Air Circulator To Help House AC?

[jyl]

My house is three levels (ground 1000 sf, second 1000 sf, finished attic 500 sf) with a full basement (1000 sf). It has a central AC/heat system, which makes the basement chilly, the ground floor comfortable, does little on the second floor, and the attic is roasting on hot days. The ducts to the second floor and attic just aren’t big enough, and there’s no room for larger ducts. The basement is chilly because of all the exposed AC ducts and because it’s the basement.

I’d like to solve this problem.

One way would be to install mini-splits, but I’d need a bunch of them - four bedrooms on the second floor, people aren’t going to want to sleep with their bedroom doors open, plus attic.

So I thought of something. Suppose I run a 10x10 duct from the basement to the attic, on the outside of the house, with a 500 cfm inline fan, to move cold air from basement to attic. Long duct run so maybe I only get 250 cfm. In 40 minutes it’ll move 10,000 cf which is the volume of the basement. The cold air will sink from attic to second floor to ground floor to basement. I could put it on a timer. In the winter, I could reverse the flow.

What do you all think?

[cstreit]

The idea makes sense. You'd need to insulate it of course.

...so you have returns?

Maybe block off the ground floor returns and make sure the upper ones are open.

[jyl]

Errrr . . . returns . . . not so much.

I’ll describe the HVAC system.

The house is a 1911 “American Four-Square”, one of the most common types of old house here. https://www.oregonlive.com/hg/2016/09/four-square_portland_houses_hu.html

The layout is typical: ground floor has foyer, living, dining, kitchen, bathroom. Second floor has four bedrooms, bathroom. Attic is one room.

Like an old car, the house didn’t come “from the factory” with AC. It was heated with fireplaces; I don’t know if there was originally any other heat source. In the late 1990s, it was retrofitted with central heat/air. The furnace/AC is in the basement. Each room on the ground floor has a roughly 12” x 12” supply vent in the floor, there is a large return in the living room floor. Ducting runs to the second floor through a vertical duct right at the center of the house, boxed into the wall between kitchen and dining room. Each room on the second floor has a roughly 6” x 12” supply vent in the floor, and no return. The attic has a roughly 6” x 12” supply vent in the floor, and a similarly sized return in one of the knee walls, that goes where I don’t know - there are not access doors in those knee walls.

So I am reading more about house AC, and starting to get the impression that since the bedrooms have no air returns, the central AC just can’t work well in those rooms if people sleep with their doors closed, as people tend to do. (I’d thought the problem was just the smaller supply vents - which I still think are inadequate, since the AC doesn’t do much in the bedrooms even with all doors open.) I am also starting to realize that my air circulator idea will only bring cold basement air into one part of the second floor, which doesn’t solve the problem of cooling the bedrooms when their doors are closed.

Hmm. I could fit door returns, but they wouldn’t look right on these old solid wood doors.

Maybe I shouldn’t be so quick to write off mini-splits. If I use units with two wall units, I can do all the bedrooms with two such units, putting cold air directly into the bedrooms with no need for returns.

[908/930]

A couple of mini splits sounds like a good plan. If you were trying to get the existing system to work, getting the hot air from upstairs using a blower down to the AC unit in the basement will help lots, not sure about running the duct outside though. Here is where returns located high in the room work well.

[dad911]

You only need 1, unless you want more zones. Ducted minisplit in an upstairs attic space or closet, and branch off ducts to the bedrooms.



I did 2 of these in a vacation house (1 each level) as the ductwork was nasty and the old air handlers took up a whole closet on each floor.

[jyl]

Originally Posted by dad911

You only need 1, unless you want more zones. Ducted minisplit in an upstairs attic space or closet, and branch off ducts to the bedrooms.



I did 2 of these in a vacation house (1 each level) as the ductwork was nasty and the old air handlers took up a whole closet on each floor.

I’d still have the problem of no returns in the bedrooms, though?

[A930Rocket]

Somehow, you need to add returns on the second floor and attic. Heat rises and the upper rooms get hotter.

Is there anyway to add a chase from the upper levels to the basement, where the air handler is? Located in a closet or corner, as straight as possible?

Having the ductwork with electronic dampers will help direct airflow as needed as well. Instead of sending it to the basement, he goes to the rooms/floors needed.

[cstreit]

You know if its really just for bedrooms/sleeping - why not just invest in some of those portable AC units for the hot months.

I would imagine if you could cut down on use of central AC trying to cool it - it might not cost you more. Can you vent the attic space/room better? Putting a power vent in our attic lowered the ceiling temps upstairs for us by about 10 degrees.

[dad911]

Originally Posted by jyl

I’d still have the problem of no returns in the bedrooms, though?

You would be putting the AC where you need it, and at least pulling return air from the same level. 3500 sf 4 levels is too much for 1 air handler 1 zone. Even with ducts and zone controllers it would be pulling the cooler air from the lower levels first. I suspect with the older conversion it is also undersized.

[jyl]

Originally Posted by cstreit

You know if its really just for bedrooms/sleeping - why not just invest in some of those portable AC units for the hot months.

I would imagine if you could cut down on use of central AC trying to cool it - it might not cost you more. Can you vent the attic space/room better? Putting a power vent in our attic lowered the ceiling temps upstairs for us by about 10 degrees.

