The wine shed - a concept, and some horrible maths..

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uncle tom
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The wine shed - a concept, and some horrible maths..

Post by uncle tom » 07:48 Sun 04 Feb 2018

This is a long post – so please refresh your glass first..

One of the great revelations of my youth was the realisation that not only could reference books be wrong, but also that the authors of reference books copied each other’s mistakes.

Until a definitive work was published in the 1970s, countless authors had repeated the myth that Oak trees were slow growing, when in fact their dominance on dry clay soils in England is a consequence of the exact opposite.

Most people can remember the old Popeye cartoons and the tins of spinach – a throwback to a very old mis-analysis of the vegetable that led to the belief that it was exceptionally rich in iron. In fact it contains no more iron than other leaf vegetables.

Even today the myth is repeated that the Black Death was spread by rats, despite the abundant evidence that it spread across Europe at around 3-4 miles per day – a pace of movement entirely at odds with the habits of a rodent that likes to return to its nest each night.

So what about the oft repeated mantra that wine should be stored at a steady 10C/50F – who, I wonder, was the first person to put that notion into print?

Aside from being a nice round number on both temperature scales, it is clear that such conditions virtually never occurred before the days of industrial refrigeration.

The British Geological Survey states that seasonal temperature changes descend about 15m into the soil – or nearly six storeys down. This in turn is backed up by the Met office data for soil temperatures at 1m depth in the south of England, which show a consistent seasonal curve ranging from about 7C to 17C – so little attenuation at that depth of the surface temperature averages.

http://www.bgs.ac.uk/reference/gshp/gshp_report.html
https://www.researchgate.net/figure/225 ... th-East-UK

This data casts doubt on whether sub surface wine storage is actually worth the hassle, so it seems worthwhile to ponder the feasibility of constructing a surface ‘wine shed’.

So first, what are the actual needs?

10C is the year round average temperature in parts of central and eastern England, but in Bordeaux it is a full 3.5C warmer, and reaches nearly 15C in Porto.

It seems likely then that in the deepest and grandest Bordeaux château cellars, the temperature may never drop as low as 10C – yet it doesn’t seem to do any harm.

My own home observations also confirm that seasonal fluctuation is not an issue – the cellar under my home cycles through a range of about 9C summer to winter. Ullage measurements of sound mature bottles indicate a typical weight loss of around 100-200mg p.a.

Although neck profiles vary, the difference in weight terms between an IN level and a VTS level ranges from about 15 to 25g; so at the loss rates I am recording, it could take two centuries or more to achieve that degree of ullage. That’s good enough for me.

So it seems pretty safe to conclude that in moderation, summer/winter temperature fluctuations really aren’t a problem.

There are of course two other sets of fluctuations:

First the day/night fluctuations; these can range from virtually zero in overcast breezy damp weather to 10C or more when its dry, clear and still. Then there are intra seasonal fluctuations, such as a heat wave or cold snap. These happen constantly throughout the year to varying degrees, but in the UK, the 24hr average doesn’t often deviate by more than 5C from the seasonal average.

It is common currency that the first of these should be avoided at all costs, although the evidence to support that is a bit flimsy. My own observations suggest that problems arise when bottles are stored in places that see these day/night changes amplified, such as attics, vehicles and freight containers.

When stored in places that attenuate these daily temperature swings, such as below stairs cupboards, there is no obvious problem.

However, a design that eliminates day/night changes and moderates intra seasonal swings, seems sensible and sufficient, for the UK at least.

To combat the first of these fluctuations in our wine shed without using chillers requires a combination of insulation and thermal mass.

Every substance has a thermal conductivity, measured as watts per cubic metre when there is a one degree difference in temperature across the block.

This varies considerably – an insulator like expanded polystyrene has a thermal conductivity of 0.038 whereas a dense concrete block has a conductivity of 1.13

Thermal mass on the other hand, is derived from the specific heat of a substance.

The specific heat capacity of a substance is the amount of energy needed to raise the temperature of one kilogram by one degree. To derive the thermal mass this then has to be multiplied by the density of the substance.

Thus the thermal mass of expanded polystyrene (as EPS70) is it’s density of 15kg/m3 times its specific heat 1400J/Kg/C making a thermal mass 21000J/m3/C

Dense concrete on the other hand is around 2000Kg/m3 with a specific heat of around 1000, resulting in a thermal mass of 2000,000J/m3/C – or nearly 100 times more than expanded polystyrene.

