The Brass-Seal™ Forged Brass Mail Slot System was independently tested to ASTM E283 by Intertek (Report No. T4376.01-301-44-R1). Among the first mail slots with published third-party air leakage performance data, the system recorded the following verified results at the standard test pressure of 75 Pa:

Interior Unit (standalone): 0.12 cfm/ft² infiltration / 0.06 cfm/ft² exfiltration
Exterior Unit (standalone): 0.20 cfm/ft² infiltration / 0.11 cfm/ft² exfiltration
Paired System: 0.20 cfm/ft² infiltration / 0.11 cfm/ft² exfiltration

A typical unsealed mail slot creates a direct opening through the door and can allow significantly higher air infiltration than this tested performance.

This calculator provides an illustrative estimate based on modeled airflow reduction, Intertek ASTM E283 test results, regional climate ratios, and average energy-rate assumptions. Actual savings vary and are not guaranteed.

The estimate compares the Brass-Seal™ verified ASTM E283 performance against expected air leakage through a typical unsealed mail slot opening. It applies a natural-pressure adjustment factor of 0.5, consistent with ASHRAE fundamentals and EnergyPlus-style infiltration modeling, and multiplies by the mail slot opening area to derive the airflow reduction. That airflow reduction is then converted into annual energy impact using local climate data.

Heating savings are calculated using local Heating Degree Day (HDD) ratios sourced from DOE/EIA climate data. For gas systems, savings are converted to therms using a standard 80% furnace efficiency factor, then priced at regional gas rate assumptions modeled from EIA residential energy-rate data. For electric resistance and heat pump systems, savings are calculated in kWh using regional electric rate assumptions. Heat pump savings apply a seasonal COP of 2.5 to reflect the efficiency advantage over resistance heating.

Cooling savings are calculated using local Cooling Degree Day (CDD) ratios sourced from DOE/EIA climate data. A SEER 14 baseline is applied, the federal minimum efficiency standard for central air conditioning, using an effective seasonal COP of 3.0. Cooling savings use local electric rates regardless of heating system type. Colder climates show greater heating savings; hotter climates show greater cooling savings.

Gas and electric rates are modeled using regional average assumptions based on EIA residential energy-rate data. Electric rate assumptions range from $0.11/kWh to $0.32/kWh across the 46 markets; gas rate assumptions range from $1.10/therm to $1.85/therm. The calculator matches your ZIP code to the nearest regional market. ZIP codes outside covered markets use a national average rate.

Mail slot leakage is frequently identified during professional blower-door tests as a measurable contributor to whole-house air infiltration. Sealing this penetration can improve the overall building envelope performance that energy auditors measure.