[GSBN] Fwd: Modeling or measuring mass effect of interior plaster

Sun May 12 03:25:29 UTC 2013

Martin Holladay, as if he were listening to our discussion, just published
an excellent summary "All About Thermal Mass"
<http://www.greenbuildingadvisor.com/blogs/dept/musings/all-about-thermal-mass?utm_source=email&utm_medium=eletter&utm_content=gba_eletter&utm_campaign=green-building-advisor-eletter>
at
Green Building Advisor.com, with references to several studies that have
been done.

Most of this has been covered in this discussion.  One thing he makes
explicit is that mass is most effective in lowering energy usage when the
diurnal temperature swing is above and below the indoor temperature (ie:
warm days, cool nights).  He also points out that mass is most effective in
reducing energy usage in cooling environments because the thermal lag will
shift air conditioning usage to the cool night hours, when air conditioners
are more efficient.

It's a good read.

On Wed, May 8, 2013 at 12:23 PM, Laura Bartels <laura at greenweaver.com>wrote:

> Luc,
>
> I'm so grateful to see this. And it brings back some of my 9 years of
> French study in school. Good to take a stab at reading first without google
> translate.
>
> But, since I'm still challenged by translating, including technical terms
> (and google translate seems to be limited here), can you translate inertie
> quotiedienne cote interieur and how to understand it numerically in
> non-metric terms? And also how the dephasage or (phase shift or thermal
> lag) was calculated and what the exterior and interior climate assumptions
> were?
>
> Perhaps these are explained in text I am not translating correctly.
>
> Thanks,
> Laura
>
>
> Begin forwarded message:
>
> *From: *Laura Bartels <laura at greenweaver.com>
> *Date: *May 8, 2013 10:02:00 AM MDT
> *To: *Global Straw Building Network <GSBN at sustainablesources.com>
> *Subject: **Re: [GSBN] Modeling or measuring mass effect of interior
> plaster*
>
> Luc,
> I'm so grateful to see this. And it brings back
>  *
>  Laura Bartels
> GreenWeaver Inc.
> 520 S. Third St., Suite 5
> Carbondale, CO 81623
> 970-379-6779
> www.greenweaverinc.com
>
> *
>
>
> On May 8, 2013, at 5:43 AM, Luc Floissac wrote:
>
>  Hi,
> I've studied several kinds of wall in my book "La construction en paille"
> (in french...)
>
> http://www.amazon.com/construction-paille-fondamentaux-Techniques-r%C3%A9alisations/dp/2360980815
>
> You can find here attached an extract of the book
> I've and measured the mass effect on the internal side ("inertie
> quotidienne du côté intérieur" in french)  in respect with ISO 13786
> document (see p. 36).
> The nature and thickness of the outside coverage of a SB wall have a very
> little influence to the inside thermal performance.
>
> I've also realized some mass effect statistics on the 40 SB building
> studied (see p. 37). You can see that many SB buidings have strong or
> middle internal mass.
>
> Regards.
> Luc
>
> --
> Luc Floissac - Conseiller environnemental
> Eco-Etudes à "En Pommel" 31570 LANTA
> tél. 09 77 36 92 04www.eco-etudes.comluc.floissac at wanadoo.fr
>
>
>
>
> Le 08/05/2013 12:29, martin hammer a écrit :
>
> Great discussion on this subject.
>
>
> I often characterize plastered straw bale walls as “a perfect balance of
> mass and insulation”.  A generalization, to be sure, but not far off, for
> almost any climatic condition.  I also often refer to them as “natural
> SIPs”.  Structural Insulated Panels, are usually thought of as having an
> insulating polymer foam core between layers of plywood or OSB, but can also
> include a similar core between layers of cement plaster (applied in situ).
>  These are sometimes called “composite panel building systems” or
> “structural insulated reinforced concrete panels”. Structurally, plastered
> SB walls (can) function like any of the SIPs, but thermally they perform
> only like SIPs with the cement plaster skins. (Though I suppose gypsum
> board is sometimes applied to the interior and cement plaster to the
> exterior of OSB SIPs, which thermally gets them closer to SB walls.)
>
> The systems with cement plaster skins usually use a welded steel wire
> space frame that ties the skins together through the insulating foam core.
>  If you squint hard and ignore petro-chemical insulations and the Portland
> cement based plaster (I know that’s impossible), then in terms of
> structural and thermal performance its a great system.  This might be like
> saying “except for the fact that it’s terrible, it’s great!”, but there’s a
> valid point in there somewhere.  And one could presumably use lime plaster
> or soil-cement (or even clay plaster?) with one of these foam-wire-core
> systems (anyone done that?) that would significantly reduce the
> environmental downside but maintain the thermal performance and structural
> capacity (with careful consideration of the weaker plasters for the
> particular application).
>
> Of course instead of messing with any of that one could just build SB
> walls.  I’m just making a comparison to “similar” industrialized systems,
> that to be fair, have certain advantages.  One advantage is SIPs (with wood
> panel or reinforced cement plaster skins) can be used structurally for
> floor and roof elements and plastered SB cannot (notwithstanding SB vaults).
>
> One observation on the very good article Bohdan shared, is that the
> mid-mass building gets you far in terms of thermal performance (compared to
> the low-mass building), whereas the high-mass building then demonstrates a
