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Water - The Wonder and the Danger

We live on a watery planet. 70% of the earth's surface is water (the same percentage of water in our bodies). It is the font and sustainer of life (SETI looks for water on other planets as the sine qua non of life). So why have our modern "green" building practices turned it into a monster? And how can we stop fighting it and turn it back into an ally?

Asked by Anonymous
Posted Nov 28, 2010 10:58 PM ET


101 Answers

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First, let's explore the magic and mystery of this most wonderful of all substances in the Universe.

Water is the only terrestrial substance that naturally exists in three distinct states: liquid, solid, vapor.

Water is essential for metabolism, photosynthesis and the thermoregulation of our bodies & the earth.

Solid water (ice) is less dense than liquid water and hence floats – this makes lakes freeze on top which allows aquatic life to survive the winter.

Water has an abnormally high melting point, which allows liquid water to cover the earth and create a breeding ground and habitat for life.

Water has the highest specific heat of all liquids except ammonia, which facilitates heat transfer in the atmosphere and oceans and moderates temperature extremes.

Water has exceptionally high surface tension, which allows drop formation and rain as well as capillary movement within plants and trees as tall as 450 feet.

Water absorbs infrared and ultraviolet light, which encourages photosynthesis and regulates atmospheric and oceanic temperatures.

Water is an excellent solvent for ionic salts and polar molecules (the universal solvent), which facilitates the transfer of nutrients in metabolism and in hydrologic cycles.

Water has the highest heat of vaporization of any molecular liquid.

Water has the highest thermal conductivity of any liquid (except for liquid metals)

Hot water freezes faster than cold water.

Boiling water will turn instantly to snow at temperatures below -25°.

Water has at least 5 liquid phases and 14 solid phases (remember Ice 9?)

When supercooled, water will turn instantly to ice when disturbed.

When superheated, water will turn instantly to vapor when disturbed.

Water at -184° F turns super-viscous like molasses.

Water at -211° F turns amorphous like glass.

Homeopathy is correct that water has a "memory" of what was once dissolved in it and retains the "essence".

There is evidence that water also retains thoughts, moods & conscious intentions (see Dr. Emoto's research).

Answered by Riversong
Posted Nov 28, 2010 10:59 PM ET


How do buildings get wet, what happens when they do, and how do they dry out before getting into trouble?

First, it's essential to note that, as building scientist Anton TenWolde states, "You need to assume that the building will get wet, somehow, at some point in time. Stuff happens."

We all know that buildings often get wet from exterior leakage: through poorly-detailed flashings or failed caulk joints, or by wind-driven rain, or solar vapor drive, or ice dams on unventilated roofs. Mitigating those problems is largely a matter of good design, good craft, and good maintenance.

We also know that building envelopes get wet from the inside: from vapor diffusion and air movement – mechanisms of mass transfer that are facilitated by modes of energy flux. We also now know that movement of warm moist air is an order of magnitude greater a problem than vapor diffusion because of the time scale: air moves quickly, vapor diffuses slowly. But, the more air-tight we make our homes (and any home built to today's energy codes is relatively tight) the more we need to consider the long-term (seasonal) ramifications of vapor diffusion and consequent condensation and accumulation (more on this later).

But no evaluation of moisture dynamics in a building is complete without consideration of short- and long-term moisture storage, redistribution and drying potential in building materials.

As TenWolde explains: "A moisture problem occurs when wetting exceeds drying over a long period of time. But it is important to know several things: How wet does it get? How long does it stay wet? And what is the temperature while it is wet? Because if it is cold enough the mold won’t grow well, and decay organisms won’t do well. How does this information translate into the design of a building? …So you need a moisture-tolerant design."

Answered by Riversong
Posted Nov 28, 2010 11:01 PM ET


Martin's recent blogs ("Calculating the Minimum Thickness of Rigid Foam Sheathing" and "How To Avoid Condensation in Your Walls") have attempted to clarify the notion of condensation, though I think they may have added to the confusion.

Martin has begun to differentiate between "condensation" (which he now puts in quotes) and moisture accumulation. While it's true that moisture accumulation is the problem, absent bulk water leakage it occurs either by prolonged high relative humidity or because of condensation of water vapor that is transported either by air movement through openings or by diffusion through building materials. So condensation is an important concept that must be properly understood.

Martin: "Condensation occurs when water vapor condenses on a cold, hard surface like glass or an aluminum beer can. Condensation generally does not occur on a hygroscopic material like wood framing, plywood sheathing, or cellulose (however, frost can occur on these materials)."

This confuses two uses of the term "condensation": the simple change of state of water vapor to liquid water (scientific), and the visible droplets of water that we see on a cold window (vernacular). The first is a dynamic process, the second is the visible result. The confusion should be evident in his parenthetical qualification – frost forms when water vapor freezes as it condenses; or, in other words, the dew point surface is below freezing. Since there cannot be frost without condensation (except in extreme cold), condensation occurs even within fibrous insulation.

It's clear where Martin's confusion comes from. He quotes two respected building scientists who are struggling to clarify this common misunderstanding.

William Rose: "Condensation is the change in phase from vapor to liquid water. Condensation occurs typically on materials such as glass or metal that are not porous or hygroscopic and on capillary porous materials that are capillary saturated. Use of the term “condensation” to refer to change in phase between vapor and bound water in capillary or open porous materials is discouraged."

Rose's first sentence is the scientific definition. His second sentence, however, uses the term "condensation" more in the vernacular sense as visible or tangible condensation and discourages the use of the term as applied to hygroscopic or porous materials, even though it's scientifically correct, because he believes it leads to erroneous conclusions for lack of a more complete understanding of hygro-thermal dynamics.

Anton TenWolde: "We thought there would be a problem with condensation in the insulation, but all the action happens on the sheathing and the interior vapor barrier. We’ve confirmed this by opening up walls. The action is never in the insulation."

What TenWolde is saying is that the "action" or the accumulation and consequent moisture problems happen at the interfaces of materials where the moisture goes "bump" against a relatively impermeable substance.

Answered by Riversong
Posted Nov 28, 2010 11:01 PM ET


The reason for the confusion and the attempts at clarification is because of the complexity of the more subtle moisture dynamics within relatively "open" materials. These dynamics are very difficult to model.

For instance, there are as many as five difference hygric phases or regimes within a porous hygroscopic material and it's quite possible for moisture to move in two opposite directions simultaneously within the same material. Water vapor, which is driven by vapor pressure differential, can move from inside to out while liquid water can move by surface diffusion, driven by relative humidity differential and solar drive, from outside to in. Until the capillaries are saturated with liquid water, water vapor can move within the open pores wherever it's driven, even against the flow or the water that lines the pores. After saturation, it requires the forces of kinetics (wind) and gravity to move the bulk water.

