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

[uncle tom]

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

[flash_uk]

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.

[SushiNorth]

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

[DRT]

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

Or, simply buy more Port!

[DRT]

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.

[uncle tom]

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

[uncle tom]

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

[uncle tom]

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..)

[Andy Velebil]

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.

[PhilW]

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.

[PhilW]

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

[LGTrotter]

Thanks Phil.

Glad that's all cleared up.

[LGTrotter]

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.

[jdaw1]

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.

[flash_uk]

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.

[uncle tom]

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.

[PhilW]

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).

[uncle tom]

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

Will have another look..

[jdaw1]

radiation is often also a huge consideration in practical circumstances.

Please say more.

[uncle tom]

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.

[uncle tom]

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.

[uncle tom]

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..

[SushiNorth]

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)

[SushiNorth]

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

[SushiNorth]

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.

[DRT]

This is all very impressive stuff from a technical perspective, but given the apparent complexity of building the optimum wine shed I am very happy that I am paying Seckford Wines £7.30 per case per annum with insurance at replacement value included in the cost

[uncle tom]

This is all very impressive stuff from a technical perspective, but given the apparent complexity of building the optimum wine shed

Although the technical stuff may seem complex, the build is surprisingly simple. Unless you live in a conservation area, or want to build your shed in front of the house rather than behind it, you will probably be exempt from needing either planning permission or the rigours of building control.

Celcon blocks are inexpensive to buy and the fastest of all builds from the standpoint of a bricklayer. Indeed, none of the materials needed is costly - I estimate that a shed with a capacity for up to 200 cases (3.6m x 2m internally) could be built for around £4.5K. Even if you only used it at 60% capacity, you would recoup your investment in a little over five years, and you won't have to go trekking up the Suffolk coast whenever you need a particular bottle!

[DRT]

you won't have to go trekking up the Suffolk coast whenever you need a particular bottle!

That raises the question of whether or not a willpower coefficient should be incorporated into the maths. My present solution requires no willpower whatsoever as I can't get to Suffolk when an overwhelming thirst emerges

[PhilW]

I estimate that a shed with a capacity for up to 200 cases (3.6m x 2m internally) could be built for around £4.5K.

Note that the above discussions regarding thickness and temperature applied to the scenario of a hole in the ground, where the ground is deep enough to be roughly constant temperature, and the external varying temperature was being applied to a single face, and did not include the effects of radiated heat.

Once you extend the model to a "shed" (assuming one side to not-deep ground surface, and 5 sides to the external temperature, and depending on plan/structure regarding incident radiated heat), the results could be quite significantly altered regarding required thicknesses etc. So "shed" would require some much clearer definition for the context of this discussion, even at a simplified level.

[uncle tom]

Note that the above discussions regarding thickness and temperature applied to the scenario of a hole in the ground, where the ground is deep enough to be roughly constant temperature, and the external varying temperature was being applied to a single face, and did not include the effects of radiated heat.

The whole purpose of this concept was to get away from the 'hole in the ground' notion, which incurs a lot of extra costs that a surface structure avoids, such as the need to make the walls strong enough to withstand the pressure of the soil, the cost of removing a large volume of soil, constructing steps down as well as a door, and of course, keeping it dry.

Although radiated heat (sunlight) can raise the temperature of a solid surface above the temperature of the air around, the time taken to form a thermal gradient remains the same. Moreover, if the exterior is painted white, the increased temperature due to sunlight will be quite modest, and can be further reduced by planting vegetation close to the southern aspect of the building.

[PhilW]

Note that the above discussions regarding thickness and temperature applied to the scenario of a hole in the ground, where the ground is deep enough to be roughly constant temperature, and the external varying temperature was being applied to a single face, and did not include the effects of radiated heat.

The whole purpose of this concept was to get away from the 'hole in the ground' notion, which incurs a lot of extra costs that a surface structure avoids, such as the need to make the walls strong enough to withstand the pressure of the soil, the cost of removing a large volume of soil, constructing steps down as well as a door, and of course, keeping it dry.