The thermal mass matters because when heat is applied to one side of a brick or block, it does not immediately manifest itself on the opposite face. The block itself has to warm up first to create a thermal gradient before any heat transfers.

Calculating this transfer time is significant, since if the walls of our wine shed take more than 12 hours to warm up, the day/night temperature fluctuations will cancel each other out with only the faintest temperature ripples apparent on the inside face.

The maths here is a bit counter-intuitive, and as I’ve not been able to find any clever formulae to assist me, I’d be grateful if others would scrutinise my calculations. I also thought someone would have given this warming up period a clever name, but as I’ve drawn a blank on that as well, I’ll call it hysteresis.

Getting my head round the calculation for this was harder than I expected.

The first thing I deduced was that as the amount of energy needed rises in proportion to the temperature differential, so the amount of time needed for hysteresis will remain the same, irrespective of the temperature difference.

The second curiosity is that the progress rate of heat through a block as it forms a temperature gradient does not appear to be linear – it appears to start very quickly, slow towards the middle and then speed up again towards the end.

Less surprising was that the calculation gives an exponential result. The hysteresis time quadruples as the thickness doubles.

The only way I could make sense of the calculation was to consider the subject as a succession of 1mm thick slices, and using a spreadsheet calculate the time each successive slice would take to reach the requisite temperature, given the distance from the starting face, and the fact that the thermal gradient demands less and less energy for each successive slice.

I worked on the assumption that the source of heat would be absolute to give a worst case figure, and then totalled the times for each of the slices.

Does this give me the correct answer? I’m bugged that I might have missed something..

Having drafted a spreadsheet to compute this, it was only a simple matter to then compute the thickness of various materials needed to achieve the 12 hour hysteresis target.

If you haven’t already descended into a comatose state, this is where it gets interesting – well I think so, anyway..

If your walls are made of dense concrete, the thickness needed for a 12 hour hysteresis computes as 383mm, but if they are polystyrene that figure rises to 685mm. Despite far superior insulating properties, heat will emerge from the opposing face of a polystyrene slab far sooner than a concrete one of the same thickness, although the amount of heat passed by the concrete will be very much greater once the hysteresis period is over.

Now consider the properties of an aerated concrete block, commonly known as Breeze or Celcon blocks in the UK, Cinder blocks in the US. These lightweight blocks combine a moderate amount of thermal mass (just over 30% that of dense concrete) with moderately good insulating properties (polystyrene is four times better)

Putting the data on my spreadsheet revealed a 12hr hysteresis thickness of just 249mm.

One of the standard sizes for these blocks (in the UK) is a thickness of 275mm. The blocks are inexpensive, light, easy to cut and very quick to lay.

It seems ideal for eliminating the day/night element. However, before I get carried away working out a cost effective system for muting the intra seasonal fluctuations, and address issues like floors, ceilings and doors, I would be very grateful if those whose maths is not quite as rusty as mine would check my calculations.

The essential data for these blocks (taken from the Celcon data sheet for their standard block) is:

Density – 600Kg/m3
Specific heat capacity – 1050J/KgK
Thermal conductivity – 0.15JmK
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Re: The wine shed - a concept, and some horrible maths..

Post by flash_uk » 12:11 Sun 04 Feb 2018

I managed to stay the course on the whole post Tom 😀

I’ll let someone else prove the maths. On the subject of the ceiling, wouldn’t it be possible to lay wooden joists covered with blockboard and then put a layer of breeze blocks on top? You could still have a pitched roof above that if desired.

The door would be the most challenging area to address for thermal insulation I would guess.

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Re: The wine shed - a concept, and some horrible maths..

Post by SushiNorth » 22:33 Mon 05 Feb 2018

So, this post came at an ideal time as I'm in the midst of a cellar rebuild. Interestingly, my last cellar was made of two 6mil plastic sheets, with 3" between, and it required intermittent AC (5K BTU) to keep the space 15-20F lower than surrounding space.

The new cellar has 4-5" dense cement around two sides. Its temperature is stable up to about 4' above floor level, then it fluctuates with outside temp (relative). I am going to put
2" R13 rigid foam insulation on the upper 4' of the concrete
R30 fiberglass batt in the ceiling above (closed in with gypsum dry wall on the cold side and vapor barrier on the warm side)
2" R13 rigid foam in the two non-cement walls, likely another 1" of pink R5 behind that, and spray-foam to seal it in -- sandwiched between gypsum.

