Heating/cooling system recommendations for this small house?

Question

I will soon build my first house and I need to choose what type of heating/cooling system I'll have installed. I know very little about this and I'm seeking recommendations, ideas, suggestions, etc.

The details: The house will be in the city limits of Asheville, NC. It will be a three story house with a basement foundation (I'm counting the basement as the bottom floor). The footprint of the house is approximately 24'x24' (I'm still working on the design/plans), and the top two floors will be approximately 1000sf. The main/first floor will be open, essentially one big room with kitchen/dining/living room/half bath, and the top floor will be two bedrooms and a full bath. The walkout basement will be finished as a den with storage area and full bath and sauna. The home site is very shady, under huge oak trees, so using passive solar is not really an option. In terms of my priorities the order is 1) simple/low maintenance, 2) efficient/low operation cost, 3) up front cost, and 4) "green".

I'm interested in heating using a wood stove because it's such a simple system (i.e. very few moving parts to break), it seems like a low maintenance way to go, and the wood stoves available now are very efficient. However I feel like I should have a wood stove as my back up heating system, even if I do use it most of the time, for resale value purposes (many folks don't want to bother with chopping wood, loading/cleaning the stove, etc.). Another aspect of a wood stove that's attractive to me is that I can still heat my home during a power outage. Around here wood is plentiful.

A geothermal heat pump is also interesting because of its high efficiency and because it also doubles as an AC system. It's also likely to be very attractive to buyers if I ever sell the house. However I'm concerned that a geothermal heat pump system is pretty complex (it's not likely that I could fix any part of it myself) and may require considerable maintenance, and it won't blow very warm air (I've slept under a heat pump vent/register in the winter and it felt like I was under an AC unit -- not pleasant).

Can you comment as to which HVAC options are appropriate for someone in my situation? I know there are numerous other alternative heating/cooling systems available that I've not yet considered, and the two mentioned above are probably on opposite ends of the spectrum.

Answer 1

For central A/C, you'll need ducts and vents. Once you have the ducting in place anyway, you might as well use it for both your heating and cooling.

For a three floor house, you definitely want some kind of zoned system, with a thermostat on each floor. (I wish my 2-floor house was zoned.) You may want multiple cooling systems, or maybe one system with motorized dampers to control airflow to the various floors. Your HVAC contractor should be able to make a reccomendation of what will work best.

Whatever you do, do not skimp on the ductwork. Your HVAC contractor should run calculations on how big the ducts need to be. For many home builders, HVAC is a minor concern in the bulding plan. Make sure everything is sized correctly. Changing ductwork after the fact is very difficult. And if you don't have proper ducting, it won't matter how good your central heating using is.

For new construction, Geothermal is usually a good candidate. It can provide heating, cooling, and hot water with crazy efficiency. The installation cost is MUCH higher though. (There are tax credits that will offset some of the cost.) If you aren't up for geothermal, I would go for a traditional air-sourced heat pump for your heating and cooling needs. They are pretty efficient (at least in moderate climates). You are pretty much in the perfect lattitude for a heat pump.

However, I would not have the heat pump (air-sourced or geothermal) as your only heating system. Some kind of alternate (non-ducted) heat source would be a good idea. Heated floors, gas fireplace, etc. Air-sourced heat pumps lose their efficiency in very cold weather. And it can also be nice to have gentle air convection, vs a duct that is blowing in your face. You also have a backup system in case your central heat fails.

That said, ducted air is nice, because some regular circulation of air in all the rooms of the house avoids that "stagnant air" smell, as well as cutting down on dust, dander, etc.

Also, central air systems give you options for humidification and de-humification of the whole house. Look into that. It is usually a minor cost increase in the system, but can make a major difference in comfort.

Answer 2

The most comfortable heat is hydronic (baseboard water or steam registers or in-floor). The ideal cooling is forced air.

Budgets aside, I'd go with in-floor heat from a geothermal install, using the wood as you see fit for peak cold/ambiance. I'd then install proper duct work and use central air for cooling. Of course, in-floor on a 3 story house probably won't work, so floorboard might make more sense.

If it's a really small house, you could perhaps forgo central air and look into one of the mini-split systems.

Answer 3

If you're not opposed to heating with wood, consider a wood furnace rather than a simple wood stove.

You can get wood furnaces with boilers as well as forced air, so it's possible to design a system that allows you to switch from wood to another source to heat water for a radiator-based system. There are also wood furnaces that you can place outside the house, so there's no need to bring wood into the house.

Answer 4

Goal #1 is insulation. Can't say enough about good insulation and windows. Get that right during construction and everything else is easier. Also, insulation.

Cooling sounds like it'll be a bigger cost than heating, based on your location, so I would concentrate on that. Look into passive methods for cooling your house--screening with trees (sounds like you have this option available), having windows that only 'see' the winter sun via long sloping roofs, and a central "cooling stack" (probably up a set of stairs) where hot air can run to a skylight or other exhaust system. I was really impressed with the green efforts in the Zion Canyon Visitor Center; even when it was 95 degrees outside, it was 75 inside, with zero energy expended.

Then focus your cooling efforts on the hottest days and the hottest parts of your house. Zoned AC -- more zones costs more up front, but it's a lot less money to run those lines during construction. Or even through-wall AC's, though insulation around them gets dodgy.

For heating, many small heat sources provide more even heat than one big one, but they generate heat less efficiently unless they're electric. Our house has multiple small gas stoves, one in each of the outer-most rooms, and they work great and don't use very much gas at all. Small electric free-standing radiators can also warm an area right up, and with the good insulation you've put in, you won't need to keep them on much; even though electric is generally much more expensive, you're only heating the part of the house you're in. They are also really cheap (e.g., this one is $50 and heats my entire basement) and portable.