A tale of two houses

It was the best of times, it was the worst of times. (Don’t worry; that’s the end of the literary pillaging.) I poked my head  outside this afternoon at 5 PM, thinking that maybe I should open the windows to warm the place up a little. As I go outside, I noticed that the neighbor’s AC unit was running. The inside temperature in my home was 72º, outside was 88º.  So why am trying to warm up and the neighbor cool down?

Several reasons as it turns out.  I’m living in an ICF (insulated concrete form)  house that has one of our whole house fans installed. Whereas the neighbor’s house is a  low mass stick framed house, and certainly has no whole house fan.

Of course whole house fans are great – but what seems to be a great combination is lots of mass to store “coolth” (made up word meaning the opposite of heat). I’ve been able to survive quite well all summer with just a whole house fan for cooling – no AC.  That said,during the second week of 105º  days, AC would have been nice for about 4 hours per day.

4 thoughts on “A tale of two houses

  1. The only problem with a well-insulated house is that you need to maintain the temperature. If you go away on vacation for even a week, and the house warms-up, it’ll take a LOT of work/energy to cool it down. Even just upgrading the windows on an old house to dual-pane has this effect.

    What I’m really interested is ways to combine a whole-house fan with automated dampers, and tie it in with a standard AC/Heat system. I imagine it could be done with X10 controllers and a ‘house computer’, but are there any simpler (or, at least, pre-designed) systems to do this?

    I saw that you setup an automated system for a museum? The automated dampers in that system — is that something you could do in a residence? or were they just totally industrial-only?

    Thank you for any follow-up!

  2. You’re confusing insulation level with high mass. Let me use the comparison of a refrigerator. Without well insulated walls and a well sealed door heat would flow into the refrigerator at a much higher rate.

    The other part of the equation is cool-down or warm-up time. Take a single warm beer into your refrigerator; now put 60 warm beers into your refrigerator (hey it’s a party..). You can do the experiment, and you’ll see that the higher mass of the extra beers requires additional work on the part of the refrigerator. Since it can only operate at a certain heat transfer rate, it will clearly take longer to cool down the extra beers.

    Both analogies are useful in understanding how your house functions. Of course houses have additional issues like internal loads (lights,etc), and solar loads.

    Setting up an automated system: At this point, if you want to integrate a whole house fan with your HVAC system, you’re on your own for details, although we’d be happy to review your scheme, and make sure that you interface with our systems properly.

    If you have a window that could be motorized, that would be much easier (and prettier) than using one of our dampers for automatic inlet air.

  3. Yes, you’re right, I was mixing-up the issue of thermal capacity with insulation. I only mentioned it because the house I just moved into has better insulation than my previous, but also has a lot more thermal capacity so it’s actually been HARDER to maintain a cool temperature 🙁

    The only automated windows I’ve been able to find were small casement windows with a crank handle to which you could attach a remote-controlled motor. Connect the motor to an X10 controller etc and you could EVENTUALLY create an automated system. But why hasn’t anyone designed something pre-built??

    Ideally, I’d like to build something that could tie-in to a standard thermostat, maybe as the “stage 1” of a 2-stage A/C system? Not quite sure how that works but the idea would be that when the thermostat is just trying to ‘maintain’ the temperature it would actually trigger a circuit which compared the inside/outside temperatures and ran the ventilation rather then the compressor. Or, do you know of any A/C systems that already know how to do this?

  4. All good ideas… Why don’t we have automated systems and controls for “free cooling” ? In one sentence: cheap energy. Keep watching for an announcement on our first step into the WHF automation world.

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