Where is your thermostat located? What is the condition/amount of your attic insulation?

Wait, are you saying that on a 70 degree outside WITHOUT the furnace or A/C running your upstairs gets to 79?

This post was edited by saltidawg on Sun, Oct 27, 13 at 18:48

Thermostat is in the master bedroom which is just off the landing at the top of the stairs.

Yes, it is not uncommon for me to turn the a/c on to cool the upstairs when it is 78-79 degrees upstairs and only 70-72 outside.

Got attic insulation?

"My upstairs bedrooms are more like attic bedrooms than a regular bedroom. "

It sounds like you have a finished attic which are being used as bedrooms. I assume the bedroom ceiling is the roof deck. Is this correct?

Insulation in attic and good windows...

Adequate return(s)

Correctly sized and designed ductwork for BTUs to second floor...

IMO

It's the result of heat riseing from your indoor hot tub. The laundry dryer venting into space between floor and downstairs ceiling is also contributing to the problem. They overlooked radiant barrier on roof and South facing wall during construction. The attic space has insufficent ventilation and insulation. There is a natural hot spring running beneath the Southeast corner of the foundation causing thermal heat to enter the living space.
That information will save contractors you hire to fix it a lot of time that would ordinarly be spent researching and testing to find out what is wrong.
If you included a few facts about the house,someone would helped you sooner instaed of guessing at answers.

is this a problem you are having NOW? this week? its 70 outside and you think 79F in your bedroom is too hot? 79F in my bedroom around NOV 1 with NO heat on would be awesome.

"79F in my bedroom around NOV 1 with NO heat on would be awesome."

lol

and I was wondering how klem1 knew all that stuff!!

my guess as to what OP is saying is
that there is a lot of heat gain in warm temps
and probably cold gain in cold temps...from
the attic space on the other side of the walls
of this second floor space.

if that is the case..then here is my advice.
in addition to walls shared with attic space needing
insulation, they also need to be air sealed.
see page 5 of pdf linked.
http://www.southface.org/default-interior/Documents/airsealingkeypoints.pdf

using a sheet material like foam sheathing
installed to attic side of walls, with seams taped
& foam sheathing caulked to top & bottom
plates of walls will go a long way to making
these rooms easier to condition.
continuing the foam sheathing between floor
joists to ceiling of first floor...(as in pdf) and
caulking to air seal will eliminate air
movement between floors.

we have these issues here in my hot humid
climate often. instead of more tons of a/c
either sealing as described by southface inst.
or foam insulating the roofline is usually
the solution.

these rooms that share walls with attic space
are surrounded by extreme attic temps.
sides from walls shared with attic, at ceilings
and at floors. these rooms are surrounded
on all six sides by attic that can reach 130 degrees
in the summer & lows of winter.
insulation isn't enough in the walls, ceiling
or between floors.
air movement has to be minimized or these
areas will be difficult and expensive to condition.

providing more comprehensive info would
ensure better replies.

best of luck.

Even when it's only 70 degrees outside it will get up to about 79 degrees upstairs and I'll have to turn the air conditioner on.

Open a window upstairs and one downstairs and let the hot air out.

1.) Insulate the attic.
2.) They make reflective or white roofing material...cover your roof with it.
3.) Plant deciduous trees to the south of your house to shade your roof.
4.) Put in a Sky Light you can open...heat rises. (WARNING: This one could create problems with leaks if not done properly.
5.) Make sure there is proper ventilation in your attic. (Soffit vents at a minimum...)