[Greenbuilding] Green Bozos

Bob Korves bkorves at winfirst.com
Sun Feb 22 22:54:43 CST 2009 

Perhaps we are all looking at mass heat storage a bit too simplistically.

A house is not necessarily like an amorphous 8X8X8' R-20 cube, that neatly 
fits Nick's simplistic calculations.

Real buildings can have the sun shine on the equator side, and can radiate 
heat away to the cold sky on the polar side.  Traditional adobe buildings, 
with very low R values, can act like Trombe walls with the alternating sunny 
days and cold nights.  Some adobe aficianados even talk of timing the heat 
of the sun traveling throught the walls at a predictable rate per inch of 
wall thickness, allowing tailoring of heat delivery by the design of the 
wall thickness, based on wall material used.  Maybe so, but it would sure be 
difficult to build a set of calculations that would model and predict that 
behavior reliably for others to copy.  I suspect is is more like a rule of 
thumb -- copy closely what worked for somebody else down the road...

My own situation would not work well with high mass.  We are gone to work in 
the daytime, and are often gone on weekends.  We like to sleep in a cold 
room, and also enjoy saving the energy of not heating the house at night and 
when away.  We awaken and are up in the morning for an hour or two, and then 
are gone for the day.  A house with lots of mass takes lots of time to heat 
up and cool down.  We want to only heat the space when we are home, and we 
do so.  Our house is an ordinary 1983 tract ranch house, 1300 square feet, 
2x4 (R-11) walls, ~R-25 attic insulation, single pane aluminum windows, slab 
on grade fully exposed at the edges, stucco walls.  Not close to optimum by 
conventional (or green) wisdom, but we would be happy to compare energy 
bills with people who think they have efficient and green houses.  Lifestyle 
choices also matter, as does where you live.  We are in Sacramento, 
California USA -- not the most difficult climate, and a major reason why we 
choose to live here.

Nick's statements about mass not helping unless the diurnal temperature 
range include the interior temperature are absolutely correct, as far as 
they go.  Thermal mass serves mostly to help even out the diurnal 
temperature swings to a mean value.  If that mean is not your desired 
temperature, then you will need to heat or cool all that mass until you get 
the temperature where you want it.  The mass does not get magically warmer 
or cooler just by it's existence.

Some people are trying to heat their houses near 100% by solar means.  If 
you can expect several or many days in a row of clouds, then thermal mass 
can help keep your house warm during that time -- so long as it is well 
insulated on the outside and has a way of attaining the desired temperature 
range initially!

Perhaps we need a more -- dare I say it -- holistic view of why and where we 
desire thermal mass in our buildings, and how we use it to help meet our 
needs.  Some time thinking and studying about how heat moves from cold to 
hot, how it is stored, conducted, radiated, convected, excluded, collected, 
and sensed, will allow us to design what will meet our individual 
requirements.

Why do people need to think that one size should fit all?
-Bob Korves

----- Original Message ----- 
From: "Jeannie" <jeannie at babb.com>
To: <greenbuilding at listserv.repp.org>
Sent: Sunday, February 22, 2009 12:19 PM
Subject: Re: [Greenbuilding] Green Bozos


