Two-Story Homes in Phoenix (sale, home builders, construction)

[sierraAZ]

Originally Posted by Bungle

My two story home has one A/C unit and the upstairs master bedroom is the coldest place in the house.

Really? That's bizarre.

I moved to my house recently, so I haven't spent a winter there yet. The floor downstairs is all tile, so it's considerably colder there. I was thinking that if I am to keep the first floor warm enough in the winter, the 2nd floor may get too hot with the heat going up.

[LBear]

A LOT will depend on the HVAC setup. How they run the ducting, how efficient the A/C units are, how insulated the home is, etc.

[mortimer]

LBear asked:

> How bad is it to cool off the second floor with 2-story homes in Phoenix?

As others have said, it depends on ductwork, insulation, etc.

However, during a period where I was home all day and we were running time-of-use billing, I used to set the thermostat to 74 upstairs and 72 downstairs until the peak rates kicked on then it went to 86 up and 84 down.

I found that the 'natural' difference between the upper and lower story was just over 2 degrees. As the temperature would creep up from 74 at 1 pm to 86 later on (usually about 6-7 pm), the difference was almost always 2 degrees.

If you have a good unit, the house will cool down in just a few minutes which is what happened after 8 pm when we went back on the cheap rate.

markas214 said:

> I was surprised that a second story didn't add much to the bill.

It's almost all square footage. Theoretically, no matter what people like to say, a two-story house is cheaper to cool or heat - given the same square footage. It has less surface area exposed to the ambient are. It's just physics.

My 2600 sq ft two-story had only about 1300 sq ft of roof baking in the sun.

sierraAZ then asked:

> I have one unit, but two thermostats (on each floor). ... any difference
> as far as electricity usage goes if just one of them is on or not?

Thermostats aren't really 'on' or 'off' rather they trigger the a/c to turn on or off. If they both are telling the a/c to run, then it (they system) will consume the same amount of electric power as if only one was telling the a/c to run. (They 'tell' the a/c to run when the temperature goes higher than the setting.)

If, like others do, you set the upper floor to a warmer temperature when you are not up there, you'll save money on electricity. The reason is that the upstairs thermostat won't turn the a/c on by 'telling' it to run.

The bottom line is that yes, having two thermostats will cost you more money if you don't actively manage them. If the upstairs unit (which will tend to be in a warmer place) keeps going on when you don't need the cooling downstairs, then you will just use more electricity and tend to be too cold downstairs.

If it were me, I'd keep them set two degrees apart. If you find that the setting downstairs is too hot, then you have to manually move the one downstairs to a lower setting *and* set the upstairs the same amount lower to maintain the 2 degree difference.

If no one is upstairs, having them set three degrees apart will be the same as disabling the upstairs thermostat.

[JoePAz]

I do think it takes more to cool a two story than a 1 story for equal square footage. However no two homes are equal and alot has to do with homes construction, AC ducting, floorplan, Exposue relative to floorplan (ie which rooms you occupy at certain times of the day) and exterior landscaping (trees) and neigboring homes (that neighbor's two story can really shade a 1 stroy next to it).

So rarely are things equal and as such it is not that easy to determine. In the end if you need it to be 75F inside the middle of summer it will be more expensive than if you can sustain 81 or 82.

[mortimer]

JoePAz stated:

> ... it takes more to cool a two story than a 1 story for equal square footage.

All things being equal, that's incorrect.

A two story 'seems' less comfortable because of the tendency for heat to rise up the stairs and make the upstairs warmer, but the total energy loss through the walls and roof is less.

Think of what it would take to cool a sphere vs a long tube of equal volume.

Ultimately, you pay for the amount of heat that comes through the outside surface area into the house.

This is not my opinion. It's just physics.

> ... no two homes are equal ... construction, AC ducting, floorplan, Exposue ... landscaping ...

That's totally correct and has far far more to do with your costs than number of stories.

> In the end if you need it to be 75F inside ... more expensive than ... 82.

The most important thing: personal behavior.

[LBear]

Originally Posted by mortimer

It's almost all square footage. Theoretically, no matter what people like to say, a two-story house is cheaper to cool or heat - given the same square footage. It has less surface area exposed to the ambient are. It's just physics.

You are correct!

Those who state a 1-story of equal square footage vs. a 2-story of equal sq. footage, that the 1-story costs less to heat/cool are WRONG. It stems from bad information that is circulated.

Per the National Association of Builders:

For a given interior floor space, a square-shaped house minimizes the total outside wall area. Less outside wall area means less energy loss. A two-story house is better than a single-story one because it reduces the amount of roof area for a given floor space area.

