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This patent represents the method in which the condensation is avoided in a thermal insulated envelope. The maintaining of warm vapors in a warm zone of a vapor-impermeable insulation lids to the elimination of condensation phenomenon. This is realized by extending the properties of Vapor Impermeable Insulations (VII) to the entire surface of a wall or by creating a Non-Permissive Insulation Assembly (NP-IA). Through the fact that this configuration of insulations makes it possible the avoidance of condensation in any situation in which is applied a difference of temperatures, occurs the utility of enunciating a principle to avoid condensation as fundamental method for designing enclosures. Also, is justified the record of a reference temperature towards which can be defined the terms warm and cold in relation to an optimal temperature for development of human activity.

Radoane, Marius (Lawrenceville, GA, US)
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E04B1/74; E04B1/62; F28F13/04
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1. A method for avoiding condensation in insulated enclosures constructed and subjected to significant differences of temperature, characterized in that, in order to avoid condensation the heat flow must convert the heat deficit in an insulation material or insulation assembly without vapor diffusion or any airflow carrying warm vapor to cold areas of insulation.

2. A method for avoiding condensation according to claim 1, characterized in that, the insulation applied to a envelope wall having permeable characteristics to water/air/vapors, is configured as a Vapor Impermeable Insulation (VII) or a Non-Permissive Insulation Assembly (NP-IA).

3. (not entered)



This patent is for the explanation of the method through which the condensation is avoided in building enclosures and other situations where a significant difference of Temperature and Vapor Pressure exist. In an insulation material or ensemble, the interior warm will reach the exterior cold in the field of insulation. When the warm vapors, driven by the Vapor Pressure will not reach into the insulation material/ensemble, the condensation is avoided. This patent is also a theoretical explanation for Non-Permissive Exterior Insulation and Finish Systems (NP-EIFS) Concept Technology and Details, Patent Publication U.S. 2011/0258944 A1.


Is well known in the art that preventing condensation and moisture in building enclosures is a long debated controversy, without there a law to stat how to absolute avoid condensation, regardless the thermal and humidity (higrothermal) climate loads and season variations. Control of thermal flow and prevention of condensation potentials are key to energy conservation, preservation of construction or enclosure and occupants satisfaction.

The prior art have roles, regulations and advises to avoid condensation but no methods or principles to entire avoid condensation. Situation in which the condensation is complete avoided is not stipulated or studied as a general rule or method to be applied in practice. Based on physical properties of the materials such as permeability (the tendency of a material to allow the passage of water vapor), conduction, capillarity etc. and the configuration of the enclosure, the prior art have strategies to avoid condensation by: preventing building components from dropping below the dew point; reducing water vapor entering and increasing water vapor leaving the building component; placing insulation on the cold side of vapor retardant materials; installing vapor retardant materials on the warm side of the assembly; installing breathable materials on the cold side of the assembly; avoidance of the installation of vapor barriers on both sides of assemblies and so on.

The fundamental principle of prior art to control water in vapor form is to keep it out and to let it out if it gets in, or to encouraging drying mechanisms over wetting prevention mechanisms. It gets complicated because sometimes the best strategies to keep water vapor out also trap water vapor in, and even more complicated because of climate and seasons. In general, water vapor moves from warm side to the cold side of the building assemblies. This means that we need different strategies for different climates. Also, it has to be taken into consideration the differences between summer and winter in the same strategy, which is rather impossible.

All those conduct to such legitimate questions:

Exist a situation, configuration or assembly when the condensation is complete avoided whatever the climate or season? Can we have a general method to use as principle to avoid condensation in building enclosures and not only?

The answer is YES, and it makes the object of this patent. The principle to avoid condensation can be formulated, understood and used in designing and construction of enclosures. The utility of this principle is obvious.


