirt.

I mean this one is lined with metal and mastic used on seams. Sure - there are some exposed 2x4's in the air flow - does that really "create dust".

Every wall cavity I have ever been in is dirty from construction debris not some created dirt. Now - if not sealed then other framing areas dirty with construction dust can get there but I just don't see it if sealed.

I think flex duct would be far cheaper than what they have done - so this isn't really cutting corners from a financial standpoint.

How many BTUs is your furnace and is it staged? What is your basement load? With only basement calling, I suspect your bigger issue is short cycling and excessive airflow through inadequate supplies. 60,000 btu furnace for 5,000 btu/hr load.

Zoning is really hard to get right. Basement loads are tiny. If your 2 zones are basement and 1st floor, it is really hard to get that airflow right.

Hi David,

This is the info I received from the builder. The home is 2150sf on a basement, with 1050sf finished in the basement.

Carrier 59TP6 Furnace
Carrier 24ACB7 4-Ton 16 SEER AC with 2 Stage Compressor

Wood expands and contracts according to the season and the humidity content. So mastic, even carefully applied, will always fail. Panned returns then bring in all the contaminants inside the walls and often from crawl spaces and damp basements. Furthermore, the returns are often penetrated with wires of every sort, plumbing and even A/C tubing, none of them properly sealed.

Source: BSCInfo_801_Wrong_Panned_Floor_Joist-3.pdf

Where is this house located? A new construction 2150 sq foot house should not require 4 tons of cooling. Was a load calculation done? Get the complete model number of the furnace. It will indicate the size. I would think a 80K BTU furnace and 3 ton AC should be sufficient.

Southwest Ohio. A mix of 8, 9, and 10 foot ceilings, if that matters. 2x6 exterior walls, R-19 batt on first floor, R-45 in attic, R-10 basement walls. Both the finished and unfinished parts of the basement are conditioned.

I’m meeting with the builder and “HVAC designer” tomorrow to discuss my concerns. I’ll ask about the load calculations. It is a reputable HVAC company in the region, so that gives me some hope. The builder is kind of making me feel bad for even questioning it, basically saying they do it this way in 35 homes a year and have never had issues. So maybe I’m making a big deal about nothing.
Note: I had specifically asked for a two zone system after speaking to one of their homeowners who complained about their basement always being colder than upstairs. I’m going to be working full time in the basement, so it will be important for me to be comfortable.

Your house is being built with a good amount of insulation. In my opinion the equipment is over sized, but let's see what the calculations have to say. Don't be surprised when the "HVAC designer" makes some excuses about not being able to produce the calculation document.

Using a sealed duct for the main return is a very reasonable request. Your builder is correct. The issues will appear years after the one year warranty expire when it is no longer his problem.

^^^

The mechanical permit submission for our new 5,700 sf build: 16 pages of calculations, requiring a professional engineer's review and stamp.

Includes pages on: residential foundation load calculator; envelope air leakage calculator; air leakage calculations; heat loss/gain calculations etc. etc.

Yeah - a walkout basement facing west could easily require 4 tons.

Is the basement walkout? Overall, the west facing glass amount is the most important determinant of a/c size.

So you are really conditioning 4300 sqft in total? That makes the zoning easier.

Worthy, that explanation makes a lot of sense.

No walkout basement, unfortunately. The house faces NNW, and the only window on the west most side of the house is a 1’x1’ fixed bathroom window. Yes, both levels are fully conditioned.

The heating load for the basement will be small. The cooling load is close to zero. It will be interesting to see what the load calculations will be for the basement. You made a good decision about having the basement be a separate zone.

If there is a thickened slab, and by looking at it, most likely this a load-bearing wall and they bent sheet metal to connect wall sections where plates were cut. There should be a steel plate installed instead of sheet metal to meet code compliance

R602.6.1 Drilling and notching of top plate.

Where piping or ductwork is placed in or partly in an exterior wall or

interior load-bearing wall, necessitating cutting, drilling or

notching of the top plate by more than 50 percent of its

width, a galvanized metal tie not less than 0.054 inch thick

(1.37 mm) (16 ga) and 11/2 inches (38 mm) wide shall be

fastened across and to the plate at each side of the opening

with not less than three 8d nails having a minimum length

of 11/2 inches (38 mm) at each side or equivalent. The

metal tie must extend not less than 6 inches past the opening.

See Figure R602.6.1.

Mike this isn't how you do an AC load calculation is it?

Mike didn't suggest using a rule of thumb in lieu of calculations, Ray. Rather, he called into question the capacity of the system. Indeed, he asked the OP if a load calculation was done.

It's really easy to make an incorrect entry when using manual J software and have the program spit out an incorrect result. A "reality check" using knowledge of the size of systems installed in similar homes is always appropriate.

The heating and cooling loads on the basement should be minimal, as Mike noted, so we're looking at close to 4 tons for the 2,150 SF of the home that's above grade. That sounds like a lot of cooling for home that size in zone 4 or 5. I think verifying the calculations is a good idea.