Boiler Heat or Minisplits?
- Thread starter jserr68594
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dave_dj1
Well-known member
I'LL TOSS in my .02 worth
I installed two mini splits in my ranch home this past summer, I did them primarily for the AC but figured for a few bucks more why not get them with heat pumps too. So far I am very happy with them, on AC (installed in upstate NY in August) they work fantastic and are very quiet especially compared to window AC units that ran on high all day long and couldn't quite keep up with the humidity we had this summer. I have forced hot air system which also has a water to air heat exchanger from my OWB. I haven't turned the furnace on yet or lit the OWB. It's been a learning season for us, most nights (even last night down to 28f) we didn't even have the bedroom unit on. We sleep better when it's cool.
My house was built in the 70's, 2x4 walls with plastic under the drywall and tyvec under the vinyl siding. I have lived here 22 years and have upgraded almost all of the windows to new Low E units along with insulating the inside of the block foundation.
I think the most impressive things with the mini splits is that the light bill didn't go up much at all.
I had planned on lighting the OWB on Nov 1 but after seeing the forecast I will wait until the daytime highs look to be in the 40's
As a building contractor we have replaced some antiquated systems with new high efficiency propane units and the HO's absolutely love them and their savings. One was a one zone steam system which we replaced with 4 zones and a hot water maker, guy said he's never been more comfortable in it, large two story farmhouse. Another one was a 5k sf two story home with a one zone forced air system, between the spray foam insulation and 5 new zones with a high efficiency propane boiler the HO's tell me that there isn't a cold corner in the house. YMMV
I installed two mini splits in my ranch home this past summer, I did them primarily for the AC but figured for a few bucks more why not get them with heat pumps too. So far I am very happy with them, on AC (installed in upstate NY in August) they work fantastic and are very quiet especially compared to window AC units that ran on high all day long and couldn't quite keep up with the humidity we had this summer. I have forced hot air system which also has a water to air heat exchanger from my OWB. I haven't turned the furnace on yet or lit the OWB. It's been a learning season for us, most nights (even last night down to 28f) we didn't even have the bedroom unit on. We sleep better when it's cool.
My house was built in the 70's, 2x4 walls with plastic under the drywall and tyvec under the vinyl siding. I have lived here 22 years and have upgraded almost all of the windows to new Low E units along with insulating the inside of the block foundation.
I think the most impressive things with the mini splits is that the light bill didn't go up much at all.
I had planned on lighting the OWB on Nov 1 but after seeing the forecast I will wait until the daytime highs look to be in the 40's
As a building contractor we have replaced some antiquated systems with new high efficiency propane units and the HO's absolutely love them and their savings. One was a one zone steam system which we replaced with 4 zones and a hot water maker, guy said he's never been more comfortable in it, large two story farmhouse. Another one was a 5k sf two story home with a one zone forced air system, between the spray foam insulation and 5 new zones with a high efficiency propane boiler the HO's tell me that there isn't a cold corner in the house. YMMV
danski0224
Well-known member
I wouldn't ditch the boiler for mini splits.
Also wonder WTF the "noisy mini split" crowd is complaining about. Unless it is in turbo mode, I can't hear it operate.
If the boiler is cast iron, it's probably fine *as long as it's piped correctly*. Return water temperature must be 140 degrees or higher. Boiler instruction manuals come with piping diagrams.
The attic is the absolute worst place to put HVAC. If equipment replacement is on the table, I'd make sure that the ductwork is all sealed and insulated... or spray foam the attic and make it conditioned space.
If "renovation" also includes doing stuff like adding insulation, windows and so forth to improve the building envelope, that will alter the HVAC load. If no changes are made to the hydronic stuff and the building is made tighter/more insulated, this will aggravate short cycling of the boiler and keep water temperature down, which increases fuel use and flue gas condensation.
The radiators/fin tube is sized for the heat loss, then the boiler is sized for the radiation. They go hand in hand.
I do not see boilers running residential stuff at 180 degrees, which is the common assumption for water temp and btu capacity of the radiation.