A building enclosure in general is defined as a physical system involving three interactive components: the exterior environment, the enclosure system with the so-called thermal envelope, and the interior environment. Referring to the enclosure or thermal envelope, which physically separates different environments, we can state that two physical characteristics are ubiquitous in the materials involved and we can find certainty in the hygrothermal analysis:

The thermal conductivity or heat conduction, which is related to the temperatures by using the terms Heat Flow or Cold Flow. Thermal conductivity is a physical characteristic of whatever material and varies from high to low (thermal insulation). The reciprocal of thermal conductivity is thermal resistivity. Construction industries make use of units such R-value and U-value (thermal transmittance) related to the thermal resistivity of a material used in an insulation system, R/U-values being dependent on the thickness of the insulation.

Another characteristic is the permeability, the tendency of material to allow the passage of water vapor. An associated characteristic is the permeance, the tendency of material to allow water vapor to diffuse through it, at a specified thickness. Permeability varies from very permeable to impermeable (vapor barrier).

Each enclosure is a three-dimensional element consists of multiple layers or materials that extend from the inside face of the innermost interior layer to the outside face of the outermost layer. If thermal loadings occur, conduction state that the cold flow will encounter the heat flow in the field of thermal envelope or the heat/cold flow cross the enclosure, depending on the conduction of materials and intensity of thermal flow. Reducing the conduction is a goal in constructing enclosures by increasing the insulation, but the heat transfer is never reduced to zero, the adiabatic boundary is not a real issue. Conclusive is the term “heat retardant” while defining insulations and we don't have the terms as would be “impermeable to heat”. Depending on insulation performance and thermal load intensity, the differential thermal flow converse in the field of insulation system, the conversion occurring three-dimensional in a zone that can move from cold to warm. The conversion zone can move or extend from the median line of insulation system, to the exterior surfaces allowing the heat/cold transfer to the surroundings. Of a surety, the dew point cannot be avoided or eliminated in the field of an enclosure acting as an environmental separator, even if are involved insulations with high thermal resistance values.

The other physical property of materials involved is the water vapor diffusion, associated with other forms of vapor transportation. Vapor permeance is a layer property that describes the ease with which the vapor molecules diffuse through it and is defined as the quantity of vapor flow across a unit area that will flow through a unit thickness under a unit vapor pressure difference. Vapor diffusion is the movement of moisture in the vapor state as a result of a vapor pressure difference (concentration gradient) or a temperature difference (thermal gradient) and moves moisture from an area of higher vapor pressure to an area of lower vapor pressure as well as from the warm side of an assembly to the cold side. In terms of condensation potentials, when vapor reaches the cold area, the condensation occurs.

Accordingly, we can state that in a thermal enclosure exposed to differential thermal loads, at any rate of vapor diffusion a rate of condensation occurs, somewhere in the field of permeable insulation or assembly, in the area of heat flow exchange.

Discussing materials with vapor permeance or permissive assemblies, the vapor movement is governed by two mechanisms: vapor diffusion and air transport. Vapor diffusion and air transport of water vapor act independently of one another. Vapor diffusion will transport moisture through materials and assemblies in an absence or in opposite direction of small air pressure differences, if a vapor pressure or temperature difference exists. Air moves from cold to warm driven by atmospheric pressure gradient when vapors diffuse from warm to cold driven by the thermal gradient. This is another factor that enforces the existing of condensation in vapor permeable insulations or assemblies. Other phenomenon such air flow, convection, infiltration and exfiltration, thermal bridges associated with air/vapor permeable insulations or assemblies also accentuate the condensation phenomenon.

The definition of condensation in building enclosures may be: as every material has thermal conduction, the warm vapors driven by vapor pressure from warm to cold will condensate by reaching the cold zone that is usually encountered in the field of insulation or wall assembly. More general, in a thermal enclosure exposed to thermal loads, we can state that if vapor moves by diffusion and/or air transport, condensation occur, somewhere between the interior and exterior surface, if the material is permeable to vapor diffusion and/or air transport. This is a fundamental rule to be accepted for design and construction, when there are involved permeable insulation materials.

The object of this patent is to establish another fundamental rule as method, this time for complete avoid condensation and complete eliminate this stress of building components (wetting/draying, water accumulation), people that live in the buildings (mold, fungi) designers and constructors.

