[Greenbuilding] mass-enhanced R-values :-(
nick at early.com
Mon Feb 23 03:11:27 CST 2009
Don Eyermann rants:
> IF YOU COULD GET THE WHOLE IDEA OF BURNING FOSSIL FUEL/TREES/NUCLEAR
> FISSION FOR HEATING AND COOLING OUT OF YOUR HEAD THEN MAYBE WE COULD
> HAVE A DISCUSSION.
> The Massy Walls CAN be heated and cooled effectively by natural
> geothermal/solar radiant energy by the fractional energy of a small
> pump recirculating water continuously. This system works, it has been
> reviewed by multiple third party agencies in several countries...
And the Pope.
> You are such a well brained BASIC computer language aficionado why
> don't you take the few minutes to actually figure out the minimal
> lengths of pipe it would take in 55?F earth to cool the water down and
> re-circulate it back into the walls of a 1500 sq. ft. home preventing
> the walls/interior from heating up in the first place in the summer.
OK. Send money.
> Conversely, how much solar radiant heat energy would need to be
> absorbed by the roof water heater in spring/summer/fall and be stored
> in how much well insulated area underground, served in three radial
> embedded tubing circuits, to store enough energy to augment that 55?
> during the cold periods of fall, winter and spring and raise the
> temperature 15?F to keep the house comfortably warm...
A lot. And the house will be hideously expensive.
> How long would it take you to do that calculation?
Not long. First you'd have to send lots of money so we can better define
> We're engaging an expert interested in this system to do our
>... ICF homes really do use less energy than conventional wood homes
I believe that is true, especially if they are heated and cooled by
fossil fuel, trees, or nuclear fission in every month of the year.
OTOH, ICF mass won't help a house that stores enough solar heat for a
few cloudy days, if it's always warmer than outdoor air in the coldest
> ... the original statement indicated that mass only benefits the
> occupants when the outdoor temp swings above AND below the indoor
> temp. This is simply not true.
I'm afraid it is. In rhetoric, a simple assertion demands no more than a
counterassertion. Where are your numbers?
> Having mass in your walls is always a good thing, not a bad thing.
I'm afraid it is often bad. It can add to the price and embodied energy
of a house and make night setbacks less effective in saving energy.
>... people who live in homes with thermal mass don't set their
>thermostats to let it get hot while they're away at work then cool it
>down before they come home. In a house with thermal mass, you just
>keep it the temp you want all the time, and it takes less energy to do
I'm afraid you are incorrect. This is basic 300-year-old physics,
Newton's law of cooling, aka Ohm's law for heatflow.
>A wall with thermal mass will outperform that system in virtually any
> but mass will kick ass in the desert.
Mass will kick ass almost anywhere some of the time, and kick ass in
some deserts almost all of the time, but it can't kick ass in every
climate all of the time.
> Our 8 inches of AAC is enough thermal mass that -- if there were no
> HVAC at all -- the inside temperature of the house would settle at the
> daily average and stay there without spiking or dipping.
... if it were white and all the windows were completely shaded and
nobody lived inside or used electricity indoors.
> You can argue all day about whether mass works and how well. But when
> you've lived in a home with thermal mass, you find it distasteful to
> consider anything else.
> Some configurations of high thermal mass walls improve performance
> even in climates like Minneapolis
In Minneapolis, a wall with a 10-20 hour time constant (vs 1-2 hours for
a fiberglass wall or 10-20 hours for the house itself) could save some
energy in June (min 57.6, max 78.8 F), July (63.1, 84.0), and August
(60.3, 80.7), but it won't help at all in December (10.2, 25.5), and a
house that can keep itself warm with no fuel in December can keep itself
warm with no fuel in the rest of the year and mostly cool itself with
night ventilation ("enthalpy economization") in July. With humidity
ratio w = 0.0117 in July, it might need some AC or dehumidification, or
a ceiling fan, with or without massy walls.
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