Quick question. I have an older house remodel in which I am taking out the old HVAC system from under the house to install a complete new system.
My options to reinstall would be either in the attic which would get really hot. I redid the roof with ridge vents down the length of all ridges to help with this.
I could install under the house-- however, the crawlspace is really crampped-- (I wonder how they ever got the original system in unless it was during new construction.) Yet, there is a tendancy to get a lot of moisture under the house.
What is your advice in this matter? Attic?? Under house?? Eliminate the moisture problem?? Ensure I have solved the hot attic problem??
Soffit vents? If not, your ridge vents may be totally useless.
If it's "really hot" up there, I'd look into fan-assisted, thermostatically-controlled ventilation. I did recently, as did a friend, and it works great in terms of avoiding roasting shingles and heating house from above. In your case, you may want the fan blowing in with exhaust along ridges.
As to where to put unit, I'd ask the installer- you may need all new ductwork. Furnace may enter discussion, too.
Moisture problem definitely should be addressed, with vapor barrier, ventilation, exterior swamp drainage, whatever works. DAGS on this and await a deluge of hits.
I've owned my own HVAC business for about 28 years and think I have a pretty good idea of what you should do.
Fix the water/moisture problem under your house, then put some vapor barrier (plastic, 4 mil) on the ground, then put your ductwork back under the house, use metal trunk line with metal ATDR take-offs/taps, either flex or metal for the lines and return, insulate ALL metal with 2" foil backed ductwrap after you screw and tape all seams.
I've done thousands of systems in middle tenn, in both attic and under floors, unless the house is on a concrete slab, or it's a two story, no way would I put it in the attic.
Also, about attic ventilation, I would not live in or have a home without POWERED ATTIC VENTILATION, I've had to work in attics when the temp was 180, after several tests I have performed with attic ventilation, Powered Fan Ventilation more than pays for the 1 to 3 cents per hour the the fans use compared to the 25 to 50 cents the a/c compressor uses.
You don't tell us the critical question of where you live.
If you live in the snow country, under the house would be good, because you gotta remember, an a/c system is basically a heat exchanger- throw off heat system. The fan takes the heat from the refrigeant and transfers it away, by blowing it away. Under the house would simply mean that all the heat you took OUT of the house, is now UNDER the house, and we all know heat rises....
In the attic is better, but the best is on the side of the house. Away from the house. Shaded. With a clear open view up to the sky to let the heat rise and go away. Also in the attic, the moisture condensation that comes out of your house gets deposited in you attic, and if your drip pan and pipe system ever becomes clogged up, you'll have mold, legionair's disease, mosquitoes, bugs, insects, rats, squirrels, termites, damp, rot and falling down sheet rock ceilings.
Installing a ridge vent was very wise; bang for the buck. Make sure now you have soffit/eave vents to help draw the cool air from below, up to the ridge vents to force the hot air out.
Two eave louver vents vertical at each end of the house attic is good also.
Do NOT install any of those stupid electric fans...they waste more electricity running them than you save.
Running some of that cheap 2' panels of styrofoam vents up the sides of your roof would also do a lot to make your roof last another 20 years (heat kills, not sun or weather, roofs) and lower your AC bills even further.
The best desiegned house is a giant Bernoulli vent....
I think he's talking about the ductwork ... but what would I know.
Either way ... if you've got a lot of moisture under the house, then overhead may be better. If your crawlspace is limited, overhead is better. You'll get a lot of latent heat from the attic, of course, so if you live in sunny climates where AC is more important than heat, you might consider crawlspace (you can install vapor barriers, fans, etc to remove the moisture).
Contact several A/C companies in your area for quotes, ask them where they'd install it, and ask them why ... the answers may prove enlightening.
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