The window evap cooler units are not as efficient as a wet wall on one end and exhaust fans on the other end. Mine has the later and I can keep it as cool or cooler inside than out. Today was an extreme example 100F outside which gave about 68F out of the wet wall and a high of 85F on the exhaust, hot end. With much higher dew points in summer it's still as cool inside as out with no shade cloth. The window evap units are inefficient because they mix the cool air with the hot inside and a mixture of that leaves the house. With exhaust fans pulling the cool in, the hottest driest air is pulled out. I think an efficient evaporative system would still be a huge help in MN. Much better than anything mentioned above. A shade cloth, if you can stand lower light levels, is an additional considerable help. I'm growing all kinds of fruit in a greenhouse in SW Texas without shade cloth. The crops do very well and fruit quality is very high. But most of these crops are OK at 90F high temperatures. Greenhouses with efficient evap cooler systems are used to grow tomatoes most of the summer in central TX where it is hotter and more humid than here, upper 90s highs and 70F dew points. You should be able to grow almost anything in summer in MN.

We are not completely sold on going with a heat pump..we currently have an 8 seer 2.5 ton AC and an 8 seer 3 ton AC with gas furnaces. It is a 200 dollar difference to go with the 16 i heat pump versus the 16i AC units (same VS furnace.) For a 15 the quotes were: Trane XR15 2.5 Ton Dual Fuel Heat Pump System Trane XR15 Heat Pump System 4TWR5030 Heat Pump 4TXCB031BC Evaporator Coil TUD2B060A9V36 Furnace Includes (if necessary): Condenser Pad 1" Filter Rack Honeywell IAQ Thermostat Drain Pan Water Safety Switch All Labor Warranty: 10 Year Compressor 10 Year Evaporator Coil Lifetime Heat Exchanger 10 Year Parts 5 Year Labor with on-going Preventative Maintenance Agreement Trane XR15 R-410A 2.0 Ton Heat Pump 4TWR5024 This is $12,100. For the AC option:\Trane XR15 2.5 Ton AC System Trane XR15 Split System 4TTR5030 Condenser 4TXCB031BC Evaporator Coil TUD2B060A9V3 Furnace Honeywell Pro 4000 Thermostat Warranty: 10 Year Compressor 10 Year Evaporator Coil Lifetime Heat Exchanger 10 Year Parts 5 Year Labor Trane XR15 2.0 Ton AC System Trane XR15 Split System 4TTR5024 Condenser 4TXCB025BC Evaporator Coil TUD1B060A9V3 Furnace Honeywell Pro 4000 Thermostat Warranty: 10 Year Compressor 10 Year Evaporator Coil Lifetime Heat Exchanger 10 Year Parts 5 Year Labor This XR15 AC option is 10,400. I had not heard that the 16i was not a significant upgrade over the 15...i hope an expert will chime in. The sales rep suggested a heat pump in case natural gas prices stay low you would have the option of NG heat....

Those are valid reasons and at that cost I would probably go with it, but that is completely up to you. Another way you could look at is: get the Performance 13, and when the furnaces fail replace them with variable speed furnaces that will increase the SEER by about the same amount that you would by going with the Performance 16 models now. There would likely not be a combination rating to quantify any such efficiency you would gain with the new furnaces, however. If you get the Performance 16 now you will have a documented, AHRI matched system with a specific SEER and EER. I am more concerned with what he said about his selection of ADP evaporator coils (which you have been quoted), not ones manufactured by Carrier and designed to be used with their equipment. In a straight cooling application, the ADP coils are not a problem with an indoor TEV (metering device), but I personally much prefer to match manufacturer-manufacturer with split systems. Carrier aluminum evaporator coil model number would look like CNPVP****ALA. This post was edited by ryanhughes on Sat, Aug 31, 13 at 11:18

Check the temp at the supply and return. Get some gauges and calculate the subcool. It it's a txv you can't check the superheat. Check out youtube for instructions. https://www.youtube.com/watch?v=-3vFASTwU6A