In fact, in relatively dry material conditions, vapor diffusion dominates. As materials get moist, surface diffusion of liquid (adsorption) begins to take over. And in wet conditions, capillarity and bulk flow dominates (as the pores are too full of water to allow vapor to move).

Similarly, the opposing mechanisms of evaporation and condensation are happening everywhere all the time, as well as ab/adsorption and desorption. So, to say that condensation is not occurring anywhere that water vapor can get to is simply incorrect. But, if evaporation and condensation are in balance, then there is no accumulation. The accumulation, and hence the problems, occur when the rate of condensation exceeds the rate of evaporation and the accumulation is more than the material can safely store.

It's important to note that, even in a steady-state environment, the moisture content of hygroscopic materials can rise to the danger point. This happens when there is a long period of high relative humidity, which gradually increases the equilibrium moisture content of the sorbent materials. Constant high humidity, as we all know, is a dangerous thing (except to fungi, mold and decay organisms).

So vapor pressure and temperature gradients drive vapor diffusion - while concentration gradients, relative humidity differentials and surface tension drive liquid diffusion and capillary conduction.

While those pressures and gradients determine the rate of moisture migration, it’s the hygroscopicity of materials that determines the rate and quantity of moisture storage. Hygroscopicity is a function of the vapor diffusivity of a material (rate of internal water vapor diffusion), liquid adsorptivity (rate of liquid uptake) and liquid storage capacity (porosity & absorptivity). However, for a hygroscopic material to function well as a diurnal (daily) moisture buffer, it has to have high diffusivity and moisture storage capacity (density and porosity), but only moderate absorptivity. If it absorbs water too quickly becomes saturated, then the pores will be closed to deeper penetration of water vapor. And diurnal storage and release is dependent on relatively low air exchange rates to allow sufficient contact time for sorption and release. Interestingly, air change rates of 0.25 ACH or less is ideal for moisture buffering and also for indoor air quality and energy efficiency.

The materials that perform best for diurnal moisture control are the ones least used in today's homes, such as endgrain wood and earthen plasters. After those, but considerably lower on the scale, are the traditional materials such as plaster, wood, brick and lime mortar.

As the new IRC code on the use of class III vapor retarders (vapor semi-permeable, like ordinary latex paint) indicates, there is more than one acceptable strategy for keeping a building's sheathing from rotting. The increasingly popular one is to use exterior rigid foam to keep the sheathing (most of the winter) above the dew point. But the other method recognized in the same IRC table (N1102.5 in the 2006 version and R601.3.1 in the 2009 edition) is a vapor permeable sheathing with a ventilated cladding for ease of drying to the exterior. Though the IRC doesn't include it in the chart, wooden board sheathing is the most durable and vapor open of all and, with vapor open cladding like clapboards, does not (in my estimation) require a ventilated gap except perhaps in very high rain and wind zones.

Answered by Riversong
Posted Nov 28, 2010 11:01 PM ET


I stumbled upon a pretty fine book recently
Water by Leopold Luna
The Bill Rose" Water Book" is very good too except it is $$ and not so easy to read

The Leopold Luna Book is cheap, Not-So-Thick
and Not-So-Hard-To-Read
And...... It has Pictures

I would like to hear your thoughts about this

I am smitten with water

Answered by John Brooks
Posted Nov 28, 2010 11:13 PM ET


you are a blazing typist!
you posted 4 pages while I was posting my comment.

Answered by John Brooks
Posted Nov 28, 2010 11:48 PM ET



I think you mean Luna Leopold, the son of the late great Aldo Leopold, author of A Sand County Almanac (1949), with it's powerful chapter titled Thinking Like a Mountain (which I borrowed for the title of my last and best class at Yestermorrow).

Aldo Leopold, from A Sand County Almanac:

"That land is a community is the basic concept of ecology, but that land is to be loved and respected is an extension of ethics."

"A land ethic, then, reflects the existence of an ecological conscience, and this in turn reflects a conviction of individual responsibility for the health of the land. Health is the capacity of the land for self-renewal. Conservation is our effort to understand and preserve this capacity. A thing is right when it tends to preserve the integrity, stability and beauty of the biotic community. It is wrong when it tends otherwise."

"Examine each question in terms of what is ethically and aesthetically right, as well as what is economically expedient."

And...what was it you wanted me to comment on? That you are "smitten with water"?

Answered by Riversong
Posted Nov 29, 2010 12:03 AM ET


Wow, you are a blazing typist!

When I'm channeling the Wisdom of the Universe, I can't even see my fingers moving on the keypad.

Actually, all the pages were already typed. I just posted them in installments - kind of like Burma Shave signs.

I proposed / To Ida / Ida refused / Ida won my Ida / If Ida used / Burma-Shave

Keep well / To the right / Of the oncoming car / Get your close shaves / From the half pound jar / Burma-Shave

Past / Schoolhouses / Take it slow / Let the little / Shavers grow / Burma-Shave

Hardly a driver / Is now alive / Who passed / On hills / At 75 / Burma-Shave

If you dislike / Big traffic fines / Slow down / Till you / Can read these signs / Burma-Shave

It's best for / One who hits / The bottle / To let another / Use the throttle / Burma-Shave

Train approaching / Whistle squealing / Stop / Avoid that run-down feeling / Burma-Shave

Don't take a curve / At 60 per / We hate to lose / A customer / Burma-Shave

You can drive / a mile a minute / but there's no / future in it / Burma-Shave

If you / Don't know / Whose signs / These are / You can't have / Driven very far

Answered by Riversong
Posted Nov 29, 2010 12:24 AM ET


Explain hot water freezes faster than cold water.

Answered by Kevin Dickson
Posted Nov 29, 2010 1:53 AM ET


History of the Mpemba Effect

The fact that hot water freezes faster than cold has been known for many centuries. The earliest reference to this phenomenon dates back to Aristotle in 300 B.C. The phenomenon was later discussed in the medieval era, as European physicists struggled to come up with a theory of heat. But by the 20th century the phenomenon was only known as common folklore, until it was reintroduced to the scientific community in 1969 by Erasto Mpemba, a Tanzanian high school student. Since then, numerous experiments have confirmed the existence of the "Mpemba effect"

The earliest known reference to this phenomenon is by Aristotle, who wrote:

"The fact that water has previously been warmed contributes to its freezing quickly; for so it cools sooner. Hence many people, when they want to cool hot water quickly, begin by putting it in the sun. . ."

Around 1461, the physicist Giovanni Marliani, in a debate over how objects cooled, said that he had confirmed that hot water froze faster than cold. He said that he had taken four ounces of boiling water, and four ounces of non-heated water, placed them outside in similar containers on a cold winter day, and observed that the boiled water froze first. Marliani was, however, unable to explain this occurrence.

