I have reading this forum with interest and it is VERY informative! I like to read about people who have 'been there, done that' before deciding on something. We live in south Alabama where the main concern is hot, humid summers. We are building about a 3 acre pond and a 'retirement' cabin (more like a house...2500 sq ft)using mostly all reclaimed wood and beams from old houses(will be timber frame.) We are very interested in geo thremal for the pond. It almost doesn't make sense not to go geo!I have read through these post and have a few questions. When you mention the power bill being MORE, is that just for running the system? I guess since we don't use propane gas at all,(we have an all electric heat pump) our power bill should be LESS, right? Right now our power bill runs around 250.00-300.00 a month, whole house. About what kind of savings should we expect from the geo? Also, looked at the Slim Jims. Has anyone used these and how does the price compare to the coils? ONE more question....does anyone that lives in the south feel like the air inside in the summer is comforable, in other words, not humid? I think I read somewhere this system is also a dehumidifier. We are also looking into siting the cabin to take advantage of passive heating/cooling. The south side will have quit alot of glass and am worried about overheating. Thanks for all your help! This is an awesome forum!
southernbelle,
Alot of questions here I will try to cover what I can.
I would start by trying to optimise the building envelope. There are software programs availible that you can model your building in and they will output the thermal performance. They use historical weather data to calculate the heating and cooling demand. It will calculate solar gain. Once you have the model you can optimise it by changing glass type, adding overhang, reorienting the direction, adding insulation, ect... You can see the effect of changes imeadiatly and decide what's cost effective. The one I used is called HVAC-Calc and it's ~50.00 for home-owners.
HVAC-calc The Slim Jims you refered to appear to be pretty good units. These things are installed all over place in Asia and Europe. They're duct less units so they are pretty cost effective fo retrofits. Their top of the line units use a variable speed compressor so you can try to match the output to the load. Your floorplan and lifstyle will dictate how effective a zoned system can be.
Generally speaking the geo system should cost you about .60 to the dollar, btu for btu of what a good air source HP system would cost. It depends on how mild the climate is. Up north the difference is greater and if you're on the coast it may be less. You really have to do the calculations for your specific area.
There are two types of cooling loads, sensible and latent. Sensible is dry bulb. Latent is wet bulb. The higher the humidity the higher the latent load will be. In a forced air AC system humidity is removed by passing the air across a cold heat exchanger. The water condenses on the cold surface of the heat exchanger and falls into a catch pan via gravity. It's very important that the AC system is sized correctly to deal with both type of loads.
If the system is too large it will cool the space without removing the latent load.
