I am adding a bathroom and some closets totalling 300 sf to my existing 1000 sf house. (One story, slab-on-grade, San Diego, one mile from the ocean) I have insulated the house walls with R-13 fiberglass and replaced all of the jalouise windows with double glazed. I plan on putting 1″ or 1 1/2″ of styrofoam on the roof when the remodel is done, too. It was built in 1958 with no insulation, whatsoever.

The existing heat source is a 26,000 BTU/H gas wall heater that does a fine job for the front two rooms. It’s never adequately heated the back bedrooms, though. 

I am planning on having a gas heater to heat the new bathroom and the back bedrooms. I will also need a domestic water heater. I have been reading about the MZ Boiler that does DHW and room heating in one unit. (94,500 BTU/H) It can produce 2.9 gallons/minute of hot water (How hot, I don’t know) I may need to have a tank, too. www.mzboiler.comproductsmzmz25s.html If I use this unit, would I then need baseboard finned radiators or use a fan-coil unit and duct work?

The house has no attic space. It has T & G 2 x 6 cedar plank ceilings/roof. I could put in a dropped ceiling over the new bathroom, though.

Does anyone have experience with this unit? Is 2.9 gallons/minute enough for an “American” shower? I am open to other suggestions as well.

Thanks,

Rick Barlow