Thursday, July 10, 2008

Can Air Conditioning be Green?

So we’re starting to feel a little more at home now that we have gotten the first few scratches in the new floor and have little handprints on the walls and windows. When we first moved in, it felt like we were vacationing in someone else’s house. I think this is because we were cautious about all the new floors and walls- being careful not to dent, ding or scratch anything. We still are being cautious, but the reality of having 3 kids is setting in and we realize at some point, we’re just going to have to settle for the “patina” that comes with children. I have no idea how the new wood floor is getting scratched!

One thing we’ve gotten a few questions on the last week is how can our house be ‘green” and still have air conditioning? Good question. We’ve never lived in a house with built-in air conditioning until now. We’ve had window AC units before, but never the full meal deal. So, here’s the scoop on our AC:
- The existing house had a new AC unit, sized for 2 tons. We didn’t want to toss that equipment and refrigerant in the landfill and so decided to keep it in use.
- The existing AC unit isn’t large enough to provide cooling for the entire house by normal standards, so our mechanical contractor initially recommended that we reuse that AC unit, plus add another 2 ton unit. We resisted, because we don’t like the inside air too cool in the summer- we just wanted enough to take out the humidity and keep it comfortable.
- We settled on reusing the existing AC unit and only air conditioning the upper floor (where the bedrooms are). We have an opening between the first floor and second floors which acts as a natural convection chimney, helping to move air around the house through passive ventilation. The 2-story space allows the cool air to fall down to the first floor and keep it cool as well. By doing so, the ac unit works a bit harder and stays on longer when it does run – which actually helps improve its efficiency. We also tied the return air ductwork serving the two floors together to help balance the system.

- Because we have such good insulation in the walls and roof, and good air sealing, along with great windows the house stays naturally cooler. When it cools down, it tends to stay cool. It’s the same concept as the coolers you carry to your picnic – we keep the cool air in and the hot air out. It helps that our living spaces are facing north and we have exterior sunshade above the windows on the south.
- At night, when it isn’t too humid, we open up the windows and let the cool air in. Every room has windows on at least 2 sides, so it’s easy to get cross-ventilation.
- We keep the thermostat at 78 degrees, so the AC doesn’t have to run much. In the winter, we’ll keep the temperature set at 65 degrees)

It’s not such a bad thing – actually being cool enough to sleep. We’re better rested and happier people if we haven’t stayed up all night sweating in a hotbox.


Anonymous said...

I bet you are glad you have the AC today at 100+ degrees!

Anonymous said...

How many panels does one need on the roof to feel okay about cranking the ac? Live a little, you earned it.

Kevin & Roxanne said...

Yes, we have been glad to have the AC, especially on those humid days. Don't worry, we don't feel too guilty (okay, just a wee bit).