<div>Thank you very much for your thoughts Derek.<br></div><div><div class="gmail_quote"><div dir="auto"><br></div><div dir="auto">I think the three answers I have received by now all agree on the theoretical charateristics.</div><div dir="auto">And then there is the practical application of how the theories apply in the real world.</div><div dir="auto">Very interesting.</div><div dir="auto"><br></div><div dir="auto">I got this reply from a colleague on another list:</div><div dir="auto"><br></div><div dir="auto"><span style="font-family:-apple-system,sans-serif;font-size:14.117648124694824px;background-color:rgb(250,248,247)">“Hi Lars,</span><br style="box-sizing:border-box;font-family:-apple-system,sans-serif;font-size:14.117648124694824px"><br style="box-sizing:border-box;font-family:-apple-system,sans-serif;font-size:14.117648124694824px"><span style="font-family:-apple-system,sans-serif;font-size:14.117648124694824px;background-color:rgb(250,248,247)">you can take a look at this table. It’s in french but easy to translate. You have to take a look at the « chaleur spécifique » and you can see how much energy can be stored by each materials. You can search as well on google "specific heat capacity » and compare. That’s true that cellulose is one of the best because it’s from wood (see wood fiber panels). Solid oak wood is up to 2300 J/kgK. </span><br style="box-sizing:border-box;font-family:-apple-system,sans-serif;font-size:14.117648124694824px"><span style="font-family:-apple-system,sans-serif;font-size:14.117648124694824px;background-color:rgb(250,248,247)">It’s not particularly related to weight, granite has only capacity of 774 J/kgK and hydrogen 14300 J/kgK.</span><br style="box-sizing:border-box;font-family:-apple-system,sans-serif;font-size:14.117648124694824px"><span style="font-family:-apple-system,sans-serif;font-size:14.117648124694824px;background-color:rgb(250,248,247)">In France now they start to take into account the capacity and « déphasage » which is the time that is needed for an insulation material to start to transfer the heat to the inside of the building. </span><br style="box-sizing:border-box;font-family:-apple-system,sans-serif;font-size:14.117648124694824px"><span style="font-family:-apple-system,sans-serif;font-size:14.117648124694824px;background-color:rgb(250,248,247)">On a roof, if you install the same thickness of insulation, one with glass wool and one with wood fiber boards, even if the the lambda is better for glass wool the thermic capacity is 2 time higher for wood fiber boards. It means that the material can absorb 2 time more energy before it starts to transmit it inside. It’s like a sponge that can absorb 2 times more water than an other one that will be full 2 time later and start to let water go 2 time later. </span><br style="box-sizing:border-box;font-family:-apple-system,sans-serif;font-size:14.117648124694824px"><span style="font-family:-apple-system,sans-serif;font-size:14.117648124694824px;background-color:rgb(250,248,247)">Ideal is to have a « dephasage » of 12 hours, so in summer while the sun heats the roof during whole day, the heat will start only to arrive inside when night comes and already cools down the outside. 20 cm of wood fiber is enough while you need 40 cm of glass wool to reach the same cycle and prevent over-heating during summer. This works for summer but not for winter. Energy streams are different. Having 40 cm of wood fiber wouldn’t be the best because it means that heat would start to come inside the day after when sun rise again and heat the inside of the room. Calculation of insulation have to take into account local climate on 24 hour cycle and seasonal as well to find the best ratio and equilibrium between summer and winter comfort.</span><br style="box-sizing:border-box;font-family:-apple-system,sans-serif;font-size:14.117648124694824px"><span style="font-family:-apple-system,sans-serif;font-size:14.117648124694824px;background-color:rgb(250,248,247)">Other aspect is as well regulation of vapor that has a very high thermic capacity (over 2000 J/kgK) so straw or wood again have a big advantage on mineral wool that don’t deal well with this.