Consider Radiant Heat when Finishing Your Basement

I am toying with the idea of finishing my basement in the next few years. But one obstacle comes to mind...How should I heat and cool the space? There are 2 problems with adding a new dedicated system. First off, it is expensive. A 3 ton system cost me around $8,000-9,000 last year for a high efficiency unit including installation and duct work. Secondly, There isn't a lot of room in the basement to hold another unit. I have a small area blocked off for the current HVAC system for the main level & hot water heater and I wouldn't want to have to designate more space as "unfinished" just to hold possibly unnecessary equipment.



So I started thinking. The basement shouldn't need much A/C in the summer time since it is below ground. In the past the basement hasn't gotten above 80 degrees and that's without any A/C. It is below ground so it stays cool naturally. So why not put a few vents down there that attach to the first floor unit. Add a zone board and thermostat and it's good to go. The main level A/C that I have currently isn't too taxed in the summertime, so it could probably handle the additional load (I would obviously check with an HVAC professional before doing this). The problem is that I don't think the unit could handle both levels in the winter. The basement and main level are both cold in the winter since heat rises. So I started thinking. I have a 50 gallon, 100k BTU water heater that is 95% efficient. I could run radiant floor heating in the basement to handle most, if not all of the heating needs. If I needed a boost, I could turn the zone on and draw from the HVAC system, but that shouldn't be necessary.

I read that I will need about 20-25 BTUs per square foot of space when it is 0 degrees Fahrenheit outside. So 25 x 1600 square feet is 40,000 BTUs needed when it is 0 degrees. That is only 40% of my water heater's capability. And living in Atlanta, I know that it rarely, if ever gets that cold. I have seen radiant heating systems being sold in the ball park of under $1 per square foot installed, plus the cost of the pump and zone.

So here is the math:

Tubing & Installation Material @ $0.80 per ft x 1,600 sq feet = $1,280
2" concrete slab poured over tubing: $1 / ft including material & installation = $1600
1 Zone including pump, thermostat, relay control, etc = $600
Duct work (to tie into the existing HVAC): estimating $200 x 10 supply ducts = $2,000
Zone board, thermostat and 2 dampers = $750
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Total = $6,230
But realizing that I'd need to do the ductwork even if I added a new HVAC system, I'm really only spending $4,230. Cheaper than a decent HVAC system. And since the hot water heater is 95% efficient, I'm taking advantage of an ultra efficient means of heat.

That may even leave me some money left in the budget to add a second hot water heater. Which would be good when multiple people are taking showers and be a good fail safe in case the current water heater breaks down.

And there is one other great benefit that I haven't mentioned. I'll never have to worry about the freezing cold basement floors that plague most homes. Heating from the ground up is much more comfortable than taking the top down approach!