Understandable. However, someone reading this might otherwise have thought they could take the immediate result and build a structure using 30cm breeze blocks and expect the minimal temperrature variation internally without sufficiently accounting for "for the simplified one-dimensional case the final equations seem to be as follows ...". The maths is still applicable, but the next step would involve the relative external surface area to internal volume as well as thermal mass inside the unit, as well as allowing for incident radiated heat and potentially convection also. That is not to say that sensible assumptions could not be made to keep the calculation simple while minimising error, but they do need to be clearly stated to avoid others discounting the conclusions.

Although radiated heat (sunlight) can raise the temperature of a solid surface above the temperature of the air around, the time taken to form a thermal gradient remains the same. Moreover, if the exterior is painted white, the increased temperature due to sunlight will be quite modest, and can be further reduced by planting vegetation close to the southern aspect of the building.

Indeed; the prior calculation assumed that the input of heat from the ground was negligible, which is probably not true for a structure on the surface; they may well be a small simple additive factor if the mean ground temperature near the surface close to the structure can be assumed to be sufficiently low and lowly varying in all conditions (I don't know whether this would be valid). On the other hand, if your structure were to have a 1m deep cement based foundation which was surrounded by breeze blocks, that would likely solve that assumption while still keeping your usable structure on the surface.

Similarly, your proposal to build the unit and paint it while all over is potential fine subject to practical questions (including a white roof? does it stay clean? is that practicable/acceptable for most people to have a 30x20ft all-white unit?). A simpler proposal (perhaps less practical) of building a separate but open roof over the unit and fences/bushes around would be equally valid and might also provide a simpler assumption to eliminate most incident radiated effects (and if designed well, could minimise convection also).

[flash_uk]

Note that the above discussions regarding thickness and temperature applied to the scenario of a hole in the ground, where the ground is deep enough to be roughly constant temperature, and the external varying temperature was being applied to a single face, and did not include the effects of radiated heat.

The whole purpose of this concept was to get away from the 'hole in the ground' notion, which incurs a lot of extra costs that a surface structure avoids, such as the need to make the walls strong enough to withstand the pressure of the soil, the cost of removing a large volume of soil, constructing steps down as well as a door, and of course, keeping it dry.

Understandable. However, someone reading this might otherwise have thought they could take the immediate result and build a structure using 30cm breeze blocks and expect the minimal temperrature variation internally without sufficiently accounting for "for the simplified one-dimensional case the final equations seem to be as follows ...". The maths is still applicable, but the next step would involve the relative external surface area to internal volume as well as thermal mass inside the unit, as well as allowing for incident radiated heat and potentially convection also. That is not to say that sensible assumptions could not be made to keep the calculation simple while minimising error, but they do need to be clearly stated to avoid others discounting the conclusions.

Although radiated heat (sunlight) can raise the temperature of a solid surface above the temperature of the air around, the time taken to form a thermal gradient remains the same. Moreover, if the exterior is painted white, the increased temperature due to sunlight will be quite modest, and can be further reduced by planting vegetation close to the southern aspect of the building.

Indeed; the prior calculation assumed that the input of heat from the ground was negligible, which is probably not true for a structure on the surface; they may well be a small simple additive factor if the mean ground temperature near the surface close to the structure can be assumed to be sufficiently low and lowly varying in all conditions (I don't know whether this would be valid). On the other hand, if your structure were to have a 1m deep cement based foundation which was surrounded by breeze blocks, that would likely solve that assumption while still keeping your usable structure on the surface.

Similarly, your proposal to build the unit and paint it while all over is potential fine subject to practical questions (including a white roof? does it stay clean? is that practicable/acceptable for most people to have a 30x20ft all-white unit?). A simpler proposal (perhaps less practical) of building a separate but open roof over the unit and fences/bushes around would be equally valid and might also provide a simpler assumption to eliminate most incident radiated effects (and if designed well, could minimise convection also).

I agree.

[Doggett]

As they say on FTLOP a lot... +1

Hadn’t realised how cheap it could be... I might build 2 at the end of the garden. Now I just need 400 cases too!

