Heat Flow
Keeping heat loss and gain under control is key. Heat moves from high temperatures to low so having a proper insulation barrier between the outside and inside is necessary.
Forms of heat loss are through conduction (objects that are in contact), convection (air leaking out through gaps in your insulation and house exterior), and radiation (heat from a mechanical heat source or the sun).
Pressure
Pressure moves from high to low. Items that affect pressure are wind, temperature, exhaust fans, and chimneys. Feeling cold is the effect of a hole or pressure. The ideal is to have a balanced system without warm air leaving and cold air arriving.
Moisture
Moisture wants to go from high pressure areas to low pressure areas. If a house is being heated, moisture wants to escape to the outside. When the air conditionining is on, moisture wants to come in from the outside. Warm air can hold more moisture than cold air.
Dewpoint
When water vapor changes to liquid water, a temperature has been reached that will not be good for the house. Any surface that reaches a dewpoint of 40 degrees will have liquid water on it. Keeping control of the relative humidity is important.