Theoretically analyzing a compact insulation material or insulation assembly, the two physical characteristics that generate condensation are thermal conduction which creates the cold dew point zone in the material or assembly and the vapor permeability that allow the vapors to diffuse by the cold zone. Definitely, the thermal flow cannot be stopped; the cold flow (the deficit of energy as heat) has to convert the warm flow in the environmental separator considered.

From the two emergent physical phenomenons, the vapor permeability can be stopped, or reduced from very permeable to impermeable. We can foresee that avoiding condensation is possible only by reducing vapor diffusion and vapor flow, as being the only factor of the equation that can be reduced to zero. The question is how to make a rule, and more provocative, how to apply this law in practice, to avoid condensation in all situations of thermal load variation.

The typical strategies in the relevant art involve vapor diffusion retarders, air/vapor flow retarders, air pressure control, and control of interior moisture levels through ventilation and dehumidification via air conditioning. The location of air/vapor retarders and vapor diffusion retarders varies on the concept of a wall assembly, depending on climate location to optimize the reduction of condensation. Also, vapor barriers and retarders considered for hygrothermal analysis have different gradients of vapor permeability, from semi-permeable to impermeable. Is well known in the art that a complete air/vapor barrier in a wall assembly is the worst as concept, and have to be avoided.

To clearly differentiate a vapor barrier from an impermeable insulation and to differentiate the method as a general concept has to be established appropriate terminology. As for solid body insulation materials is not provided definitive and widely promulgated definitions, this invention defines an insulation material that is impermeable to vapors or tends to zero permeance as a Vapor Impermeable Insulation (VII). Also, vapor impermeable insulation assemblies created by assembling insulation materials and vapor impermeable materials to be defined as Non-Permissive Insulation Assemblies (NP-IA). As a consequence, the avoidance of condensation has to be associated with this terminology, remaining as vapor barriers and vapor permeable insulations to be classified in the category of “manage condensation”. From the prior art, which is rife with confusion, overblown claims and bad design decisions, the exposed method can be a solid argument for concept and practice, the approach in the sense of having or not-having condensation. Both definitions, VII and NP-IA can be further defined as Environment Separators.

This method can be indeed confusing because a complete vapor barrier is the worst thing in an insulation (permeable) assembly while a Vapor Impermeable Insulation is the best configuration for avoiding condensation. A Vapor Impermeable Insulation is different from vapor barrier having a different functionality. The key physical property which distinguishes a Vapor Impermeable Insulation or Non-Permissive Insulation Assembly from a vapor barrier is that a VII is an insulation material that have zero permeance (rate of vapor movement, at a specified thickness), also the NP-IA is a vapor impermeable insulation assembly and perform as a vapor barrier and thermal retarder while a simple vapor barrier is only a vapor separator, lacking the thermal gradient. This method practically combines and associates the physical properties of a material to be thermal insulation and vapor impermeable as key phenomenon to avoid condensation.

A vapor barrier has two surfaces, but both surfaces have the same temperature, at a specific point of thermal flow. When a difference of temperature exist, at a certain time the vapor barrier became a condensation surface for the warm vapors, on the side exposed to the vapor flow.

A VII or NP-IA is configured as two vapor impermeable surfaces, separated from an insulation field. If the insulation value is in accordance with the thermal loads, the heat flow pass the warm side surface of VII/NP-IA and the temperature of the surface raise above the dew point, so as the condensation does not occur. The warm flow will pass the warm side surface into the field of insulation, and convert the cold flow in the field of insulation. If the warm vapors of the warm side of the Environmental Separator[:] VII or NP-IA does not penetrate into the insulation to reach the cold zones, the condensation is avoided.

