Opinions on adding a window AC to master bedroom with Central Air

[DarkManX]

I moved into a newly rebuilt row house in the city with central air (brand new). I live alone, I sleep in the master bedroom on the top level (third floor not counting basement). My central air is split into two zones, top 2 levels, and bottom 2 (including basement). The top level gets extremely hot from the sun, since I live alone would it make sense to add a window unit to my bedroom? The house is about 1200 sq ft.

 

[Pick2]

Yes a window unit would work , just a small one sized for that room. You could try partially closing the vents downstairs to give more central air to the upper floors. You might have to reverse the procedure for the heat in the winter. If you are not really using the basement much , close them almost all the way off. Put a thermometer on each floor and adjust the vents a little at a time till you get it right. Good luck !

 

[DarkManX]

my "dual zone" system is technically what I believe they call a "split" system? I have a single compressor and unit but they duct work can be regulated for which zone to send air to. So far it seems like the downstairs zone never seems to kick in and only the upstairs thermostat calls for AC. I have two ecobee thermostats so I have been keeping tabs on things.

 

[NutBucket]

Not a terrible idea. Looks are subjective but it should save you some money.

EDIT: Makes sense that the downstairs wouldn't come on given heat rises. In the winter there may be enough heat rising from the first floor that the second floor won't turn on.

 

[yottabit]

This is something I've also considered doing so I'm curious how it works out if you try it. For me there's only a couple of the hottest days of the year where the central AC doesn't do a good enough job upstairs so I've held off.

I've also read that some furnace blowers need to be adjusted for a higher velocity for summer cooling vs winter heating (I think they typically have 3 fan speed settings). That could be something worth looking into

3rd floor is quite a reach though and cold air naturally doesn't want to rise.

I would still check into the HVAC more long term. How is the velocity and temp of the air on the 3rd floor compared to the 1st?

Are the ducts well insulated? Is there actually an air return near your 3rd floor bedroom (if not this will make its job even harder). Although its widely considered a band aid fix you could consider adding a booster fan to your 3rd floor duct.

I'm sure there are some HVAC guys that would come and give consultation for free. Or you can get a cheap digital anemometer to do your own airspeed readings at the ducts

 

[DarkManX]

Just to clarify, I am not complaining about my current systems ability to keep me at a comfortable temperature. This weekend was on the "hot" side but certainly not peak temps and the system did just fine. I am only considering the window unit as a way to conserve energy. I also like to be on the colder side, so I just hate the idea of having to blast the AC for myself, alone.

 

[edcoolio]

Just to clarify, I am not complaining about my current systems ability to keep me at a comfortable temperature. This weekend was on the "hot" side but certainly not peak temps and the system did just fine. I am only considering the window unit as a way to conserve energy. I also like to be on the colder side, so I just hate the idea of having to blast the AC for myself, alone.

You would conserve energy, obviously. Having done this in the past, I can tell you the problem is that it would likely take a couple of years (or more) to make up the cost of the window air conditioner in utility bills.

I ended up having to buy 2. The first one I bought was small, but it said on the package/internet that it would cover the room. It did, but it ended up breaking. The second was "overpowered" (but not super huge) and lasted until I sold the home.

What I found out, after the first one died, is that if you get one that is on the smaller side it will not last! (duh)

Basically, that tiny compressor will end up running longer and turn on/off a lot. That means heat. That means a burnt out compressor. It also means that a larger one will cost you more money.

The tradeoff is hassle. If you get a bigger one for $350, that means you could have bought 2-3 of the smaller ones. Making them disposable and probably worth the gamble. However, I don't like the labor of replacing those things when they die on a very hot summer night, then waiting for central air to cool things back down.

Maybe I should have bought 2 of the small ones and always kept a spare handy...

 

[NutBucket]

Just don't buy a portable one. It won't work nearly as well.

 

[96Firebird]

I have a window AC in my room, the house as central air. I like to sleep with it very cold, so I set the window AC to 67°F and run it at night while I'm sleeping. The thermostat for central air is set for 77°F, 79°F when I'm not home. Seems to be working out just fine for me, my central air also has a hard time cooling the second floor where the bedrooms are.

 

[DarkManX]

I am looking at a 6000 BTU unit, so the up front cost will hopefully be offset much quicker. The bedroom is only about 120~ sq ft, with a descent sized walk in closet, there is a descent sized bathroom but I will attempt to keep that door closed.

 

[Aikouka]

I've been wondering... what are people's thoughts on ductless systems? It seems like a ductless system could solve room imbalances (like the one in this thread), but you don't see them used often if at all on normal homes -- even on small houses.

 

[Mike64]

I am looking at a 6000 BTU unit, so the up front cost will hopefully be offset much quicker. The bedroom is only about 120~ sq ft, with a descent sized walk in closet, there is a descent sized bathroom but I will attempt to keep that door closed.

Given your description, I'd be strongly inclined to go with an 8000 BTU unit. Yes, serious overkill is a Bad Thing where window ACs are concerned, but I don't think just 2K BTUs of extra capacity will be a problem as far as that's concerned, and it'd be better to spend a little more now than wind up replacing the 6K unit the first time there's any sort of heat wave lasting more than a couple of days...

The thing is, those broad-guideline-ratings on the boxes don't factor in things like the room being on the top floor of a house (which gets it from both ends, so to speak), and that's all the more true if any of the room's exterior walls face south or west (or HVAC-gods forbid, both south and west). At the very least, I'd find one of the more sophisticated (using the term loosely) BTU calculators floating around on the web, that factor in things like your climate zone, number of external walls (and/or ceiling), and the direction and extent of their exposure to sunlight rather than relying on those usually-optimistic manufacturer ratings. Another thing to consider is the overnight guest issue - people actually generate more heat than you might think, and a second person in a room with an AC that's just able to manage could tip the scale into the less-than-ideal comfort zone... On the other hand, if you'll be using it more or less only at night, the direct-sun-generated heat won't be an issue once the room has cooled down, or if you'll be running the central air most of the time, then switching over to the window unit only at night.

 

[dphantom]

I've been wondering... what are people's thoughts on ductless systems? It seems like a ductless system could solve room imbalances (like the one in this thread), but you don't see them used often if at all on normal homes -- even on small houses.

We put a ductless system in our log home. It had hot water heat so no duct work nor could any be put in. They worked great. We had 2 zones, main floor and upstairs master suite. The master suite was about 350 sq ft. Very, very quiet and inexpensive on our utility bills. We were able to use them to heat the home too during late fall/early spring. About as cheap as natural gas.

 

[Greenman]

I moved into a newly rebuilt row house in the city with central air (brand new). I live alone, I sleep in the master bedroom on the top level (third floor not counting basement). My central air is split into two zones, top 2 levels, and bottom 2 (including basement). The top level gets extremely hot from the sun, since I live alone would it make sense to add a window unit to my bedroom? The house is about 1200 sq ft.

I'm having trouble picturing a house that's 300 square feet per floor, and 4 floors high.

 

[DarkManX]

its a city row house, 3 floors are finished.... 300-400 sq ft per floor plus unfinished basement.