12x12 building Enthalpy based economizer

ToddT · 02-03-16, 06:05 PM

I'm no engineer to help with enthalpy and please forgive if my comments are too simplistic, but as an efficiency nut, I have a few points to suggest.

First, go for as true a white roof as possible. Years ago, a friend with some mobile home rental units painted the roof of one silver and one white. He then turned off the AC and put a thermometer in each unit. Want to guess the temperature differential? The white one was 32 degrees F cooler than the "reflective" silver roof. Can you imagine if it was a black roof?

When I lived in Louisiana, I experimented with water on the roof and on the AC outside unit. An alternating brief water spray followed by a 15 minute evaporation sequence will keep the roof cool with low daily consumption (.1 gallon per square feet per day). Even with high humidity, I recorded a 12 degree drop in interior temperature at the ceiling. However, this benefit is less the more R-value you have in the roof.

As for the AC units, I put a fine fog mist water spray on the outside unit. I saw a 7 degree drop in the air coming out of the central AC register. However, many newer window units are designed to splash the condensate up on the condenser coils.

To assure no condensation, what would be the humidity goal inside? I find 50% is the magic number for comfort but equipment is different. I have a feeling anything much over 60% R.H. would have a tendency to sweat.

02-03-16, 06:05 PM	#11
ToddT Lurking Renovator Join Date: Jan 2014 Location: Arkansas Posts: 9 Thanks: 9 Thanked 0 Times in 0 Posts	I'm no engineer to help with enthalpy and please forgive if my comments are too simplistic, but as an efficiency nut, I have a few points to suggest. First, go for as true a white roof as possible. Years ago, a friend with some mobile home rental units painted the roof of one silver and one white. He then turned off the AC and put a thermometer in each unit. Want to guess the temperature differential? The white one was 32 degrees F cooler than the "reflective" silver roof. Can you imagine if it was a black roof? When I lived in Louisiana, I experimented with water on the roof and on the AC outside unit. An alternating brief water spray followed by a 15 minute evaporation sequence will keep the roof cool with low daily consumption (.1 gallon per square feet per day). Even with high humidity, I recorded a 12 degree drop in interior temperature at the ceiling. However, this benefit is less the more R-value you have in the roof. As for the AC units, I put a fine fog mist water spray on the outside unit. I saw a 7 degree drop in the air coming out of the central AC register. However, many newer window units are designed to splash the condensate up on the condenser coils. To assure no condensation, what would be the humidity goal inside? I find 50% is the magic number for comfort but equipment is different. I have a feeling anything much over 60% R.H. would have a tendency to sweat.