HPHWH in conditioned basement
Hello again;
As part of our basement remodel, we’re planning to install a Mitsubishi 9k mini-split to condition the space. Since it’s mostly below grade, the load is light. We’ll likely only need dehumidification in the summer.
And, we have solar, and extra capacity, and thought of switching to a HPHWH from indirect natural gas hot water as we may need a larger capacity unit as we’re adding a bathroom in the basement too. The gas does hydronic heating too.
The mechanical room is in the basement and will be part of the conditioned space. It’s not well separated from the rest of the basement.
I can see that the mini-split will be moving heat from outside to the basement and the HPHWH will move the heat from the basement to the DHW.
Silly?
This is also part of a bigger plan to switch our cooking to inductive and therefore be able to turn off the natural gas for the warmer months and turn back on as it gets colder. The fees for this with VTGas make it worth while. Climate zone 6 – northwestern VT.
And, philosophically, I HATE seeing the furnace exhaust in warmer weather just to heat the water.
Thanks again.
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Replies
Not silly. Still more efficient than a electrical resistance water heater and a utility room in the basement is ideal as long as you have enough air volume.
The HPWH will do some dehumidification on its own. You may not need the mini split to do that for you in the summer.
+1
In reasonably air tight & waterproof insulated basements an HPWH would cover most, if not all the latent cooling load in a VT basement.
What might be silly is the FH09, unless it's a walk-out basement with some big glass sliders. Even the FH06 would cover the design heating (& cooling, which is solely latent) loads of a 1000-1500' code-min insulated mostly below grade basement that doesn't have a lot of window area.
BTW: " I HATE seeing the furnace exhaust in warmer weather just to heat the water". Furnaces don't heat water- they heat air. What you have is a hydronic boiler, not a furnace. The terms aren't interchangeable in most the HVAC world, though there are some regional dialects that seem to conflate them.
Dehumidification varies, but expect only a few pints/day from a HPWH. It's likely that you need several times that - so expect to still need a dehumidifier. No, the mini-split won't serve that function.
Thanks folks. Yeah, I conflate boiler and furnace...whoops.
We will need to heat the basement in the winter. Right now, w/o ANY conditioning, the temp stays right around 60 in the winter. I didn't know there was a FH06 (going by what the contractor recommended).
Total square footage of the basement is ~680 sq-ft. Added a scribbled on drawing. Some of the scribbles are likely outdated and not applicable.
I'm wondering if the cool exhaust air from the HPWH will bring the temperature of the basement to a level below whats normally comfortable.
"Since it’s mostly below grade, the load is light. We’ll likely only need dehumidification in the summer."
I'm in central MA with a 600 SF finished basement, R15 walls, mostly 7' below grade and in 5 years has never gotten above 68* in the summer. I also have a HPWH, but its in an adjacent unfinished utility room. If I had it in the finished side it may drop the temp even more....68 is borderline comfortable for me in the summer.
Ducting the water heater inlet/outlet could be an option.
>"I'm wondering if the cool exhaust air from the HPWH will bring the temperature of the basement to a level below whats normally comfortable."
Most people wonder about that, but it's rarely an issue. If the basement ceiling is NOT insulated from the fully conditioned space above it may not drop the temperature of a 600-700' basement by even one degree F. If it's insulated from the conditioned space it might be more than a degree.
>" I also have a HPWH, but its in an adjacent unfinished utility room. If I had it in the finished side it may drop the temp even more....68 is borderline comfortable for me in the summer."
If it's all inside the R15 basement, the difference in temp between the finished and unfinished side shouldn't be very different, especially if the partition wall has R0.5 wallboard only on the finished side, which translates into a "whole-wall R" of about R1.5 after factoring in air-films. If there's wallboard on both sides the "whole-wall R" of the partition wall is about R4, or about 2/3 less heat per degree-F difference.
I have an unfinished ~R15-wall mostly-below grade ~1600 square foot basement in central MA that used to never exceed 67F in summer or below 64F in winter. (No heat pump water heater, no active heating.) Since installing a Lunos e2 HRV dedicated to the basement it now has excursions outside that range, but not by much.