Building a timberframe home in Mid-Maine...Walls R21 plus sheathed with 1/2 foil polyiso/Roof is SIPS R42. Should be pretty tight.
For cost cutting reasons Im contemplating going from propane tankless BBHW to a wall mounted direct vent propane monitor heater. I realize a single heat source vs baseboard throughout has a bit of a comfort drawback but the plan is extremely open on the layout. I have several ceiling fans planned.
These units run up to 55K BTU so thats plenty. I have one in my camp thats 35K BTU/theromstat controled and it works flawless. 
I know install is a good 10K cheaper so Im really tempted. BTW,I have a woodstove that will be in the home also.
Im wondering the difference effeciency wise Id gain or lose ?? Any thoughts on one vs the other ? Different units you like ?

Thanks for your input.

Mark

Geez...nobody here using a monitor type direct vent unit ? Someone must know something.
Thanks in advance.
Mark

I would check you propane costs carefully. You may be able to heat with electric baseboard units for less utility cost than propane, and at a lower installed cost too. This will depend on your local utility rates but where I live propane is more per Btu than electricity.

Dennis

Mark, you might have better luck posting on the radiant heating forum. They are the experts on btu's. Good luck

Here you go. Coldham & Hartman Architects in Western Mass have done extensive research in monitor heaters vs. central systems in low-energy houses.

Simple answer seems to be yes. Leave bedroom doors open, make sure you've got a ventilation method worked out (exhaust only vs. HRV depending on tightness / cost etc.)

We're doing a few houses like this now.

Link to ASHRAE paper including data from monitored buildings: http://coldhamandhartman.com/whitepaper.php?id=72

Great find on that article. Thanks for all the input. Any of you folks 'looked at/experience with' different brands and effieciency levels ?
Im leaning much more toward the direct vent wall unot.