[GSBN] Heat storage capacity of wall systems. Hempcrete and Decrement Delay

Sat May 4 00:32:33 UTC 2019

Great, thanks Herbert.
Lars

fre. 3. maj 2019 kl. 12.52 skrev <asbn at baubiologie.at>:

> Dear Lars
>
>
>
> What an interesting discussion. I followed only partly, but some of the
> comments and analyses are really great for me, too.
> E.g. I never calculated the water in natural fibres as main heat storage
> capacity, as mentioned by Barbara.
>
>
>
> I just want to additionally mention, that the temperature differences
> between straw bale houses (or those insulated with cellulose) are not just
> an effect of the heat storage capacity due to higher masses and water
> content, this is also (and I would say mainly) the effect of the
> moisture-storage capacity of clay plasters and the cooling effect due to
> evaporation, when outside or indoor temperatures rise.
>
>
>
> Liebe Grüße / kind regards
>
> Herbert
>
> asbn – austrian straw bale network
>
> ESBA – European Straw Building Association
>
>
>
>
>
> *Von:* Gsbn [mailto:gsbn-bounces at sustainablesources.com] *Im Auftrag von *Rene
> Dalmeijer
> *Gesendet:* Donnerstag, 02. Mai 2019 21:29
> *An:* Global Straw Building Network
> *Betreff:* Re: [GSBN] Heat storage capacity of wall systems. Hempcrete
> and Decrement Delay
>
>
>
> Lars
>
>
>
> I once had the occasion to visit 2 identical pre-fab wood frame houses. It
> was very hot 35+ The cellulose insulated house was comfortable the the
> glass fiber batt wasn’t. Which shows in practice what the theory tells. I
> found it hard to accept that the big difference was only due to the phase
> shift effect. It really makes a substantial  difference, mainly in the
> summer at least with substantial dinural temperature swings.
>
> Sent from my iPhone
>
>
> On 2 May 2019, at 19:35, Tom Woolley <tom.woolley at btconnect.com> wrote:
>
> Lars
>
>
>
> You have raised a very important debate which perhaps could be the subject
> of a scientific conference .
>
> Maybe we should organise one!
>
> What I find interesting is that no-one has yet referred to *Decrement
> delay*
>
>
> https://www.new-learn.info/packages/clear/thermal/buildings/building_fabric/properties/time_lag.html
>
>
>
> Thermal mass is important in terms of the thermal performance of buildings
>  but its effects cannot be fully understood without also considering
> decrement delay
>
> The Concrete centre in the UK makes great claims about the benefits of the
> thermal mass of concrete for instance
>
>
>
> However measuring thermal mass in itself is not helpful without
> considering the decrement delay factor
>
>
>
> High thermal mass may not be beneficial if the time lag/decrement delay is
> too slow , as it is with concrete
>
> Despite what August says I am pretty clear that heat release from concrete
> is not quick but extremely slow
>
> This is why so-called night calling using exposed concrete floors is
> rarely heard of these days as the decrement delay in concrete means that it
> doesn’t warm up or cool down at the right time
>
>
>
> One of the reasons we have become fans of hempcrete is that it evens out
> temperature fluctuations on a 24 hour cycle and so the temperature in a
> building with 30 cm thick walls remains constant whatever fluctuations are
> taking place outside, without any heat input
>
> This is why it has become popular with the wine and food storage industry
> as they know they can store things in a space at a steady temperature of
> about 14 Degree C without any heating on cooling.
>
>
>
> Sadly we have very little scientific data to back this up based on
> measurements at buildings.
>
> Its just we know it happens from observation.
>
>
> https://www.ukhempcrete.com/hempcrete-buildings-thermal-performance-and-costs/
>
>
>
> My experience of any lightweight insulation materials such as cellulose or
> any of the synthetics is that they are poor at storing heat and their
> decrement delay is too short.
>
> My own study that I am sitting in here is insulated with wood fibre boards
> and lightweight hemp flax quilt but on a cold day it loses heat far too
> quickly and heat has to be added
>
>
>
> However our hempcrete house stays comfortable all day and night long with
> minimal heat loss because of its excellent combination of insulation and
