Old Home full remodel in Zone 5A — need advice on new ductwork design, Manual J/D, attic ducts

Where in Michigan? It gets pretty cold in the UP……….

The way I have avoided head bangers in low basements is by running the trunk along the outside wall. You can even run the trunk on edge so it takes up less space and frame it into the basement walls. In your case with pocketed beams, I would put the air handler in one of the corners and run a trunk on either side of the basement. From there you can do short takeoffs to registers.

General rule of thumb, put a register under every window and by outside walls if they are long.

There is absolutely no reason to run ducting in the attic, it just complicates your life and a pretty big energy penalty. Generally you run a bulkhead along the ceiling of the main floor (usually above built in cabinetry so you don't see it) and run the takeoffs from there to feed the rooms on the 2nd floor.

Important bit for good cooling comfort is a large return on the 2nd floor near the ceiling. This will take up space and you need to find a spot for it. There are many places you can hide it with careful design up front.

Generally a sunroom has very different load profile from a house. Usually those are best served by a dedicated minisplit.

The comfort issue @Jamie Hall mentions comes from bad design and oversized single speed units. With a decent envelope, good ducting design, proper load calculation and modern modulating units, the heat is so even you don't even notice.

Do a man J and a rough draft of the duct layout and post it. We can help you dial it in from there.

"Today's tight homes" … yeah right. Good luck with that on a house originally built in 1880! Those houses were meant to breathe. If they are allowed to breathe, they will last for centuries. If you tighten them up to modern standards… there is quite an interesting varieties of evils which will happen.

My grandmother’s home was built in the 1930s and was heated with hot water radiators. There were beautiful radiator covers over them in most rooms. In the 1950s, air conditioning was added, and that was completed with high-velocity 2" ductwork. I know this because of this story:

In your situation, I would take a serious look at using a high-velocity system for your ductwork. I also like @Jamie Hall's suggestion of considering a boiler for heating . You have so many possibilities: fan coils for the high-velocity system, radiant floor heat for the bathrooms or even for the entire home, panel radiators, or even selecting some beautiful cast iron radiators sourced from places like eBay or Craigslist for that special period look in your home (if that is what you are going for). You could even melt the snow from your entry walkway with a boiler.

Here is a 2-ton high-velocity system duct design where the main trunk is 8" in diameter with 1" insulation (10" outside diameter) and 20 or so 2" outlets in all the first-floor rooms. A load calculation may find that you only need 1.5 tons for the first floor. This solves the problem of those 3 main beams by using the perimeter Trunk Duct idea that @Kaos referred to.

I would separate the sunroom, with all that glass, with a mini-split system for cooling and heating. If needed, on cloudy days near design temperature, a hydronic radiator of some sort might be appropriate and can be added later if you find that the mini-split HP is insufficient. Just rough in some 3/4" oxy barrior tubing inside the wall where you might like to set that (those) radiator(s)

For the second floor, I would use 1½" insulation on the trunk duct and place all the outlets in the ceiling. The turbulent airflow from high-velocity systems will cause the room air to mix from top to bottom, eliminating stratification in the heated space even though the heat is entering from the ceiling. That is one of the benefits of high-velocity systems.

Just be sure your installing contractor uses sound-attenuating ductwork for the last 4 to 5 feet of the supply runs. here is why: a new customer with big bucks has a noise problem in Cape May NJ. He didn't know he had the problem until i did a test:

@Jamie Hall That is a very common often reported myth. People need to breath, houses don't, they need to be able to dry (a lot of house heat leaking through the walls is defiantly a good way to dry them). Old houses sometimes do come with some ugly issues but those can be fixed during a gut job.

@EdTheHeaterMan High velocity is great for retrofit where it is easy to fish the smaller pipe through existing walls. They are pretty spendy to buy and not cheap to run (that high velocity takes a lot of blower power). With the place open, you can put in regular ducting and avoid all those costs. Ducting inside the conditioned envelope also does not need to be insulated.

Before even talking about any heating and cooling equipment, one needs a good man J.

From there, sometimes the answer is hydronic heat, sometimes regular ducts. Sometimes adding a couple of extra inches of insulation can save the cost of fancy equipment.

The answer is never an air hander in the attic though.

Not a myth. If — and only if — you can make the structure so tight, and locate the insulation and vapour barriers in such a way that you never get condensation in the walls or roof structure, you'll be fine, granted.

The problem isn't air movement — draughts — the problem is moisture. Or let me put it a little differently. Wood which is kept underwater — soaked — will rot very slowly, if at all. Wood which is kept with a moisture content below around 20% — that is never in contact with liquid water — will simply not rot at all. If wood is allowed to come into contact with liquid water, as will occur in a wall or roof structure which allows — for whatever reason — the temperature of the wood to drop below the local dewpoint (this may be a result of excess humidity or cold exterior temperature or some combination) it WILL rot and it WILL grow mould.

Not that this can't be managed; it can, with a genuinely tight interior vapour barrier, and this, of course, can be done in a gut rehab — although the level of craftsmanship required is often not there.

The worst combination is an exterior vapour barrier or "house wrap" and heavy, but not vapour tight, insulation.

