Half my house is freezing the other half is hot

[DaveC426913]

TL;DR Summary

What are my options for balancing the A/C in my 3-level backsplit house?

Been in my new house for a month now.

• It's an n-level backsplit (value of n depends on whom you ask)
• It has central air heating/AC.
• There are two families: my wife and I are in the lower flat (red) and our boy and his fam are in the upper flat (blue).
• Upon closing we had a wall (with door) put in between their flat and ours, (magenta) which was heretofore open.

• It came with a NEST controller (green) located in their dining room.
• I do not know if there are any (other?) thermostats in the house.

The problem:
It is too warm up on the top floor, it is optimal on their main floor.
It is too cool on our main floor and it is (naturally) cold in the basement.
Now, that a bit tricky, since we sleep on our main floor, and it's got to be cool.

I don't really know how these Nest things work. You can buy thermostats as separate units and distribute them about the house.
I don't know if the controller itself also acts as a thermostat. So I don't know if there should be at least one thermostat somewhere in the house. We have not found any. It would not surprise me if the previous owners tossed them in a box while packing. Do I need to have at least one? Should I get another?

My boy is talking about a booster (which has nothing to do with the Nest technology). It sounds like it's just a fan to help the air reach farther rooms.Help?

 

[Lnewqban]

Location of air handler unit(s)?
It seems that the magenta new wall has blocked the free return of the suplied air back to the air handler unit.

 

[DaveE]

I'm not sure of your HVAC setup, but I doubt it's the thermostat that's the problem. Unless you have individual control of different HVAC circuits, one thermostat can't do it. Even if the controller(s) could say heat the lower level but not the upper level, or vice-versa, could your HVAC system do that? All one thermostat can do is set a good average temperature.

Normally there is some relatively fixed ratio of flow between different rooms controlled by dampers (valves) or register vents. That may need to be addressed. Why not hire an HVAC guy to come in and make some suggestions or adjustments?

 

[DaveC426913]

Location of air handler unit(s)?

What's an air handler unit? (I've never lived in a house with central air, so the only central thing Ive ever known is a furnace)

There's the big contraption with the air ducts in the basement, and there's an AC blower thingy outside.

 

[DaveE]

What's an air handler unit? (I've never lived in a house with central air, so the only central thing Ive ever known is a furnace)

There's the big contraption with the air ducts in the basement, and there's an AC blower thingy outside.

It's like your old furnace with a big fan, but it can probably also cool the air, so they gave it a newer name. Air comes in, is heated, cooled, dehumidified, filtered, etc., and is then blown out to the house with a fan.

https://www.trmillerheatingandcooling.com/a-comprehensive-guide-to-air-handlers/

 

[Lnewqban]

What's an air handler unit? (I've never lived in a house with central air, so the only central thing Ive ever known is a furnace)

There's the big contraption with the air ducts in the basement, and there's an AC blower thingy outside.

Your question suggests that you will need assistance from an AC company in evaluating and remediating the air distribution problem that you have.

They will probably need to install a transfer duct that solves the interference to the path of air that the new wall has created (especially if the top end of the stairs to the basement is on your side of the house).

They can also do a test and balance of all the diffusers and grilles in the house in order to achieve a better air distribution via the central duct system.

If all that fails, they can install duct automatic dampers controlled by thermostats located at the four main zones and/or duct booster fans where needed.

Please, see:
https://www.thisoldhouse.com/heatin...s-before-you-install-central-air-conditioning

 

[Rive]

you will need assistance from an AC company in evaluating and remediating the air distribution problem that you have.

It may help a lot if you check the comfortable temperatures for every area first, since it may differ depending on external circumstances (with different wording: you may feel the same air temperature hot or cold depending on external circumstances).

 

[russ_watters]

Can you mark on the drawing the location of all supply and return grilles? More pointedly; is there one return in each room or just a single big one in the basement by the big contraption with the air ducts air handler?

This is no doubt a balancing (where the air is going) problem that may have been caused/exacerbated by putting in the wall.