I've already rigged the humidity system, and will keep the 5K BTU AC for now (will eventually switch to 10K to minimize humidity changes). But one thing I've been thinking a lot about is how to add thermal mass. Think of it like leaving big water bottles in the freezer. What if I put two 55 gallon plastic drums of water in the wineroom? What if I used a temp-retaining stone on the floor?

Just thoughts
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Re: The wine shed - a concept, and some horrible maths..

Post by DRT » 22:53 Mon 05 Feb 2018

SushiNorth wrote:
22:33 Mon 05 Feb 2018
But one thing I've been thinking a lot about is how to add thermal mass. Think of it like leaving big water bottles in the freezer. What if I put two 55 gallon plastic drums of water in the wineroom? What if I used a temp-retaining stone on the floor?
Every time you drink a bottle of wine, Port or water just fill the empty bottle with water and put it back in the cellar :wink:

Or, simply buy more Port! :990066: :lol:
"The first duty of Port is to be red"
Ernest H. Cockburn

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Re: The wine shed - a concept, and some horrible maths..

Post by DRT » 23:09 Mon 05 Feb 2018

I am watching this thread with interest, Tom. I can't help with the maths but I share your skepticism about temperature stability. A fine example is the cellars in VNG, which are about as thermally stable as my back garden. Whilst it seems to be true that bottle matured wines age slightly faster in VNG than they would buried under 300ft of chalk in the UK, I have tasted many bottles of old VP from those cellars that were very fine indeed.

As an extreme example, I recently tasted a bottle of VP from the mid 1990's that had been lying undisturbed in a disused barn in the Douro for 20 years. The temperature variation in that barn in an average year would go from approximately 0 to 40 degrees C and it had experienced that 20 times. The day/night fluctuation would not be so extreme but would still have been way beyond what is experienced in the average non-air-conditioned house in a temperate country. Whilst it was by no means showing at its best, it was still drinkable.

Whilst not advocating storing VP in an extreme environment like that described above, I do think that some of the paranoia around absolute stability is somewhat misguided.
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Re: The wine shed - a concept, and some horrible maths..

Post by uncle tom » 06:56 Tue 06 Feb 2018

What if I put two 55 gallon plastic drums of water in the wineroom? What if I used a temp-retaining stone on the floor?
Water is by some margin the best source of thermal mass, at 4200J/L/C Stone or concrete varies a little but mostly comes in at just under half that figure.

Something that intrigues me is the availability of stackable 10L jerrycans - often sold for camping purposes.

https://www.theplasticbottlescompany.co ... ident-cap/

These can be stacked to form a wall that is either 190mm or 220mm thick, depending on which way round you stack them.

A square meter of these bottles arranged edge on would carry 162L of water and require 677KJ to raise it by 1C. If stacked against a wall of 275mm Celcon blocks, a 5C deflection in the average outside temperature resulting from a heatwave would take over three days to raise the water temperature by just 1C - a degree of moderation that seems quite sufficient.

However, what I don't know is how stable they are when stacked, how high you can stack them, and whether they deform if stacked for very long periods. I'm hunching that it may be important to ensure they are 100% full to avoid distortion.

If you're planning to include some liquid thermal mass into your design, it would be useful if you experimented with some of these and reported back on their stability when stacked.

Edit: I notice the availability of a 25L version of the same, which could be stacked to make a wall 245mm thick:

https://www.ebay.co.uk/itm/25-Litre-ltr ... sKbr8QZ4IQ
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Re: The wine shed - a concept, and some horrible maths..

Post by uncle tom » 09:03 Tue 06 Feb 2018

To take some of the uncertainty out of stacking bottles, although it does take up slightly more space, one could purchase 300mm deep racking such as this:

http://www.bigdug.co.uk/shelving-c2/val ... ving-p1304

And load it with 12 of these:

https://www.taylor-davis.co.uk/products ... litre.html

If your cellar ceiling height is 2m that would provide 166L of water per m2 - slightly more than than the stack of 10L bottles, but taking up 80mm more depth..

