window units vs.central a/c

[vojacek]

we are building the 2 story universal cottage in southeast texas. we plan to use wood in winter. summer here is very long, hot, and extremely humid. energy effiency is of top concern. so window units or central a/c?  

[Bart_Cubbins]

Do you need to cool the whole house or just one or two key rooms??

[glenn kangiser]

At our house in the valley -similar to Texas temps-maybe not as humid, when we remodeled we put in two fairly large window heat/cool units but mounted them in their own frame so we could either cool the living room-kitchen area or the master bedroom/bath independently.  We also had a small unit in the study.  Between my wife and I we usually only used a small portion of the house at one time.

This seemed to be a good way to keep our energy use down.

We originally heated with wood but my wife wanted to cut down on the ash dust so we switched to the Monitor diesel oil heater (discussed in forum earlier) which only burns about 100 gallons of off road diesel per year, keeping most of the house fairly warm- unused room doors were kept closed.  House is about 1800sf.

[vojacek]

the 2story is actually an addition to our existing small house. we have a 1200sqft. house now w/ window units. this area will be turned into a family room and guest. the new addition will be upstairs bedrooms for all our kids, and a large kitchen and foyer downstairs. so yes, we will need to cool most of the new house most of the time.

[Amanda_931]

Some combination of shade, ventilation, insulation, and thermal mass does make all the difference.

I'm personally considering a sleeping porch.  Very little shade up the hill in the middle of the field.  Light-weight building, no insulation or thermal mass, just get down to the outside temperature and have a nice fan.

But the well-shaded community center at the nearby intentional community is usually pretty comfortable in the summer.  I've never really noticed that it doesn't have AC.  ditto for a couple of the houses over there.

Friends with a sunny very high thermal mass house put up awnings and plants on vines on the south side.  North side is mostly in the ground.  They get by nicely with one small AC window unit for their maybe 1000 sf house, claim that that is mostly for humidity control.

I lived in the San Fernando Valley (LA--didn't quite spend enough time there to become a Valley Girl) one summer and it was without AC.  I did flee in the mid-afternoon.  It was tolerable by eight or so thanks to a nice exhaust fan.

And spent the dreaded summer of 1980 in Rayon City Tennessee (part of the greater Nashville area), where the highs for the day for the entire month of July were over 100 with a good exhaust fan, not closing the house and turning on the dreadfully creaky AC over three times.  The fact that we had a high of over 100 means that we had a low of over 80.  Someone who lived down here at the time remembers how really COLD 75 felt on about the third of August as he sat on his deck drinking his morning coffee.

But I now really NEED AC in the car.  Getting old.

Consider AGS or PAHS.  Especially if you are building anywhere but on top or at the bottom of a hill.  This will, if worked correctly, do for both heating and cooling.

[Amanda_931]

And since it's not quite part of the same rant....

More conventionally, consider split system AC.  These can be available as zoned.  Probably right expensively.  Plain split systems were common additions to older (all-concrete) houses in the Western Pacific when my parents were still alive.  Require only a 3-inch hole through the wall.


This guy tries to sell you his full information, but a decent search engine would probably get you something, and asking family and friends, the rest, including semi-trustworthy local installers.  "mini-split ductless" if you have to make a choice on this site.  Might also look at "mini-duct pressurized" for 2-inch ducts with a central air system.  Especially favored for installation in historic houses.

http://www.dulley.com/laircondi.shtml

Ventilation--right number of air changes per hour is still important.  Pressurizing the house can keep unfiltered air out.

[Daddymem]

If you have to look into heating for the addition (or if your current heating is outdate) you might look into a geothermal heatpump.  It is really quite simple, you heat the air below ground (or cool it) to the desired temperature.  Since the air below ground is ambient throughout the year there is less heating (or cooling) to do.  A heatpump in its most simple form is like putting an air conditioner in your window backwards.  The newer geothermal heatpumps don't even require the catacomb pipes running through your yard; they use your water well (or a well specific for it).  You can add air-to-air heat exchangers, humidifiers, and hepa filters to the modern geothermals.

[Amanda_931]

That'll work too.  Any heat pump will.  Although I wasn't happy about the heating performance of the air-to-air one I had in Nashville.

On just straight AC options, here's a cost vs performance and good looks of through-the-wall, mini-duct, and ductless, from a couple of years ago.
 