You may just need to close supply grilles where it is cold. ...and may also need a transfer duct/grille.

You have one ac unit so one thermostat. That isn't a problem.

What's an air handler unit? (I've never lived in a house with central air, so the only central thing Ive ever known is a furnace)

Central air and central heating are basically the same: a furnace is also an air handling unit.

 

[Tom.G]

Furnace: A big sheet metal box. When the house gets cold the box starts a fire and blows the hot air into the house.

Air Conditioner: A big sheet metal box. When the house gets hot the box gets cold by moving its heat outdoors (just like your refrigerator does). The cold box then blows the cold air into the house.

Both fall under the umbrella name of an "Air Handler System."

For efficency, each of them accepts already heated (cooled) air from the house, heats or cools it again, then sends that air back into the house.

It sounds like your new wall may have blocked the heated (cooled) air from returning to those sheet metal boxes.

The "Nest" is just a thermostat with a tiny 'brain' added, and, like anything tiny, can't really do much beyond telling the heater or cooler to turn On and Off.

Hope this helps!

Cheers,
Tom

 

[sophiecentaur]

The "Nest" is just a thermostat with a tiny 'brain' added, and, like anything tiny, can't really do much beyond telling the heater or cooler to turn On and Off.

The Nest and also Hive do more than just provide a thermostat. Firstly, they can operate a number of different independent zones within the house. Secondly, they will give you a 'Ready By' facility which will establish a zone temperature by turning the boiler on at a time so that your room is the required temperature 'by' your chosen time. My Hive also gives you a graph or temperatures over the day and tells you when the boiler was actually switched on.

 

[russ_watters]

So it's an above average residential grade thermostat...

I have a Honeywell Residio T9, with all of the above as well. Multi-zone sensing without independent control can be problematic, but for me as the only one in the house it enables me to select (or motion sense) which room I'm in for control. For @DaveC426913 multi-zone sensing would be informative and may help with balancing and allow averaging the readings. You can buy add-on remote sensors for the Nest.

 

[DaveC426913]

The Nest and also Hive do more than just provide a thermostat. Firstly, they can operate a number of different independent zones within the house.

For @DaveC426913 multi-zone sensing would be informative and may help with balancing and allow averaging the readings. You can buy add-on remote sensors for the Nest.

Yeah but only if your house is set up with independent zones and ducting actuators to service them.

Secondly, they will give you a 'Ready By' facility which will establish a zone temperature by turning the boiler on at a time so that your room is the required temperature 'by' your chosen time. My Hive also gives you a graph or temperatures over the day and tells you when the boiler was actually switched on.

I see this as stuff for enthusiasts. I don't really want to turn my household climate needs into a hobby.

 

[russ_watters]

Yeah but only if your house is set up with independent zones and ducting actuators to service them.

Not exactly. You can pick which sensor gets "satisfied" or average them. It also provides information on where you need to direct the airflow rather than just relying on feel.

 

[StandardsGuy]

TL;DR Summary: What are my options for balancing the A/C in my 3-level backsplit house?

Been in my new house for a month now.

• It's an n-level backsplit (value of n depends on whom you ask)
• It has central air heating/AC.
• There are two families: my wife and I are in the lower flat (red) and our boy and his fam are in the upper flat (blue).
• Upon closing we had a wall (with door) put in between their flat and ours, (magenta) which was heretofore open.

I've heard of cases where the builder didn't put in return ducts where they should have. You need a thermostat in the upper floors that determines when the AC unit runs, and you need one in the lower floors to determine when/if to open a duct to the lower floors. In the winter it will be opposite. In the mean time go to the thermostat and set it so the fan goes full time. The booster may be necessary. The lowest floor will always be too cold unless you have heat available. Is it noticeably different if you leave the door open? I would guess not. I have a 2-level house with a door at the bottom of the stairs. It doesn't make a lot of difference. I use an electric heater in the room I am in often downstairs.

