[GSBN] Modelling or measuring mass effect of interior plaster
John Swearingen
jswearingen at skillful-means.com
Wed May 8 01:32:33 UTC 2013
Actually, when I was in Brazil and Uruguay it was precisely the early
morning sun that disoriented me. I can handle the sun being in the North
sky, because who knows whether the sun is in the north or the south sky,
anyway, without a compass. But East and West correspond to "left of sun"
and "right of sun", and THOSE switch in the hemispheres, proving, beyond a
shadow of a doubt (was the shadow on the north or south side??) that the
earth spins the same way in both hemispheres, even if water (reputedly)
doesn't. Is this a digression?
On Tue, May 7, 2013 at 5:32 PM, Derek Stearns Roff <derek at unm.edu> wrote:
> If John "Earth has two hemispheres?" Swearingen got up early enough in
> the morning to see the sunrise, he would notice that some sun comes in the
> north windows of the houses that he builds in California, for about three
> months a year. But in fact, he just has a good sense of humor. John was
> probably a consultant on that John Wayne war movie, which showed the sun
> setting in the east, too.
>
> Derek
>
> On May 7, 2013, at 5:21 PM, Bohdan Dorniak wrote:
>
> Bear in mind that we are talking about the Southern Hemisphere.****
> We haven’t fallen off the earth as yet!!!****
> Bohdan Dorniak****
> “Architect still hanging onto the earth”****
> ** **
> *From:* GSBN-bounces at sustainablesources.com [mailto:
> GSBN-bounces at sustainablesources.com] *On Behalf Of *John Swearingen
> *Sent:* Wednesday, 8 May 2013 5:55 AM
> *To:* Global Straw Building Network
> *Subject:* Re: [GSBN] Modeling or measuring mass effect of interior
> plaster****
> ** **
> Well, it's hard to take seriously anyone who thinks the sun shines into
> north-facing windows, but outside of that, the results are very much in
> line with our observations--more mass equals temperature moderation and
> comfort. The paper stresses (over and over) that this is for mass in
> visual contact with the sun, because the buildings are designed as solar
> collectors. Similar advantages in temperature moderation apply to mass
> that does not have direct solar contact. (Also for wood-stove heated
> buildings, when the mass can absorb excess heat in the burning cycle). ***
> *
> ** **
> The question I have is whether you can have too MUCH thermal mass, and
> at what point does that occur. Any thick mass walls in a building with
> eventually reach an average ambient temperature, and will only release (or
> absorb) heat very slowly, in the long term. In my experience, plastered
> bale walls hover pretty close to room temperature, and like mass walls,
> aren't experienced as cold. A slab floor, by location, thickness and
> generally low insulation values, can tend to be experienced as cold if it
> isn't heated by sun or other means.****
> ** **
> Sometimes single-level homes with a collector slab will, at night, tend
> to stratify. The efficiency of heat transfer can be improved by just a
> slight level change to drive the convection loop. Even one step between the
> bedrooms and living area is enough to make a significant increase in air
> circulation during the night.****
>
> ** **
> On Mon, May 6, 2013 at 6:05 PM, Bohdan Dorniak <
> bohdan at bdcoarchitects.com.au> wrote:****
> Hi All****
> This is a note that has been published by the Australian Institute of
> Architects regarding Thermal Mass.****
> I thought that you may find this interesting? Any comments John?? Laura??