That’s possible. I have a Whynter portable AC (14K BTU?) in my office and in the attic. It works okay in the office, borderline in the attic when it’s >95F outside. They cost about $500.

If I could DIY a minisplit, it would be say 3x the price. Would do heat as well as cool. Doesn’t take up floor space. Does take up some outdoor space. Hmmm.

[jyl]

Originally Posted by A930Rocket

Somehow, you need to add returns on the second floor and attic. Heat rises and the upper rooms get hotter.

Is there anyway to add a chase from the upper levels to the basement, where the air handler is? Located in a closet or corner, as straight as possible?

Having the ductwork with electronic dampers will help direct airflow as needed as well. Instead of sending it to the basement, he goes to the rooms/floors needed.

Unfortunately, the way the house is built, there isn’t any way to add returns internal to the house, without some significant work - tearing out 100 year old built-ins, building new walls, etc. Four squares are very tightly arranged.

[jyl]

So, tell me about DIY’ing a minisplit.

I can do electrical, drill holes through walls, mount stuff to walls, etc.

[jyl]

Just for fun, I asked Bard (Google’s AI)

“do I need a return in a room with a mini-split?”

and it replied

“No, you do not need a return in a room with a mini-split. Mini-splits work by drawing air from the room, cooling or heating it, and then returning it to the room. The air is not exhausted to the outside, so there is no need for a return. However, if you want to improve the air quality in the room, you can install an air purifier or humidifier.

Here are some of the benefits of not having a return in a room with a mini-split:

It saves space. A return takes up valuable space in a room. Without a return, you can use the space for other things, such as furniture or storage.
It is easier to install. A return requires more installation work than a mini-split without a return. This can make the installation more expensive.
It is more efficient. A mini-split without a return is more efficient than a mini-split with a return. This is because the air is not exhausted to the outside, so the mini-split does not have to work as hard to cool or heat the room.
If you are considering installing a mini-split, you should weigh the pros and cons of having a return. If you do not need a return, you can save money and space by installing a mini-split without a return.“

How do you think Bard did?

[billybek]

Split systems with multiple evaporators and variable refrigerant flow are available.
Link to a Daikin example.
https://daikincomfort.com/products/heating-cooling/multi-zone
A few different indoor coil options.
Most manufacturers will offer something similar.

[Baz]

Originally Posted by jyl

So, tell me about DIY’ing a minisplit.

I can do electrical, drill holes through walls, mount stuff to walls, etc.

Previous threads on here are loaded with info!

https://forums.pelicanparts.com/off-topic-discussions/1122946-window-air-conditioner-mini-split-my-garage.html

https://forums.pelicanparts.com/off-topic-discussions/1125146-mini-split-ac.html

https://forums.pelicanparts.com/off-topic-discussions/1038987-split-ductless-ac-unit-bedroom.html

https://forums.pelicanparts.com/off-topic-discussions/843546-how-well-does-mini-split-ac-heat-hold-up-garage.html

https://forums.pelicanparts.com/off-topic-discussions/1028323-replace-mini-split-c-fix.html

https://forums.pelicanparts.com/off-topic-discussions/872147-experience-mini-split-ac.html

And there's a WHOLE LOT more threads dealing with cooling and AC in addition to just the ones above that are specific to Mini-splits.

Just do a search like I did and you'll find them:

https://forums.pelicanparts.com/search.php?searchid=25068047

[wdfifteen]

Do you want cool bedrooms or cool beds?
If you just want to sleep in a cool bed consider Ooler bed coolers.

https://sleep.me/product/ooler-sleep-system?variant=41176366350519&gclid=CjwKCAjwo7iiBhAEEiwAsIxQETgN9FOo3slA0z1brhrW EOSgzlUum96fclvEOZ9Q0oqlGGQOIqw73xoC8bsQAvD_BwE&gclsrc=aw.ds

We were pumping our bedroom down to the 65 degrees my wife needs to sleep comfortably every night. Cooling 6000 square feet every summer night was costing $$$. We considered a mini split for the bedroom so we could cool only that room, but someone here mentioned the bed cooler. It cost $600 and it is perfect for us. We can both sleep comfortably and the AC isn't running constantly. It probably saved us the purchase price in electricity the first summer.

[A930Rocket]

That’s interesting WD. How does the device cool the water down? Is the device like a mini refrigerator?

Reminds me of a DonJoy for cooling therapeutic use in joints. I have adapted one to work with a cool shirt in my track car and use ice and water.

[wdfifteen]

^
I think it has a thermoelectric pad in it. It is too quiet to have a compressor. It sounds like it only has a fan running. It can heat the water or cool it, which a thermoelectric pad is capable of.

[A930Rocket]

Interesting. I’ve never heard of that.

I like a cold room, but I sleep with only two blankets. The initial outlay is high, but in the long run, using less AC would pencil out.

Sorry for hijacking the thread, JYL

[jyl]

Originally Posted by A930Rocket

Interesting. I’ve never heard of that.

I like a cold room, but I sleep with only two blankets. The initial outlay is high, but in the long run, using less AC would pencil out.

Sorry for hijacking the thread, JYL

Not a hijack. That’s a very interesting option!