 

[Bystander]

I've heard of cases where the builder didn't put in return ducts where they should have

"Surely you jest...and the inspectors didn't catch it?" Goes on all the time.

 

[russ_watters]

I'm the 2nd owner of my house; about 3 years old when I bought it. Soon after, I went into the attic for a look-around, and the main return duct for upstairs was just sitting there open to the attic next to the distribution header it was supposed to be connected to. Prior owner spent 2 summers with it like that.

 

[sophiecentaur]

Yeah but only if your house is set up with independent zones and ducting actuators to service them.

I only have experience of wet CH systems. Warm Air CH was popular for a short while in the UK during the 60s and not since (afair). Water valves are very easy for controlling zones and, of course, under-floor heating mixes well. But local rules apply for so many aspects of domestic engineering.
PF has given me another surprise with all this talk of air ducts and the like. Where are the advantages with air, especially when the living volume of new homes is reducing on a yearly basis?

 

[DaveE]

Where are the advantages with air

No boiler is one big advantage. The basic engineering can be really simple. A fire, a fan, and a bunch of tubes.

 

[russ_watters]

PF has given me another surprise with all this talk of air ducts and the like. Where are the advantages with air, especially when the living volume of new homes is reducing on a yearly basis?

Heating and cooling in one piece of equipment.

Prior to the advent of air conditioning it was much more common to see hydronic heating solutions. But now that almost everyone has air conditioning it s much more common to see central air based systems. In the UK are fewer people have air conditioning and those who do run it for much less than is run in the us. So nobody cares about the crappiness of window air conditioners.

I work with a uk-based client and their engineers don't get how much hotter and colder it is in the US than in the UK. And sorry Dave, Toronto is essentially northeastern US.

Other side of the coin of course is that until I looked up the stats after that bad heat wave last year I had no idea how few people have air conditioning in the uk.

Also I don't know about the UK or Canada but in the US house sizes continue to get larger.

 

[DaveE]

especially when the living volume of new homes is reducing on a yearly basis

Not in California. The choice now days is big homes or a tent under the freeway.

 

[russ_watters]

Not in California. The choice now days is big homes or a tent under the freeway.

2.5x larger in 75yrs in the US:

https://www.visualcapitalist.com/cp/median-home-size-every-american-state-2022/#:~:text=Over the last century, home,drastically depending on the location.

 

[sophiecentaur]

Not in California. The choice now days is big homes or a tent under the freeway.

2.5x larger in 75yrs in the US:

https://www.visualcapitalist.com/cp/median-home-size-every-american-state-2022/#:~:text=Over the last century, home,drastically depending on the location.

Wow. A different world in UK. Compact living has been the norm for people moving into recently built homes. A recent law has attempted to change building regs to increase the area per person but this may be a two edged sword because it means new builds may become too expensive. This will be more so as the mortgage interest increases have resulted in repayments being beyond the means of so many people.
But the areas of rooms in the majority of UK decreased steadily since WW2. It's often a selling point for more elderly homes.
But the same Physics applies on both sides of the Atlantic. [Edit: are there no commercial pressures to limit house prices?]

 

[DaveE]

are there no commercial pressures to limit house prices?

In the Bay Area and LA it's all land cost. If you can afford the land, you'll spend a bit extra to build a big house. Much of this is the decline of urban housing in favor of suburbia. Developers make more money building big houses on expensive land. Suburban infrastructure doesn't support small living very well.

There are a couple of great divides at work polarizing the market: Affluent white collar types vs. Declining blue collar families; and desirable growing economic areas vs. declining areas. Houses are cheap in Detroit, but everyone still wants to move to LA where they aren't cheap because of employment.

This drives much of the political polarization here. Which I can't talk about without getting in trouble, LOL.

 

[russ_watters]

Yeah, in the US/CA we have a lot of space so we spread out, and big houses seem to be part of that. This says for current new houses anyway the US and CA are similar and more than double the size of those in the UK:
https://shrinkthatfootprint.com/how-big-is-a-house/

Edit: are there no commercial pressures to limit house prices?