Later, in the 1600's, it was apparently common knowledge that hot water would freeze faster than cold. In 1620 Bacon wrote "Water slightly warm is more easily frozen than quite cold", while a little later Descartes claimed "Experience shows that water that has been kept for a long time on the fire freezes sooner than other water".

In time, a modern theory of heat was developed, and the earlier observations of Aristotle, Marliani, and others were forgotten, perhaps because they seemed so contradictory to modern concepts of heat. However, it was still known as folklore among many non-scientists in Canada, England, the food processing industry, and elsewhere.

It was not reintroduced to the scientific community until 1969, 500 years after Marliani's experiment, and more than two millennia after Aristotle's "Meteorologica I". The story of its rediscovery by a Tanzanian high school student named Mpemba is written up in the New Scientist. The story provides a dramatic parable cautioning scientists and teachers against dismissing the observations of non-scientists and against making quick judgements about what is impossible.

In 1963, Mpemba was making ice cream at school, which he did by mixing boiling milk with sugar. He was supposed to wait for the milk to cool before placing it the refrigerator, but in a rush to get scarce refrigerator space, put his milk in without cooling it. To his surprise, he found that his hot milk froze into ice cream before that of other students. He asked his physics teacher for an explanation, but was told that he must have been confused, since his observation was impossible.

Mpemba believed his teacher at the time. But later that year he met a friend of his who made and sold ice cream in Tanga town. His friend told Mpemba that when making ice cream, he put the hot liquids in the refrigerator to make them freeze faster. Mpemba found that other ice cream sellers in Tanga had the same practice.

Later, when in high school, Mpemba learned Newton's law of cooling, that describes how hot bodies are supposed to cool (under certain simplifying assumptions). Mpemba asked his teacher why hot milk froze before cold milk when he put them in the freezer. The teacher answered that Mpemba must have been confused. When Mpemba kept arguing, the teacher said "All I can say is that is Mpemba's physics and not the universal physics" and from then on, the teacher and the class would criticize Mpemba's mistakes in mathematics and physics by saying "That is Mpemba's mathematics" or "That is Mpemba's physics." But when Mpemba later tried the experiment with hot and cold water in the biology laboratory of his school, he again found that the hot water froze sooner.

Earlier, Dr Osborne, a professor of physics, had visited Mpemba's high school. Mpemba had asked him to explain why hot water would freeze before cold water. Dr Osborne said that he could not think of any explanation, but would try the experiment later. When back in his laboratory, he asked a young technician to test Mpemba's claim. The technician later reported that the hot water froze first, and said "But we'll keep on repeating the experiment until we get the right result." However, repeated tests gave the same result, and in 1969 Mpemba and Osborne wrote up their results.

In the same year, in one of the coincidences so common in science, Dr Kell independently wrote a paper on hot water freezing sooner than cold water. Kell showed that if one assumed that the water cooled primarily by evaporation, and maintained a uniform temperature, the hot water would lose enough mass to freeze first. Kell thus argued that the phenomenon (then a common urban legend in Canada) was real and could be explained by evaporation. However, he was unaware of Osborne's experiments, which had measured the mass lost to evaporation and found it insufficient to explain the effect. Subsequent experiments were done with water in a closed container, eliminating the effects of evaporation, and still found that the hot water froze first.

Subsequent discussion of the effect has been inconclusive. While quite a few experiments have replicated the effect, there has been no consensus on what causes the Mpemba effect.

However, I'll explain the cause in the next posting. It's really quite simple.

Answered by Riversong
Posted Nov 29, 2010 2:40 AM ET


Why Does Hot Water Freeze Faster than Cold Water

Liquid water exists in at least three distinct states:
1) when it's quite hot, the molecules have enough kinetic energy to dance alone
2) at mid-temperatures, the molecules tend to cluster together into icosohedrals
3) at cold temperatures, the clusters clump together in a very slow motion dance

In order for water to freeze, four conditions are necessary:
1) it must be at or below 32°F
2) it must separate into individual molecules (overcome the strong hydrogen bonds)
3) find new hydrogen bonding partner molecules
4) and re-arrange into hexagonal structure (ice crystals)

When cold, sluggish, clumped water molecules are cooled to freezing, it takes them forever to break away from their dance partners and rearrange into symmetrical hexagonal prisms – in fact, they often have to fall well below freezing before they get around to it. Moderate temperature water molecules can dissociate more quickly to find new dancing partners, but they're still a bit slow. Very hot water molecules, already solo dancing and full of energy, can immediately collect a set of dance partners for the crystal dance when they're quickly cooled to the freezing point.

And that's why most Zambonis use 140° to 160° water to resurface skating rinks.

Answered by Riversong
Posted Nov 29, 2010 3:04 AM ET


Thank you for a wonderful tutorial on the pleasures and perils of water. And also for the first lucid explanation of the Mpemba Effect I've ever seen. Concerning building details would you, in general, consider the Pacific Northwest as sufficiently wet and windy as to justify the use of a rainscreen siding design?

Answered by Anonymous
Posted Nov 29, 2010 4:46 AM ET


I think you mean Luna Leopold,

YES, sorry...... Luna B. Leopold...the title is simply "WATER"
1966 Time Inc
Available used from around $6

After reading Leopold's book .....I think I can go back and better understand Bill Rose's book
(If my good friend would only return it)hint,hint
It is impossible to buy Bill's Book Used .. no one wants to give it up
And if you get a copy DO NOT LOAN IT OUT ;---)

I should have said I am looking forward to your (Robert's)comments.
Your comments came blazing thru before I could post
Your comments were worth the wait ;--)

Answered by John Brooks
Posted Nov 29, 2010 7:19 AM ET


Hello Robert,

I cannot comment on all you wrote here. There’s quite a bit, as another commenter noted. The summary you gave of what I wrote on condensation is accurate. Common use of the term does drift away from the scientific use. One can argue that ad/absorbed water is in fact condensed—it is—but the energies involved in binding water to sites in wood and brick vary widely, while the energy in forming droplets of pure water is singular.

“Condensation” on windows is (sort of) binary, while wetness in porous and hygroscopic materials forms a continuum from very dry to saturated and beyond. The term “condensation” does a poor job of capturing what happens in opaque building systems, so I recommend dropping it from such use. ASHRAE 160 does a pretty good job of applying pass/fail criteria to assemblies with moisture storage. I suspect that the confusion arises because people want no more than a binary understanding about the condition of their building assemblies—ok or not ok. The use of the term “condensation” regarding buildings occurred more than 100 years ago in the architecture literature, while its first mention in the engineering literature is from the mid 1930s, with the introduction of insulation. The architects wanted to know only if it was going to be ok. “Condensation” is a convenient framework for making an analog continuum look binary.

