Interior wall cavity used as a supply duct

[TheGadfly]

After living in my 1970s home for the last 6 months, I just noticed that all of the return registers on the second floor are not connected to metal duct work. Instead, the original builder just used the space between the studs and sheet rock as an airway to the supply trunk in the floor. After doing a little research, I'm seeing that 1) this is very common in older homes, 2) this is definitely not up to code and 3) can lead to all sorts of air quality and efficiency issues. 

What I'm not seeing is whether and how to fix it. I figure I can cut away the sheet rock from the register to the floor, install a metal duct and drywall over it. Is this allowed? Or do current codes require that new supply ducts be installed in the attic? I'm having trouble understanding the new codes.

Also, I can see why the builder didn't bother installing actual duct work in the wall because, in most cases, there's a wire going through the studs (see photo attached). How do I re-route this wire?

[Jon Bon]

It actually is 100% up to code, of a house that age......

My first advice would be to relax. Is this your first home that you purchased? I am sure there are all kinds of things in your house that are no longer up too code. Just like a car for 10 years ago does not have the latest required safety features. If you want a house up to 2019 code you need to buy a house built in 2019. Houses from the 1970s are generally going to have most of the modern building materials. Upgraded electrical, no lead or asbestos. Proper roofing, decent insulation,  etc the list goes on.

I assume that is a picture of your ductless duct? If that is your existing duct, its 50 years old and looks fine to me, why would you even want to go in and tear apart your existing house just to put some cheap sheet-metal in?

The cost of such a project would be pretty crazy. It would require off the top of my head:
HVAC/Electrical/Carpentry/Paint/Millwork/etc etc

So I guess my question is what is your objective here? We can give you better advice when we know what direction you want to move in.

[Model96]

If it looks that good after 50 years, there's definitely nothing to fix!

[Papa bear]

That’s still done on many occasions.  In the grand scheme of things, no big deal.  It’s definitely not worth the time or effort to hard pipe it in.

Re routing the wire around that, though? Go up and over, or down and under.  Neither would be fun to do.


Sent from my iPhone using Tapatalk

[TheGadfly]

So I guess my question is what is your objective here?

Yeah, you answered it. I'm looking for someone to say, "yes, fix it because..." or "Don't bother because..."

I think my main concern is the efficiency and effectiveness of the HVAC system. The house only has one zone (thermostat in the 1st floor dining room) and the second floor doesn't get as much heat or A/C as the first. This could be a contributing factor, although I realize it's probably not the main factor.

I agree, it's an extraordinary amount of work. Just looking to see what others think and determine whether it's worth fixing at some point in the future

[solon]

I just finished my basement - so it is brand new in 2019. The builder did it just this way. There is no reason to do it any other way.

[CNM]

If you're concerned that your 2nd floor isn't as warm/cool as you'd like, I'd look into pricing out a mini split system.  It'd probably be cheaper than reducting.

[Jon Bon]

There are lots of little things you can do for efficiency. And cleaning your ducts out is most definitely one of them. However the picture you took looks like a very clean duct. So putting in sheet metal ducts would gain you nearly nothing. Off the top of my head:

clean supply/return ducts
change filter
clean blower/coils
insulate r22/r410 line
tape up any joints/gaps
replace old equipment

However likely none of this would help your upstairs. There usually you are suffering from undersized returns and bad thermodynamics. My house pre-dates AC so it does not take that into account. The best bet for us is to leave the fan on all night, that way it circulates the air all night. Not the most elegant solution but better than anything else. In terms of changing a house I think retrofitting HVAC has to be one of the most difficult.

[driftwood]

That wire - no issue at all. The beauty of this setup is that a wire or two isn't going to mess with your air flow. And return air flow isn't going to mess with a wire or two. These return ducts are great the way they are. Also, yes, that looks really clean for being so old. Wow!

[Sibley]

Can I show you my ducts? I'm not even sure my furnace is pulling from the return grates, and I have to order custom made vent covers for some because they're so nonstandard. Seriously, this is fine.

Honestly, do a bit more education. Because if you think this is a big problem, that tells me that you probably don't know enough in general about how houses work. And never buy an old house (70s isn't old), you'd probably hate it.

