Question
I have lost 2 very large trees on the south side of my house and now the sun shining on my A. C. unit is costing a fortune.  I am going to build a louvered shed over the A. C. unit and plant shrubs around the unit.  At what angle do I put the louvers so the air from the fan can escape and not let in the sunshine?  I live in Birmingham Alabama.  Also what type of shrubs do I need to plant that will take the constant air coming into the A. C. unit?

Answer
Richard,
Don't believe the hype! Sun on your condensing unit is most likely not costing you significant money. More than likely it is the loss of shade on your house that is the real issue. I have never heard that sun on a condensing unit can cost a significant amount of money since the metal housing shades the coils inside. However it is well known that a single mature shade tree can cut cooling bills by 10-50%. There are many studies to prove this and that is why there is nothing better for cooling than a well placed large deciduous shade tree. I would spend some time researching the internet on sheltering and shading an AC unit. It is not typically a good idea to do this without a very open and well ventilated structure. I have seen wood arbors with vines over them but they are well clear with probably 5-6 feet of space between the arbor and the top of the unit at a minimum and no sides at all. There are national and local electrical codes and fire codes that will likely apply and require setbacks for enclosures and specify the amount of open space you must maintain. You need to consult a local AC specialist to determine the exact set backs but my guess us that you will need probably 3 to 5 feet of clearance around the unit on all sides. I have no idea about the louver angle. The amount of air movement will be critical, I would not recommend louvers at all.

Search the internet for "enclosing an AC unit" and you will quickly see this is a bad idea unless the enclosure is very open.

As for shrubs, any evergreen shrub that grows in your area should be able to take the air flow coming into the sides of the unit but I would plant them well away from the unit to ensure it works effectively. The minimum clearance I would allow is 3' from the outside edge of a hedge to the unit. This means if you are planting a new shrub I would plant it at least 6' from the unit so it has some room to grow.

Best of Luck

Sean J Murphy, LA, ISA, LEED AP
www.seanjmurphy.com