Your comment #1 is an interesting and edifying summary of what water is and does. I'm skeptical of the more mystical properties you assign to water such as memory. Open—but skeptical.

I once wanted to test the theory that hot water freezes faster than cold water, being skeptical. I took two identical glass containers, filled one with hot tap water and one with cold, and stuck thermocouples in both, and placed them side-by-side in the freezing compartment of the 60 year-old Hotpoint refrigerator in our break area. Imagine my surprise when, yes, the hot water took a giant nosedive into colder temperatures and froze much more quickly than the cold water did. So I opened the fridge and took out the cold-water container, then the hot-water container, but it didn't budge. While the cold-water container had rested on a thin layer of frost in the freezer, the hot-water container had melted the frost, and formed a strong thermal bridge to the chilled aluminum enclosure. Oops, bad experiment. Gotta watch those boundary conditions. I tried it again, this time resting both containers on a scrap of polystyrene. This time the results seemed to indicate that the rate of temperature loss, assuming all boundary conditions are managed, is the same for hot and cold water. The curve from 60F to freezing was the same for both samples, even though one had started up at 130F. It undercut the “memory” theory.

I must stop now, and probably will not be able to get back to this blog any time soon, and won’t be able to provide followup. Good luck with the discussion.

Bill Rose

Answered by Bill Rose
Posted Nov 29, 2010 11:07 AM ET


Bill Rose,
It is all your fault.
It was your book that started my quest to TRY and better understand water.
I have a long way to go.... but I am trying

So... You are going to tease us and then run away? :-0

Thanks Robert for posting.

Answered by John Brooks
Posted Nov 29, 2010 12:27 PM ET


Thanks for your explanations and introduction of this topic. I agree with you that board sheathing is robust, and I have long advocated board sheathing. Most of the homes I have built included board sheathing.

I certainly strive to avoid confusion, and I don't agree with you that my blogs on this topic are evidence of confusion. I agree with Bill Rose that "The term 'condensation' does a poor job of capturing what happens in opaque building systems, so I recommend dropping it from such use."

Lately, I have been striving to avoid the use of the term "condensation" when discussion moisture accumulation in sheathing; occasionally, however, I have been overruled by other editors at GBA. (That's how the word "condensation" ended up in the title of one of my recent blogs.)

All discussions of this topic, including your recent posts, are welcome, as we all strive to banish confusion and educate each other on building science topics.

Answered by Martin Holladay
Posted Nov 29, 2010 1:09 PM ET


Bill Rose said: "I tried it again, this time resting both containers on a scrap of polystyrene. This time the results seemed to indicate that the rate of temperature loss, assuming all boundary conditions are managed, is the same for hot and cold water. The curve from 60F to freezing was the same for both samples, even though one had started up at 130F. It undercut the “memory” theory."

Do I understand Bill to say that there is no Mpemba effect, only the surprising results from a poorly designed experiment?

Answered by John Hess
Posted Nov 29, 2010 4:36 PM ET



I think what Bill Rose was saying is that his own experiments were poorly designed and controlled for the multitude of variables. What Bill was apparently measuring was only the rate of heat loss, not the rate or timing of freezing, which is the core of the Mpemba effect.

There have been many laboratory replications of the Mpemba effect, though little consensus about the cause.

Here is a link to a graph of the heat loss and freezing times for hot and cold water. The slopes are identical (heat loss rate), but because the hot water starts farther upslope it takes longer to get to freezing temperatures. However, once there, the hot water starts freezing sooner, requiring less supercooling, but takes longer to completely freeze.


Answered by Riversong
Posted Nov 29, 2010 5:01 PM ET


Here are some more anomalies of water from an excellent (and very technical) website about water.

Anomalous properties of water


The anomalous properties of water are those where the behavior of liquid water is quite different from what is found with other liquids. Frozen water (ice) also shows anomalies when compared with other solids. Although it is an apparently simple molecule (H2O), it has a highly complex and anomalous character due to its intra-molecular hydrogen bonding. As a gas, water is one of lightest known, as a liquid it is much denser than expected and as a solid it is much lighter than expected when compared with its liquid form. An interesting history of the study of the anomalies of water has been published.

As liquid water is so common-place in our everyday lives, it is often regarded as a ‘typical’ liquid. In reality, water is most atypical as a liquid, behaving as a quite different material at low temperatures to that when it is hot. It has often been stated that life depends on these anomalous properties of water. In particular, the high cohesion between molecules gives it a high freezing and melting point, such that us and our planet is bathed in liquid water. The large heat capacity, high thermal conductivity and high water content in organisms contribute to thermal regulation and prevent local temperature fluctuations, thus allowing us to more easily control our body temperature. The high latent heat of evaporation gives resistance to dehydration and considerable evaporative cooling. Water is an excellent solvent due to its polarity, high dielectric constant and small size, particularly for polar and ionic compounds and salts. It has unique hydration properties towards biological macromolecules (particularly proteins and nucleic acids) that determine their three-dimensional structures, and hence their functions, in solution. This hydration forms gels that can reversibly undergo the gel-sol phase transitions that underlie many cellular mechanisms. Water ionizes and allows easy proton exchange between molecules, so contributing to the richness of the ionic interactions in biology.

At 4°C (39°F) water expands on heating or cooling. This density maximum together with the low ice density results in (i) the necessity that all of a body of fresh water (not just its surface) is close to 4°C (39°F) before any freezing can occur, (ii) the freezing of rivers, lakes and oceans is from the top down, so permitting survival of the bottom ecology, insulating the water from further freezing, reflecting back sunlight into space and allowing rapid thawing, and (iii) density driven thermal convection causing seasonal mixing in deeper temperate waters carrying life-providing oxygen into the depths. The large heat capacity of the oceans and seas allows them to act as heat reservoirs such that sea temperatures vary only a third as much as land temperatures and so moderate our climate (for example, the Gulf stream carries tropical warmth to northwestern Europe). The compressibility of water reduces the sea level by about 40 m giving us 5% more land. Water's high surface tension plus its expansion on freezing encourages the erosion of rocks to give soil for our agriculture.

Notable amongst the anomalies of water are the opposite properties of hot and cold water, with the anomalous behavior more accentuated at low temperatures where the properties of supercooled water often diverge from those of hexagonal ice. As (supercooled) cold liquid water is heated it shrinks, it becomes less easy to compress, its refractive index increases, the speed of sound within it increases, gases become less soluble and it is easier to heat and conducts heat better. In contrast as hot liquid water is heated it expands, it becomes easier to compress, its refractive index reduces, the speed of sound within it decreases, gases become more soluble and it is harder to heat and a poorer conductor of heat. With increasing pressure, cold water molecules move faster but hot water molecules move slower. Hot water freezes faster than cold water and ice melts when compressed except at high pressures when liquid water freezes when compressed. No other material is commonly found as solid, liquid and gas.