</span><br style="box-sizing:border-box;font-family:-apple-system,sans-serif;font-size:14.117648124694824px"><span style="font-family:-apple-system,sans-serif;font-size:14.117648124694824px;background-color:rgb(250,248,247)">You can find on the web some studies or calculation about the time releasing for each material and straw.</span><br style="box-sizing:border-box;font-family:-apple-system,sans-serif;font-size:14.117648124694824px"><span style="font-family:-apple-system,sans-serif;font-size:14.117648124694824px;background-color:rgb(250,248,247)">I don’t remember density of EC panels but it should not be too difficult to calculate the whole capacity of a panel. This capacity cycle is particularly important for the roof because it receive direct sun heat. It’s less important for a wall and big capacity can be interesting to maintain higher inertia of the building.</span><br style="box-sizing:border-box;font-family:-apple-system,sans-serif;font-size:14.117648124694824px"><br style="box-sizing:border-box;font-family:-apple-system,sans-serif;font-size:14.117648124694824px"><span style="font-family:-apple-system,sans-serif;font-size:14.117648124694824px;background-color:rgb(250,248,247)">Have a good day,</span><br style="box-sizing:border-box;font-family:-apple-system,sans-serif;font-size:14.117648124694824px"><br style="box-sizing:border-box;font-family:-apple-system,sans-serif;font-size:14.117648124694824px"><span style="font-family:-apple-system,sans-serif;font-size:14.117648124694824px;background-color:rgb(250,248,247)">Denis</span><br style="box-sizing:border-box;font-family:-apple-system,sans-serif;font-size:14.117648124694824px"><br style="box-sizing:border-box;font-family:-apple-system,sans-serif;font-size:14.117648124694824px"><span style="font-family:-apple-system,sans-serif;font-size:14.117648124694824px;background-color:rgb(250,248,247)">Materiaux densité [kg/m3] conductivité thermique λ [W/mK] chaleur spécifique [J/kgK] energie grise [kWh/m3] Ouate de cellulose soufflé 24 0.042 1900 15 Ouate de cellulose injecté 45 0.042 1900 100 Ouate de cellulose panneaux 70 0.042 1900 150 Fibre de bois panneaux 50 0.039 2100 60 Polystyrène expansé 15 0.039 1450 500 Laine de verre panneaux 35 0.039 1030 470 Laine de roche panneaux 70 0.042 1030 430 Laine de chanvre panneaux 40 0.040 1700 40 Liège expansé panneaux 125 0.049 1560 450 Paille 80 0.050 1330 0 Perlite en vrac 70 0.060 900 330</span><br style="box-sizing:border-box;font-family:-apple-system,sans-serif;font-size:14.117648124694824px"><br style="box-sizing:border-box;font-family:-apple-system,sans-serif;font-size:14.117648124694824px"><span style="font-family:-apple-system,sans-serif;font-size:14.117648124694824px;background-color:rgb(250,248,247)">Densité ou masse volumique ρ [kg/m3]”</span><br></div><div dir="auto"><span style="font-family:-apple-system,sans-serif;font-size:14.117648124694824px;background-color:rgb(250,248,247)"><br></span></div><div dir="auto"><span style="font-family:-apple-system,sans-serif;font-size:14.117648124694824px;background-color:rgb(250,248,247)">Best, Lars</span></div><div dir="auto"><span style="font-family:-apple-system,sans-serif;font-size:14.117648124694824px;background-color:rgb(250,248,247)"><br></span></div><div dir="auto"><span style="font-family:-apple-system,sans-serif;font-size:14.117648124694824px;background-color:rgb(250,248,247)">- - - </span></div><div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">tor. 2. maj 2019 kl. 16.50 skrev Derek Roff <<a href="mailto:derek@unm.edu" target="_blank">derek@unm.edu</a>>:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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Perhaps I am misunderstanding the scenario, but I’m skeptical, Lars, that the difference in heat storage capacity of different kinds of insulation is very important to the building performance question. In the example that you quote, of wall insulation absorbing
heat from solar influx when available, and later releasing that heat to the room, an important distinction is whether the scenario assumes sunlight falling on the outside of an insulated wall, or on the inside of an insulated wall.
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<div>When sunlight heats the outside of an outside wall, we need enough insulation that very little of that heat ever makes it inside the building. Super-insulated buildings are designed to prevent heat movement from outside to in or inside to out.