> more modest improvement.  Like anything else, the first steps in the right
> direction have the largest payoff, with still-valuable but diminishing
> return after that.
>
> One other thought is that the mass on the interior of a plastered SB wall
> is more important than the mass on the exterior in terms of thermal
> performance.  I wonder if anyone has therefore used a thicker interior
> plaster than exterior.
>
> Martin
>
>
> On 5/7/13 5:23 PM, "Derek Roff" <derek at unm.edu> wrote:
>
>  Thanks for posting the article on thermal mass, Bohdan.  I found it very
> interesting.  Based on the data it contains, I have a few comments relevant
> to Laura's situation.
>
> As John mentioned, the article emphasizes that it is addressing thermal
> mass with direct solar exposure/gain.  However, I didn't see anything
> quantifying what amount of time the sun needs to shine on each bit of
> thermal mass floor and wall each day, in order to attain the listed
> results.  As the sun moves across the sky, some parts of the floor and
> walls will receive direct sunlight for only a few minutes, while other
> locations will be in the sun for several hours per day.  The amount of
> furniture, area rugs, and wall decorations will also affect how much sun
> shines on thermal mass.  I'm thinking that as the amount of time in the sun
> decreases, the needed surface area of the thermal mass needs to increase,
> to get the same thermal mass effect.  The total mass of the thermal mass
> might need to increase a bit, too.
>
> At 6000 sq ft/560m3, Laŭra's project will likely have a higher floor area
> to wall area ratio than smaller houses.  By itself, this might decrease the
> importance of the thermal mass in the walls.  However, depending on the
> number of stories and the floor plan, a large project might have a smaller
> percentage of floor and wall area accessible to direct sun.  That would
> increase the importance of maximizing the surface area of the thermal mass.
>
>
> Laura didn't say where this project will be built, but I'm guessing it
> might have a climate closer to the "cold European climate" listed in the
> article, rather than to the alternative Melbourne figures.  The article
> quotes Vale and Vale as suggesting 1,200kg of thermal mass for each square
> meter of floor area.  It's worth noting that all this thermal mass could
> not be in the floor.  If it were, the thermal mass floor would need to be
> about .5m/20" thick.  Not only is that absurd from a construction
> perspective, but much of the mass in a slab that thick would not respond to
> daily temperature variation.  My reading is that walls have to be involved
> in the thermal mass equation, to get the results described.
>
> At the top right of page 7, the article says that temperature modeling for
> the three reference building variations (low-mass, medium-mass, and
> high-mass) are predicted to have similar maximum temperatures.  However,
> the numbers in the chart paint a different picture, as I see it.  Table 3
> shows the maximum temperature at the hottest part of the summer as 32
> degrees C/90 degrees F for the low mass house, contrasted with 25 C/77 F
> for the high-mass house.  To me, that's the difference between the average
> American demanding air conditioning (or feeling that they are suffering),
> versus a temperature that many would find acceptable.  23 C/77 F is pretty
> comfortable, when the radiant surfaces (ceiling, walls and floors) are at a
> similar temperature or lower, as they would be in a well-insulated home.
>  That temperature can feel uncomfortable, if the radiant surfaces have
> heated up to 30 C/86 F or more.
>
> Table 3 also shows surprising figures for the morning lows in the hottest
> month.  The low-mass building is predicted to be at 16 C/61 F on a summer
> morning.  Some residents would be turning on the heat in the morning, and
> the air conditioning in the afternoon.  The high-mass building will get
> down to a comfortable 20 C/68 F on the same summer morning.  To the extent
> that covering the walls with barn wood will diminish the effective thermal
> mass, as Laura describes, it could have a significant impact on comfort in
> the summer.  The winter figures indicate substantially greater differences
> between high-mass and low-mass temperature variations.  I also conclude
> that Hobart has a pretty pleasant temperature range.
>
> I agree with David, that uninsulated thermal mass can easily be a
> liability.  I'm not sure the same is true for well-insulated thermal mass.
>  A large amount of thermal mass combined with a well-insulated building
> envelope will result in small daily temperature variations.  At some point,
> adding more thermal mass will have little effect, because of the low
> temperature swing and the resulting low delta T across the thermal mass.
>  After this point, adding more thermal mass wouldn't help much, but I'm not
> seeing how it would have a negative effect, either.  Unless the residents
> found consistent temperatures monotonous.
>
> Derek
>
> On May 6, 2013, at 7:05 PM, Bohdan Dorniak 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<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 <tel:970-379-6779>
> www.greenweaverinc.com <http://www.greenweaverinc.com>
> **
> *
> <image001.jpg>
>
>
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>  <p 035-038 - Inertie Extrait de La construction en paille - Luc Floissac
> - Editions Terre vivante.pdf>
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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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