Two options - one, separate it from your home with new , quality french doors and sidelights - ideally in wood for thermal reasons. In summer, open the windows there and shut the doors between - let it be warm during the day but not drag your house down.

Second, replace your air conditioning with a larger unit rated for your expanded square footage. If the sunroom is a metal sort of addition, the first solution is likely a better solution.

We had the same problem. East facing sunroom in Utah. On sunny days we would hit 100 degrees with the AC on all day.

We tinted the windows, that got us 5 or so degrees but was quite expensive.

We then added an exhaust fan Panasonic whisperquiet that moves >400 cfm. We put the fan on a swamp cooler thermostat so it only turns on when needed. That was much less expensive but added a little noise to the room when the fan is on. However it got us about 10-15 degrees cooler. I still only get to 80 or so on hot sunny days but that is a ton better than before.

I understand you can get retractable shades for the outside of the windows. They are probably the most effective, however We thought that it would ruin the point of the sunroom.

Hope that helps!

We added Coolaroo sunshades to the outside, they've helped considerably not just with the heat but also with light control. And they're fairly inexpensive and available on Amazon.

Older sun rooms tend to be hot boxes due to a simpler design that had little to no insulation. As codes change over the years, one place they have especially tended to focus recently is insulation values. New windows have dual-glazed argon filled glass and tinting to help with heat. Roof insulation is now R-30 minimum in Southern California for new roofs which also helps a lot.

If both of these areas are up to code you are on the right track. If not at least this is a place to start. Boosting A/C power can also fix it but this will help keep any cold air from escaping too quickly.

Great ideas! Do you know who originally installed the sunroom? They may be able to make repairs or replacements that would fit your room--sometimes they may be the only ones with the required products.

For example, Four Seasons Sunrooms (our manufacturer) has Conservaglass Select, which is a specially insulated, self-cleaning glass (12 layers, Krypton/Argon filled). If this might be a fit, you can find more details, like its UV transmission, relative heat gain, U and R values, etc. in our Maryland Sunrooms Guide.--We're based in Maryland but the information is good anywhere!

In terms of shading systems, we've had success with The Solarium Shade Company out of Boulder, CO. They have the added bonus of having several specialty products specifically for Four Seasons Sunrooms, though they have many other options as well.

We agree with Nick that you'll want to make sure your sunroom is insulated before putting too much effort with A/C units. Once you have secured the insulation, you might want to think of a through-the-wall heater/air conditioner (less expensive) or a split system HVAC (quieter, more efficient, but also pricier--like a Mitsubishi Mr. Slim).

Good luck!