[Greenbuilding] distribution of radiant heat

[Corwyn]

On 1/8/2011 12:03 PM, Chris Koehn wrote:
> Hey Corwyn, If you'd like more info before jumping to conclusions just ask:

I worked with what you provided.

> The "open fireplace" is not open: it's an enclosed, sealed combustion
> unit with outside combustion air and heat circulation. Not my
> preference, but again, I'm not the architect.

'fireplace' around here means open fireplace.  Sorry that that caused 
confusion.

> The clients have in place a 12 KW propane generator. We won't be
> powering the home exclusively with solar; solar will be used to top up
> the batteries when the genset isn't running.

Barged over propane for a 12kW generator doesn't make me feel _less_ 
anxious about the idea of this contrivance.

> I am building a case to revamp the design to abandon the fireplace (on a
> gable wall- largely aesthetic) in favour of a centrally located masonry
> heater.
> Propane has to be barged over, so it's usual cost and efficiencies are
> not applicable here.

Sort of.  You will need to barge over the fan and ducting as well. 
Unless you can convince me that those materials are going to be less 
weight or volume than a corresponding amount of propane, I stand by my 
assessment.

> There is currently no heat source called out for the bathroom, so your
> assumption that we're starting with 65 degree air is invalid.

Which only makes it worse.  The air is bringing over 145 BTUs / °F.  The 
thermal mass of the bathroom is at least 600 BTUs / °F.

If the bathroom is 57°, you get 73-57 * 145 = 2320 BTUs out of the air. 
  Which raises the temperature of the bathroom 3.8°, to 60.8°.

> We are working with 4500 HDD but heating typically starts in late
> September and ends in early June. It's oceanfront, so there's a really
> big 45 degree mass out there.
> It may prove to be more efficient and practical to provide a separate
> propane heat source for the bathroom area but the clients have asked me
> to look for alternatives and so I am.

Try increasing the insulation in the house, and see how much heat that 
saves.  If the heat isn't leaving in a hurry, it will have time to 
migrate to all areas of the house.

Thank You Kindly,

Corwyn

-- 
Topher Belknap
Green Fret Consulting
Kermit didn't know the half of it...
http://www.greenfret.com/
topher at greenfret.com
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