Thoughts on my water heating / HVAC plan?

[polar8]

I have a 550sf detached garage located about 70 feet from my house in San Jose CA. Right now it has no utilities but I've pulled the permits to add them.

My goals are:

1. Add a guest bedroom and bathroom which will get used about 2-3 nights a month
2. Heat/cool the space as I'll be using it as a home office

Other info:

1. The building has no attic or crawlspace (vaulted ceilings)
2. I'd like to reduce the amount of space used by appliances like a furnace or a water heater tank
3. I live in temperate CA and the garage insulation is top notch
4. In terms of utilities at the house, I have 100A service (which will get upgraded when I rewire the house) and gas.

My questions are:

1. What is the best way to heat/cool the space? I was thinking of using a 12k BTU mini split
2. For the water heating, would you run a gas line just for that, or try to make it work with an electric tankless?

Thanks for the input!

 

[dmitrysgarage]

My questions are:

1. What is the best way to heat/cool the space? I was thinking of using a 12k BTU mini split
2. For the water heating, would you run a gas line just for that, or try to make it work with an electric tankless?

Thanks for the input!

1. I just did a 24k (2t) BTU MR COOL DIY minisplit and it was plenty for my space ~(1,500sqft, well insulated). Simple install and no ducting. 12K (1t) should be plenty for 500sqft. A lot of it is insulation quality. I've seen 3.5t fail to cool the same space 2t cools easily after good insulation.

2. I'd probably go tankless if you're trying to save space like you said. Since you don't have an attic to use there.

 

[mrpizza]

I second the mini split option.

 

[polar8]

Mini split it is! Now about the water heater, would you go gas or electric?

 

[Jackfre]

With PG&E rates. Go gas!

 

[glentre]

Will you be using any of this garage to actually house a car, yard equipment etc? If you are, that drastically changes what approach you will be allowed to take regarding heating and cooling and fire wall construction. If no car and the space is entirely open for use as a bedroom/office and a small bath, then a mini split heat/cool unit and tankless water heater might work fine. If a car is involved, that is another issue altogether.

Glen

 

[ct03911]

I never got smart about the mini-split deal.
My garage is 750 square feet, 12’ ceiling and well insulated, and I went with the biggest window ac unit I could find. It works great.
I have propane Hawt Dog heater and it was sized correctly and comes on rarely
I’m happy with the setup. Ac unit comes out in the winter.
Place stays dry and good temp.
My room over the garage is now just storage. In the future, if ever an apartment, it may need its own ac but the heat could come off the propane line to the main garage.

 

[pgray007]

I went through a similar process (see my build thread for the gory details) and ended up with a 24k Daikin mini split for the upstairs and down. I had a huge dilemma on water heating since I didn’t want to run a gas line. I thought about tankless Electric, but you’re talking 75A to get one that will reasonably run a shower and sink, so I ultimately went with a 40 gal electric tank, connected to a “smart switch” so I can turn it off when not in use. I also dropped a 120V POU heater under the slop sink in the shop so I can get hot water for washing up, etc without leaving on the big tank. I seriously considered a 20gal RV style until mounted to the shop ceiling, but it seemed like a lot of trouble and a few $hundred in hardware when I could just put the water tank in an otherwise awkward place and lose about 3 sq ft of floor.

Also for reasons I don’t understand, 40 gal seems to be the “sweet spot” in terms of price and was cheaper than the 30 gal and several of the 20 gal WH’s I looked at. Plus with electric you don’t need to put it on a stand in my AHJ.


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[polar8]

After reading reviews of some tankless electric heaters I'm not so sure anymore. Sounds like they just don't have the power to keep up with a normal shower. Anyone have a good experience with a tankless electric?

 

[pgray007]

After reading reviews of some tankless electric heaters I'm not so sure anymore. Sounds like they just don't have the power to keep up with a normal shower. Anyone have a good experience with a tankless electric?

I searched high and low for positive news on electric tankless since I really wanted to love it. It’s cheap, takes minimal space, and theoretically is perfect in a low/inconsistent use environment. However, they just don’t seem to work for much more than hand washing unless you go with a 100A+ monster and I didn’t want to trip the 100A subpanel breaker every time I wanted to do something crazy like wash my hands AND have a light on, or listen to someone complain about a lukewarm shower.

I hate to loose the space to a tank, but it works, and won’t use all my juice.


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[bobbyjean]

ductless sounds good... are you running water service to garage now? how about running hot water from house with a recirc setup? sounds hokey but may be cheapest $$$$....for 2 or three uses a month

 

[aunsafe2015]

After reading reviews of some tankless electric heaters I'm not so sure anymore. Sounds like they just don't have the power to keep up with a normal shower. Anyone have a good experience with a tankless electric?

Some of the units on Amazon have generally good reviews. Stiebel eltron in particular.

 

[Climatecreator]

I'd have to say ductless for sure on the HVAC for apartment office area. They're not crazy about saw dust however....

Tankless for the HW. Gas. Especially if you already have natural. Otherwise I'd go propane before EVER doing electric.

And the reason 40 gallon free standing tanks are cheaper is because it's the standard and they sell/produce the most of them. Seams dumb to over size heaters just because they're cheaper but that's what happens.

Tankless at least only runs as needed AND modulates to the load. Depending which heater you select you may also need a buffer tank to help with surging as the unit varies the water flow to regulate temperature.



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