The condensation problem became a lot simpler. The heat flow has to warm the exposed surface or the wall assembly in contact with warm vapors, separated from a VII or NP-IA by the cold environment. The warm side surface of VII/NP-IA and the air/vapor permeable volumes in the warm side has to accumulate enough heat to maintain a temperature above the dew point. The temperature of VII or NP-IA interface has to be on the range of dew point temperature limits, given by factors such Relative Humidity, Vapor Temperature or Vapor Pressure, so as the temperature of the first condensing surface within the wall assembly, namely the warm side insulation interface is raised above the dew point because of the insulation value of the VII/NP-IA. The key element set to be a zero rate of vapor diffusion state that warm vapors drive by the vapor pressure to not pass the interface surface of warm side of the VII/NP-IA. When the insulation value is dimensioned in relation to the thermal loads (heat flow versus cold flow), the heat flow convert the cold flow in the field of insulation, as stated in the conduction physical properties of the insulation material. The conversion is a three dimensional area where usually is encountered the dew point temperature in relation to the warm vapors, this zone being remote from the warm side surface. As in VII/NP-IA is considered that air transported moisture and vapor diffusion is complete eliminated, the vapor reaches only a dew-point-free temperature at a first condensing-free surface.

The term cold is misnomer scientifically. Temperature values are from absolute zero (0° K., −273.15° C., −459.67° F., etc.) to infinite, the heat to which it refers is always relative to a reference system. This makes it useful to adopt a reference temperature for a particular system considered.


In terms of physical and thermodynamically, the calculation of energy as heat takes in consideration the Kelvin scale, so as is reported to absolute zero, the minimum possible of thermal energy where is considered that any atomic and molecular movement stops. Consequential, heat has only positive values. To maintain a system in equilibrium is need an intake or deficiency of heat that compensates a lack of energy or decompensates a surplus of heat energy around a reference value.

The reference temperature currently adopted is the freezing temperature of pure water, at the base atmospheric pressure, accepted as the zero degree on Celsius scale. Apparently, Celsius scale makes the first reference to warm and cold by freezing and thawing of water, but normally this reference is made by people in relation to human activity.

Without taking in consideration a reference temperature, we can say that iron melts at very cold because on the Sun is currently over one million ° K. and at North Pol is very hot as against Pluton where current temperature is 50° K. However, human exposure even for short time at such temperatures becomes fatal.

Appears therefore the need of adopting a reference temperature in relation to the human activity relative to the current needs of the large public. This exposure proposes to adopt reference temperature for human activity in value of 70° F. (≈21° C.) and a reference interval of 18÷24° C. The 21° C. (70° F.) represents an optimum of comfort temperatures to be achieved for human activity, function of systems and utilization of materials.

In general, temperatures above 24° C. (75.2° F.) are perceived as hot and temperatures below 18° C. (64.4° F.) are received as cold. For humans in general and for construction in special is a purpose in itself to bring and maintain the ambient in the temperature reference interval mentioned. Thus, the heat deficit must be compensate by contribution of thermal energy (generating of heat) and the excess of heat has to be decompensate through a deficit of thermal energy (generating of cool), so as the ambient system to be achieved is maintained in the comfort interval or the reference interval.

As definition, we can say that the reference temperature 21° C. or 70° F. is the temperature against which currently humans feels the warm and cold and makes it possible to define heat and cold in the acceptance of human perception. Practical, the human existence and activity is carried around this value of temperatures, not in relation to zero absolute and not even in relation to frizzing temperature of water, 0° C.

Because the human temperature reference interval is extremely narrow compared to the infinity of thermal values, is considered justified to record this value by adopting the reference temperature and interval 21° C.±3° C. The zero degree of reference thermal energy becomes heat corresponding to a system having the temperature 21° C.

The warm flow is represented by the quantity of energy transferred as heat from a system having temperatures above the reference temperature and compensates a deficit of thermal energy so as the system temperature is raised toward the reference interval.

The cold flow is represented by the deficit of energy as heat of a system which decompensates the transfer of thermal energy from the reference temperature so as the temperature system is lowered toward the reference interval.

Further features and advantages of the present invention will become more apparent from the following description taken in connection with the diagrammatic drawing wherein:

FIG. 1 schematically shows a sectional view of an insulation considered vapor impermeable, exposed to differential thermal loads, and a diagrammatic figuration of the temperatures in relation with the dew point afferent to the hygrothermal conditions of the warm vapors.