[Frugal Lizard]

Based on our experience with our 1969/70 house:  make sure that the top of the supply duct is sealed tight so that the heat doesn't continue up into the unconditioned attic and out your roof vents and turns the corners into the register supply runs. 

We also had to cap the cold air returns as they were all acting like chimneys for warm air going up into the attic. It was just a matter of some 2x4's horizontally between the studs and some caulking or spray foam.

We also just did some work on balancing.  We had a couple of baffles installed on the supply runs right at the plenum so that more air goes to the long run to the far end of the main floor.  Too much warm air was heading to the small runs that were nearest the thermostat.  One is now half shut down and the other is now two thirds shut down.  And now the far end of the house is super toasty.  We haven't yet had some really cold weather yet so we will be adjusting through the winter months, but hopefully son's room will be colder and the living room warmer.

[Cadman]

Yes, what others have said, leave it alone, you're in fine shape.

Now, if you're having performance issues, you might consider having a static pressure test done. This'll tell you if your system is overtaxed, and if the restriction is on the supply or return side of things.

[TheGadfly]

Thanks everyone!

As many of you have noticed, I'm a super amateur when it comes to home improvement, which is why I'm consulting the MMM brain trust. 

What I'm reading this that this isn't something I should be concerned about and that there are other, more significant factors that are likely causing uneven heating in the home. I'll look into those.

Thanks again

[Kaydedid]

We found the same thing in our house.  There was a major difference between the upstairs and downstairs temp.  We were tearing out the wall at the time, so we added the duct work because my husband's a perfectionist.  It did help a little, but the big difference was when we added returns to the rooms that didn't have them.   

[zolotiyeruki]

Built in the 70's?  Personally, I think you'd be far better served by pulling out the insulation in the attic, sealing all penetrations and seams up there, putting the insulation back in, and then adding more insulation.

Besides the attic insulation, I'd be willing to bet that both your supply ducts and returns leak a lot of air. You might consider Aeroseal--they basically close off all your vents, pressurize the system, and spray in an airborne caulk-like substance, which seals all the air leaks in your ducts.  It doesn't improve your home's efficiency per se, but it makes sure that all the air gets to its intended destination.  We have a couple bedrooms that don't get enough air, and it's due in part to long duct runs that were poorly sealed when the house was built (in 2006!).  Earlier this year, I did a bunch of work in the basement to seal up all the joints that were accessible, and it made a noticeable difference.

[TheGadfly]

Personally, I think you'd be far better served by pulling out the insulation in the attic, sealing all penetrations and seams up there, putting the insulation back in, and then adding more insulation.

I actually just did this over the weekend!

You might consider Aeroseal--they basically close off all your vents, pressurize the system, and spray in an airborne caulk-like substance, which seals all the air leaks in your ducts.

I've heard of this. Any idea how much it costs on average? I am in the process of sealing up the leaking duct work that I have access to in the basement, which may help a bit.

[zolotiyeruki]

I seem to recall (from researching it several months ago) that it's in the range of $1,500-2,000.  It sounds kinda steep, but they have to seal off all supply and return vents, tap into your supply trunk, plus the cost of equipment, overhead, the actual material that gets blown in, etc.

Someone needs to come up with a DIY version, where you seal up your own vents, set your thermostat to blow the fan constantly, drill a small hole in your supply trunk, and insert a wand that mists the caulk.

[Jon Bon]

Kind of feels like the last thing I would probably do to gain efficiency.  For $2000 you are approaching new furnace levels. Going from an 80% to 95% would make a much bigger difference then plugging tiny holes in conditioned space.

Something that is both fun and effective? Buy a temperature gun. They cost <$20 and you get to play cold air detective. I end up using mine all the time for the strangest things.

One of the fancy visual temperature guns would be better but cost 10x as much.

[TheGadfly]

Yeah $2000 is a no-go from me, especially since I'm not sure that the caulk will work properly within those interior wall cavities anyway, right? I think I'll try sealing up the ducts that I actually have access to first.

I'll definitely get a temp gun! That sounds useful and fun