You should have a dedicated water heater (could be a 30 gallon, doesn't have to be 40) for your radiant heat, some kind of pump and thermostat to control the temp. The tubing shouldn't be expensive, but that sounds like a pretty good deal if that $700 includes all the parts. If it is just labor, no way. It should take no more than three hours to do. What state do you live in? If you live close to me, I could give you a few resources of who to call. Hubby does radiant heat on a large scale. He gave me all this info.

Hi David Cary. Ionized is right. I have two beach houses, both with unsealed crawl spaces and the a/c ducts are in them. If the crawl space smells bad, the a/c smells bad. I have smart vents in one of the houses so was able to install a high efficiency dehumidifier which has done the job of keeping the moisture low enough to reduce the odor. Also, be careful what kind of insulation is used in the crawl space (between floor joists). In one of our homes, Dow Pink Panther was used and it smells like cat urine when it gets damp! We have high velocity in our city home (retrofit 120 yr old house). We are very happy with it but I wouldn't install it in a new build, It's expensive, loud and not as efficient as a standard system. You can really hear the air rushing out of those small ducts.

We recently did a renovation with an extensive high-velocity system. It's working great so far (three months or so). A big advantage is that it requires far less returns than conventional - a second floor with three bedrooms has only one return.

For comparison, here is a link to some unico (not affiliated) high velocity ac house plans. Sample 1, for example, is a 3500 sq ft house with a cooling load of about 60000 btuh, and they've used 18 outlets and 3 returns. It seems a bit of a sprawling floor plan, so the number of returns might be more than needed in a more traditional stacked house (we're counting on one return on the first floor servicing the whole thing, but it just depends on the situation). So, you could look at these as a starting point. There are so many variables in hvac--kind of makes it fun. Our third floor AC was performing terribly the month after we bought our house--until we figured out that the previous owners had set the thermostat on our attic vent fan to 175F!!! We turned it down to 90, attic is now vented regularly, ducts sit in a cooler space--voila! AC works like a champ. I hope your problem has such an easy fix. You've probably already done this, but you should visually inspect every connection you can see in the system. We're housesitting for our neighbors while they're out of town. I happened to notice that I could see into their basement through a grate in the dining room. Odd, I thought, so I went down to investigate. In the basement, I find 8' of 12" flex return duct coiled in a heap on the floor under the return grate; the whole thing's come loose. I shudder to think what their heat was like if this had gone unnoticed all winter, feeding cold basement air into the system instead of simply boosting warmish return air--yikes!. These installers are human with deadlines, and I can easily see a rushed connection failing and throwing off the system. I'm not defending it--heck, I work in quality assurance on projects that require high reliability. I just shake my head at what goes on in the "real world" where there is little inspection, oversight, or feedback on most people's daily work. In such a setting, I've learned that (no surprise) mistakes are the norm. Here is a link that might be useful: High velocity ac plans