BPI Envelope study guide
BPI Envelope · Work through your exam, one topic at a time.
BPI publishes a family of home performance certifications and certificates, and its stated mission is "to advance the home performance industry by providing nationally recognized standards and credentials that ensure homes are comfortable, healthy, safe, durable, and energy efficient." The Envelope Professional credential is aimed at practitioners who assess and improve the building shell - insulation, air sealing, moisture control, windows and doors - and who need to demonstrate that knowledge to employers, programs, and homeowners. This study page is an independent preparation resource and is not affiliated with, endorsed by, or sponsored by the Building Performance Institute. The BPI Envelope study guide has 6 sections and about 1,987 words.
01Building Science Principles
Every BPI-style question about building science starts with the idea that a house is a set of coupled flows: heat, air, and moisture move through the enclosure, and a change to one changes the others. Candidates must be comfortable with the three heat-transfer modes (conduction, convection, radiation) and with the distinction between the building envelope (the thermal and pressure boundary) and the structural frame.
359 words, about 2 min02Air Sealing and Insulation
Air sealing stops the movement of air; insulation slows conductive heat flow. Candidates must explain why both are required: a well-insulated wall with a leaky top plate still underperforms because wind washing and convective loops bypass the insulation.
345 words, about 2 min03Moisture Management
Moisture enters as bulk water, capillary suction, vapor diffusion, and air transport. Air transport is the dominant path in most assemblies because it moves large amounts of vapor quickly through leaks.
349 words, about 2 min04Ventilation and Indoor Air Quality
Homes are tighter than they used to be, so pollutants and moisture build up without deliberate ventilation. Candidates should know the main pollutant classes: moisture, combustion byproducts (CO, NO2), volatile organic compounds, particulates, radon, and biological contaminants.
294 words, about 1 min05Windows and Doors
Candidates must read NFRC labels: U-factor (heat loss), solar heat gain coefficient (SHGC, solar gain), visible transmittance (light), and air leakage. SHGC choice depends on climate: lower SHGC reduces cooling loads in hot climates, while higher SHGC can be beneficial for heating in cold climates.
314 words, about 2 min06Pressure Diagnostics and Testing
A blower door measures envelope airtightness by pressurizing or depressurizing the house and recording airflow at a reference pressure, usually 50 Pa. The result is CFM50, often normalized as air changes per hour at 50 Pa (ACH50) or as leakage area.
326 words, about 2 min