the truth about wine cellars

8/14/2019 The truth about wine cellars

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The Truth About Wine CellarsBy Joseph W. Lstiburek, Ph.D., P.Eng., Fellow ASHRAE Its the Goldilocks principle: not too hot, not too cold, but

just right. How did the French pick 55F (13C)? Traditionmostly. Wine was stored in cellars, which is why we call themwine cellars. Who knew? If you have an old-fashioned FrenchChateau handy , you will nd the temperature in the cellar isabout 55F (13C) .

What about relative humidity? Notice, earlier I said bottles.Most of the wine in the Chateaus start out in barrels ( Photo1 ). Drinking out of the barrel is complicated. Barrels cant bemoved easily to the dining room, and so you need a guy with atap that extracts the wine directly from the barrel ( Photo 2 ) andsquirts it immediately into a waiting glass. The French, beingthe innovators they are, realized small bottles made from glasswould be more convenient.

Why not pour wine into glass bottles right away? Not so fast. The barrels are made out of wood, and the wine needs the woodfor it to taste like wine. Or rather, the wine needs the wood so it

will taste like good wine. The type of wood the barrel is made outof is a big deal. Oak is the wood of choice. French oak is prefer-

able for French wine, American oak is preferable for Americanwine, and Slovenian oak is preferable for Italian wine.

Back to the barrels, the ones made out of wood, they are notimpermeable. Wood is not a vapor barrier. It is not an alcoholbarrier and it is not an oxygen barrier. Water diffuses out as does

love wine. People think I must know something about the stuffbecause I drink a lot of it. I dont really know that much, but Ido know what I like: red, French, and with a cork. Most of the

questions I get, I have no clue about, and so I make up stuff. I am aconsultant after all. I have answers to questions about how to storethe stuff. That is, I know whom to ask about storing the stuff.

If you want to know something about wine just ask theFrench. * Here is the magic information you need to know aboutstoring wine: 55F (13C) at 70% relative humidity. Where doesthat come from? Old French guys. That is not the temperatureof the wine for drinking, but the temperature and relative hu-midity for storage. And, we are talking bottles here, not barrels.Drinking temperatures are more difcult to pin down. I like 65F(18C) for Bordeaux, however, there is no consensus. Preferredtemperature varies by type of wine and by nationality. Most

folks are lunatics about drinking temperature.

The colder you store wine (and most other things), the longerit lasts. The Arrhenius equation tells us why. So why not colder?Because we actually want it to age, which means we want somechemical reactions to continue to occur in the bottle for a longtime. If it is too cold, these reactions dont occur. There is adifference between preserving wine and aging wine.*Yes I know that other folks make good wine. However, you ask Canadians about hockey, even though other folks play some good hockey; you ask Americansabout baseball, even though other folks play some good baseball. I have learned to ask the difcult questions of the older, more crotchety, opinionated ones whowear natty suits. Well, thats true about hockeywith wine questions the suits dont matter.Ive heard that ASHRAE legend Ole Fanger carried around a gold thermometer with him to make sure the wine he drank was at precisely the correct temperature.I never got to drink wine with the late professor. Maybe I will get a chance in the great wine cellar in the sky.Some wine manufacturers do this part of the process in large stainless steel vessels that they spike with wood chips. Notice I used the word manufacturers.These are not craftsmen. A pox on their houses.

Photo 1 (left): Cell ar f or B arrels. Barrels need hi gher humidity conditi ons than bottles. Photo 2 (ri ght): Pr ofessional at Work. I just lovethis pictur e. Note the mold on the walls. No respirator and bio-suit.

I

The following article was published in ASHRAE Journal, June 2008. Copyright 2008 American Societyof Heating, Refrigerating and Air-Conditioning Engineers, Inc. It is presented for educational purposes

only. This article may not be copied and/or distributed electronicallyor in paper form without permission of ASHRAE.


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alcohol while oxygen diffuses in. Thediffusion outward of water and alcoholconcentrates the avors and the diffusioninward of the oxygen governs the chemi-cal reactions.

It is important during the wine-makingprocess that the vapor diffusion outwardis controlledslowed down, but notstoppedand this is done by storing thebarrels at a high relative humidity. Howhigh? Back to the French again. What isthe relative humidity in the cellar of aFrench chateau?

A cellar in France is around 55F (13C)and 80% to 90% relative humidity. Ap-parently, those are the ideal conditions

for storing barrels of French wine. Youwont nd those conditions in a cellar inCalifornia unless you get help from anASHRAE member. And, even with helpfrom an ASHRAE member, you wont getidentical conditions to those of France.

You will get close, but it will not be thesame. You will get California conditions inCalifornia, so you are going to get wine thattastes differently. It will taste likewait foritCalifornia wine.

French wine tastes French because it ismade in France out of grapes grown inFrench dirt and stored at the temperatureand relative humidity found in the cel-lars of French chateaus in wood barrelsmade from French oak made by Frenchcraftsmen the French way. The staves aresplit, not sawn (and yes, this makes a dif-ference). Size also matters the ratio ofsurface area to volume is a big deal.

