Tall irrigated hedge to pre-cool A/C condenser? Answered

Transpiration (plant evaporation/cooling) to the point where we would notice it works on a large scale, like with big trees. However, its effect is easily eliminated by a breeze. A hedge won’t have enough scale, and what effect it does have will quickly be eliminated by the volume of air moved by the ac unit. A dense enclosure might actually create a heat well with recirculating hot air.

The other contributor of a large tree is shade. Considering a hedge for shade, in Chicago, at the summer solstice, a 6-foot hedge to the south of the unit will only provide 2-feet of shade. It won’t even shade all of the access space, much less the ac unit. With six foot hedges to the east and west, the ac unit will be fully exposed for about five hours. An ac unit, tucked up against the east side of the house, with eaves, is the best location. It is in the shade for the hottest part of the day.

Humidity, in and of itself, has little effect on the condenser efficiency. Misting can help but introduces a whole bunch of new problems like scale, corrosion, and operating an electric device in a wet environment.

So, what can you look at to improve efficiencies?

1. Vent dead attic space. This helped my house considerably. The cutouts under the vents were only about half of the area that could be used. I also went with more efficient passive vents. They don’t leak in rainstorms and they don’t squeak because they don’t turn. I once talked to a guy who specializes in new big houses that won’t cool. He vents the dead attic spaces and viola, the houses cool. Also, a well ventilated attic is important in the winter to prevent condensation.
2. Make certain eave vents aren’t blocked. In my house, a previous owner had blown in insulation and it covered over half of the eave vents. That, coupled with #1, made the attic not vent properly.
3. Clean the outside coil. Around here, it is needed at least two times a year. I use a toothbrush on the outside of the fins and a hose end sprayer from the inside. Cottonwood fluff is really bad for efficiency, as are grass clippings.
4. Change out the filter regularly.
5. Weatherize. I went around my house with a cheap non-contact thermometer to look for heat or cold entering or exiting. I did it both winter and summer. I found that the area around the back door hadn’t been sealed or insulated. The interior and exterior trims were the only things keeping the heat in or out and they didn’t do it well. They also did a lousy job of keeping the bugs out. I also put a threshold strip on the furnace closet door because it is open to the attic.
6. Dehumidify, it is easier to cool air if it is less humid.
7. Have the inside coil cleaned.
8. Make sure the system is balanced. If the inside coil is dirty, the system won’t balance and will run less efficiently.

To give useful suggestions, we really need to know where in the world you are, soil conditions etc,

Your best sources of information are your local garden centre, or have a stroll around your local area to see what your neighbours are growing successfully - if you see something you like, knock on the door and ask what the species is. If they don't know, ask nicely for a twig to use for ID purposes.

As far as I know, all higher plants shed something.

You might try for something that does it all at once - like in the fall. Lilac is easy to grow and trim. It likes being mowed to within 12" of the ground from time to time. The flower heads are easy to cut off... in bud, in flower, or as seed heads, so you needn't have flower bits getting into things. The leaves are big enough to be easy to rake, and if I remember correctly, tend to fall all at once.

I suggest avoiding anything with needles or tiny leaves that could fall into the condenser Plants have needles to reduce water loss through transpiration. I think in general, plants that are drought resistant also try to reduce water loss that way.