01. The whole point of being energy efficient is to ensure as much energy as possible isnt wasted. This sounds straightforward but when you really get down to where energy is wasted it gets complicated.
The main problem I see is the hot climate. The big energy waste comes from cooling the air in the house. Energy is lost because over time the hot air will "leak" into the house, and you have to continually cool the house. A way to stop this would be to build the house or part of it underground. If you do this you might NEVER need the air conditioning. Also maybe plant trees on the south side of the house to keep it in shade and hence cooler.
Recycling water is also a good idea. Use shower water to water lawn, same with laundry water. Things like that. If you need to dump a glass of drinking water out, pour it outside, or into a potted plant. This isnt quite house design though.
You could heat water using outside heat. Maybe a big obnoxious water heater with a metal background to heat the water. This might not heat all the water, but it would save on gas or electric costs by heating some of it.
Those are the big ones I can think of. There also is your standard energy saving tips. Turn lights off, use CFL lightbulbs, dont let water run when not using it, take showers....etc
02. Look to see if you have windows that will create a cross flow through the apartment. Basically if you have a window on one wall and a window on a wall at a right angle to the first, there will always be a pressure difference between those two windows when a wind is blowing simply because one or the other window will have more of a venturi effect from the wind regardless of the wind direction. Unfortunately, many apartment floorplans have all the windows on one wall but in these plans, the front door tends to be at a right angle to those windows hence leaving the front door open and the window furthest from that door open will cause a flow of air through the apartment.
03. Will your landlord let you hang bamboo curtains on the outside of your windows or shade screens? I live in Arizona and shade screens are big out here. You have to cover the entire window to take advantage of them. Sun reflecting lining on your curtains will help, keeping them closed during the day will too. Keep all your windows and curtains open at night when you are sleeping to capture the cool air, then close them before the sun comes up. Ceiling fans do not have to go at full speed to help cool. Even the lowest setting will work and do not cost as much to run. Buy the spray canned foam and seal up all the cracks around the windows, doors and floor boards. Just pull back the carpeting and spray the foam all around the outside of your apartment (and the uncarpeted rooms also). Do you have a paper shredder? Shred all your newspapers, junk mail, clean out your files, etc. This shredded paper will make great insulation over your head. If there is a crawl space entrance in your bathroom or hallway you can spread the paper around up there very thickly. Here is hoping you keep cool.
1) light coloured blinds, drapes or curtains
2) If this is possible: for long term coolness plant a tree. The leaves will keep the hpuse shady in summer and when the leaves fall off the sun can get through in winter.
3) Open the windows at night time or some cold time. Close them during the day or hot parts to stop the hot air getting in.
4) Internal heat also causes rooms to heat off. This means turn off appliances when not in use.
5) Avoid cooking in the hottest part of the day
6) Humidity makes things hotter, don't do activities such as laundry during the hot parts in a day.
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