BPI BSP cheat sheet
BPI BSP · Keep the key ideas within reach.
Building Science Fundamentals and the House as a System
A house is a system: enclosure, HVAC, occupants, and outdoor environment interact, so a change in one component alters heat, air, and moisture flows elsewhere.
Stack effect pressure difference increases with building height and indoor-outdoor temperature difference; warm air rises and exits high while outdoor air enters low.
The three principal transport flows are heat, air, and moisture; air movement usually transports more moisture through assemblies than vapor diffusion.
The building enclosure separates conditioned from unconditioned space and manages rain, air, vapor, thermal, and ground moisture control layers.
The pressure boundary is the continuous air-control surface; aligning it with the thermal boundary reduces the chance of condensation within the assembly.
Sensible heat changes temperature; latent heat changes moisture phase; total heat equals sensible heat plus latent heat.
One BTU raises one pound of water one degree Fahrenheit; heating and cooling capacity is often stated in BTU per hour.
Tightening the envelope without controlled ventilation can trap pollutants and moisture; the typical sequence is air seal, insulate, then ventilate.
Heat, Air, and Moisture Flow
Conductive heat flow is calculated as Q = U × A × ΔT, where U is assembly conductance, A is area, and ΔT is temperature difference.
Assembly thermal resistance is the sum of layer R-values plus surface film resistances; U-value equals 1 divided by total R-value.
Heat moves from warmer to cooler regions by conduction, convection, and radiation; all three can occur simultaneously in a building assembly.
Air leakage is driven by stack effect, wind pressure, and HVAC fan pressure; leakage carries both heat and water vapor.
Moisture transport from largest to smallest is generally bulk water, capillary flow, air transport, and vapor diffusion.
Dew point is the temperature at which air reaches saturation; condensation forms on surfaces at or below the dew point.
Relative humidity equals water vapor present divided by the saturation amount at the same temperature, times 100; warmer air holds more vapor.
Vapor retarder location is climate dependent: cold climates typically place it on the warm-in-winter side, while hot-humid climates place it near the exterior.
Cooling air without removing moisture raises relative humidity; dehumidification reduces the latent cooling load.
Building Enclosure, Insulation, and Air Sealing
Insulation resists conductive heat flow; air sealing resists convective heat flow; an effective enclosure addresses both.
Approximate R-values per inch: fiberglass 3–4, cellulose 3–4, EPS 4, XPS 5, closed-cell spray polyurethane 6–7.
Air barrier continuity is required at penetrations, transitions, top and bottom plates, and fenestration openings.
Thermal bridging through framing, fasteners, and structural members reduces effective R-value; continuous exterior insulation reduces this effect.
Vapor retarder classes: Class I is below 0.1 perm, Class II is 0.1 to 1.0 perm, and Class III is 1.0 to 10 perms.
A rain screen includes cladding, a drained and ventilated cavity, a water-resistive barrier, and sheathing so bulk water drains and the wall can dry.
Flash-and-batt uses a thin layer of closed-cell spray foam for air and vapor control plus batt insulation for additional thermal resistance.
Attic air sealing is completed before adding insulation, and soffit-to-ridge vent clearance is maintained to preserve attic ventilation.
Window performance metrics include U-factor for heat loss, solar heat gain coefficient for solar gain, and air leakage rate.
Heating, Cooling, Ventilation, and Water Heating Systems
AFUE equals useful heat output divided by fuel energy input over a heating season; higher AFUE indicates greater efficiency.
SEER2 rates seasonal cooling efficiency, and HSPF2 rates seasonal heating efficiency for heat pumps; higher values indicate greater efficiency.
Heat pumps move heat rather than generate it; COP equals useful output divided by electrical input and can exceed 1.
The refrigerant cycle order is compressor, condenser, expansion device, and evaporator.
Duct leakage and poor duct insulation reduce delivered capacity; ducts located in conditioned space reduce distribution losses.
Combustion appliances require adequate combustion air and proper venting; building depressurization can cause spillage or backdrafting.
Ventilation strategies include exhaust-only, supply-only, and balanced systems; HRVs and ERVs are balanced ventilation devices.
An HRV transfers sensible heat between exhaust and supply air, while an ERV transfers both sensible heat and latent moisture.
Water heating options include storage tank, tankless, and heat pump water heaters; distribution losses and setpoint affect overall efficiency.
Health, Safety, and Indoor Environmental Quality
Carbon monoxide is colorless, odorless, and produced by incomplete combustion; CO alarms are installed near sleeping areas.
Combustion safety evaluation includes draft measurement, spillage checks, backdrafting testing, gas leak inspection, and CO monitoring.
Indoor relative humidity is commonly maintained around 30–50%; elevated humidity supports mold, dust mites, and condensation.
Mold requires moisture; controlling leaks, condensation, and high humidity at the source limits mold growth.
ASHRAE Standard 62.2 specifies minimum residential outdoor air ventilation and local exhaust requirements.
Radon is a radioactive soil gas that enters through foundation openings; testing and sub-slab depressurization are common mitigation steps.
Lead and asbestos are hazards in older homes; disturbance requires safe work practices and appropriate protections.
VOCs and formaldehyde emit from building materials and furnishings; source control and ventilation reduce indoor concentrations.
Attached garages require an air-sealed separation from living space to prevent vehicle exhaust and fuel vapors from entering.
