HVAC recommendations for a 1 bedroom, 700 sq ft outbuilding?

[TitaniumVT]

I've got a one acre property in a Seattle suburb. The climate is fairly mild here, with typically only a few weeks of temperatures in the 20s or 30s each winter, and above that otherwise. I'd like to build a 2 car garage outbuilding with a ~700 sq ft occasional use apartment on the second floor. For the forseeable future, it would only be used by guests, but eventually (years from now) my mother-in-law may live there full time.

What would be the most economical/efficient HVAC system I could use for the outbuilding? I don't need the garage area heated (but it will be insulated at the walls and ceiling). I just want to heat the 700 sq ft apartment above it, so it's comfortable enough for people to live there:

1. Would a forced air system be a waste for heating such a small space? On the surface, it doesn't seem like it would be worth the cost/hassle.

2. If I put radiant flooring in (covered by pergo and/or ceramic tile), would that heat the space sufficiently to keep it comfortable and avoid burst water pipes in the dead of winter? We do get a few nights to a few weeks a year of below freezing temperatures, but it doesn't typically last long. I'll plan to insulate the pipes carefully when I build the structure, and use PEX instead of metal plumbing.

3. Would electric registers or a small electric furnace be the way to go? Natural gas is available in the street, but hasn't been run to the property. I'm not sure if it makes sense to get a natural gas hookup just for the apartment. My 2 to 3 year goal is to replace the old farmhouse that's on the property (currently heated with an electric furnace) with a custom home. At that point, I'll definitely run natural gas.

4. Are there any better options I haven't considered?

I'm essentially looking for the most economical/rational solution from an installation cost/complexity perspective. I don't mind going with a system with higher fuel costs, since this is an occasional use structure. Unless I have guests staying there, I expect to keep the thermostat at 50 degrees for the few weeks in the winter that I need to prevent cracked pipes, and otherwise just keeping the system turned off. I like the idea of an electric solution, since I could eventually look at adding a passive solar system to defray the operating costs (though I'm not sure the math adds up yet to go solar today).


Thanks for any guidance you can provide!

[beenthere]

Radiant heat isn't cheap to install.
A heat pump might be less costly to install.

[coors66]

+2 on the heat pump. They have come a very long way and are seemingly efficient.

[TitaniumVT]

Thanks for the quick reply, guys. So after doing a bit of research, it seems like a heat pump would offer advantages in heating efficiency, even heat distribution, and relatively straightforward installation. Plus they seem ideally suited for moderate climates like mine, and can be used for cooling in the summer. It all sounds great!

I'm assuming the install cost of an air-source heat pump would be less than a ground source? Would $ be a reasonable estimate for what it would cost to buy the pump and have it installed? Do you think that would be cheaper (assuming a payback period of say 5 years) than simply installing electric baseboard heaters for occasional heat? I think I could get baseboard heaters for less than $, and they just need to be hardwired into the electrical system. The install cost should be minimal.

Lastly, any opinions on mini-split heat pumps for new construction? And any recommendations on brands and/or BTUs to consider for a 700 sq foot space?

Thanks again!

[HVACJOEK]

Considering this apartment will be over the garage and the potential for carbon monoxide infiltration exist. I would be sure of a good seal seperating between the spaces,and that the heat pump runs on a positive enough stratic pressure to prevent any flow from garage to apartment space.:cool:

[TitaniumVT]

That's a really great point I hadn't even considered. Thanks Hvacjoek.

On the West Coast, gas furnaces are typically installed in people's garages (very few homes around here have basements). Would the carbon monoxide infiltration risk be the same regardless of whether I used a heat pump or a conventional furnace that was installed in the garage? Or is there something inherently different about a heatpump that increases the danger?

[beenthere]

Less risk with a heat pump.

[Rhizzlebop]

I believe what these guys are saying, is that the carbon monoxide risk is not related to the way you condition the space, its the fact that you can have a vehicle running in the garage below, putting off the carbon monoxide.

People have died from a vehicle being left running in the garage for a while.
The heat pump is probably the way to go.

If its one big open space, you can look at a PTAC type heat pump (think hotel wall unit). It'll be better on the wallet, but it wont distribute the air around all that well. If it's to be more like one large room, it has a better chance of working alright.

[TitaniumVT]

Thanks very much for all of your input, guys. After doing some more research this weekend, I'm thinking about just going with basic electric baseboard heaters. They seem to be the simplest and most economical solution for heating a 700 sq ft occasional use space...No expensive system to install, no ducts to run. Just hardwire to a handful of baseboard heaters in strategic locations and call it good. It'll work out to 1/4 to 1/8th of the cost of installing a heatpump system.

The heat pump would be a more elegant solution and put out higher quality heat, but for the amount of use it'll get, it's not worth it. I am going to seriously consider a heat pump for the larger house though!

[jm0711]

Take a look at ductless heat pumps. Some models qualify for the federal tax credit.

[green jumper]

Minisplit heat pump? Also if you live in california since you said west coast, prices on electricity and natural gas in alot of areas dont make sense to put a heat pump in instead of a gas fired furnace.

[360dart]

I would consider a mini split heat pump if you don't mind the look of something hanging on the wall. Some models are very good in efficency. (SEER) Plus you have the advantage of AC if you want it.

[coors66]

I would consider a mini split heat pump if you don't mind the look of something hanging on the wall. Some models are very good in efficency. (SEER) Plus you have the advantage of AC if you want it.

I am a big fan of these. I have one in my addition. Sleek looking, quiet, efficient, and very affordable. Great for well insulated ductless applications.

[TitaniumVT]

I would consider a mini split heat pump if you don't mind the look of something hanging on the wall. Some models are very good in efficency. (SEER) Plus you have the advantage of AC if you want it.

Now you guys have me thinking again. :-) I don't know much about them, but with all of your recommendations, it's certainly worth investigating mini-split heat pumps further. I did a quick search and found this overview: http://www.toolbase.org/Technology-Inventory/HVAC/ductless-mini-split-heat-pumps It indicates that ductless mini-splits are designed primarily for cooling. Is that a fair assessment, or would you say they're equally well suited for heating?

If it makes a difference to what you'd recommend, I'm in Seattle - it's cooler than California, and electricity prices aren't quite so insane. Temperatures generally range between the 40s and low 80s over the course of a year.