It's Summer - how do you set your air?

Never ever??? Not even in the middle of winter??? Well, that's okay. I'm prejudiced against the Old South anyway.

 

I'm sure SC has many things to recommend it (my folks have taken several vacations there to birdwatch), but the climate isn't one of them.

I lived in the Washington DC area as a kid, and I'm tellin' ya, you're going to have to drag me kicking and screaming before I leave this cool Pacific Northwest climate in the summer.

(Though as Dave says, we're going to go through 3 days of ~90-100F weather. And then back to the 70s on Monday. Poor us. :violin: )

 

Hot Climate

I live near Dallas. I designed my house to be an active / passive solar home and the design has rewarded me with a comfortable house with extremely low energy bills. It's the "Prius" of houses.

We keep it around 78 (day) and 76 (night) in the summer. Two-speed A/C keeps the dew point low so it's very comfortable.

Check it out at http://www.enerjazz.com/house/

Paul

 

Re: Hot Climate

Wow, looks like you put alot of thought into building that house. Excellent work on it. I may have to drag you up to my neck of the woods, to see what else can be done with mine. :mrgreen:

 

Re: Hot Climate

Nice house. A bit too clean for my taste, though. Needs more cat hair scattered around, to give it that lived-in feel.

 

enerjazz:

awesome house!!
i consider myself a conservationist but i can only dream of the dedication and acomplishment you have achieved.

 

Only air conditioning we have is in the bedroom since I have to sleep during the day (work third shift). The house stays very comfortable most of the time since the west side is shaded by some big oak trees. I keep the car at 73 all the time. We both like it there and I don't think it affects the mileage that much.

 

i agree with air conditioning not affecting mileage much.

here is a screenshot of my screen today.

background, it was HOT!!

as you can see, the temp is 99º and i had air fan speed set to med and temp set at 72º

was on freeway driving bet 55-70 mph (around here your speed isnt dictated by signs, its controlled by traffic)

as you can see, my mileage didnt suffer much.
obtw, it was 101º yesterday!!

http://www.geocities.com/daveinolywa/image...es/hot54.2.html

 

Mine is set to 74 rising to 78 at mid day. In western Washington it is rarely activated, though this year may be different, we will see. Nights are cool into the 50's and the air is off and the doors open. Sometimes the blankets are necessary even in August. The weather this year seems weird.

 

I keep my "air conditioning" all the way on the cold side of the slider (Blazer of DOOM does not actually have A/C, just "cold" and hot on the temp slider..."cold" isn't really cold at all...ugh). And to cool my home, it's all windows open and all ossilating fans on high. House is surounded by 200 foot cedar trees, so is always in shade no matter what time of day. It's blissful.


When is it going to raaaaiiiinnnnn?!?!?!?!

 

It rained really hard yesterday as well as Sunday!
.... Oh, you meant where YOU are ;-)

The house had a window A/C when I bought it (15 years ago). Probably a really inefficient unit now given it was hardly new then. We only used it the first summer each of the girls was an infant. After that, we just tough it out, it sits in the basement mess. I could afford to run it but 1) I'm CHEAP and 2) It doesn't come under the concept of 'need' with respect to using energy. I'm sure that would be different if we lived in a place where the overnight low was 85 or 90 but MOST nights, it gets down at least to the low 70s.

Shades during the day, open the windows at night (knocking on a REALLY big piece of wood), we haven't had skunk issues this year. Ceiling fans in 2 bedrooms, floor standing fan in the other and one in the living room.

I am thinking it would be smart to add a "goes on when the attic is hotter than outside" fan in the gable end. I don't think the "soffet and ridge vent" systems pull the heat out very efficiently. Better than passive gable vents, but not ideal. On the other hand, the insulation in the ceiling is R-48 so maybe it doesn't matter how hot the attic gets?

 

This is the only part of the advice that seems questionable to me, maybe because it relies on unstated assumptions or maybe because of my ignorance. In a house in which the return air ducts run through the attic (like mine) running the fan constantly would continually expose room air to heating/cooling (summer/winter) in the attic. In other words the return ducts are themselves heat exchangers; hopefully pretty well insulated and therefore not very good heat exchangers, but they would nonetheless add to the cooling/heating load.

In the spirit of your other advice I've long since closed off most of the returns in my one-floor open-spaces house except for one very large one immediately adjacent to the HVAC unit. (Yes, it is sized to provide adequate return.) Most return air thus passes through the living spaces and avoids additional attic heating/cooling. The return grille is a filter type to keep the HVAC and all the ductwork clean.