Therefore, we can’t expect useful heat transfer into the living space from sun shining on the outside of an insulated wall. The wall is designed to prevent precisely that. </div>
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<div>If sunlight is coming trough a window or skylight and shining on the inside of an insulated wall, then there is some hope that this solar energy will help thermal performance of the house. The surface of the wall being struck by the sunlight
will heat up to above the average ambient temperature in the room, and then (immediately) begin to release that heat through radiation, conduction, and convection back into the room, tending toward temperature equilibrium. </div>
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<div>Several problems come to my mind in considering trying to store useful solar heat in an insulated wall. The first is that I wouldn’t expect very much sunlight to strike the inside surface of an insulated wall. Light coming in through windows
and skylights will mostly strike the floor, furniture, and interior (uninsulated) walls. As I imagine a normal house, I wouldn’t think that even ten percent of the sunlight entering the building envelope during the course of a day would touch the inside of
an insulated wall. For a larger, commercial building, the percentage would be even smaller. </div>
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<div>Next, the insulated wall is coated with something. Clay, I hope, but certainly something less insulating and of higher density than the insulation itself. Assuming a clay coating, for the moment, it will heat up above average room temperatures
when the sun strikes it. As a dense, fairly conductive material, it will store a fair amount of heat, and change relatively little in temperature. That is what we want it to do. Therefore, the clay plaster will ‘protect’ both the air in the room and the
insulation behind it from experiencing the higher temperatures that might otherwise occur from the solar influx. That’s a good thing for comfort in the room, since it moderates temperature swings. So now we have a slightly heated clay surface in contact
with the room air on one side and with the insulation on the other side. Certainly, the clay will conduct some heat into the insulation that it touches. But temperature differential (delta T) is small, and the insulation wants to resist that heat flow. Therefore,
we can’t move very much heat very far into the low-mass insulation. This gives us a small temperature change in a small amount of mass within the insulation, which equals low heat storage. On the room side, the slightly heated clay wall surface will give
up some heat to the room through radiation, conduction, and convection. That is what we want, and that is where most of the heat will go. So, what percentage of the heat stored in the clay plaster is transferred first to the insulation behind it, and then
later, re-transferred to the clay plaster and returned to the room? I’d be surprised if it was over one percent. </div>
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<div>If these guestimates are anywhere close, then the difference in heat storage capacity of different kinds of insulation won’t make any significant difference. To summarize: 1) We can’t get much solar influx to heat the insulation, because little
sunlight strike the inside of an insulated wall; 2) The surface coating of the wall will have more mass and greater conductivity than the insulation, and it will be the surface that is struck by the sunlight, therefore, it will do almost all of heat storage
that might happen in the insulated wall; 3) Delta T will be low between the wall surface and the insulation behind it, minimizing the heat transfer to the insulation, and therefore minimizing the contribution to heat storage made by the insulation; 4) Differences
between heat storage by different types of insulation will be insignificant in overall effect, because of all the preceding factors. </div>
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<div>Am I missing something important? </div>
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<div>Derek</div></div><div style="word-wrap:break-word;line-break:after-white-space">
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<div>Derek Roff</div>
<div><a href="mailto:derek@unm.edu" target="_blank">derek@unm.edu</a></div>
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<div>On May 2, 2019, at 6:37 AM, Lars Keller <<a href="mailto:larskeller@gmail.com" target="_blank">larskeller@gmail.com</a>> wrote:</div>
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<div><span style="font-family:-apple-system,sans-serif;font-size:14.117648124694824px">
<div dir="auto">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.</div>
</span><br style="box-sizing:border-box;font-family:-apple-system,sans-serif;font-size:14.117648124694824px">
<span style="font-family:-apple-system,sans-serif;font-size:14.117648124694824px">
<div dir="auto">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.</div>
</span><br style="box-sizing:border-box;font-family:-apple-system,sans-serif;font-size:14.117648124694824px">
<span style="font-family:-apple-system,sans-serif;font-size:14.117648124694824px">I would like to hear thoughts about whether my understanding is correct.</span>
<div dir="auto"><br style="box-sizing:border-box;font-family:-apple-system,sans-serif;font-size:14.117648124694824px">
<span style="font-family:-apple-system,sans-serif;font-size:14.117648124694824px">I assume straw would share the benefit of the cellulose option.</span><br style="box-sizing:border-box;font-family:-apple-system,sans-serif;font-size:14.117648124694824px">
<span style="font-family:-apple-system,sans-serif;font-size:14.117648124694824px"><br>
</span></div>
<div dir="auto"><span style="font-family:-apple-system,sans-serif;font-size:14.117648124694824px">Does anyone know if we have / there is numbers to back this up ?</span><br style="box-sizing:border-box;font-family:-apple-system,sans-serif;font-size:14.117648124694824px">
<br style="box-sizing:border-box;font-family:-apple-system,sans-serif;font-size:14.117648124694824px">
<span style="font-family:-apple-system,sans-serif;font-size:14.117648124694824px">Best, Lars</span><br style="box-sizing:border-box;font-family:-apple-system,sans-serif;font-size:14.117648124694824px">
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