17 December 2009

Our First Change Order

Alternate title for this post: "The Water Heater Chronicles, Volume 8."

We've been working toward a possible change to our HVAC (heating, ventilation, and air conditioning) system since we got home from Hawaii. I haven't mentioned it because I wasn't sure it was going to work out, for two reasons: cost, and it would have to be decided before the slab was poured. Last week, we had considered it and dismissed the idea, although the HVAC contractor continued working on the bid and payback numbers. This week, the cost was recalculated a fair bit lower, and we found an Austin Energy rebate that would save some more (although not nearly as much as the federal rebate, which will pay for 30% of our HVAC costs).

So what's this fabulous new system, you ask? And what does it have to do with the water heater?

A geothermal heat pump. (I'll get to your second question in a little bit.) The HVAC contractor will bore three holes about 300 feet deep in our yard and run piping all the way to the bottom. During the winter, those pipes will carry heat from the earth (which, that far down, maintains a pretty constant temperature throughout the year) and use it to heat our house. During the summer, the pipes will carry heat away from the house. We had already planned for a very efficient version of a traditional air conditioning system, but this will be even more efficient.

AND there's an option to tie the water heater into the middle of the system to heat water with some of that heat that's being sent back and forth! That option has a bigger city rebate and seems to pay for itself almost immediately. We're fairly certain the city will allow us to use an electric water heater with this system (they're usually not allowed in Austin), meaning that when we finally get solar panels, the sun will be powering everything but the stove, fireplace, and grill on the back patio. We are actually excited to see how low our utility bills are going to be, given all the efficiency we've worked into the house.

Plus -- and this is the part Steve is most excited about -- we'll be able to omit the indent in the house where the outside air conditioning unit was going to sit, which will give us 18 square feet of additional space in the master closet. If I had known we were going to make this change, I probably would have configured the master closet and bathroom area totally differently, but it's still nice to have the extra space. The real excitement, though, is the efficiency of the system that is responsible for the majority of our energy consumption.

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