CENTEX builders use 2x4 construction in the outer walls but get a R-19 for the walls. The ceiling/attics get a R-38 rating. To cool a 3,200 sq.ft, 2-story home costs $150.00 per month, on avg. They run 2 A/C units, one for each zone/floor.

[sierraAZ]

Originally Posted by mortimer

sierraAZ then asked:

> I have one unit, but two thermostats (on each floor). ... any difference
> as far as electricity usage goes if just one of them is on or not?

Thermostats aren't really 'on' or 'off' rather they trigger the a/c to turn on or off.

C'mon now... technicalities... can't you tell I'm technically challenged?!

The bottom line is that yes, having two thermostats will cost you more money if you don't actively manage them. If the upstairs unit (which will tend to be in a warmer place) keeps going on when you don't need the cooling downstairs, then you will just use more electricity and tend to be too cold downstairs.

I manage them very actively! Any HVAC guy will go nuts if he knows how I manage them. See, the thing is that let's say it's 76 downstairs and 80 upstairs naturally. I like it at 80. If I am to achieve 80 downstairs, with the hot air moving upstairs, it'll probably get warmer than 80 upstairs. If I do what the instructions say, that'll kick off the AC upstairs... I don't really wanna run heat downstairs and AC upstairs... Come to think of it, is it even possible...? Excuse my ignorance, but I've only lived in a 1.5-story house with one thermostat before.

If it were me, I'd keep them set two degrees apart. If you find that the setting downstairs is too hot, then you have to manually move the one downstairs to a lower setting *and* set the upstairs the same amount lower to maintain the 2 degree difference.

If no one is upstairs, having them set three degrees apart will be the same as disabling the upstairs thermostat.

Yeah, I've been trying to read the manual ...certainly did the first night when I woke up frozen thanks to the preset settings! I tried some option in it that was making the heat and the AC coming on alternatively almost every few minutes, so I got rid of it. Now I managed to make the thermostats work simply and I'm adjusting them manually and as often as needed, as I like to open windows as well. I'm just afraid of messing the system up, since it's a pretty expensive toy to play with. Can you tell I'm not into programmable crappola?!

Thank you very much for your response. I'll read it again tomorrow. It's Fri night and too late to absorb much hated tech info. Just asked out of curiosity. I'd always rather pay more than deal with annoying gadgets.

[mortimer]

sierraAZ wondering what that button on the side of their oven does:

> I manage them very actively! ....

... as you should ...

> ... say it's 76 downstairs and 80 upstairs naturally.

Are you sure about that? I'm not saying it's not possible, it just sounds like a large difference.

> I don't really wanna run heat downstairs and AC upstairs...
> Come to think of it, is it even possible...?

Probably not unless you have two systems. Heat pumps have to be changed from 'heat' mode to 'cool' mode, so if the temperature goes too low in the cooling season, the pump just doesn't come on.

> ... make the thermostats work simply and I'm adjusting them manually

As long as it works for you, that's all that matters. Also; think of the good exercise you are getting running up and down the stairs.

> Can you tell I'm not into programmable crappola?!

Um. Yeah. Using two programmable thermostats with only one unit doesn't sound workable to me.

> I'd always rather pay more than deal with annoying gadgets ...

One thing you could do is block off part of the vents in all the downstairs vents. You can just stuff some old rags in there to reduce the flow by 25-30% in each vent which would have the effect of forcing more air into the upstairs duct work. It might require some trial-and-error on your part.

Alternatively.1: you could just sleep downstairs at night and let the upstairs get hot.

Alternatively.2: you could get a window a/c and just use it to sleep at night in your upstairs bedroom.

I'd pick alternative.1 first and .2 second.

Basically, a two story house with only one pump is a hard beast to tame.

[Monster Daddy]

SRP mailed out a brochure confirming it is more expensive (on average) to cool 1 story homes than 2 story homes. But...

During the hottest parts of the summer, my southward facing upper story loft won't cool down no matter how much I run my A/C! Part of it is layout and circulation but consider that with a 1 story you at least have an option of placing shade trees to block the sun.

Getting ready to move into a basement home and I really hope it will help cut down on bills AND be more comfortable.

[wsugrad03]

All things being equal, it takes much more energy to cool a 2 story home than a 1 story home. Heat rises, cold air falls. It's as simple as that. You're probably seeing more 2 story homes because developers can cram more homes on smaller lots by having 2 stories.

The important thing with being energy efficient is to start with solid construction (i.e. 2x6 construction rather than cheap 2x4). You need at least R-19 insulation in the walls and at least R-30 in the ceiling. I'm not sure of the exact numbers, but the more the better. Of course, there's other things you can do to reduce the power bill such as installing solar powered attic fans.