[DRT]

As they say on FTLOP a lot... +1

Hadn’t realised how cheap it could be... I might build 2 at the end of the garden. Now I just need 400 cases too!

You only need one case of Port and 399 cases of water to get going

[Alex Bridgeman]

So what's the conclusion? Do I build a shed out of polystyrene bricks or not?

[uncle tom]

Do I build a shed out of polystyrene bricks or not?

Yes but no..

Build it, but not out of polystyrene..

1) On most sites the simplest foundation will be a rigid reinforced concrete raft. You can pay a hefty sum to a structural engineer to draw up a specification for you, or deploy a slightly over-designed 200mm slab specification that I've used several times on some pretty horrible soft clay soils, without any problems:

i) Clear the topsoil down about 9" from the surface. The surface below needs to be level and compact - you can hire compactors, also known as whacker plates. If the soil below is dry and not claggy you can set the concrete directly onto the subsoil, otherwise add a small amount of fine hardcore (usually scalpings) to level the site and assist compaction.

ii) Order enough A252 (8mm bar, 200mm x 200mm spacing) reinforcing mesh to place two layers of mesh across the slab. Where mesh sheets meet, allow at least half a metre of overlap. Thinner mesh will work, but it is springy and easily displaced when you make the concrete pour.

You can get little supports to keep the mesh layers clear of the ground and clear of each other, but half bricks work just as well. The steel must not come within 50mm of any surface of the concrete, else there is a risk of blistering (aka concrete cancer)

When ordering your mesh, also order a couple of 6m sticks of 12mm rebar to help support your shuttering.

iii) Never underestimate the ability of freshly poured concrete to push over shuttering! Get some 12mm shuttering ply cut into 200mm wide strips, then with a few blocks of timber, screw together your shuttering cage to support and form the edges of your slab. Also cut your rebar into half metre long pins with an angle grinder to drive in to support it. Make sure the shuttering is level and square - use the 3-4-5 triangle method to check the corners, and ensure that the pins are driven fully in (or cut off if not possible) so your tamping board is not obstructed. Make sure the shuttering is fully sound and rigid before ordering your concrete.

iv) Phone round your local ready mix concrete suppliers to find the one who can deliver the quantity you need at the best price. Don't try forming a reinforced slab with an ordinary cement mixer - it's very hard work and doesn't give a good result. The grade of concrete you want is called C25. You may want to include admixtures to delay setting time, or achieve a degree of water resistance - discuss with your supplier. Fully waterproof concrete is very costly however.

Consider how you are going to get the concrete to the site if the mixer can't drive right up to it. Concrete pumping trucks are fairly expensive to hire, but work really well - they can easily articulate over the roof of a house and deliver concrete accurately in the garden behind. Barrowing concrete may be an option, but you will need plenty of labour (and builder's barrows) as it's very hard graft.

Order enough to complete the job, and a tiny bit besides. Have a good use lined up for the leftovers, as concrete trucks need to completely empty themselves.

As the concrete is poured, have rakes and shovels on hand to help spread it, and then start tamping straight away. You need a good straight rigid plank for this that can span the slab - eight by two is usually favourite. Tamping has to be done by two people - one on each end with the board on edge. Keep working back and forth until the slab is nicely level.

After the concrete has gone off, don't let the surface dry out too quickly, especially if the weather is hot and dry. Use a watering can to keep it damp, but not too soon or you'll mess the surface of the slab. Keep an eye out for your pets as the concrete is setting - make sure they don't leave a permanent impression with their paws!

More soon..

[uncle tom]

So, you’ve got a nice rigid concrete base to build off, but will this cause thermal bridging under the walls? Will the daily cycle of outside temperatures travel down, through the slab under the walls and back up again?

More horrid maths, and the answer seems to be yes, but not massively. There seem to be four options:

1) If the top of your slab is close to the outside soil surface, and it’s a damp part of your garden, you might want to elevate the floor level to lift it clear of its surroundings. In that event, a layer of 100mm or 150mm aerated blocks laid flat across the floor will deal with both issues.