Answered by Riversong
Posted Nov 29, 2010 5:04 PM ET


And below, from the same author, is a discussion of the vital importance of the properties of water for the existence and continuation and evolution of life, including a discussion of the threat to life posed by a rather small deviation in the existing strength of those magical Hydrogen bonds.

That water is not only so mysterious and anomalous in its properties, but also so perfectly poised between possible variations to allow life to exist in the Universe is perhaps the strongest scientific indication of the Intelligence of the Universe (or God, if you'd like).

Water Structure and Science
by Martin Chaplin

Hydrogen bonding in water

Hydrogen bonding forms in liquid water as the hydrogen atoms of one water molecule are attracted towards the oxygen atom of a neighboring water molecule.

In a water molecule (H2O), the oxygen nucleus with +8 charges attracts electrons better than the hydrogen nucleus with its +1 charge. Hence, the oxygen atom is partially negatively charged and the hydrogen atom is partially positively charged. The hydrogen atoms are not only covalently attached to their oxygen atoms but also attracted towards other nearby oxygen atoms. This attraction is the basis of the 'hydrogen' bonds.

Can life exist without water?

Water and life are closely linked. This has been recognized throughout history by civilizations and religions and is still the case with scientists today. Liquid water is required for life to start and for life to continue. No enzymes work in the absence of water molecules. No other liquid can replace water. We are very fortunate, therefore, that our planet is so well endowed. Water is a common material in the Universe, being found as widely dispersed gaseous molecules and as amorphous ice in tiny grains and much larger asteroids, comets and planets, but water needs particularly precise conditions to exist as a liquid as it does on Earth. It is most likely that this water arrived from multiple sources, such as comets and asteroids, somewhat after solid planet Earth was formed.

Water possesses particular properties that cannot be found in other materials and that are required for life-giving processes. These properties are brought about by the hydrogen-bonded environment particularly evident in liquid water. If aqueous hydrogen bonds were actually somewhat stronger, then water would behave similar to a glass, whereas if they were weaker then water would be a gas and only exist as a liquid at sub-zero temperatures.

It is found that if the hydrogen bond strength was slightly different from its natural value then there may be considerable consequences for life. Water would not be liquid on the surface of Earth at its average temperature if the hydrogen bonds were as little changed as 7% stronger or 29% weaker. The temperature of maximum density naturally occurring at about 4°C (39°F) would disappear if the hydrogen bonds were just 2% weaker. Major consequences for life are found if the hydrogen bonds did not have their natural strength. Even very slight strengthening of the hydrogen bonds may have substantial effects on normal metabolism. Water ionization becomes much less evident if the hydrogen bonds are just a few percent stronger, but pure water contains considerably more H+ ions if they are few percent weaker. The important alkali metal ions Na+ and K+ lose their distinctive properties if the hydrogen bonds are 11% stronger or 11% weaker respectively. Hydration of proteins and nucleic acids depends importantly on the relative strength of the biomolecule-water interactions as compared with the water-water hydrogen bond interactions. Stronger water hydrogen bonding leads to water molecules clustering together and so not being available for biomolecular hydration. Generally, the extended denatured forms of proteins become more soluble in water if the hydrogen bonds become substantially stronger or weaker. If the changes in this bonding are sufficient, present natural globular proteins cannot exist in liquid water.

Consequences of changes in water’s hydrogen bond strength

No Hydrogen-bonding at all - No life
Hydrogen bonds slightly weaker - Life at lower temperatures
No change - Life as we know it
Hydrogen bonds slightly stronger - Life at higher temperatures
Hydrogen bonds very strong - No life

Intriguingly, liquid water acts in subtly different manners as circumstances change, responding to variations in the physical and molecular environments and occasionally acting as though it were present as more than one liquid phase. Sometimes liquid water is free flowing whilst at other times, in other places or under subtly different conditions, it acts more like a weak gel. Shifts in the hydrogen bond strength may fix water’s properties at one of these extremes to the detriment of processes requiring the opposite character. Evolution has used the present natural responsiveness and variety in the liquid water properties such that it is now required for life as we know it. DNA would not form helices able to both zip and unzip without the present hydrogen bond strength. Enzymes would not possess their 3-D structure without it, nor would they retain their controlled flexibility required for their biological action. Compartmentalization of life’s processes by the use of membranes with subtle permeabilities would not be possible without water’s intermediate hydrogen bond strength.

Quite small percentage changes in the strength of the aqueous hydrogen bond may give rise to large percentage changes in such physical properties as melting point, boiling point, density and viscosity. Some of these potential changes may not significantly impinge on life’s processes, (e.g. compressibility or the speed of sound) but others are of paramount importance.

Strengthening hydrogen bonding has particularly important effects on viscosity and diffusion.

Effect of water hydrogen bond strength on melting and boiling point

Bond strength increases affect the melting point and how bond strength decreases affect the boiling point. The resulting relationship shows that water would freeze at the average surface temperature of Earth (15°C / 59°F) with a 7% strengthening in water’s hydrogen bond or it would boil on a 29% weakening. At our body temperature (37°C / 98.6°F) the strengthening required for freezing is 18% and the weakening required to turn water into steam is 22%.


It is apparent that small changes of a few percent would not be threatening to life in general but changes in excess of 10% may cause a significant threat. The overall conclusion to be drawn is that water’s hydrogen bond strength is poised centrally within a narrow window of its suitability for life.

Answered by Riversong
Posted Nov 29, 2010 5:23 PM ET


I took the Bill Rose comments the same way as John H.

Answered by John Brooks
Posted Nov 29, 2010 5:39 PM ET


"Homeopathy is correct that water has a "memory" of what was once dissolved in it and retains the "essence".

There is evidence that water also retains thoughts, moods & conscious intentions."

I'm disappointed that your enumeration of the Magical qualities of water didn't include any empirical evidence for the above characteristics.

Answered by John Hess
Posted Nov 29, 2010 9:04 PM ET



A list is a list, not an explanation.

I did, however, point you to the man who has done extensive research into water's "higher" qualities, and the extremely dilute solutions of homeopathy and flower essence medicine has been studied for many years. Perhaps you don't want to bother doing your own research.

From the same scientific source as the recent posts:

Liquid water is clearly a very complex system even before the further complexity of molecular clusters, gas-liquid and solid-liquid surfaces, reactions between these materials, the consequences of physical and electromagnetic processing and the addition of ethanol are considered. Any or a combination of these factors may cause 'memory' of past solutes and processing in water. Some of these solutions are capable of causing non-specific clinical effects whereas others may cause effects specifically linked to the solution's history.