Considering an enclosure separated to the exterior environment by a Vapor Impermeable Insulation or Non-Permissive Insulation Assembly 5, FIG. 1 shows in section the heat transfer from Ti Warm to Te Cold. The thickness of insulation 4 leads to an R-value that confers the possibility that the Heat Flow to “push” the Dew Point temperature from the surface Si in contact with warm vapors. The first volume 1 of the VII/NP-IA, including the interior surface Si becomes a Dew Point Free Zone in relation to the warm vapors condensation conditions Ti, RH (Temperature of interior air and vapors, Relative Humidity). The Heat Flow converts the Cold Flow in a three-dimensional zone 2 which can be assimilated with a Dew Point Limit where the warm vapors can condensate if reach to that zone. As stated, in VII/NP-IA vapors doesn't pass the interior (warm) surface Si as being considered vapor impermeable insulation materials/assemblies, so as the condensation does not occur.

If the insulation material/assembly considered is permeable (vapor diffusion and/or air transported vapors), the Dew Point Limit 2 become the Condensation Zone for warm vapors that reach in to this zone. The volume 3 affected by the Cold Flow is considered a Dew Point Zone where warm vapors certainly will condense, if transported in terms of permeability.

In the condition of a high R-value of a VII/NP-IA 5 the Temperature Tis of the interior (warm) surface Si becomes approximately equal to the interior (warm) temperature Ti of air/vapors, so as the surface Si in contact with vapors certainly cannot be a condensation surface. The interior (warm) surface of VII/NP-IA can be extended and assimilated with a wall frame, sheathing or even a cavity wall, and as long the Si considered as volume is in the range of the Dew Point Free Zone 1, “cold protected” by the VII/NP-IA insulation 5, the condensation does not occur, even this volume is permeable. A permeable wall volume attached to a VII/NP-IA with high-insulation value can be considered as any other object of the environment, considered in the context of condensation.

The diagrammatical figuration 10 shows a schematic variation of temperatures in view of Dew Point in relation with interior (warm) vapors. If the difference between the warm temperature Ti and colt temperature Te is in a normal range (Ex. Ti=20° C. and Te=0° C.) the Dew Point Free Zone 1 will decrease to an axial volume of the VII/NP-IA 5 where the Dew Point Limit 2 (condensation zone) in relation to warm vapors can occur. If difference of temperatures is extreme (Ex. Ti=20° C. and Te=−20° C.) the Dew Point Free Zone 1 will usually get smaller, the Dew Point Limit approaching to the interior surface Si. This is where the R-value and the thickness 4 of the VII/NP-IA 5 have to be dimensioned so as the Dew Point Limit 2 in extreme temperature conditions to not interfere with the interior surface Si, so as to avoid that Si to become a condensation surface.

This is the only rule that has to be considered if an insulation or wall system is the VII/NP-IA 5 described, to achieving the goal to avoid condensation. Usually, the insulation is dimensioned to reduce energy loss, for this purpose aiming a smaller conversion of heat flow in a longer time, surpassing the goal of avoiding condensation condition.

The seemingly innocuous requirements for air/vapor permeable building envelope assemblies bedevil builders and designers because the techniques that are effective controlling condensation in cold climates becomes ineffective in hot-humid climates and vice versa, and it gets even more complicated because of the seasons.

The good news is that in VII/NP-IA 5 that comply the Principle to Avoid Condensation, the situation presented can be reversed at any time, so as the cold side to become warm (hot-humid season) and the warm side to be cooled by air conditioning (cooling and humidity control), without any effect change in relation to the condensation phenomenon. The simple rule in VII/NP-IA 5 is that the surfaces and vapors in contact to have similar temperatures (in the range of Dew Point Free in accordance with vapor characteristics) and the vapors to not pass the first insulation surface.

By the facts exposed is established a principle as method and general rule for avoiding condensation.