> ****
> Regards****
> Bohdan Dorniak****
> ****
> *From:* GSBN-bounces at sustainablesources.com [mailto:
> GSBN-bounces at sustainablesources.com] *On Behalf Of *John Swearingen
> *Sent:* Tuesday, 7 May 2013 9:38 AM
> *To:* Global Straw Building Network
> *Subject:* Re: [GSBN] Modeling or measuring mass effect of interior
> plaster****
> ****
> Laura,****
> ****
> Modeling thermal mass is generally difficult because of the large
> variable conditions of heat transfer related to air circulation. We've done
> this in Energy-10 with some success, and usually our projections have come
> out on the conservative side--the temperature swings have been less than we
> calculated. ****
> ****
> The other very large variable is climate--temperatures and sunshine at
> different times of the year. Everyone I know who does this successfully had
> dialed it in from years of experience in one particular climate, with which
> they are familiar.****
> ****
> As to whether the walls make a difference, the short answer is, I
> think it makes a big difference, and that many of the lauded
> characteristics of thermal comfort in straw bale buildings may have as much
> to do with the thermal mass on the walls as with the insulation. Modulated
> temperature swings can influence occupant behavior positively, reducing
> reliance on mechanical systems, over and above straight Btu calculations.*
> ***
> ****
> The ultimate efficiency of thermal mass is tied to the heat-transfer
> mechanism for exchanging heat between the mass and the rest of the building
> (air). A floor slab is thick and of limited surface area; bale walls are
> thin with a much larger surface area. So floor slabs are longer term
> storage, and walls function very effectively to modulate temperature
> swings on a short term (diurnal) cycle which can reduce loads on mechanical
> systems and increase comfort in passive buildings. I don't think there is
> too much danger of over-massing, and haven't seen it in our buildings,
> because the relatively thin mass of the walls, backed by insulation and
> actively transferring heat, stays close to room temperature and so isn't
> felt as too cold or hot.****
> ****
> Temperature modulation can result in significant changes in how
> mechanical heating and cooling are used by the occupants: if the building
> is slow to cool off at night, for instance, the occupants don't call for
> heat early in the evening. The key here is responsiveness, which is
> related to surface area. Mass walls also help to distribute Btu's somewhat
> between warmer and cooler areas of the building: cooler walls will absorb
> heat more readily than warm walls, so they are somewhat of a magnet for
> warm air when located in cooler areas of the building. ****
> ****
> Well, hope this helps!****
> ****
> John.****
> ****
> ****
>
> ****
> On Mon, May 6, 2013 at 12:39 PM, Laura Bartels <laura at greenweaver.com>
> wrote:****
> Hello All,****
> ****
> I'm writing to ask if anyone has had experience with modeling or
> measuring the mass effect of interior plaster of bale walls versus other
> interior finishes. This has come up on a straw bale project in design phase
> I've involved in which has a net zero energy goal. The project is large,
> about 6000 sf. The owners are interested in barnwood interior wall
> surfaces (over plaster) on all or some walls. With the net zero goal, the
> question is what we might lose in having wood rather than exposed plaster.
> There will be adobe floors which will already provide direct and indirect
> gain mass. ****
> ****
> Anyone tackled this topic or have a guess about how to look at this?
> Our team has talked about estimating direct vs. indirect gain wall surfaces
> through sun studies in ArchiCAD as a starting point. ****
> ****
> Looking forward to hearing any thoughts on this.****
> ****
> Laura****
> ****
> ****
> *Laura Bartels*****
> *GreenWeaver Inc.*****
> *520 S. Third St., Suite 5 *****
> *Carbondale, CO 81623
> 970-379-6779
> www.greenweaverinc.com*****
> * *****
>
> <image001.jpg>****
> ****
>
>
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> ****
> ****
> --
> John Swearingen
> Skillful Means Design & Construction
> 2550 9th Street Suite 209A
> Berkeley, CA 94710
> 510.849.1800 phone
> 510.849.1900 fax
>
> Web Site: http://www.skillful-means.com
> Blog: https://skillfulmeansdesign.wordpress.com****
>
>
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>
> ****
> ** **
> --
> John Swearingen
> Skillful Means Design & Construction
> 2550 9th Street Suite 209A
> Berkeley, CA 94710
> 510.849.1800 phone
> 510.849.1900 fax
>
> Web Site: http://www.skillful-means.com
> Blog: https://skillfulmeansdesign.wordpress.com****
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>
> Derek Roff
> derek at unm.edu
>
>
>
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--
John Swearingen
Skillful Means Design & Construction
2550 9th Street Suite 209A
Berkeley, CA 94710
510.849.1800 phone
510.849.1900 fax
Web Site: http://www.skillful-means.com
Blog: https://skillfulmeansdesign.wordpress.com
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