Newer thermostat Home is approximately 2100 square feet with 15 supply registers 4 return air grills through home. Customer is explaining that she wakes up cold in middle of night and raises setpoint on thermostat. It takes “from 3am she is lucky to reach 70 degrees on thermostat.†Heat seems to take a long time to go through home. Furnace had an error code of E12 that was a warning. This error code was a static pressure high check filters and ducting. Filters were very dirty. Recommended customer to install a 20x25 filter with power off to electronic air filter. Error code still was present. Furnace ducting appears to be undersized for system. Blower is running at a reduced capacity due to static pressure being high. Informed customer of findings. Customers supply ducting is 16x19 then transitions into 12x16 then transitions again to 1ft x3ft and has multiple 90 degree bends which create more restrictions on air flow. Restrung air temp was lower then inside air temp by ten degr