I don't think that the small split systems were that expensive in the Western Pacific (everything was shipped, usually low-volume retailers--made prices very high, but often direct from Japan, which lowered them) when I knew somthing about them.  But the zoned jobs probably are.  And finding a dealer who knows--or cares--about them may still be a problem.

http://www.oldhousejournal.com/magazine/2003/august/keeping_cool.shtml

[Shelley]

Amanda, I grew up where you are...b4 AC was in the reach of the common man.

Nights on the porch.  Then to bed and don't let one body part touch another.

But, you ain't seen nuthin' til you spend time where he's building.  SE Texas gives new meaning to the word sweltering.  He needs all the AC he can get

[Amanda_931]

Very likely.

Only time I've been to south-east Texas it was on the coast--Padre Island, for instance, driving through to Mexico.

And we do know that the phenomenal growth of the South has been due to air conditioning.

[vojacek]

i grew up in a small town 20 miles from parde. my granparents stiil live there without ac!!! my granmother claims she's USED TO IT. whatever!!! i spent the last two summers here pregnant, (no i'm not an elephant, just really fertile!)so i know all about sticky parts! every summer there are cases here of peolpe found dead in their homes from heat.  A/C is such a huge issue for us and this 2 story. window units will cost $2000, central can run $6000-8000.  i just don't think running window units constantly during the summer in almost every room is gonna be very effeicent. but, is the savings (if there is any)from the central unit worth the inital cost?

[glenn kangiser]

Kinda sounds to me like you may need a whole house solution, but I think this is a place where you should find a knowledgeable, reputable local professional and get his or her opinion also.  Be sure to check references with friends and other ways -BBB etc.  There are a lot of jerks out there also.

Johns designs are already well insulated I believe.  Another thing that seems to help in our cabin is having the front porch enclosed as a buffer between inside and outside temps.

BTW, I also may look pregnant, but am not.

[vojacek]

hey glenn, my husband has found that reducing beer consumption will also reduce that pregnancy look. for me, it just reduces the chances of real pregnancy!!

[Bart_Cubbins]

If you're cooling down the whole house, a single larger central unit is bound to be more efficient.

You might want to consider one of the high velocity mini-duct systems. The higher speed airflow mixes up the air in the entire room, and the small duct size makes it easier to retrofit existing construction. No experience with them personally, but they seem to be getting quite popular....

http://www.hi-velocity.com
http://www.unicosystem.com
http://www.spacepak.com

Here's a good place to get some free HVAC advice...

http://hvac-talk.com/vbb/

Bart

[Epiphany]

I'm in NE Texas, near Dallas.  Grew up here without AC but did use swamp coolers (evaporative) at night.  But we also left all the doors and windows open for the breeze, which we can't do now.  

One more reason I want to build one of John's small houses - lower utilities.  

Lower cost to build, lower utilities, lower taxes, less to clean and maintain.....

[glenn kangiser]

Hey Mrs. V, (sounds a bit formal doesn't it)
I wish it was a beer gut, but too much beer usually gives me a head ache so I only do one once in a while.  They tell me I'm crazy enough without it.

It's not too bad - just a few months along.  
Actually I've been investing in ice cream, but I keep eating up my stock, and my profits keep melting away. :-/

[vojacek]

we're from texas....Blue Bell  creamery is down the road from us  and Shiner Bock on tap in every bar. so trust me, i feel your pain. i'm sure building a 2- story universal cottage in the middle of summer, in texas, (and in 2 weeks!) will give me back my more girlish figure. that is of course,if it doesn't kill me!

[glenn kangiser]

I picked up a case or two of Shiner Beer in Shiner Texas when I was trucking -direct from the brewery outlet or warehouse as I remember.  I used to haul loads of tool boxes from Winters, TX to Fresno, CA.

Nothing like sucking the the top off a frozen frothy mug of Shiner after a day of concrete work in the hot Texas sun.  Now I'm getting thirsty.

I wonder if going back to concrete work would give me my girlish figure back

[vojacek]

why wonder? come on down to texas, we could use the hands. all the free shiner you want. it's so good, you don't wake up with a headache, you wake up still buzzed!

[glenn kangiser]

 If you folks were a bit closer I'd definitely be there to help.