There are books/resources to figure out the btu capacity of your installed radiation. You will also need a room by room load calculation.
If you want to "save money" the boiler stuff has to be sized properly.
Either find someone that knows how to do it, or do it yourself.
Good luck.
In New England it was very common for houses to be built w/o AC. My brother had a very nice house with cast iron baseboard and very basic ductwork for the AC --- that never would have worked for heat. My sister a more modern design with no ductwork at all ... I would hear all the time north of Boston -- we don't need AC.
Minisplits are perfect for house with hot water heat and no AC .... on more expensive builds where ductwork was installed for AC along with the hot water .. changing to a heat pump is a great think to do. Turning on the heat pump to take the chill off of a house in the Am is going to be faster and in cases with oil or propane -- cheaper.
Trying to heat a house in a cold climate with mini splits can be done but you have to be careful with sizing the units and also what type of space they are going into.
It's also been my experience that with some thought --- placement of mini can be done w/o much design impact. They do go away. That's not to say I have not seen some poorly placed ones that are ugly
Minisplits are perfect for house with hot water heat and no AC .... on more expensive builds where ductwork was installed for AC along with the hot water .. changing to a heat pump is a great think to do. Turning on the heat pump to take the chill off of a house in the Am is going to be faster and in cases with oil or propane -- cheaper.
Trying to heat a house in a cold climate with mini splits can be done but you have to be careful with sizing the units and also what type of space they are going into.
It's also been my experience that with some thought --- placement of mini can be done w/o much design impact. They do go away. That's not to say I have not seen some poorly placed ones that are ugly
fitter30
Well-known member
1/2" pex about 32 btu's per ft. Have to watch what type of floor coverings wood floor 80°
We always sized hydronic floor heat by the feet of tubing in the floor. Like Fitter30 says, about 30 BTU per foot of tubing.
It doesn't make much difference what the load is on the building is you have only so many feet of pipe. You can add more tube, but it gets to a point where you can stuff only so much heat into the floor. We always figured 1 foot of tube for every sqft of floor. So 38x44=1672 sqft so 1672 feet of tube @ 30 BTU per foot comes to 50K BTU.
Firebrick43
Well-known member
What kind of crappy minisplits are you sitting next to? Our mitsubishi hyper heat can hardly be heard and is quieter than most central air systems.
75gmck25
Well-known member
If you leave the boiler and use the hydronic heat, the attic is not a bad location for a traditional A/C unit, especially if you foam the attic and turn it into conditioned space.
Heat rises, so with the A/C in the attic you get your best air flow to the 2nd floor because its the shortest path, and that is where you get most of the heat. If the attic space is unconditioned you will also need good insulation on all the ducts, but if you foam it and make it conditioned space you can just use metal duct-work.
It can be challenging to get ducting all the way down to the 1st floor unless you are willing to steal some 2nd floor closet space and/or frame off some corners to box in the vertical ducts. We found a couple locations where we could run a fairly large vertical duct down to the space between the 1st floor ceiling joists and then T out in both directions to cover a wider area. However, this depends a lot on how the house was framed.
Heat rises, so with the A/C in the attic you get your best air flow to the 2nd floor because its the shortest path, and that is where you get most of the heat. If the attic space is unconditioned you will also need good insulation on all the ducts, but if you foam it and make it conditioned space you can just use metal duct-work.
It can be challenging to get ducting all the way down to the 1st floor unless you are willing to steal some 2nd floor closet space and/or frame off some corners to box in the vertical ducts. We found a couple locations where we could run a fairly large vertical duct down to the space between the 1st floor ceiling joists and then T out in both directions to cover a wider area. However, this depends a lot on how the house was framed.
fitter30
Well-known member
Kezorm
Active member
Hydronic heat pumps use a baseboard heaters that run at 120° with a high btu output. Difference is a lot more fins that are enhanced. The price refects it both in equipment and time to retro fit. Then for cooling there are wall units. Here's one brand but there's others. Wouldn't surprise me the cost will be more that geothermal. Check with your eletric company for rebates and tax breaks state and fed.
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