Other interesting examples of the memory of water are the Mpemba effect and the observation that hot water pipes are more likely to burst than adjacent cold water pipes. In both effects, water seems to remember whether it has been recently hot or cold even when subsequently cooled. The Mpemba effect is a well proven phenomenon that also seems to be caused by unexpected solute and time effects.

Answered by Riversong
Posted Nov 29, 2010 9:47 PM ET


ASKED BY ANONYMOUS - Nov 29 10: Concerning building details would you, in general, consider the Pacific Northwest as sufficiently wet and windy as to justify the use of a rainscreen siding design?

By the way, I didn't miss this question, I ignored it - since I am not inclined to have dialog with nameless people.

If you'd share your full name, I'd be glad to answer.

Answered by Riversong
Posted Nov 29, 2010 9:58 PM ET


And how can we stop fighting it and turn it back into an ally?

Well? Are you asking US?
Or do you have a solution?

Answered by John Brooks
Posted Nov 30, 2010 7:08 AM ET


Drink at least four glasses of water every day (must be in a glass, as this effects the ortho-molecular structure and the memory imprinting of the water).

Answered by Riversong
Posted Nov 30, 2010 9:59 AM ET


Oh, perhaps you mean in terms of building technology?

As I've stated many times in this forum, I believe that a deep understanding of hygro-thermal principles and mechanics (hardly seem like sufficient terms to describe the mysteries of water and energy, which science doesn't yet fully understand) would lead one to the conclusion that it is as foolish to try to "control" moisture as it is for the US Army Corps of Engineers to try to control the Mississippi River or the bayous of Louisiana.

Hence, it's an exercise in futility (or hubris, or both) to attempt to design and build the "perfect wall", if by this one means a building envelope that can resist all the potential incursions and impacts and consequences of moisture.

The "solution" to living with the Mississippi River or the Gulf Coast weather is not to dam it up and limit and control its flow, but rather to adjust our lives and our built environment to coexist with forces of nature that are much greater than civilization (whatever that is*).

The "solution" to creating livable and durable shelters is not to try to dam up the water and energy flows but to use methods and materials that have evolved with nature's fluid environment and have an innate intelligence that is greater than our own.

[* endnote: When a journalist asked Gandhi what he thought of Western civilization, he responded "I think it would be a good idea".]

Answered by Riversong
Posted Nov 30, 2010 10:13 AM ET


I don't agree that "Other interesting examples of the memory of water are the Mpemba effect and the observation that hot water pipes are more likely to burst than adjacent cold water pipes."

This has nothing to do with the Mpemba Effect, which most scientists, including Bill Rose, do not give any credit to.

The reason that hot water pipes freeze first is the existence of a toilet in most domestic plumbing systems. Toilet tank valves provide a convenient way for cold-water pipes to relieve the pressure of an expanding ice plug.

Hot water pipes have a relief valve at one end of the system (the PT relief valve on the hot-water tank), but not on the far end of the ice plug -- and so the hot water pipe is the first to burst.

Answered by Martin Holladay
Posted Nov 30, 2010 10:17 AM ET



The quote you disagree with is not mine, but that of one of the word's leading authorities on water, Martin Chaplin, BSc, PhD, Chartered Chemist, Fellow of the Royal Society of Chemistry, Emeritus Professor of Applied Science at London South Bank University.

The Mpemba effect has been replicated by many scientists, though not with the consistency that would allow for general acceptance (though this is undoubtedly related to poorly controlled variables, such as in Bill Rose's quick and dirty refrigerator trials). I think most scientists, contrary to your claim, accept that this occurs but cannot agree on a cause - and that is because water is the least understood and most complex substance on earth, if not in the universe.

The effect has been documented in peer-reviewed journal articles, such as D. Auerbach, Supercooling and the Mpemba effect; when hot water freezes quicker than cold, Am. J. Phys. 63 (1995) 882-885 and J. D. Brownridge, A search for the Mpemba effect: When hot water freezes faster then cold water, arXiv:1003.3185v1 [physics.pop-ph] (2010).

Your explanation of the bursting of hot water pipes before cold pipes is self-contradictory and incorrect. You claim that cold water pipes can relieve pressure at one end through toilet fill valves while hot water pipes can relieve pressure also at one end through temperature/pressure relief valves, but somehow which end makes a difference.

Water freezing in a pipe is a local phenomenom - it begins at a precise location and the ice plug expands as it freezes isotropically - in all directions. The slight expansion (10% max) has almost no effect on the water pressure on either side of the plug, but is more than sufficient to stretch a copper water pipe to failure as it expands perpendicular to the pipe walls.

Answered by Riversong
Posted Nov 30, 2010 12:24 PM ET


Here's why it matters which end the pressure relief is located: If there is no pressure relief between the ice plug and the last fixture on the plumbing run, the pipe will burst. The PT relief valve at the hot water tank can't relieve the pressure buildup between the ice plug and the last fixture on the run.

Answered by Martin Holladay
Posted Nov 30, 2010 12:28 PM ET


Bill Rose measured elevated water pressures between the freeze and the end of the pipe due to lengthwise expansion of the water in the pipe. the ice crystals froze from the perimeter of the pipe and grew in towards the center (like those donut shaped ice cubes at hotel ice makers.) There was very little expansion due to ice on the walls of the pipe, the failure was due to water pressure between the ice plug and the fixture. Pipes with poorly installed insulation with intermittent gaps at the connections and elbows saw more damage that pipes with continuous insulation or none since pipes with no insulation tended to fail at a single point and intermittent insulation had the potential to create multiple failures necessitating multiple repairs.

A simple solution would be to add a Tee in the 3/8" pex line under the furthest sink and allow a small amount of cross connection between hot and cold at that point (between the shut off and the vanity faucet hot and cold. You could limit this with a valve or a piece of rubber in the tee fitting so you would still be able to draw cold water at the sink but, if the hot pipe had a pressure build up due to ice, the pressure could push water through the tee into the relief at the toilet fill valve.

Answered by Michael Chandler
Posted Nov 30, 2010 12:50 PM ET



According to your theory, cold water pipes would burst upstream of the ice plug and hot water pipes would burst downstream of the plug. But that's not where they burst and certainly doesn't explain the difference in rate of bursting.

It's not the widely-disbursed slight increase in water pressure than makes any difference, and the very slight expansion of ice will have almost zero effect on the static water pressure in a pipe.

1/2" copper M pipe is rated for a working pressure of 500 psi, but expanding ice can exert a local pressure of 40,000 psi (enough to crack rock and lift buildings).

Pipes burst at the ice plug, not where there is still liquid water to absorb the very slight decrease in volume.