I could write paragraphs on my experiences with buildings — tight or otherwise. Ranging from genuinely airtight houses (reliant on HRVs or ERVs for maintaining carbon dioxide and oxygen levels, never mind odours and VOCs and the like) to Cedric's home — built between 1780 and 1893, in stages. Along the way I've encountered efforts at tightening up pre World War II houses — which have invariably been dismal failures, either for succeeding too well with air quality, or rot and mould and structural failure from dampness to spending a lot of money with no real decrease in air exchange rates.

Obvious stuff — insulation where it's feasible, but always open cell or breathable. Good storm windows. On newer structures with poured concrete foundations, draught stopping at the sills. That sort of thing. o it, and worth the money (not on concrete block foundations, never mind stone!).

Blower door tests, where they are feasible — they aren't, always — are useful in determining infiltration rates. They are NOT useful to saying "too much draught".

Ed,

Around me, ducting is always inside conditioned space. Even builders put it there, that means it is the lowest cost option. This makes sense as all the ducting can now be bare pipe, no need to insulate air handlers or deal with drainage in the attic. You are also not working on your hands and knees in 140F attic but like a human in a comfortable basement when installing.

It amazes me to see all this attic ducting south of the 49th parallel. I can see why it would be common in places where slab on grade construction is the norm, but it makes zero sense elsewhere.

The big energy issue with attic installs is not the lack of insulation but air leaks.

Any air that leaks out of the ducts/air handler/registers goes to heating the attic so it is 100% lost. This lost air now needs to be supplied up by de-pressurizing the house sucking in more outside air through all the leaks in the building envelope. Basically a double whammy of energy penalty. Typical number is about 25% penalty.

Like I said earlier, for major reno or new build, air handler or ducting in the attic is always the wrong answer. Somebody is trying to tell you otherwise, they are wasting your dollars both for the install and as well as operating cost down the road. Also ask them what they will charge to go and service that unit in that 140F attic down the road.

@MichaelT said "I have considered adding in radiant heating but I thought if we need to run all the ductwork for AC then we might as well use it for heating and cooling. "

Don't fall into that trap. Typically, in northern states the cooling load is much less than the heating load. If you try to combine everything into one ducted system it will be wrong for at least half the year.

Up your way I'd do steam for heating, since it would be far less prone to freezing damage if the power or fuel supply were interrupted in the winter.

avoid zoning. Straight ducting is hard enough zoning makes it even more difficult.
2stories 2systems. Both Heat pumps.
I prefer oversized HW coils in each for extreme weather with a mod con condensing boiler. As far as the 2nd floor the coil can be installed in the return duct reducing freeze up issues.

From what I see here, your top-floor ceiling has not been removed, so installing attic ductwork will require cutting the register openings through the sheetrock and deciding which way you want the system to gravitate. You can choose a duct design that works better for cooling or a duct design that works better for heating. Once you select one of them, the other will not perform as well.

However, with the newer inverter systems, you have the option of constant operation at lower speeds and capacities when the weather is mild, while ramping up to full speed when conditions are more extreme. This tends to minimize the duct design compromise because the constant airflow helps combat temperature stratification, resulting in more even temperatures throughout the home.

This brings me to my next point. I have often thought about zoning with single-stage and two-stage systems, and they always seemed to me to be little more than a band-aid on the issue. The thermostat would control the change from stage one to stage two regardless of how many zones were actually open or calling. I often thought that someone should invent an out-of-the-box zone control that understood that when only one zone is calling, there is no need for stage two and the higher airflow that comes with it.

After looking at the Arzel system information, I really like the concept. It is almost as if they were reading my mind back in the 1980s and 1990s and actually built the system I had envisioned. If I were still installing systems, I would definitely try this equipment in my own home first just to see how easy it is to install and set up.

The videos seem to support the concept of a single supply trunk and a single return trunk. One system can serve two zones—or more—simply by closing off the first-floor branch runs when the second floor needs cooling, or closing off the second-floor branch runs when all you need is heat on the first floor.

I have installed systems with as many as four zones on a single furnace or air handler and used a duct temperature sensor along with a barometric bypass damper with some success. However, I believe that the combination of today's inverter-driven systems, variable-capacity compressors, and ECM blower motors that can ramp up and down based on inputs from the Arzel panel is truly a game changer.

I wish something like this had been available years ago at what appears to be such an affordable price and with the ease of installation that Arzel seems to offer.I would still look at the price of the two-system high-velocity option and compare it to the price of a variable-speed (or at least two-stage) system with zoning. In other words, compare the cost of two smaller, more expensive systems to one larger system that is capable of staging and equipped with multiple zone dampers. You may find that both approaches cost about the same.

Rest assured that either approach will solve your temperature stratification problems.

Just don't go cheap while the house is in this condition. If you can get basement ducts to the second floor while the walls are open like this, you can have an excellent system with only one set of equipment.

On the other hand, if you decide on the high-velocity system with all the ductwork buried in the attic insulation and an insulated mechanical room in the attic for the air handler, that is also a very good option. Pairing it with a modulating-condensing boiler opens up additional possibilities. The boiler can provide space heating, domestic hot water, snow melting for the walkway, and perhaps even radiant floor heating for the bathroom.

There are many good choices available today. The important thing is to take advantage of the access you have while the house is open and invest in a system that will provide comfort and flexibility for decades to come.