Record the new pattern
Keep the insulation work record, including treated areas and air-sealing changes. Note outdoor conditions, room and target temperatures, operating mode, backup indications, and when the dip occurs.
Does it happen during morning recovery, steady heating, or a brief change in operation? Does the room recover or stay below the setting? Compare similar weather before and after where records allow.
Do not disable auxiliary heat to test whether insulation was worthwhile. Needed backup and a setup problem can look similar on a display.
Compare output with the updated need
Ask the provider to review the heating-load calculation using current home conditions. A load is the amount of heat the home needs.
PNNL's sizing guidance compares the home's calculated need with the exact equipment's output at local winter conditions. Insulation and air leakage are inputs. PNNL sizing guidance.
Request installed models, relevant manufacturer performance data, startup records, and current operating findings. Ask whether backup should be needed in the conditions you recorded and what the intended control sequence does.
If the calculation shows sufficient output but temperatures still fall, ask what checks will investigate operation, airflow, controls, and actual backup delivery. If output is insufficient, request a remedy that explains how it meets the remaining need.
Verify the event, not just the recovery
A reading after the dip ends does not establish what happened during it. Ask whether approved monitoring or observation during relevant conditions would help.
The insulation contractor documents its work; the HVAC provider assesses equipment and controls. Have them identify any dependency before another purchase is proposed.
Your next step is to send the insulation record and temperature timeline for a post-improvement operating review. Keep appropriate backup available until its role and operation have been verified.