We have a digital control panel in our house to control our heating and air. We usually keep it set to 72 degrees. Lately (especially on really cold nights) the house will not heat properly and we wake up to a freezing home with a temperature in the low 60s. We tried setting the temperature up to 80 and it only changed the temperature to around 68 degrees in the house. The heat runs constantly but does not seem to improve the temperature. Any ideas or suggestions on what might cause this? Thanks so much!