> thermal mass and its near perfect decrement delay properties
>
> One of the mysterious things about hempcrete is due to its hygroscopic
> properties. Hemp can take in and release water vapour and its absorption of
> water actually assists with its thermal performance. Water has good heat
> retention capacity
>
>
>
> Strawbale in my experience is not as good as hempcrete in terms of
> decrement delay but if built well and depending on the plaster/render it
> can have good decrement delay properties
>
>
>
> The pioneering work on decrement delay was done by *Steven Szokolay* in
> his wonderful book *Introduction to Architectural Science* first
> published in 2004
>
>
> https://www.bookdepository.com/Introduction-Architectural-Science-Steven-V-Szokolay/9780415824989
>
>
>
> Neil May of Natural Building Technologies in the UK, who sadly died
> recently at a very young age, was an expert on decrement delay but its hard
> to find what he published on this
>
> This important report makes some references
>
>
> http://goodhomes.org.uk/wp-content/uploads/2017/05/GHA-Critique-of-the-Green-Guide-to-Specification-051208.pdf
>
>
>
> Simply comparing thermal mass without considering decrement delay will not
> give the full picture
>
>
>
> Tom
>
>
>
>
>
> Tom Woolley
>
>
>
>
>
>
>
> On 2 May 2019, at 17:56, August Hasz <hasz at reginc.com> wrote:
>
>
>
> Lars-
>
>
>
> To do a comparison of this one single aspect of the insulation options,
> you need to compare the heat capacity (typically listed as energy stored
> per unit weight)+ the weight of the different materials. Resistance to heat
> transfer (R-vlaue or U-value) is typically the most important
> characteristic to consider. This is pretty straight forward math to do if
> you have access to the thermal properties of the materials being
> considered. With natural materials getting an exact reading can be a bit
> difficult because changes in moisture content (particularly for straw, wood
> and other organic properties) will alter the heat capacity, with and
> resistance to heat transfer significantly, but you should be able to find
> some general average values to use in a comparison.
>
>
>
> The story of how this unfolds in buildings is a big more complicated
> though because we need that mass to be ‘active’ to be of use. For example,
> a similar thickness of some wood products will store as much heat as that
> thickness of concrete because of the difference in heat capacity, but
> concrete will release this heat more quickly, so if we are purely
> considering heat storage the concrete is likely superior BUT wood is of
> course renewable, has lower embodied energy and in many applications the
> increased resistance to heat transfer is a plus.
>
>
>
> Is that helpful at all?
>
>
>
> Thanks, August
>
>
>
> August Hasz, P.E.
>
> President
>
> REG
>
> Resource Engineering Group
>
> Direct: 970.713.0984
>
> Cell: 970.275.3603
>
> hasz at reginc.com
>
> www.reginc.com
>
>
>
> On May 2, 2019, at 6:37 AM, Lars Keller <larskeller at gmail.com> wrote:
>
>
>
> We have a discussion in Denmark where some people argue, that if you
> compare two walls with similar insulation values, one being insulated with
> mineralwool, and one with wood cellulose or paper cellulose, then the wood
> cellulose option can retain / contain more heat thatn the mineralwool
> solution.
>
>
>
> The advantage of this for the wood cellulose is, that this solution is
> then capable of absorbing more heat when there is eg more solar influx, and
> later release the heat into the room again, thus creating more comfort. I
> assume that this is a result of the cellulose option being heavier than the
> mineralwool option.
>
>
> I would like to hear thoughts about whether my understanding is correct.
>
>
> I assume straw would share the benefit of the cellulose option.
>
> Does anyone know if we have / there is numbers to back this up ?
>
> Best, Lars
>
> --
>
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>
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Om vores firma ~ link
Om vores masseovne ~ link
Om vores workshops ~ link
Kontakt-info
skype
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Home +45 8668 0505
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