Hot water pipes burst before cold water pipes because they freeze sooner. Just ask Mpemba.

Answered by Riversong
Posted Nov 30, 2010 12:55 PM ET


Cold water pipes don't burst upstream from the ice plug because pressure relief upstream of the ice plug is provided by either (1) the plumbing system's pressure tank (in the case of a rural home) or (2) the nearly infinite size of the municipal water system (in the case of an urban home).

Answered by Martin Holladay
Posted Nov 30, 2010 1:19 PM ET


I regularly freeze liquid foodstuffs in glass jars in my freezer, and seldom have had one break. But it is absolutely necessary to leave plenty of headspace between the liquid/ice and the jar cap. Usually a "volcano" forms on top of the ice as the last little bit of liquid freezes in the center of the jar, which has no place to expand to except up towards the lid. If there is not sufficient headspace this "volcano" will press against the lid of the jar and break out the bottom of the jar. While the liquid is freezing there appears to be minimal radial pressure of the ice against the jar as long as there also is liquid that the ice can expand into. But there must be some radial pressure, for when I freeze liquids in squareish plastic containers they do bulge out.

Answered by John Hess
Posted Nov 30, 2010 1:41 PM ET


Pipes have burst everywhere in Adirondacks camps. We install compression fittings at the new locales and undue them next Fall closing.

As to hot water... heating water changes the dissolved gas quantities yes? What effect does that have on all these prior discussions?

Answered by aj builder
Posted Nov 30, 2010 3:09 PM ET


If someone can link me to a study (Rose's?) that demonstrates conclusively that water pipes burst at places other than the ice plug, I'd like to see it.

The multiple web references to this alleged "fact" all seem to come from the same source, a publication of the Institute for Business and Home Safety titled Freezing and Bursting Pipes (http://www.ibhs.org/natural_disasters/downloads/freezing.pdf). This publication refers to research conducted by the Building Research Council at the University of Illinois (Bill Rose's hangout), which also claims that wind chill can play a major role in accelerating ice blockage in pipes. But wind chill is the subjective experience of cold on a human body in a windy environment (making it feel colder than the air temperature), while wind will accelerate cooling but cannot lower the temperature of an inanimate object below the air temperature.

Since the actual burst strength (as differentiated from working pressure) of a ½" copper water pipe is 6,000-8,000 psi (2 to 3 times the compressive strength of concrete), one would expect to see compression fittings on supply risers and washerless faucets rupturing before a pipe would burst if downstream water pressure were the culprit.

Answered by Riversong
Posted Nov 30, 2010 3:10 PM ET


"But wind chill is the subjective experience of cold on a human body in a windy environment (making it feel colder than the air temperature), while wind will accelerate cooling but cannot lower the temperature of an inanimate object below the air temperature."

Not germane to the discussion of freezing pipes, but wind can chill water below the ambient temperature via evaporative cooling. Another magical quality of water... :)

Answered by John Hess
Posted Nov 30, 2010 3:35 PM ET


Hello all,

The pipe bursting report has recently been committed to pdf. It is in 3 parts, approx 30MB. If GBA could provide an upload ftp site, I'd be glad to let you have it. It should go a long way toward answering many of the questions posed here.

One unfortunate part of the report is our use of the term "wind chill". It was used in the report to show that, under our field conditions, we were only able to create ice blockage with cold temperatures plus a fan to lower the film resistance. The meterology use of the term is more important, and includes evaporation, not just film resistance reduction. Evaporation was not occuring in our studies, of course. Poor choice of term. Can't go lower than ambient.

The report should be convincing that the burst occurs due to elevated fluid pressure due to the piston-type action of a growing ice block against a confined water quantity. The burst will occur at the weakest point downstream from the blockage, which is usually the pipe. And if it's copper pipe, it's likely to occur where pipe is least ductile, and that is where it is coldest--at the margin between the ice and the water. Toilets can act as pressure relief valves. We're pretty sure, but not positive, that that's why repairs are more common in hot water lines than in cold.

Answered by Bill Rose
Posted Nov 30, 2010 3:40 PM ET


"Toilets can act as pressure relief valves. We're pretty sure, but not positive, that that's why repairs are more common in hot water lines than in cold."

Thanks, Bill. If you can e-mail me the pdf, I'll determine whether GBA can somehow put it online (with your permission, of course.)

Answered by Martin Holladay
Posted Nov 30, 2010 3:55 PM ET


"Toilets can act as pressure relief valves. We're pretty sure, but not positive, that that's why repairs are more common in hot water lines than in cold."

Too bad you didn't shut off the toilet supply valve. Then you would know. Or maybe the test wasn't done on an actual plumbing system?

Answered by John Hess
Posted Nov 30, 2010 4:26 PM ET


Perhaps even more fascinating than the study on bursting pipes is the 2008 Documentary, Water: The Great Mystery. I just ordered a DVD and I'll offer a review once I see it.

"Water is the driving force of all nature."
- Leonardo da Vinci

"We live by the grace of water."
- National Geographic Special Edition, Nov. 1993

"Water is H2O, hydrogen two parts, oxygen one, but there is also a third thing, that makes it water and nobody knows what it is."
- D H Lawrence

"This film is about water, the most amazing yet least studied substance. From times immemorial, scientists, philosophers and theologians tried to understand its explicit and implicit properties, which are phenomenal, beyond the common physical laws of nature."

"Witness recent, breathtaking discoveries by researchers worldwide from Russia, Kazakhstan, Switzerland, Israel, the USA, Britain, Austria, Japan, Argentina, China and Tibet."

"The arguments expound upon unexpected and challenging assumptions enlightening many years of research to open humankind to new horizons, such as the applications of structured water in agriculture, or the use of water in treatment for the most serious diseases and more."

"The Geography of the film spans the globe. The implications go beyond the solar system, suggesting that water has the ability to convey messages faster than light, perhaps linking water with the absolute. Water is so unique, and so profound, its miraculous properties are still awaiting to be discovered."

Answered by Riversong
Posted Nov 30, 2010 5:16 PM ET


Great thread!
Whenever I hear or read a report on new developments in a particular field I am often surprised to find a line like "...it turns out that the processes are far more dynamic than previously thought".
Who would have guessed that life just isn't that simple ;-)

Answered by Lucas Durand
Posted Nov 30, 2010 7:28 PM ET


Great thread!

I will Second that !!

Answered by John Brooks
Posted Nov 30, 2010 7:40 PM ET


Who would have guessed that life just isn't that simple

In a similar vein...my late uncle Murray, MD & PhD from Harvard, life-long practicing physician, life-long professor of Medicine, on President Kennedy's medical advisory commission, traveled the world to almost every international medical conference (including behind the Iron Curtain during the Kruschhev years), married to a physician, three children who each went into medicine...