The principle to avoid condensation can be enunciated thus:

    • When differences of temperature exist, and an enclosure is interposed between the interior higher temperature and the exterior lower temperature (or vice versa), to avoid condensation, the heat flow have to convert the cold flow (heat deficit) in an insulation material or insulation assembly without vapor diffusion or any air/vapor flow that transport warm vapors towards cold zones.

After a deep understanding of the phenomenology and configuration of Vapor Impermeable Insulations or Non-Permeable Insulation Assemblies, the Principle to Avoid Condensation can have a simple enunciation:

    • The condensation is avoided when the heat flow convert the cold flow in a Vapor Impermeable Insulation or a Non-Permissive Insulation Assembly.

Like other devices and assemblies created before on principles ulterior enunciated, in the prior art exist constructive elements or assemblies as would be window panels, sandwich panels etc. that follow the principle to avoid condensation, without it being enunciated and considered as a principle itself. The knowledge of this principle arrive as a starting point in designing insulated enclosures and in any situation where is meant to avoid condensation. Even if this patent is for a method, the utility of this principle cannot be ignored.

The term “permissive” includes all ways in which air/vapor leakage affects and interacts with the enclosure, as would be: vapor diffusion, enclosure air flow (airtightness), infiltration/exfiltration, wind washing or forced convection, looping in air permeable insulation, looping through gaps around insulation, water absorption and capillarity. In the “non-permissive” insulations, all these factors are eliminated, remaining only the thermal conduction and heat flow analysis, with the presumption that the problems of condensation are eliminated. Also, the true R-value is not affected by permissive feature.

In practice, the theory of non-permissive insulations separates the insulation from the wall structure, so as the insulation have the role of separating the warm environment from the cold environment, including the passage of vapors (through the insulation), when the wall has the structural role. A Non-Permeable Insulation Assembly is applied preferably continuous on the exterior of a support wall. The structural wall can be made less air tightness, so as the unidirectional drying (breading) is easily realized. The NP-IA takes the role of the environmental separator that keeps the substrate wall dry and performs the saving of energy as heat with outstanding benefits for building and occupants. The actual concept of walls having air/vapor flow all the way from interior to exterior (from warm to cold) is a wrong concept that leads to the problems generated by the wetting/drying cycles, when the NP-IA applied on the exterior of wall is the best configuration that only dries the substrate wall and transpose in practice the theoretical (in laboratory) insulation coefficients of material.

As is apparent from the foregoing specification, the exposed method is suitable of being embodied with various constructive situations. A selective illustration is required, so as the understanding of basic features to be more clear distinguishable.

A material that partial follows the method of Principle to Avoid Condensation as VII is the wood. For exemplification, an exterior wood door having a thickness of 5 cm (2 inch) does not make condensation even the difference between interior and exterior temperature is significant. The wood have an R-value approximately 1/inch, so for 2 inch, R=2. This insulation is sufficient to enable the interior (warm) surface of door to have a temperature higher than dew point. Also, wood have a very low vapor-permeability, and the protective layers (varnish and paint) makes wood even more impermeable. Thereby, condensation is avoided and the rate of wetting from condensation is insignificant. In other words, condensation is practically avoided, but theoretically small increases of humidity in wood exist because of vapor diffusion.

A different exemplification is the apparently of avoiding condensation. A wall made of massive assemblies of non-water sensitive materials such as brick masonry that have a middle to low insulation value, have the interior surface and a portion of wall in the zone of dew point free 1. The warm vapors diffuse to the dew point limit 2, inside the wall and condensate. The condensation water is stored in the mass of wall assembly in the cold seasons until drying by diffusion (evaporation) that occurs to either the exterior or interior in the warm seasons. Apparently, the principle to avoid condensation is accomplished because on the interior surface of wall condensation does not occur, and the wall has only a small increase of wetting. In fact, the principle to avoid condensation is not accomplished because of vapor diffusion in the mass of wall, the vapors condensing in the zone of dew point limit 2 without any deterioration of the wall.

