Heating finished basement: add hydronic zone or use AC/heat pump?

[millinghill]

Hi.

I'm finishing my basement (open floor plan, 800sqft, walk-out, full height, cinderblock walls, no water issues, in New York). It will have 2" EPS ins ulation on interior of cinderblock walls, covered with sheetrock. I have hydronic radiators in main floor of the house (oil-fired boiler) and I also have just installed a mini-split A/C & Heat pump system for all rooms of h ouse with capacity for one more unit of 18,000BTU. I'm going to install th at last one to air condition the basement.

My question is: should I rely on that mini-split to heat the basement, or s hould I install a new hydronic zone for the basement and install some baseb oards?

I just don't want to be done and then have to tear open walls to install pi pe and baseboards if it's going to be too cold to watch tv and hang out dow n there.

All comments and opinions appreciated, especially if based on experience. Thanks Theodore

[Unquestionably Confused]

If I'm understanding you correctly, the min-split system both heats and cools, correct? And you have the capacity to place one more air handler unit that will afford you an additional 18K BTU?

If it were me, I would do my calculations based on the square footage and glass, etc on the walkout end and take into consideration that both your heating and cooling requirements will be reduced by virtue of it being below grade. Talk to the folks who designed the unit or installed it and see what they say. You may need nothing further.

If it's a question mark or they say, "Well you're just going to have to see what happens over a couple of winters" I would rough in a loop for the hydronic heat and leave it sealed up behind the wall. If you wind up needing, cut out a small square of drywall and go for it.

One potential benefit of doing it this way is that if it turns out that your setup inadequately heats the main floor, adding an additional hydronic zone beneath it will help to cure that problem. Heat rises

[Ed Pawlowski]

In my area, it is pretty much a conclusion that any heat is cheaper than electric. What is the operating cost of that mini-split compared to your water heater? That would be step one and would drive the rest of the decision.

[Ralph Mowery]

I'm finishing my basement (open floor plan, 800sqft, walk-out, full height, cinderblock walls, no water issues, in New York). It will have 2" EPS insulation on interior of cinderblock walls, covered with sheetrock. I have hydronic radiators in main floor of the house (oil-fired boiler) and I also have just installed a mini-split A/C & Heat pump system for all rooms of house with capacity for one more unit of 18,000BTU. I'm going to install that last one to air condition the basement.

My question is: should I rely on that mini-split to heat the basement, or should I install a new hydronic zone for the basement and install some baseboards?

I just don't want to be done and then have to tear open walls to install pipe and baseboards if it's going to be too cold to watch tv and hang out down there.

My question is how cold does it get where you are at ?

If many days below about 25 to 30 deg F , that mini-split will probably not be able to make enough heat, especially at 25 and below. For the southern half of the US they usually work fine in many areas, but it does not get below 25 for too many days.

[Unquestionably Confused]

Efficiency wise (and cost wise), you're probably spot on, Ralph. But it being a split A/C and Heatpump would suggest to me that the unit has a built-in resistance unit for just those cold snaps you suggest. OTOH, depending upon just how much of the walkout basement is exposed at grade, he may not need a helluva lot of heat to raise an average year round ground temp (below frost line) to the 65 - 70 degree range.

[clare]

We KNOW the hydronic will do the job. We SUSPECT the mi i-split will need to run the electric coils at least part time to do the job if it is capable of doing the job. I'd put in the hydronics. The mini-split will still be used for AC - correct???. If so, the mini-split can provide heat when the basement is a bit cool in the summer /spring/fall and the hydronic boiler is not fired up.

[Art Todesco]

And, the walls are either at ground lever or some of them below. It will always feel cold by the walls. A lot depends on what the space will be used for. But a nice perimeter of heat will go a long way to feel good when it is really cold outside. The mini split units usually have an air handler on the wall. When heating, it is ideal for the heat to be low and keep the tootsies warm. Blowing around heat pump air will usually make you feel cold even though the temp may be 70 or above. Although I have a heat pump and a zoned furnace and I usually don't feel the drafts. But I do feel the cool breeze in bed, when the heat pump de-ices. Plus when it is too cold for the heat pump, my backup is propane which can supply lots of heat .... probably much more than heat coils. BTW, I am in western NC where it is certainly not as cold as in NY.

[trader_4]

If it was above ground, I would agree that would be a major consideration. But it's a basement. My basement is about 55F all winter, here in the NYC area. So, it's not going to take much to keep it warm. Still hyrdronic would likely have a lower operating cost, especially if it's gas fired. But then they need the minisplit system for AC anyway and we don't know what the payback time is for adding the hydronic would be. I think that's the governing factor. Also the hydronic lasts a long time, the ms AC not as long. How much of one of those systems life spans is determined by usage as opposed to just it's age, IDK, but assuming usage for heat shortens it's life, then that may be another factor in favor of hydronic.

[millinghill]

I was leaning in the same direction.