As a math guy I'd advise that no matter how technical someone sounds (including myself) if they can't disclose how they got their data (the numbers they are using), bounding cases (what makes this a maximum or minimum value) or their methodology (how they got to the answer they gave) . Then what you are reading is opinion. Now certainly not all opinions are equal and in many cases we can't collect or evaluate all the data required and so we rely on people with expertise. Often the way we judge this is by assuming that 'expert' is synonymous with 'professional'. That is, when I don't have any information about differentiating between plumbers I still generally call a plumber instead of a non-plumber (we are essentially assuming that market forces are at work here that keep the worst plumbers from working). The problem with the internet, is that all bets are often off. Posts are made without attributing to research on the subject. People can claim to be experts but in a public forum there's no way to be sure and there's little in the way of economic incentive or accountability to help ensure give good advice. You might argue there's a 'social' payback but it's hard to say that such a system is 'as good' as a monetary one. Even websites we would assume to be reputable (like the Department of Energy) don't say how they got to their conclusions (incidentally they believe you can save up to 10% by shading your external A/C unit). So without any kind of assurance of expertise you are really left with applying critical reasoning skills to the information you see. Let's take the alleged experts bounding case that shade can never make more than a 10 degree difference. A simple unshaded thermometer can show a differential of 30 degrees on a sunny day. This is why we go to great lengths to control the impact of sunlight on weather stations. This is on an object that is very small so is not going to be absorbing much radiant energy. From that we're to believe that an object orders of magnitude larger, during the largest period of sunny days (summer is when we run these things), in direct sunlight (otherwise why would we be shading it?) can't ever rise more than 10 degrees above the ambient temp? So it would appear that their estimate is wrong by up to a factor of three. On top of that I'd say that it's worth looking at what experts "don't say". For example wouldn't the amount of savings be influenced by the number of hours in the sun? So you would expect that any useful advice should be expressible as "You would need X hours of operation in direct sunlight to achieve Y watts of savings". Without that, then how do we know that the savings would be small? Not to mention the area we are trying to cool. A 1900sqft house and a 2900sqft house are, all other things being equal going to use different amounts of power. So what might be a negligible savings in one environment could be a useful savings in another. Anyway, it's conceivable that the gains from shade are small but until someone expresses it either as a function of environmental variables or provides a proper bounding case then one persons opinion isn't demonstrably better than another.

YYour systems need fresh air to be efficient. If units blowing up a tree do not need to block air flow or it with return back to the system MFG rule of thumbs if units is 36" tall at less 36" from ANY plants ( but being a service tech. We love dirty unit and lack for air flow "SERVICES CALL" OF DIE SYSTEMS. UNIT THAT CANNOT GET FRESH AIR TAKE AWAY EFFICIENT. COST YOU MORE MONEY ON YOUR LIGHT BILL. TREE SHADING UNITS MEAN ON RAIN TO HELP CLEAN THE COILS. COVER UNIT NO ROOM TO WORK ON OR TO WASH THIS UNIT WILL PUMP THE OIL OUT OF THE COMPRESSOR :) MONEY :) TO MAKE. PS IF NEW SYSTEM THIS WILL VOID ANY MFG WARRANTY.

I designed my house and was active in reviewing the contractors recommendations based on the Manual J analysis. When all is said and done the old adage of 12,000 btu (a ton) for every 500 sq ft of floor space is pretty accurate, except I would modify that for any known major variable that you know would cause a problem. In my case, I had shade trees all around so there's less direct sunlight load, but I have 9' ceilings which is more air to condition. My split system has a 13 SEER that was sort of cutting edge for 1996, a single speed scroll compressor. The blower is a variable speed one, which is key to my system because I have a humidistat installed (inexpensive). During the heat of the S. Texas day it will run at higher speed for maximum cooling due to the heat load, but since it runs for like 12 minutes, humidity is totally wrung out. In the pre-dawn hours when the humidity is like 85%, but temp is 72, it doesn't run much cause there's no heat load. When it does run, the humidistat tells it its getting humid in here so it runs at slow speed so it wrings out the air, slowly getting to the selected temp setting. I have the humidistat set for like 63%, so if it achieves 64% or higher it automatically shifts to high speed. I like it alot. Last week it was 97 outdoors, the AC ran like 12 minutes then was off 18 minutes. Before you select your SEER, you should understand that number directly relates to your energy bill. Ex: Since a 16 is 33% more efficent than a 12 (diff of 4 divided by 12), an electric bill that would be $100 with a 12, will now be $67 with a 16 (of course a 16 costs more to buy, but rebates/tax credits help). Good luck.

There are one pipe steam systems which have radiator vent at one end. As the steam enters from the opposite end, moist air is released into the room. It helps keep the humidity high in the winter. I suppose the humidifier would be integrated with the air handler. But it will need to be wired so the condenser does not turn on. It is not a common set up. The refrigerant in use is R410a. Systems were R22 are no longer allowed to be manufactured. Air handlers can be single. multiple, or variable speed. AC condensers come in single and 2-stage varieties. If you live in Virginia (not sure about DC itself) the minimum SEER rating allowed is 14. You want a contractor who will size the equipment to your house and climate and install it properly. He should also inspect the duct work for problems and size. In my opinion a small to medium sized family owned business who is an authorized dealer of one the major brands who be a good choice.