First, some basic science:
A. Heat naturally flows from warmer areas to cooler areas. Its speed of movement depends upon how much a difference there is between these two temperatures. The greater the difference, the faster the flow.
B. Heat flow can be reduced by insulation.
C. Heat can be artificially made to travel in the opposite direction – from cold to hot. This is done by any device that “pumps” heat. Air conditioners pump heat out of the home. Pumping heat costs about one third the cost to create heat.
D. When heat enters your home, during the summertime, it must be removed by the air conditioning system.
E. Radiative heat, from the sun, can easily flow through glass. It heats up whatever it lands upon. Because of certain physical characteristics (called “black-body” radiation) that heat can’t pass back through glass. It is effectively trapped. This is called the “greenhouse” effect.
F. When you install or provide something which operates without need for additional energy, this is called a passive operation.
Okay – so based upon these simple rules, here are 10 basic actions that will improve a home’s energy efficiency which will save you money. I’ll mention the rule and then what you can do:
1. Rule B – Insulation is likely one of the best investments you can make. There are few actions that can give you a better cost to benefit ratio. This is passive in that it takes no energy to operate (rule F).
2. Rules D and E – Increasing the size of your eaves and other overhangs will reduce sunlight entering your home which just has to be removed by your air conditioner (costing money). This is also passive (rule F).
3. Rules D and E – Windows on the west side tend to bring in the most heat from the sun. It is best to limit western exposure either by design or by blocking the windows with shrubbery. This is a passive action (rule F)
4. Rule E – Using reflective glass can be extremely helpful. Curtains and shades do not work because by the time the sun light hits them it has already entered the home (remember greenhouse). Any time something heats up in your home your air conditioner will have to remove that heat. Sunlight must be stopped before it goes through the glass. This is a also a passive method and will save both energy and money during the summer.
5. Rule A – Place foil on the bottom of the plywood roof sheathing of your home. This is easiest to do while building a new home. If your home exists, then consider a radiation barrier in the attic. This will keep the attic cooler. This is also passive (rule F)
6. Rule A – Ventilate the attic. This can be passive or active. It reduces the attic temperature which slows the flow of heat into your home. The active, but effective, way is with a powered fan system which operates only at high attic temperatures. An advantage is that this will not operate in the winter when you DO want heat flow into your home. The passive method of ventilation is by effective venting that operates when the wind blows. This is excellent in the hotter states. This requires good air flow both into the attic and out of the attic.
7. Rules A and B – Your air conditioning ductwork is exposed to attic heat which flows into the cool air that flows through them. Placing these ducts inside the air conditioned space of the home will significantly reduce heat flowing into the ducts. Another way is to place good insulation over top of the ducts to help isolate them from the attic heat. This is also passive (rule F).
8. Rule D – Water heaters should be outside of any air conditioned space. They leak heat. If they leak heat into the home then the air conditioner has to remove it. This action is passive.
9. Rule D – Dryers, ideally, should be outside air conditioned space for the same reason as water heaters. This action is passive (rule F)
10. Rule C – Water heaters heat their water with heating coils. This is the creation of heat and is relatively expensive. Alternatively one can take advantage of the savings of pumping heat by installing a system which takes the waste heat that is being pumped to the outside by the air conditioner and routing it into the water. This allows for the heat to be pumped into the water (which is cheaper) though, actually, during operation, it is totally free since the AC is pumping heat to the outdoors anyway. This is an excellent way to save energy and money.
Once you understand the basic rules you will be able to think of many other ways to save energy.