When vapor permeable materials are used in the configuration of wall and the materials are water/moisture sensitive, usually the accumulated moisture exceeds the safe of tolerable wetting storage capacity of material and deterioration occurs.

It should be known that analytical techniques used to predict condensation potential and teachings saying that condensation can be avoided by the judicious use and placement of insulation and breathable and retardant materials are only for reducing the effects of wetting and drying, but this cycle is not removed.

The benefits of avoiding condensation and use of the full insulation coefficient of the insulation (laboratory test R-value) are likely to occur only if the principle to avoid condensation is applied. The resultant enclosure will show very satisfactory weather resistance and insulation without any need of preventing the wetting effects. All of these, by preventing vapors to diffuse to an insulation system, or otherwise said, insulation assemblies have to resist to vapor pressure.

The most relevant exemplification of a NP-IA that meet in practice the principle to avoid condensation are the so called “sandwich panels” composed by an air/vapor-impermeable insulation core in the form of closed cell polyurethane foam or polyisocyanurate, wrapped with metal. Even more relevant in this category are the vacuum insulated panels composed with insulation cores of aerogel, silica fume, glass fiber and open cell foams, and wrapped with a vacuum-tight wrapper, usually a metal or metalized plastic film to maintain the vacuum. As is easy to understand, those Insulation Assemblies are air/vapor impermeable or Non Permissive because at least the metal wrapper is a complete air vapor barrier, and the way is assembled creates a NP-IA. Widespread products have a very long track record of performance as heat flow control layers, air/vapor and water tightness, for wall and roof systems in applications for commercial buildings, without any report of condensation problems. Used in regions with varying climatic loads and extreme temperature and vapor parameters differential, to have condensation on the inward panel surface is practically impossible, even the level of relative humidity is close to saturation. The explanation becomes obvious: the inboard surface have approximately the temperature of interior vapors, the R-value of insulation easily maintain this temperature, the insulation panel resist to the vapor pressure and the warm vapors does not diffuse to the conversion zone of potential condensation. Along with condensation, the air/vapor tightness of sandwich panels cladding eliminates the infiltration/exfiltration heat loss in both cold and hot climate building enclosures, is removed the source of moisture in the building enclosure contributing to durability and health issues, all those by fulfilling the Principle to Avoid Condensation.

In the same category of NP-IA, and very convincing as exemplification can be included the window panels. Is well known that an average window panel is made of two glass panels separated by an inert gas that performs as insulation, the glass panels being sealed all around to create a complete air/vapor tight Insulation Assembly. The heat flux allowed to occur to window panels, during a cold winter day has long been much larger than through walls. A window panel with a U-value of 0.35 allows about five times as much heat flow on a cold day than a throe R20 wall enclosure (R20, common R-value for sandwich panels). The glass is known as the most propitious surface for condensation. Nevertheless, even in a cold day, we don't see any moisture on the window. Knowing the Principle to Avoid Condensation, the explanation became simple: the heat flow warm the interior glass surface and raise the condensing surface temperature above the dew point, the inert gas insulation keeps this temperature in the limit of dew point free, and because the Insulation Assemble is air/vapor impermeable, all problems of condensation are avoided. The situation where the dew point zone 2 occurs on the inward window surface is very rarely encountered.

In the category of Vapor Impermeable Insulations can be included the development of a wider range of closed cell, spray foam products. Closed cells sprayed polyurethane insulation forms a seamless bond with building components and creates an insulation and air/vapor-infiltration barrier, together with the physical property of closed cell polyurethane foam to have very low vapor permeability. The first condensing surface of polyurethane foam is warm, the other elements or surfaces in contact with warm vapors are kept warm because of the insulation value, and if vapors don't migrate to cold dew point zones, the condensation is avoided. Comparative studies carried out on wall cavity closed-cell spray applied polyurethane foam insulations and other air/vapor-permeable insulations, reveals that the analysis reports a zero hours of potential winter time condensation for cavity sprayed foam, compared with the permeable insulations that have thousands potential winter time condensation hours.

