Hybrid Slab, more on...

["Bion D. Howard" <bdhoward@ix.netcom.com>]

Some excellent points.  You might want to check the back article
forthcoming in March 2001 _Energy Design Update_ for my take on
environmentally more efficient hot water service.  Emphasis on the term
"service."  

One bugaboo is always evaluating whether to add, or not to add (mix), solar
heat and auxiliary heat (purchased fossil or nuke...) energy into the same
storage mass/media.  

This issue requires some careful analysis to keep it simple, avoid
sub-systems that fight each other, and to have the whole equal at least as
much as the sum of the blessed parts. The sub-systems should also work in
concert with the rest of the design.  Otherwise, unexpected problems and
under achievement of performance may result.

Combining solar hot water service with a hydronic heating approach embedded
in a floor slab would be fine, if properly engineered and controlled (let
alone built right).

The air-core system I must say is best in conditioned spaces where passive
solar is nudging up against or beyond the ability of intrinsic thermal mass
to resolve temperature swings to an acceptable amplitude on mild sunny
winter days.  (In plain English - it helps in real passive solar designs
where there may not be agreement between diurnal ~ 24hr period ~ heat
storage available compared to gross collected solar heat that would
otherwise overheat the space.)

All part of holistic "tuning" of 
    the building that I love to do -- 
     art, science and a little VooDoo  
        (certainly not Haiku...)

   ~  Bion

== you wrote (edited some)....................
>Date: Mon, 26 Feb 2001 09:35:41 -0700
>From: RET John <retjohnd@home.com>
>Subject: Re: [GBlist]  Re: Hybrid Slab
>
>> Winston, yes. ... a Kachadorian-style slab may
>> be useful if it is heated by warm air (positive pressure), and the heat
>> transfers back into the living space by radiation and conduction - as in a
>> hydronically-heated slab.  I still think that the resources devoted to
>> building the plenum, and devising a means of blowing air into it, would pay
>> for all or a large part of a solar DHW system.
>
>I also know that moving AIR is much more energy intensive than moving WATER.
>Water stores MUCH more energy than air every will. I agree that money spent
>on air ducts and plenums should go towards a radient foor heating system AND
>a solar  hot water heating system. That way you have the best of all worlds
>- an efficient, quiet  and clean heaying system, a LOW cost operating
>heating system and if you installed a solar hot water system to heat the
>water used in the radient floor loop then you could provide up to 100% of
>your hot water via of solar energy depending on your climate and minimize
>the use of fossil fuels which are costign more and more and will continue on
>that path....after all they are not making anymore oil or natiral gas on a
>daily basis! (they just have to go deeper and farther to find it!)
>
-
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