Building Envelope

Dew point

The temperature at which condensation begins

Material R Value

Thermal resistance of a material

Building materials are considered:

permeable, semi permeable, semi impermeable, impermeable

Conduction

phenomenon of heat transfer between the molecules of a material that are in direct contact with another

overhangs

protect walls and other penetration points

Water

roof leaks, poorly sealed penetrations, poor flashing (causes rot)

The term 'hygrothermal' refers to

the movement of heat and moisture through buildings

Vapor diffusion

the movement of moisture in the vapor state as a rest of moisture pressure difference, and air pressure difference.

radiation

the transfer of energy between two objects in the form of electromagnetic waves

'"P" Value is

thermal resistivity of each material, if the P is large then the material has a high resistance and is considered a thermal insulator (or thermal conductor)

drained screened walls

utilizes the assembly of materials to expel water

storage mass walls

utilizes the assembly of materials with enough mass to absorb rain and expel later

Water is the _____!!!!

Enemy

Where a building is being construction + what a building wall be used for =

How the building envelope is constructed

Solid (ice)

Ice Dams, foundations/hardscape (freezes and causes structural damage)

perm & perm rating

a quantitative value that measures the relative ease with which moisture (water vapor) will pass through a material

The building envelope:

an engineering system that meshes elements such as structural integrity, moisture control, temperature control and air pressure boundaries constructed in layers with various building materials into a single design strategy

Perfect barrier walls

assembly with materials that stop water at the initial plane

3 modes of heat transfer

conduction, radiation, convection

Gaseous (vapor)

leaks that are trying to dry out, condensation from poor insulation, air transmission (causes mold and rot)

Moisture pressure difference

moisture moves from higher water vapor density to lower density

air pressure difference

moisture moves with pressure from high pressure to low pressure

convection

occurs only is gases or liquids and is a transfer of energy through the bulk motion of gas or liquid