Installing continuous layers of rigid and semi-rigid vapor impermeable insulation materials such extruded polystyrene or faced boards is one of the preferred methods of increasing enclosure performance. Insulation systems developed by prestigious companies such BASF, Dow, Owens Corning uses sprayed foam and extruded polystyrene, products that acts as rain, air, vapor and heat flow control of an assembly. Products such XPS insulation boards and spray foam are particularly Vapor Impermeable Insulations but only installation methods that provide continuity at joints and sealing at intersections can make those products to perform as a Non-Permissive Insulation Assembly, in the spirit of Principle to Avoid Condensation. However, the use of VII materials led to spectacular results on wetting control, evidenced by a much smaller number of potential condensation hours.

The NP-EIFS, (US 2011/0258944 A1) is an Exterior Insulation and Finish System invented to solve all problems related to these systems. NP-EIFS is based on the Principle to Avoid Condensation, without enunciating or even mentioning this fact. The concept, materials used, application technology and the details presented leads to an EIFS that complete avoid condensation and intruding water. VII materials such XPS and closed-cell expandable polyurethane foam are used in combination with polymer based sealant materials to create an air/vapor-impermeable insulation assembly. The joints between VII boards are double sealed with expandable foam and polymer sealant, and the intersections with other constructive elements are triple sealed with expandable foam, polymer sealant and silicone sealant. All details of intersections, penetrations and terminations of the system are designed to complete avoid air/vapor infiltration, vapor diffusion and thermal bridging, so as VII materials are assembled to create a NP-IA that comply with the Principle to Avoid Condensation.

An experimental wood facility having installed NP-EIFS as cladding has been tested in the very cold December of Chicago. Three days after starting the heat inside, the wood frame decrease in humidity from 11% to 8% and the sensors installed between insulation and OSB sheathing doesn't show any sign of condensation. This leads to the fact that NP-EIFS installed as cladding creates the only wall system that dries in the cold seasons, all other vapor permeable wall systems accumulating water. NP-EIFS preserves the frame, unlike vapor permeable insulation systems and the related wetting-drying cycles that leads to mold and degradation. In the hot-humid summer of Atlanta, the wood frame humidity of the experimental facility remains constant.

It is good to mention that a NP-IA is the only insulation system that can be installed as interior insulation, without having condensation and mold problems. The insulation value retain the heat flow while the thermal conductivity of non-insulation exterior wall conducts the cold flow through the inner surface of wall assembly, so as behind the interior applied insulation is a permanent dew point surface for the interior warm vapors. Any flux of vapors leads to moisture, right behind insulation. If the insulation system is a NP-IA, vapors don't reach the cold dew point zones, and the condensation is avoided.

Here a question arises: what's happen behind insulation, if the insulation doesn't “breathe”?

If NP-IA is applied as interior insulation, vapors don't pass the insulation and there is no condensation, but the conductivity of insulation still allows a small heat flow that will create a slightly positive vapor pressure immediately behind insulation, and the vapors will have the tendency to move out. This means that applying a NP-IA as interior insulation, the wall will dry, instead of accumulating water.

If the NP-IA is applied normally, on the cold side of the wall, the wall accumulates the heat and the temperature is maintained above the dew point in the entire wall assembly, so as the condensation does not occur. The experiment made on NP-EIFS reveals that the walls dry inwards.

Applying the concept of Principle to Avoid Condensation eliminates condensation both ways regardless of the thermal perspectives, being the only good solution to separate two environments, without having the condensation stress.

It is good to know that, when vapors are stopped, water has no chance. This means that non-permissive insulations can have also the utility of waterproofing.

As is apparent from the foregoing specification, the principle is susceptible of being embodied with various enunciations and formulations which may differ particularly from those that have been described in the preceding specification and enunciation. For this reason, it is to be fully understood that all of the foregoing is intended to be merely illustrative and is not to be construed or interpreted as being restrictive or other-wise limiting of the principle, excepting as it is set forth and defined in the hereto-appended claims.