Not much apparently. As @DaveE says, a lot of people move to California and buy big/expensive houses and then complain about the price and/or commute but they still do it.

 

[DaveC426913]

the living volume of new homes is reducing on a yearly basis?

Dunno. My home is 3400 square feet. (That's actual, not Real Estateeze)

 

[russ_watters]

Dunno. My home is 3400 square feet. (That's actual, not Real Estateeze)

Including garage? That's really big to only have one HVAC system. Do you happen to know the capacity? It's probably in the model number on the sticker on the outdoor unit (condensing unit).

 

[DaveC426913]

Including garage? That's really big to only have one HVAC system. Do you happen to know the capacity? It's probably in the model number on the sticker on the outdoor unit (condensing unit).

Not including garage. But it is including finished basement (which might not have been in the specs when the system went in).

I'll check the capacity.

 

[sophiecentaur]

No boiler is one big advantage. The basic engineering can be really simple. A fire, a fan, and a bunch of tubes.

So what do people do for hot water? Plumbing effort must be a lot less than installing ducts - especially if you suddenly need to re-route.
The dry / wet system arguments put me in mind of the endless 120/240V, ring main, two phase mis-understandings we get into so often.

Dunno. My home is 3400 square feet. (That's actual, not Real Estateeze)

but not in UK?
Wander around a 'show home' on a new development in UK and note the special small furniture that's placed so you don't notice the matchbox sizes of some rooms. UK is in a special situation with regard to land availability and many 'new world' countries don't have that problem.
Otoh, look at the millions of tiny apartments in large cities all over the world. That started off in the Soviet style blocks that dear old Joe Stalin put up.

 

[DaveC426913]

UK is in a special situation with regard to land availability...

Are they?
Is it that there isn't enough land, or is it - like here in Canada - that the only land people want is in cities?
Because, for a tiny nation, UK seems remarkably rife with green space.

 

[russ_watters]

So what do people do for hot water?

A stand alone water heater. What do people do in the UK for domestic hot water? The systems have to be separate, but could be linked via heat exchanger. That's common in commercial or apartment buildings here.

Plumbing effort must be a lot less than installing ducts - especially if you suddenly need to re-route.

Again, you seem to not be considering air conditioning. This logic doesn't hold when you have both heating and air conditioning.

The dry / wet system arguments put me in mind of the endless 120/240V, ring main, two phase mis-understandings we get into so often.

I don't understand what you mean.

 

[DaveC426913]

Do you happen to know the capacity? It's probably in the model number on the sticker on the outdoor unit (condensing unit).

Can you deduce anything from this?

 

[russ_watters]

Can you deduce anything from this?

030 in the model number means 30,000 BTU or 2.5 Tons. It's about half the capacity I expected. By comparison I'm in Philadelphia and my 1,500 sq ft townhouse has a 2.5 Ton unit.

Are there areas of the house with no supply vents? You only have one of those outdoor big fan cube thingies condensing units, right?

 

[DaveC426913]

030 in the model number means 30,000 BTU or 2.5 Tons. It's about half the capacity I expected. By comparison I'm in Philadelphia and my 1,500 sq ft townhouse has a 2.5 Ton unit.

I'm about twice as far north?

Are there areas of the house with no supply vents?

I don't think so. Would a basement normally have vents?

You only have one of those outdoor big fan cube thingies condensing units, right?

Yes.

 

[russ_watters]

I'm about twice as far north?

Twice as far as what? You're about 220 mi north of me. Anyway I checked design weather data and your 0.4% design day (it is hotter 0.4% of the time) is 89F whereas mine is 91F. Not that far apart.

For the record, London: 83F, 700 mi north of Philly.

I don't think so. Would a basement normally have vents?

Finished basements sometimes but not always.

Anyway, if it is overall cool enough so be it.

 

[DaveC426913]

Twice as far as what?

Play on words (and, I guess, numbers).