Edit: An email from Taylor Davis quotes a quantity price of £5.18 each delivered, VAT inc. for the 25 litres jerrycans - so total cost, including the racking for the thermal wall would come to a £133/m
Last edited by uncle tom on 12:05 Tue 06 Feb 2018, edited 1 time in total.
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Re: The wine shed - a concept, and some horrible maths..

Post by uncle tom » 11:08 Tue 06 Feb 2018

On the subject of the ceiling, wouldn’t it be possible to lay wooden joists covered with blockboard and then put a layer of breeze blocks on top?
Yes, a hazard in unheated buildings is condensation, and a wooden underside to the ceiling helps reduce that risk considerably. It is probably wise to align the end edges of the blocks with the joists which in the UK would normally mean 440mm centres. Allowing space for some non-load bearing thermal mass, and assuming that you are building a corridor style cellar with a working width of 2m, the span required might be about 2.6m. The blocks will create an imposed load of 1.62kN/m2 and the dead load will bring this up to about 1.75kN.

According to the tables, the smallest joist size that will bear this load is 38mm x 140mm finished size (using standard graded timber type SC3 which is usually marked C16) However, given that the building will be unheated, it is probably wiser to elect for 47 x 147 or 47 x 195. Bear in mind that ungraded wood can be very much weaker.

The choice of board depends on what is cheapest in your locality - I would probably elect for the 12mm OSB board known as Sterling board.

As the blocks above will be laid dry, I would put a layer of 500 gauge polythene between the boards and blocks to prevent draughts.
You could still have a pitched roof above that if desired.
A simple pitched roof is much simpler to construct than a flat one. Even with insulated roofing panels however, the roof void will tend to heat up under direct sunlight, so important to leave a small ventilation gap where they meet the side walls and to install a large air brick or louvre at the top of each gable. It would be prudent also to cover the blocks underneath with foil to reflect back any radiation from the panels.

When nailing on corrugated insulated panels it is very easy to send the nail through at a slight angle - so use wide purlins to reduce the risk of missing your target. The nails should always be sent through the peaks and not the troughs - else you'll get leaks.

(All things I've learned the hard way..)
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Re: The wine shed - a concept, and some horrible maths..

Post by Andy Velebil » 17:43 Tue 06 Feb 2018

DRT wrote:
23:09 Mon 05 Feb 2018
I am watching this thread with interest, Tom. I can't help with the maths but I share your skepticism about temperature stability. A fine example is the cellars in VNG, which are about as thermally stable as my back garden. Whilst it seems to be true that bottle matured wines age slightly faster in VNG than they would buried under 300ft of chalk in the UK, I have tasted many bottles of old VP from those cellars that were very fine indeed.

As an extreme example, I recently tasted a bottle of VP from the mid 1990's that had been lying undisturbed in a disused barn in the Douro for 20 years. The temperature variation in that barn in an average year would go from approximately 0 to 40 degrees C and it had experienced that 20 times. The day/night fluctuation would not be so extreme but would still have been way beyond what is experienced in the average non-air-conditioned house in a temperate country. Whilst it was by no means showing at its best, it was still drinkable.

Whilst not advocating storing VP in an extreme environment like that described above, I do think that some of the paranoia around absolute stability is somewhat misguided.
And recall that refrigerated shipping containers are a relatively modern thing used to ship wine with. I am of the belief that a slow change in temperature over time (seasonal changes) does no harm at all. And perhaps is actually good for the development of the wine. I say that after having old wines stored since release in an abnormally cold cellar from a well known restaurant in Florida. The maturing level was drastically slowed down, I'd dare say artificially so.

I say this a lot, wine is far more durable than people today think and the whole "It must be stored at 55 degress" is total hogwash.

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Re: The wine shed - a concept, and some horrible maths..