Building Science Fundamentals and the House as a System
A house is a system: enclosure, HVAC, occupants, and outdoor environment interact, so a change in one component alters heat, air, and moisture flows elsewhere.
Stack effect pressure difference increases with building height and indoor-outdoor temperature difference; warm air rises and exits high while outdoor air enters low.
The three principal transport flows are heat, air, and moisture; air movement usually transports more moisture through assemblies than vapor diffusion.
The building enclosure separates conditioned from unconditioned space and manages rain, air, vapor, thermal, and ground moisture control layers.
The pressure boundary is the continuous air-control surface; aligning it with the thermal boundary reduces the chance of condensation within the assembly.
Sensible heat changes temperature; latent heat changes moisture phase; total heat equals sensible heat plus latent heat.
One BTU raises one pound of water one degree Fahrenheit; heating and cooling capacity is often stated in BTU per hour.
Tightening the envelope without controlled ventilation can trap pollutants and moisture; the typical sequence is air seal, insulate, then ventilate.
Heat, Air, and Moisture Flow
Conductive heat flow is calculated as Q = U × A × ΔT, where U is assembly conductance, A is area, and ΔT is temperature difference.
Assembly thermal resistance is the sum of layer R-values plus surface film resistances; U-value equals 1 divided by total R-value.
Heat moves from warmer to cooler regions by conduction, convection, and radiation; all three can occur simultaneously in a building assembly.
Air leakage is driven by stack effect, wind pressure, and HVAC fan pressure; leakage carries both heat and water vapor.
Moisture transport from largest to smallest is generally bulk water, capillary flow, air transport, and vapor diffusion.
Dew point is the temperature at which air reaches saturation; condensation forms on surfaces at or below the dew point.
Relative humidity equals water vapor present divided by the saturation amount at the same temperature, times 100; warmer air holds more vapor.
Vapor retarder location is climate dependent: cold climates typically place it on the warm-in-winter side, while hot-humid climates place it near the exterior.
Cooling air without removing moisture raises relative humidity; dehumidification reduces the latent cooling load.
Building Enclosure, Insulation, and Air Sealing
Insulation resists conductive heat flow; air sealing resists convective heat flow; an effective enclosure addresses both.
Approximate R-values per inch: fiberglass 3–4, cellulose 3–4, EPS 4, XPS 5, closed-cell spray polyurethane 6–7.
Air barrier continuity is required at penetrations, transitions, top and bottom plates, and fenestration openings.
Thermal bridging through framing, fasteners, and structural members reduces effective R-value; continuous exterior insulation reduces this effect.
Vapor retarder classes: Class I is below 0.1 perm, Class II is 0.1 to 1.0 perm, and Class III is 1.0 to 10 perms.
A rain screen includes cladding, a drained and ventilated cavity, a water-resistive barrier, and sheathing so bulk water drains and the wall can dry.
Flash-and-batt uses a thin layer of closed-cell spray foam for air and vapor control plus batt insulation for additional thermal resistance.
Attic air sealing is completed before adding insulation, and soffit-to-ridge vent clearance is maintained to preserve attic ventilation.
Window performance metrics include U-factor for heat loss, solar heat gain coefficient for solar gain, and air leakage rate.
Heating, Cooling, Ventilation, and Water Heating Systems
AFUE equals useful heat output divided by fuel energy input over a heating season; higher AFUE indicates greater efficiency.
SEER2 rates seasonal cooling efficiency, and HSPF2 rates seasonal heating efficiency for heat pumps; higher values indicate greater efficiency.
Heat pumps move heat rather than generate it; COP equals useful output divided by electrical input and can exceed 1.
The refrigerant cycle order is compressor, condenser, expansion device, and evaporator.
Duct leakage and poor duct insulation reduce delivered capacity; ducts located in conditioned space reduce distribution losses.
Combustion appliances require adequate combustion air and proper venting; building depressurization can cause spillage or backdrafting.
Ventilation strategies include exhaust-only, supply-only, and balanced systems; HRVs and ERVs are balanced ventilation devices.
An HRV transfers sensible heat between exhaust and supply air, while an ERV transfers both sensible heat and latent moisture.
Water heating options include storage tank, tankless, and heat pump water heaters; distribution losses and setpoint affect overall efficiency.
Health, Safety, and Indoor Environmental Quality
Carbon monoxide is colorless, odorless, and produced by incomplete combustion; CO alarms are installed near sleeping areas.
Combustion safety evaluation includes draft measurement, spillage checks, backdrafting testing, gas leak inspection, and CO monitoring.
Indoor relative humidity is commonly maintained around 30–50%; elevated humidity supports mold, dust mites, and condensation.
Mold requires moisture; controlling leaks, condensation, and high humidity at the source limits mold growth.
ASHRAE Standard 62.2 specifies minimum residential outdoor air ventilation and local exhaust requirements.
Radon is a radioactive soil gas that enters through foundation openings; testing and sub-slab depressurization are common mitigation steps.
Lead and asbestos are hazards in older homes; disturbance requires safe work practices and appropriate protections.
VOCs and formaldehyde emit from building materials and furnishings; source control and ventilation reduce indoor concentrations.
Attached garages require an air-sealed separation from living space to prevent vehicle exhaust and fuel vapors from entering.