[GSBN] Modeling or measuring mass effect of interior plaster
Luc Floissac
luc.floissac at wanadoo.fr
Wed May 8 11:43:58 UTC 2013
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 04
www.eco-etudes.com
luc.floissac at wanadoo.fr
Le 08/05/2013 12:29, martin hammer a écrit :
> Re: [GSBN] Modeling or measuring mass effect of interior plaster 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, Lau(ra'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] *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>
>
>
> _______________________________________________
> GSBN mailing list
> GSBN at sustainablesources.com
> http://sustainablesources.com/mailman/listinfo.cgi/GSBN
>
>
>
>
>
> _______________________________________________
> GSBN mailing list
> GSBN at sustainablesources.com
> http://sustainablesources.com/mailman/listinfo.cgi/GSBN
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.sustainablesources.com/pipermail/gsbn/attachments/20130508/611561c1/attachment.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: p 035-038 - Inertie Extrait de La construction en paille - Luc Floissac - Editions Terre vivante.pdf
Type: application/pdf
Size: 790189 bytes
Desc: not available
URL: <http://lists.sustainablesources.com/pipermail/gsbn/attachments/20130508/611561c1/attachment.pdf>
More information about the GSBN
mailing list