Post by PhilW » 17:48 Tue 06 Feb 2018

Some maths. Having worked through some partial differential equations, for the simplified one-dimensional case the final equations seem to be as follows. For an incident temperature sine wave at the exterior surface, the temperature at a depth below this surface is given by:

T(x) = A + B.e^(-x.sqrt(pi/(k*T))).cos(-x.sqrt(pi/(k*T)) + 2*pi/(k*T)t)

where

A = Mid-point of incident temperature
B = Amplitude of additional sinusiodal variation
T = period in seconds of sinusiodal variation
k = thermal diffusivity of material
x = depth below surface
t = time

Therefore, the proportion (p) of the external variation seen at a depth (x) is given by:

p = e^(-x.sqrt(pi/(k*T)))

and for the delay of variation at depth x to equal half the variation period:

x = sqrt(pi*k*T)

Considering soil, polystyrene, concrete and breeze block (aerated concrete) therefore:

k = thermal diffusivity = thermal conductivity / (density * specific heat capacity)
k(soil) = 0.275 / (1.6x10^3 . 0.85x10^3) ~= 0.2x10^-6
k(conc) = 1.13 / (2.0x10^3 . 1.0x10^3) ~= 0.6x10^-6
k(poly) = 0.038 / (15 . 1.4x10^3) ~= 1.8x10^-6
k(bree) = 0.2 / (0.6x10^3 . 1.0x10^3) ~= 0.3x10^-6

Considering the daily cycle (period 24hr); for a phase offset of half the period ("hysteresis" of 12hr in Tom terminology):

x(soil) = 0.23m; p(soil) = 0.043 (4% of external daily variation)
x(conc) = 0.40m
x(poly) = 0.62m
x(bree) = 0.29m

Considering the yearly cycle (period 365days); for a phase offset of half the period ("hysteresis" of half-year in Tom terminology)

x(soil) = 4.5m; p(soil) = 0.043 (4% of external yearly variation)
x(conc) = 7.7m
x(poly) = 11.8m
x(bree) = 5.5m

Given the above, you can then derive the acceptable internal variation by day, and/or by season (though Tom's argument above is that the seasonal aspect can essentially be ignored, with short-term variation being the primary factor of concern). Note also that the above takes account of heat transfer by conduction only, where radiation is often also a huge consideration in practical circumstances.
Last edited by PhilW on 18:23 Tue 06 Feb 2018, edited 2 times in total.

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Re: The wine shed - a concept, and some horrible maths..

Post by PhilW » 17:49 Tue 06 Feb 2018

(I do wish phpbb would not remove all white space at start of line, prevent simple use of space or tab for indenting!)

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Re: The wine shed - a concept, and some horrible maths..

Post by LGTrotter » 19:06 Tue 06 Feb 2018

Thanks Phil.

Glad that's all cleared up.

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Re: The wine shed - a concept, and some horrible maths..

Post by LGTrotter » 20:04 Tue 06 Feb 2018

But seriously a very impressive looking bit of maths. I am unqualified to comment on it.

I have always taken the view (and suited the action to the thought) that I put celotex on the outside of my wine store (the insulation) and the breeze blocks on the inside (thermal inertia). I have no idea if this actually makes any difference but I have a feeling it should.

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Re: The wine shed - a concept, and some horrible maths..

Post by jdaw1 » 23:11 Tue 06 Feb 2018

You mentioned a liquid barrier. If the liquid is a single connected mass, then it insulates much better. One wall is heated by the sun, but the whole mass of water (some of which could be underground) acts as the thermal buffer. This would not be true of jerry cans.

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Re: The wine shed - a concept, and some horrible maths..

Post by flash_uk » 00:49 Wed 07 Feb 2018

jdaw1 wrote:
23:11 Tue 06 Feb 2018
You mentioned a liquid barrier. If the liquid is a single connected mass, then it insulates much better. One wall is heated by the sun, but the whole mass of water (some of which could be underground) acts as the thermal buffer. This would not be true of jerry cans.
I also thought that gaps/breaks of any sort in insulation materials create a heat sink that badly impairs the overall efficiency of the intended insulation.

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Re: The wine shed - a concept, and some horrible maths..

Post by uncle tom » 07:46 Thu 08 Feb 2018

Many thanks Phil - that looks like a phd level deduction!

I wondered why your figure for polystyrene was lower than mine but that for breeze was higher, then realised that you'd used different core data.

Running your equation with the Celcon data of 0.15 conductivity and SHC of 1050 gives a depth of 254mm which still leaves our respective methods around -2% adrift on the breeze but +10% adrift on the polystyrene, so the inevitable error from my 'slice' approach seems to deliver a strange pattern of discrepancy.

Still, I'm quite relieved that my method wasn't totally barking!

I tried Googling the term 'phase effect' and found nothing. Although my word 'hysteresis' is used in other branches of physics, it's dictionary definition reads: "the phenomenon in which the value of a physical property lags behind changes in the effect causing it" - which seems about right to me..