Now let us think about the consequencesof temperature and relative humidity con-ditions relating to 55F (13C) and 80%to 90% relative humidity. This is great formaking wine and storing wine barrels, butnot so great for the space. Without fail, you

will get all kinds of mold ( Photo 3 ).Is this mold good or bad? The mold onthe walls does not seem to be a problem.It does not hurt the wine if it stays onthe walls. It also does not seem to botherthe French. The French are pretty coolabout mold, health, and food in general.

They dont seem to overdo pasteurizationwith food, even though Louis Pasteurwas French. However, they do seem tosmoke a lot.

Photo 3: M old in Cell ar. I am shocked, justshocked, to see mold in a cellar. This is oneof the reasons French wine tastes differentthan California wine.

Fi gure 1: Wine Cellar Psychrometr ics. Vapor ow occurs in to the wine cellar dur ing thesummer and out of the wine cell ar dur ing th e winter.

The problem with the mold is if it iscleaned off the walls with bleach. Thecleaning with bleach leads to somethingcalled TCA (2,4,6-trichloranisole). Ifthe TCA gets into the wine, the winebecomes tainted. Thats a polite way ofsaying it tastes like crap. The French donot worry about the mold on the walls intheir wine cellars that store barrels. Theyalso never use chlorine in their wineriesfor cleaning purposes. Instead, they usesoap and water and elbow grease. Also,they tend to build the wineries out ofrocks and wood rather than paper-facedgypsum board and engineered lumber. Itis harder to get mold on rocks and woodthan the stuff we use in North America.

In America, particularly in California,where we have a high preponderance of

mold-fearing lunatics, the zeal to elimi-nate mold with chlorine has lead to tens ofmillions of dollars worth of tainted wine.I love to watch the French in California,especially near food or near a winery.

Their heads explode. We also put chlorine in water. It is not a

good idea to have chlorinated water any-where near a winery or a wine cellar.

What the French worry about is moldin corks. This becomes more of problemonce we take the wine out of barrels and

store it in bottles. We now have lots of

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Typical SummerIndoor Condition

Ideal Conditions toStore Wine Bottles

Typical WinterIndoor Condition

Dry-Bulb Temperature (F)

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Memo to the French: the rest of us think the folks in California are crazy, too.


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Fi gure 2a (left): Wine Cellar Enclosure. Bi direction al vapor ow through semivapor impermeable extruded polystyrene. Note the backventi lated in terior li ning and the absence of paper-based materials. Fi gure 2b (ri ght): Wine Cell ar on Wood Fl oor. Note the absence of avapor barr ier between the tile and the cement board underlayment.

corks to worry about. Too much humidity, and we get moldycorks. Too little humidity, and we get dry corks. With a drycork, air can get into the bottle, which leads to spoilage. Also,dry corks lead to evaporation from the bottle. That is why wineis stored sideways, so that the wine keeps the cork wet on oneside, helping to maintain the seal.

So why not get rid of the cork and use something that sealsbetter for longer? I mean, the only reason we used cork inthe rst place is that it was the only technology that we hadavailable at the time. Oh, wow. You want to start an argu-ment? It is like the designated hitter rule in baseball. Therewill never be peace between the American League and the

National League. The folks who want to get rid of the corkare American League types. Why use bad technology (i.e.,cork), and why watch a lousy hitter (i.e., pitchers). The folkswho want to retain the cork are National League types. Theyare purists and traditionalists.

So, if we have cork in wine bottles, and we want to store thewine, what do we do? Back to the answer at the beginning of thisstory: 55F (13C) at 70% relative humidity. The 70% relativehumidity is about the maximum relative humidity that we canmaintain without damaging corks. It is also a good humidity forkeeping the cork from drying out. It really is about the rate. Whatis the rate of moisture entry into the cork on the wine side versus

the rate of evaporation on the outside seal side? We have 100%

relative humidity on one side and 70% on the other. Seems towork. How do we know? Weve been watching lots of bottles forlots of years.

What else do we have to worry about? The label. You have got tobe kidding, right? Nope, the label is a big deal. If you trash the labelhow do you know what is in the bottle? The value of a wine bottleis determined to a large extent by the condition of the label. At70% relative humidity we are pushing the limits for damaging thepaper-based label. Why not go to a non-paper based label? See theprevious discussion about cork and the designated hitter rule.

Some folks wrap the label with sealable polyethylene to protectthe label from the relative humidity ( Photo 4 ). In my limited experi-

ence, limiting the relative humidity to 70% protects the label. Onceyou get above 80% you pretty much have to wrap the label. And,that only buys you time. How much time? Years, not decades.

What does 55F (13C) and 70% relative humidity mean forwine cellars? Well, for the French and their chateaus it meansthey have to install dehumidiers in their cellars if they want tostore their wine in bottles with corks and paper labels.

