REPLACED BOTH ELEMENTS GOT HOT WATER FOR 1 SHOW THEN IT GOT COOLER AND COOLER AND NOW ITS COLD ONLY?

Find a reputable HVAC contractor to do a room by room analysis with heat and cooling loads calculated and units sized and duct requirements and compare to what you have.

The air not being cold is not necessarily an indicator of anything malfunctioning. High efficiency units for instance don't produce cold air.

Since you have had someone look at it, the duct work may be collapsed which restricts air flow or uninsulated which warms up the supply air. Either one is a possibility. Any Cox Cable guys been stompin' around your attic lately? Wouldn't be the first time.

Usually, when the air coming out of the vents is not cold enuf it's because your freon level is low. Probably leaking, but they can usually recharge the freon and it will work for a while. Try another repair company and see if they can recheck the freon level.

We have a high efficiency unit and it produces cold air, so I don't know what previous poster is referring to. Air conditioners are supposed to blow cold air.

Sorry, to tell ya but it is normal if the outdoor temperatures are much below 45 degrees. Below 45 degrees there is little heat outdoors for the heat pump to grab to heat the home so it will run 24/7 and blow cool or cold air. Below 45 the temp of the air coming out the vent will decline and you will get no heat from the heat pump itself as you near freezing.

Your emergency heat or auxiliary heat is electric strip heat. But it only kicks in during normal operation if the temp in the house drops 3 degrees below the setting. (some tstats if can be 5 deg.) Otherwise the heat pump will blow cool or cold air the rest of the time if it is too cold out.

To prevent it from running all the time and blowing cold it is recommended if the temp outside is falling below 45 degrees you should just switch to the emergency heat setting, which shuts the pump outdoors off, and just heat with the electric.

But if there is no heat outside the heat pumps will blow cold. They are the cheapest and most efficient forms of heat but only as long as the outdoor temp is above that 45 deg..

I'm guessing that if you haven't experienced this you live in some place with moderate winter temperatures like in Northern Florida and rarely get very cold winter temps like the freezing you have seen there recently.

It will likely blow much warmer when the outdoor temp rises.