> Is massy a word?
>
> Anyway, 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.  Having mass in your walls is always a good 
> thing, not a bad thing.  The only exception I can come up with is if you 
> allowed the house to get too hot during the summer, then it would take 
> longer to cool it off b/c some heat would be stored in the walls.  That's 
> why 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 so.
>
> It is true that the benefit of thermal mass in the walls is most 
> pronounced in areas with a lot of temperature swing, such as the desert. 
> However, this does not mean that thermal mass is ineffective or bad in 
> areas with less temperature variation.  It's all relative, and what we're 
> comparing to is systems WITHOUT much thermal mass, e.g. 2x4 with batt 
> insulation.  A wall with thermal mass will outperform that system in 
> virtually any climate.... but mass will kick ass in the desert.
> I live in north Georgia, which is a mild climate with a fair amount of 
> day/night temperature swing.  Our home has 8-inch thick SafeCrete AAC 
> walls.  Our bills are consistently less than our neighbors' bills, even 
> though they're fairly well insulated for sticks and bricks.  Our heating 
> system kept up just fine during the record-length cold snap we had this 
> winter -- even though one of our three units was out of service, and 
> another one had been accidentally turned off by the children.
> 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.  We've tested this a 
> few times by turning off the HVAC while on vacation, and the house is 
> always at the average daily temperature when we come home. That is the 
> best you can expect from any wall system (sort of passive solar or other 
> means of heating/cooling.)  By contrast, a stick home will quickly rise to 
> the peak temperature -- which in this area can be 20 degrees higher than 
> the daily average -- and the temp will fluctuate throughout the day and 
> night according to the outside temperature.
>
> 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.  To me, living in a stick frame house has as much 
> appeal as living in a tree or a box.  It doesn't seem like those are 
> "real" walls.  They don't keep out heat or cold, they don't keep out 
> noise, they feed fires rather than stopping them, they harbor insects, 
> they rot, etc.  A wall with thermal mass seems "real" to me.  I guess 
> after the apocalypse I'll be one of those people who lives in a cave 
> instead of a tree.
>
> J.
>
>
>
> Corwyn wrote:
>>
>>
>> RT wrote:
>>> On Sun, 22 Feb 2009 12:24:01 -0500, Nick Pine <nick at early.com> wrote:
>>>> For the umpteenth time, your massy walls will only work better than 
>>>> low-mass walls on days when the outdoor temp swings above and below the 
>>>> indoor temp.
>>> If the outdoor temperatures never swing above and below the indoor 
>>> temperature, then why would one need any walls (massy, low-mass or 
>>> otherwise) at all ?
>>>
>>> [He says while scratching his ... *head* ... in puzzlement ]
>> I think he meant: If the daily temperature variation does not include the 
>> desired indoor temperature.  (e.g if it is always colder on a particular 
>> day than the inside temp).
>>
>> Thank You Kindly,
>>
>> Corwyn
>>
>> ------------------------------------------------------------------------
>>
>> _______________________________________________
>> Greenbuilding email list
>>      Environmentally-preferable design, construction, building elements
>> List info: 
>> http://listserv.repp.org/mailman/listinfo/greenbuilding_listserv.repp.org
>> List email: Greenbuilding at listserv.repp.org
>> Managed by BuildingGreen, Inc. http://www.buildinggreen.com
>>       publisher of Environmental Building News and GreenSpec
>> Hosted and archived by REPP / CREST http://www.crest.org
>> To get on the list:
>> 
>> http://listserv.repp.org/mailman/listinfo/greenbuilding_listserv.repp.org
>>   or mailto:greenbuilding-request at listserv.repp.org?subject=unsubscribe
>> To get off the list:
>> 
>> http://listserv.repp.org/mailman/listinfo/greenbuilding_listserv.repp.org
>>   or mailto:greenbuilding-request at listserv.repp.org?subject=unsubscribe
>>   ------------------------------------------------------------------------
>>
>>
>> No virus found in this incoming message.
>> Checked by AVG - www.avg.com Version: 8.0.237 / Virus Database: 
>> 270.11.1/1960 - Release Date: 02/19/09 10:48:00
>>
>>
>
> _______________________________________________
> Greenbuilding email list
>     Environmentally-preferable design, construction, building elements
> List info: 
> http://listserv.repp.org/mailman/listinfo/greenbuilding_listserv.repp.org
> List email: Greenbuilding at listserv.repp.org
> Managed by BuildingGreen, Inc. http://www.buildinggreen.com
>      publisher of Environmental Building News and GreenSpec
> Hosted and archived by REPP / CREST http://www.crest.org
> To get on the list:
>  http://listserv.repp.org/mailman/listinfo/greenbuilding_listserv.repp.org
>  or mailto:greenbuilding-request at listserv.repp.org?subject=unsubscribe
> To get off the list:
>  http://listserv.repp.org/mailman/listinfo/greenbuilding_listserv.repp.org
>  or mailto:greenbuilding-request at listserv.repp.org?subject=unsubscribe

More information about the Greenbuilding mailing list