If you dont happen to be French and have a chateau with acellar and a dehumidier what do you do? You construct a winecellar using a psychrometric chart and some building science.Figure 1 shows typical indoor summer conditions and typicalindoor winter conditions relative to ideal wine cellar conditions

for houses in most parts of North America. Note that we have

Uninsulated Wood Frame/Wood Floor Above(Must Not Be Steel Studs)

Two Layers of 1 in. Thick Unfaced ExtrudedPolystyrene (XPS) With Joints Offset

Horizontally and Vertically; Each LayerTaped With Exterior Sheathing Tape

Untreated 1 x 4 Wood Furring WithStainless Steel Screws

Acrylic Latex Sealant(Applied as Each Layer

of Foam is Installed)

See Figure 2b(Right) for

Alternative WoodFloor Detail

Uninsulated Wood Frame

Interior Lining (Wood/Nonpaper-FacedGypsum Board Skim Coated With Plaster)

A

Interior Lining (Wood/Nonpaper-

Faced Gypsum Board Skim Coated with Plaster)

Two Layers of 1 in. Thick UnfacedExtruded Polystyrene (XPS) With

Joints Offset Horizontally and Vertically; Each Layer Taped With

Exterior Sheathing Tape

Tile Floor Adhered With Thinset to Antifracture Membrane

0.5 in. Cement BoardUnderlayment (No Wood

Fiber-Based Underlayment)

Untreated1 x 4 WoodFurring With

Stainless SteelScrews


Acrylic LatexSealant (Applied asEach Layer of Foam

is Installed)

1 in. XPS Rigid Insulation Wood Suboor

Wood/Wood-Based Floor Framing

Alternative on a Wood/Wood-Based Floor

B


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Adverti sement formerly in this space.


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vapor ow into the wine cellar during the summer and vapor owout of the wine cellar during the winter.

To make this work, I need an assembly that handles bidirec-tional vapor ow. I do not like the idea of vapor barriers on bothsides of an assembly that has vapor ow in both directions. Ilike materials that are semivapor impermeable and more or lesshomogenous. Flow is slow in both directions. However, its notcompletely eliminated in either direction. Check out Figure 2aand Figure 2b for an easy way to construct a wine cellar if youdont happen to have a cellar. If you dont like extruded polysty-rene you could substitute spray polyurethane foam.

Just to mess some of you up, I also provided assembly details

for constructing a steam room (or a sauna), which leads to verysimilar design outcomes ( Figure 3a and Figure 3b ). Note thetwo subtle differences. The steam room and sauna assembly usesfoil-faced rigid foam. The steam room and sauna assembly hasa waterproof membrane directly under the tile, above the rigidinsulation. The wine cellar oor does not have a vapor barrier(i.e., the waterproof membrane) under the tile oor above the rigidinsulation, as this would lead to a vapor barrier on the wrong sideof the assembly during the summer.

Cheers!Joseph W. Lsti burek, Ph.D., P.Eng., i s a pri nci pal of

Buil ding Science Corporation, in Somervil le, Mass. Visi t www.buildingscience.com.

Interior Lining

A Uninsulated Wood Frame/Wood Floor Above(Must Not Be Steel Studs)

Two Layers of 1 in. Foil-Faced Foam With Joints Offset Horizontally and Vertically; Each

Layer Taped With Exterior Sheathing Tape

Untreated 1 x 4 Wood Furring WithStainless Steel Screws

Acrylic Latex Sealant(Applied As Each Layer

of Foam is Installed)

See Figure3b (right) for

Alternative WoodFloor Detail


Interior Lining

B

Two Layers of 1 in. Foil-Faced Foam With Joints Offset Horizontally and Vertically; Each Layer Taped With

Exterior Sheathing Tape

Tile Floor Adhered With Thinset to Antifracture Membrane

0.5 in. Cement BoardUnderlayment (No Wood

Fiber-Based Underlayment)

Untreated1 x 4 WoodFurring With

Stainless SteelScrews


Acrylic LatexSealant (Applied asEach Layer of Foam

is Installed)

Membrane Waterproong Adhered to Cement Board Underlayment with Nonlatex Modied Mortar

Flashing

Photo 4 (left): Protecting the Label. You don t need to do thi s if thecellar does not go above 70% relative humidi ty. Photo 5 (righ t): WineCell ar. So what should the ventil ation r ate be for th is wine cell ar?Where is Standard 62.2 when you need it? Actual ly, this is an in terest- in g question. Do you venti late or not? Yes, but very li ttle. I recirculatethe air th rough a charcoal lter and don t hang out i n the wine cell ar.I provide about 1 air change every two days. H ow? With a small bal-

anced ventil ation system on a timer.

Fi gure 3a (left) : Steam Room or Sauna. Vapor ow is almost always fr om the interior of the steam room or sauna to the exterior. Th is is nota bidir ection al ow problem. Note the high vapor r esistance lin in g: foi l-f aced rigid insulat ion . Figure 3b (righ t): Steam Room or Sauna onWood Floor. Note the waterproong membr ane and ashin g. Thi s layer is also a vapor barrier.

1 in. XPS Rigid Insulation Wood Suboor

Wood/Wood-Based Floor Framing

Alternative on a Wood/Wood-Based Floor

the truth about wine cellars

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