JDAW wrote:
You mentioned a liquid barrier. If the liquid is a single connected mass, then it insulates much better.
Indeed, but I'm not looking at them as an insulator, rather as a moderator - a body of water whose temperature will rise and fall in tandem with the bottles stored, lessening the pace.

The addition of insulation to the interior walls and ceiling will reduce the pace of thermal ingress and egress when the outside 24hr average changes. Given that foam boards are currently out of favour post - Grenfell, the addition of 75mm mineral fibre boards will more than halve the flow. The semi rigid Rockwool RW5 boards are also available with a foil finish, which will reduce heat movement through radiation.
Last edited by uncle tom on 08:57 Thu 08 Feb 2018, edited 2 times in total.
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Re: The wine shed - a concept, and some horrible maths..

Post by PhilW » 08:32 Thu 08 Feb 2018

uncle tom wrote:
07:46 Thu 08 Feb 2018
I tried Googling the term 'phase effect' and found nothing. Although my word 'hysteresis' is used in other branches of physics, it's dictionary definition reads: "the phenomenon in which the value of a physical property lags behind changes in the effect causing it" - which seems about right to me..
Look up "phase shift", "phase offset" or "phase of a waveform" - you can fill your boots on google with either of those. I can see what you mean about the literal per-wikipedia definition of hysteresis, though I've only ever heard it used (in the field of electronics) in relation to control of level change, rather than waveform delay (e.g. a thermostat set to turn off as the local temperature rises above 20C, which will then not turn on again until temperature drops below 19C, to avoid continuous switching around the limit; even if the temperature drops to 19.5 and stays there for hours, the thermostat doesn't switch again [in many systems at least], i.e. although for a continuously changing system its effect is a delay in switching, its behaviour is actually determined by the level rather than being delay of the signal).

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Re: The wine shed - a concept, and some horrible maths..

Post by uncle tom » 08:57 Thu 08 Feb 2018

It would help if I'd Googled the right term.. :roll:

Will have another look..
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Re: The wine shed - a concept, and some horrible maths..

Post by jdaw1 » 22:46 Fri 09 Feb 2018

PhilW wrote:
17:48 Tue 06 Feb 2018
radiation is often also a huge consideration in practical circumstances.
Please say more.

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Re: The wine shed - a concept, and some horrible maths..

Post by uncle tom » 06:17 Sat 10 Feb 2018

radiation is often also a huge consideration in practical circumstances.
Please say more.
Static air is a really good insulator - most insulating materials achieve their properties through the entrapment of air.

Heat mostly passes through air via convection (warm air is less dense, so displaces upwards) and via radiation. Whilst one tends to think of radiation as coming only from very hot objects, cold objects radiate heat also; frosts occur under clear skies because the radiation from the ground is not compensated by radiation from the clouds above.

Trying to compute or estimate the amount of heat transfer via radiation is horribly difficult - it's easier to work on the assumption that within the confines of an insulated room, everything will reach much the same temperature fairly quickly.
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Re: The wine shed - a concept, and some horrible maths..

Post by uncle tom » 04:01 Wed 21 Feb 2018

Moving on, some thoughts about the door and ventilation..

Although the building will be used for items that are dry, experience tells me that a totally sealed box is probably not a good idea as the atmosphere will get musty with an increased risk of mould. If all other faces of the building are airtight, the small amount of air that seeps around the edges of a simple door (but without scope for a thru draught) is probably sufficient however.

The door itself cannot be insulated to fully withstand the day/night cycle. Moreover, trying to apply a very thick layer of insulation to the inside will cause practical difficulties. However, if the back of the door has 50mm of foil backed insulation applied, I estimate that the total maximum ingress or egress of energy through conduction and air movement will peak at around 10W.

The simplest way to stop that 10W impacting your bottles is to create a lobby area with some thermal mass, separated from the main body of the shed. That lobby area can also be used to store low value bottles and those intended for near term consumption – ‘cellar defenders’. It is also the case that any thief entering the building is very unlikely to know what is good and what isn’t – and will grab whatever comes closest to hand.