2) Placing a layer of 100mm aerated blocks beneath your thermal mass walls will reduce daily heat movement from thermal bridging to a negligible level.

3) After removing the shuttering and pins that supported it, butting aerated blocks against the edge of the slab will also be effective.

Or..

4) Do nothing and don’t worry about it..

Next up you will need a bricklayer. Your local pub is always a good starting place to find one, but a recommendation from a friend who had some good work done is better. Bricklayers often prioritise clients who offer to pay them in cash, and those working on large construction sites may be amenable to cash paid ‘overtime’ at weekends.

It’s important to make sure that everything they need is delivered to site in advance – it gets expensive if your brickie has to take time out to go to builder’s merchants.

When he first starts he will take a little time checking how square your slab is, and establishing the highest point (no slab is ever perfectly level). He will then take his time making sure the first course is correctly laid before letting rip on the courses above. Bear in mind that he will want to position the door frame first and then build up to it, so make that’s on site in advance.

He will want to lay the first course on conventional mortar so he can adjust for variations on the slab surface, but after that, discuss the option of using the Celfix thin mortar system for the courses above. This is a very quick method of laying aerated blocks which gives superior thermal properties, but not every brickie likes it.

Also discuss with your brickie what equipment he has, and what you will need to borrow or hire. In addition to a cement mixer, he will need scaffold boards and bandstands to rest them on, when he gets to the higher courses.

Blocks are normally delivered on pallets, unloaded by trucks fitted with a Hiab crane. The closer you can get the blocks delivered to the job, the better, as lugging blocks is not a fun job. If you can’t get them delivered close, borrow a sturdy sack barrow or trolley.

After the first course is laid, and assuming the blocks are close to hand, a good brickie should be able to get around 10m2 of blocks laid in a day.

As the walls are built, you will need a lintel to go across the doorframe. When it comes to building the penultimate wall course and the gables, switch from the 275mm thick blocks to two leaves of 100 mm + 150mm blocks. That way your brickie will be able to cut in the ceiling joists and purlins for your roofing sheets into the inner leaf only, leaving the outer leaf neat and tidy.

More soon..

[Alex Bridgeman]

A question not unconnected with the horrible maths.

What would people recommend as the minimum gap between racks to allow a cellar master to access the wines in their cellar reasonably safely and comfortably?

[winesecretary]

Are these bottle racks or case racks? For bottle racks the minimum gap mg is the wider of

- the width w of the cellar master comfortably crouching down to get to the lowest part of the rack (e.g. 50 cm; but, do measure, it's wider than you think/remember) + the distance p the longest bottles protrude from the rack on each side (e.g. 10 cm x 2) + safety margin s (about the extent of which there will be some debate);
- the distance the longest bottles protrude from the rack on each side + the length l of the longest bottle in the rack on each side + safety margin;

It is thirty-one years, I think possibly to the day, since I have done any algebra. But possibly this would be

mg = max [w+s+2p] [s+l+2p]

For most of us the former will be wider, unless you have odd large-format bottles (I have more than once tripped over a magnum of Mentzendorff Kummel I have not yet come up with a use for).

For case racks because the case weight is greater and so you need more freedom to manoeuvre and that means it's more complicated because more personal; but it is sensible to allow for increasing age/decrepitude/sciatica from our current young, fit, and healthy states.

[uncle tom]

What would people recommend as the minimum gap between racks to allow a cellar master to access the wines in their cellar reasonably safely and comfortably?

If you are planning single depth racks, specify 12" deep staves, as ones with shorter staves have stability issues at any height. Opposing 12" deep racks can be comfortably accessed with a separation of 18", but a little more does not hurt.

Double depth racks are normally about 22" deep (the rack manufacturers buy their staves in bulk from Scandinavia, I have enquired about 24" deep double racks in the past, so bottle necks don't stick out, but custom staves adds a lot to cost) You need more separation with these, partly to allow for protruding bottle necks, and partly to allow you to get your arm in to grab the rear bottles. Two of my double racks are 24" apart, which is tight - I would recommend 27".