When he was dying of cancer and realized that it was incurable by the best that modern medicine could offer (he even tried experimental neutron radiation therapy), went home to learn macrobiotic diet and transcendental meditation so that - if he could not prevent his dying - he could at least learn to die well. And the last thing he said to me, after I read him The Physician, a novel by Noah Gordon, was "We just don't have any idea what we're doing".

It took him a lifetime of dedication to science and medicine to realize the depth of his ignorance. Science and rational thought, as I have hitherto suggested, are not The Way, but merely useful tools to assist us on the Journey.

From that wise guy, Albert Einstein:

"We should take care not to make the intellect our god; it has, of course, powerful muscles, but no personality."

"The intuitive mind is a sacred gift and the rational mind is a faithful servant. We have created a society that honors the servant and has forgotten the gift."

"My religion consists of a humble admiration of the illimitable superior spirit who reveals himself in the slight details we are able to perceive with our frail and feeble mind."

"Every one who is seriously involved in the pursuit of science becomes convinced that a spirit is manifest in the laws of the Universe – a spirit vastly superior to that of man, and one in the face of which we with our modest powers must feel humble."

"Every serious scientific worker is painfully conscious of this involuntary relegation to an ever-narrowing sphere of knowledge, which threatens to deprive the investigator of his broad horizon and degrades him to the level of a mechanic ...It is just as important to make knowledge live and to keep it alive as to solve specific problems."

Answered by Riversong
Posted Nov 30, 2010 8:03 PM ET


I tend to find the reflective qualities of water most interesting. Hot or cold there is a distinctive difference. Maybe memory plays a role here? Cold still water reflects perfectly, while distortions seem to occur in still warm water.
We restored a vintage 1910 reflecting pool for a client that had lived on the property for 60+ years. The pool was originally designed as a part of the landscape design to reflect elements of the gardens to a dining area veranda.
The reflecting pool was shallow, (3') and the owner wanted to use it as walk therapy for himself and his wife. They were in their eighties and had us add a propane heat system to the pool as well.
The point of the original design of this pool was to provide a beautiful reflection of the garden's seasonal changes. It was not to be used for swimming etc. The inside was a dark green ceramic tile blend and this thing was hugh, 80'X 28'. I'm pretty sure that the original designers of this type of reflecting pool had to use some sort of science to achieve what appeared to be perfect reflection.
The owners and I both noticed a substantial difference when the pool was heated. ( no chemicals allowed).
Anyhow ~ maybe something else to reflect on.
Thanks for all the great info!
Roy Harmon

Answered by Roy Harmon
Posted Nov 30, 2010 9:28 PM ET


When a ripple turns back to stillness~ memory?

Answered by Roy Harmon
Posted Nov 30, 2010 9:40 PM ET


By the way, I didn't miss this question, I ignored it - since I am not inclined to have dialog with nameless people.

If you'd share your full name, I'd be glad to answer.

My apologies.

Answered by Timmy O'Daniels
Posted Nov 30, 2010 11:18 PM ET


Timmy O'Daniels,

With such a wonderful name, I don't know why you wouldn't share it. Apologies as well, but there's been a problem on this site with people flaming under the guise of anonymity or pseudonymity. I didn't suspect you were of that type but - just as I've made it a point of principle not to habituate any real-world venue that isn't smoke-free - I'm similarly trying to ignore cyber-world "conversations" with nameless souls. The Virtual World is a surreal enough place as it is.

Concerning building details would you, in general, consider the Pacific Northwest as sufficiently wet and windy as to justify the use of a rainscreen siding design?

I only briefly passed through the Pacific Northwest, and that was 36 years ago, so I have only a "warm water" memory of the climate. But I'll share what I offered on another thread, which I believe is a good rule of thumb:

"To Build a Better Home,” published by the APA-Engineered Wood Association, 2002:

"In areas like the Southwest that receive low rainfall (less than 20 inches annually), a housewrap or building paper should offer sufficient water resistance protection, according to most building experts. In areas that experience moderate amounts of rainfall (20 to 40 inches annually), protection against rain penetration should include an enhanced housewrap. And for wet and/or humid climates, coastal areas and hilltop exposures receiving high (40 to 60 inches annually) or extreme (60 inches or more annually) rainfall, a ventilated rainscreen assembly is recommended; a rainscreen system is also advised for areas that receive high winds in addition to rain. Rainscreen systems are recognized by leading building trade associations for their effectiveness in controlling rain water intrusion into wall assemblies in areas of high and extreme rainfall."

This advice is similar to what is proposed in the HUD PATH manual "Moisture-Resistant Homes: Best Practices Guide for Builders and Designers", which also adds overhang ratio and site-specific exposure into the formula - more roof overhang per storey, the less protection is needed for the walls beneath (A Canadian study also concluded that the overhang ratio was a primary determinant of longevity of structure).

Answered by Riversong
Posted Dec 1, 2010 12:30 AM ET


When a ripple turns back to stillness~ memory?

Of course, still water was the original mirror to humanity (and, no doubt, other sentient beings). How many of the myths of our culture involve a protagonist seeing their reflection in a quiescent pool?

Interestingly, Native Americans understand that the Stone People (the bones of the earth) are the keepers of the memory of all that has been. They are, after all, the ones who persist almost unchanging for the longest time. It's not coincidental that, for modern culture - including we who spend far too much time in cyberspace - all our digital memory is contained within silicon chips: rocks, the Stone People.

The Old Man Speaks

Do not cry tears of sadness for me, only tears of joy.
For I am not gone from this hallowed place;
my spirit remains.
I walk with you now.

The torch has now been passed
You must be the guardians of each other now.

The rocks, the trees, the water, the wind, rain and snow
All carry my life force through these mountains.

No longer do I simply sit here looking down upon you
But now I soar and sing and embrace each one of you.

Feel my spirit and care for this earth as you cared for me.
Protect it, nurture it, and feel restored as you walk among this beauty.

Gaze up on a clear and sunny day and you will see me.
Look into each other's eyes; you will find me there.

I have not died
I am here still
Only now I live

Excerpted from: "The Old Man Speaks", an elegy to the Old Man in the Mountain, Franconia NH (discovered 1805 - collapsed May 3, 2003) by Edwina Landry, Concord, NH, May 6, 2003

Answered by Riversong
Posted Dec 1, 2010 12:47 AM ET


Watts makes a toilet valve designed to be an 80psi pressure relief valve:

Since we're on the subject, I admire the Fluidmaster Leak-Sentry for the way it stubbornly refuses to waste water: http://www.fluidmaster.com/pdfs/400ls_instructions.pdf

Answered by Kevin Dickson
Posted Dec 1, 2010 1:50 AM ET

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