Do you know of any residential AC units that have an optional heat exchanger to pre-heat potable water in a storage tank, which in turn feeds the nominal hot water heater? Back of envelope calculations suggest that such a system could both noticeably help AC efficiency (because the AC compressor would be rejecting heat into ~70 F water instead of outside air at 100 F or more) and reduce the cost of heating water.

Obligatory Prius content: I keep my AC on auto but continuous recirculate and adjust the temp up and down for the right compromise between temp and fan noise. Oddly enough I seem to prefer 72 F in the morning and about 75 F in the evening.

 

Thanks! I'll keep this in mind when/if we replace our unit.

Right, but I was trying to describe a once-through system: there's no cooling tower, it just makes use of the utility water that comes in from the street as a source of not-very-chilled-but-still-cooler-than-the-summer-air water. Imagine a storage tank fed from the utility water main. The tank contains a heat exchanger to pre-cool the AC coolant that comes out of the AC compressor; the AC coolant then continues on into the usual air heat exchanger. Heated (or more accurately "warmed") water from the storage tank supplies the usual hot water heater. It may not help a lot, but the benefit comes for no more than the cost of one storage tank and one extra coil. No moving parts.

 

On the subject of using a residential A/C to heat water - yes, it's available. I have a ground source (geothermal) heat pump. In the summer it uses "waste" heat to make hot water instead of dumping it to the earth. I added solar water heating, so I get about 95% of my hot water essentially for free.

Most GSHP manufacturers offer this option. I've had my GSHP for 8 years with zero problems and outstanding energy performance. See some details on my house website:


The Westbrook House - The Prius of Homes
http://www.enerjazz.com/house

Direct geothermal info page:
http://www.enerjazz.com/house/whgeo.html

Paul

 

As much as I love my Prius, i dont think that the Prius is a match for your house.

 

Hello Tony Richard etal-
Ok, on the issue of throttling ducts to overcome stack effect, you probably shouldn't. If the system was designed properly the additional air through the remaining duct work will have a much higher velocity and will put the fan in an inefficient part of it's fan curve. You will end up with more noise and the amount of air necessary to overcome stack effect is much greater than you might imagine and more than you can accomplish in this way. Having said that, do whatever you wish but realize that if your duct sysem is in unconditioned space you the higher static pressures will also lead to greater losses from leaks in the duct system and also couse unintended interstitial air movement within the structure that can cause other problems. This is a complicated issue and takes a long time to fully explain. If you are interested, let me know and I can guide you to supporting documents to support my assertion.

If you run your fan when the unit is not calling for cooling, run it on intermittent with at least a 10 minute delay in order to let more of the condensate water to drain from the coil. The coil will still be wet and that moisture will still be re-evaporated into the space which is a waste of energy but the delay will help minimize the problem. In humid climates the problem is worse. If the recirculation of air allows for a higher set point at the thermostat, these losses may be recovered but the cost will always be higher rh within the living space. I recirc at off for 10 minutes and on for 20. I have plenty of info on this subject as well.

If anyone is interested in learning more about these sublects, let me know and I will send you some links.

Ray

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How best to cool a house has everything to do with the climate where the house is located.

For those of you who live in a climate like mine in Sacramento, Ca . . . Hot dry summer days and cool nights (90's & 100's in daytime and 60's at night) . . . there are two things that will keep you comfortable WITHOUT using a air conditioner.

1) Shade trees. Preferably deciduous so you get winter solar heating too.

2) Whole House Fan! If you don’t know what a Whole House Fan is - it is a large fan that sits in the ceiling between the attic and interior of the house. It has louvers that automatically open when the fan is on.

The concept (which works):
1) Turn on the fan at night when the outside temperature is cool. It sucks cool air into the house to chill down the interior and also blows the super heated air out of the attic (two for one).
2) Close up the house in the morning before the outside temperature rises.
3) Turn the fan back on when the outside temp is about five degrees above the interior . . . the large air movement will feel cooler on your skin.

I have yet to turn on the central air (or any air conditioner) and the inside has never gone above 80 degrees. I live in a 1920's painted redwood cottage with little insulation and original single pane windows. But I am blessed with shade trees, a Whole House Fan, and low cooling bills!

I can run the WHF all night long for less than it would cost to run the AC one hour.

If you plan on getting one . . . by all means get the large belt drive model and run it on low rather than running a small fan on high. Large fan with belt drive on low equals quieter operation. I also have an Intermatic Heavy-Duty Digital 7 Day Wall Switch Timer (SS7C) which turns on and off the fan several times during the night - otherwise all night long would be overkill.