My first thought was to erect a solid concrete wall partition, but working it through, a better and more cost effective solution would be a lightweight partition - or even just a curtain - with some thermal mass such as the racks of water canisters inside the lobby area.
I may be drunk, Miss, but in the morning I shall be sober and you will still be ugly - W.S. Churchill

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uncle tom
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Re: The wine shed - a concept, and some horrible maths..

Post by uncle tom » 04:23 Wed 21 Feb 2018

Cont..

Foil on the back of the door greatly reduces thermal movement, but will also ensure that approximately 80% of the heat will be moved by air convecting up or down the door. If the lobby ceiling is plywood, and has an area of 2.4m x 0.9m, that 8W of heat rising up will warm the wood by less than 1C before the temperature difference converts the energy to radiant heat (if my sums are right..) The radiant heat will then bounce around until it finds something cooler such as the thermal mass.

If your thermal mass is two racks of 12 x 25L jerrycans, (one on each side) that will be 600L of water to warm, which requires 2510kJ/C. If the temperature movement peaks at 10W but averages 5W over a 12hr cycle, that’s a day/night tidal flow of 216kJ – enough to warm the thermal mass by just 0.09C

It seems reasonable to conclude therefore, that adequate temperature stability will be achieved if this lobby area is simply isolated from the rest of the shed. Care should be taken to ensure that warm air rising from the door and spreading across the ceiling is obstructed from spreading to the rear. Similarly, as cooled air descends down the door and across the floor at night, it should also be obstructed from spreading further back.

Are my sums right? Do please check..
I may be drunk, Miss, but in the morning I shall be sober and you will still be ugly - W.S. Churchill

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SushiNorth
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Re: The wine shed - a concept, and some horrible maths..

Post by SushiNorth » 18:18 Fri 23 Feb 2018

uncle tom wrote:
06:56 Tue 06 Feb 2018
Water is by some margin the best source of thermal mass, at 4200J/L/C Stone or concrete varies a little but mostly comes in at just under half that figure.
Something that intrigues me is the availability of stackable 10L jerrycans - often sold for camping purposes.
These can be stacked to form a wall that is either 190mm or 220mm thick, depending on which way round you stack them.
OK, so awesome idea, but not one that is feasible for me to test. The room is relatively small, and the racks are full and bolted into place. I am thinking a bit about ways to incorporate large masses of water into the decor. i.e. a table or bench, whose support is a 55 gal barrel or 2.

Jdaw also mentioned the benefits of the water being able to circulate (to even out temperature) which may be a + for the barrel approach.
(now off to read the replies about doors)
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SushiNorth
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Re: The wine shed - a concept, and some horrible maths..

Post by SushiNorth » 18:23 Fri 23 Feb 2018

flash_uk wrote:
00:49 Wed 07 Feb 2018
I also thought that gaps/breaks of any sort in insulation materials create a heat sink that badly impairs the overall efficiency of the intended insulation.
Specifically, this is about bridging. Wood beams, nails, etc conduct heat much better than air (or insulation encapsulating air), as such they will enable heat to transfer across the barrier wall. Some of the designs I've seen call for the creation of a 6" wide wall, with 4"wide studs (alternating) in order to avoid bridging. The approach I will likely take is to add a 1/2 foam insulation on the outside of the wall, over the studs, which will then be covered with gypsum board (drywall).

I realize this isn't at all about the construction style Tom started the thread with, but it's related :)
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Re: The wine shed - a concept, and some horrible maths..

Post by SushiNorth » 18:29 Fri 23 Feb 2018

PhilW wrote:
08:32 Thu 08 Feb 2018
I've only ever heard it used (in the field of electronics) in relation to control of level change, rather than waveform delay (e.g. a thermostat set to turn off as the local temperature rises above 20C, which will then not turn on again until temperature drops below 19C, to avoid continuous switching around the limit; even if the temperature drops to 19.5 and stays there for hours, the thermostat doesn't switch again [in many systems at least], i.e. although for a continuously changing system its effect is a delay in switching, its behaviour is actually determined by the level rather than being delay of the signal).
Interestingly, such thermostats can be purchased online, to be added as controls for things like ACs and humidifiers. They usually have a turn-on-at and turn-off-at.

AC turns on at 58degrees and stays on until the temperature is below 54 degrees. If I see it switching on/off too much, it means I'm not doing a good enough job keeping the temp stable. This is particularly an issue when the system first turns on, as it takes time for the bottles to get cold enough to contribute to temp stabilization.
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