Single depth racks sitting on a 1" base board can be comfortably accessed by a person of average height up to about 21 bottles high - and with a kick stool you could easily reach up to 24 high, although I would recommend separating into 2 x 12 high racks with a support beam in between, partly to avoid excessive counting when logging where you've put bottles, and partly to avoid excessive loading of the rack's lower reaches. My largest rack, which is double depth and seventeen holes wide, carries nearly a ton of bottles, so loading is not insignificant.

Bear in mind when designing rack supports that the load bears on the front and rear edges of the rack - you do not want your rack overhanging the supports at front and rear, however the middle of the base staves have no need of support. My most recent installation is supported by 4" x 2" rectangular steel box sections.

If you are using double depth racks, it is difficult to extract the rear bottles when they are close to the ground. I use a church kneeler cushion that I found on eBay so I can get down in reasonable comfort, but it's still a little awkward. If I was starting over and had more space, I would either use a 6" plinth, or leave the bottom row empty.

Your ability to reach the rear row at height is also limited on double depths, as it's not possible to reach into holes that are more than a few inches higher than your own height. Small lightweight plastic kick stools are very useful however - but have a place to put it when not in use, so you don't trip over it when carrying bottles..

When planning racks, don't be tempted by the rack joining systems that are sometimes offered - I've been there and they are just too much hassle. Similarly, the plastic clip-on label protectors intended to stop the steel bars of the rack grazing your back labels are just too much grief to fit. Buy a roll of 2" silver duct tape and wrap a little bit on each bar - it works a treat and you can hardly see it.

Final tip: When cutting duct tape you will find your scissors fouling from the adhesive. Every three or four cuts squirt a drop of lighter fuel on the scissor blades to clean them..

[Alex Bridgeman]

Thank you both, extremely helpful.

[Christopher]

Has anyone actually turned a shed into a wine storage facility?

It’s seems to be more complicated than I had hoped!

[uncle tom]

Has anyone actually turned a shed into a wine storage facility?

It’s seems to be more complicated than I had hoped!

Retrofitting a wooden shed is likely to throw up a variety of difficulties. However if you are not too obsessive about the detail, in certain circumstances very ordinary modern standard solid above ground construction can be very temperature stable.

A garage type structure built on a thick concrete raft, with insulated standard cavity walls and a standard insulated roof, attached or close to the northern side of a building to shade it, and with trees planted nearby to reduce direct sunlight from east and west; will produce conditions that are roughly as stable as a cellar underneath a house.

Concrete raft construction is easy, straightforward and reliable, and was the norm for most houses built post-war up until the mid sixties when the building regulations were introduced. The regulations included a specification for trench foundations, but not rafts, forcing builders to get an engineering report if they wanted to use one - so on all but the softest soils, trench footings became the norm thereafter.

Where trench footings are used with a concrete floor, the concrete is relatively thin and sits on top of hardcore, and does not provide a very good stabilising thermal mass. A solid 12" thick raft however, is wonderfully temperature stabilising.

If you are using the exemption to build a garden shed without seeking planning permission (which can quite legally be built of brick/concrete) the applicability of the building regulations becomes a bit of a grey area, and in practice, DIYers don't bother with them..

[Alex Bridgeman]

Has anyone actually turned a shed into a wine storage facility?

It’s seems to be more complicated than I had hoped!

I'm going for a different approach with a purpose built outer skin, 60mm of polyurethane foam insulation on all six sides, a 1" marine ply floor and a cellar conditioning unit that can provide a teperature differential of +/-20C. If you have mains electricity, this could be an option for you.

[uncle tom]

I'm going for a different approach with a purpose built outer skin, 60mm of polyurethane foam insulation on all six sides, a 1" marine ply floor and a cellar conditioning unit that can provide a teperature differential of +/-20C. If you have mains electricity, this could be an option for you.

Bear in mind that that will leave you with no thermal mass within the cellar other than the bottles themselves. Insulating the floor could be counter-productive. Consider extending the wall insulation below ground level with a bare concrete floor in between.