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Building Science for ArchitectsIntroductionBetsy Pettit, AIAwww.buildingscience.com 2005 Building Science CorporationPR-0510a: BuildBoston 2005—Building Science for Architects IntroductionPage 1 of 24
Why Do Architects Need toUnderstand Building Science?Q: What is Building Science?A: The study of heat flow, air flowand moisture flow through thebuilding enclosure 2005 Building Science CorporationPR-0510a: BuildBoston 2005—Building Science for Architects IntroductionPage 2 of 24
The requirements for our buildings have changed We live in a society where every citizendeserves healthy, affordable,comfortable and durable homes andwhere the population is steadilyincreasing We demand more comfort and control ofour interior environments than we usedto so will not tolerate conditions that weused to tolerate We have a limited supply of energy(Hubbard’s Curve) and so we have tothink about energy conservation 2005 Building Science CorporationPR-0510a: BuildBoston 2005—Building Science for Architects IntroductionPage 3 of 24
What is different about the way we build today? We have added thermal insulation Tigher Building Assemblies– We have gone from board sheathing tosheet goods, reducing air leakage intoand out of assemblies We have removed active chimneys andreplaced them with power vented sealedcombustion furnaces. We have become an air conditioningsociety (and that requires ducted airdistribution systems) We have more new products to deal with,and these new products are gettingcombined in new ways 2005 Building Science CorporationPR-0510a: BuildBoston 2005—Building Science for Architects IntroductionPage 4 of 24
What Happens When Buildings Don’t Work? We waste energy We waste materials People are uncomfortable Conditions are unsafe Conditions are unhealthy Components or systems fail 2005 Building Science CorporationPR-0510a: BuildBoston 2005—Building Science for Architects IntroductionPage 5 of 24
Your Environmental Separator At the most basic level a building provides shelter shelter from the elements as well as from other dangers. Its’ function is to separate the inside from the outside asrequired by the local environment and the wishes of itsoccupants. A building creates an interior environment that isdifferent from the exterior environment – it is anenvironmental separator. This interior environment should be controllable by theoccupants in a manner that meets their needs. 2005 Building Science CorporationPR-0510a: BuildBoston 2005—Building Science for Architects IntroductionPage 6 of 24
The Building System - Functional Relationships 2005 Building Science CorporationPR-0510a: BuildBoston 2005—Building Science for Architects IntroductionPage 7 of 24
Building Science Building Science studies the interaction ofall of these functional relationships It tells us how buildings actually work It tells us how to design them, build them,diagnose them, fix them and operate them. 2005 Building Science CorporationPR-0510a: BuildBoston 2005—Building Science for Architects IntroductionPage 8 of 24
Building Science Energy moves from higher state to lower state– (the second law of thermodynamics) Heat moves from warm to cold (thermal gradient) Moisture moves from more to less (concentrationgradient) This is the thermodynamic potential– The psychrometric chart is a visual representation of thethermodynamic potential of water vapor It takes even more energy to counteract thisphenomena 2005 Building Science CorporationPR-0510a: BuildBoston 2005—Building Science for Architects IntroductionPage 9 of 24
2005 Building Science CorporationPR-0510a: BuildBoston 2005—Building Science for Architects IntroductionPage 10 of 24
Building Science Not all forces are equal All are important, but some are moreimportant than others Control of heat, air, moisture and radiation(HARM) stand above the rest 2005 Building Science CorporationPR-0510a: BuildBoston 2005—Building Science for Architects IntroductionPage 11 of 24
Building Science It is a science, not an art There are actual physical laws that tell us howthis all works. Everyone has opinions, but we now have the toolsto answer fundamental questions on buildingperformance The laws of physics always win over opinions 2005 Building Science CorporationPR-0510a: BuildBoston 2005—Building Science for Architects IntroductionPage 12 of 24
What does a modern building need to do?1.2.3.4.5.Control rain and ground waterControl heat flow, airflow, and water vapor flowControl light and solar radiationControl noise and vibrationsControl contaminants, environmental hazardsand odors, insects, rodents and vermin6. Control fire7. Provide strength and rigidity8. Be durable9. Be aesthetically pleasing10. Be economical 2005 Building Science CorporationPR-0510a: BuildBoston 2005—Building Science for Architects IntroductionPage 13 of 24
Why Mold, Why Now? Things are staying wetter longer.And the wet things can’t take it. The dwell time for moisture in thesystem is going up while thesystem ability to tolerate themoisture, store the moisture orredistribute the moisture is goingdown This is a rate-storage problem It’s all about energy 2005 Building Science CorporationPR-0510a: BuildBoston 2005—Building Science for Architects IntroductionPage 14 of 24
Historical Perspective All drying requires the exchange of energy. Heat flow is from warm to cold.Moisture flow is from warm to cold & more toless. Old un-insulated buildings that were heatedduring the winter were simultaneously kiln driedand freeze dried. As we reduce energy flows across enclosuresthe drying potential is reduced. Adding thermal insulation reduces dryingpotentials. Making walls more air tight reducesdrying potentials. 2005 Building Science CorporationPR-0510a: BuildBoston 2005—Building Science for Architects IntroductionPage 15 of 24
Reduction in Drying Potentials We have reduced the water vaporpermeability of the linings we install onboth the interior and exterior of thebuilding enclosure. Polyethylene vapor barriers and vinyl wallcoverings prevent walls from dryinginward during the summer. OSB sheathings reduce outward drying andfoam sheathings reduce outward dryingduring the winter. 2005 Building Science CorporationPR-0510a: BuildBoston 2005—Building Science for Architects IntroductionPage 16 of 24
Increase in Moisture and Mold Sensitivityof Construction Materials The moisture and mold toleranceof building assemblies is beingreduced as we move down theprocess stream from timber toengineered materials. Board Lumber - Plywood - OSB Hardboard - Particle Board - Paper The use of paper-faced gypsumsheathing in wet areas results inserious consequences. 2005 Building Science CorporationPR-0510a: BuildBoston 2005—Building Science for Architects IntroductionPage 17 of 24
Reduction in Moisture Storage and MoistureRedistribution of Building Materials The moisture storage capacity of buildingassemblies has decreased two orders of magnitudeover the past century!Example2,000 square foot buildingMasonry 500 gallons of waterWood Frame 50 gallons of waterSteel Stud 5 gallons of water 2005 Building Science CorporationPR-0510a: BuildBoston 2005—Building Science for Architects IntroductionPage 18 of 24
Three things destroy most buildings: WaterHeatUltra-Violet Radiation Of these three, control of water is the most important, followedby heat and finally followed by sunlight. Water and heat causethe vast majority of building durability problems A great deal of water can be transported by air. And water isoften referred to as “moisture”. Hence the acronym “HARM” 2005 Building Science CorporationPR-0510a: BuildBoston 2005—Building Science for Architects IntroductionPage 19 of 24
Building Science Control of heat, air and water deals withover 80 percent of the problems faced bythe construction industry. Heat, air, water and radiation (HARM)control are the key to building science 2005 Building Science CorporationPR-0510a: BuildBoston 2005—Building Science for Architects IntroductionPage 20 of 24
Building ScienceH A M (heat, air, moisture) Heat, air and moisture control worktogether Heat control is the same everywhere Air control is the same everywhere Moisture control is differenteverywhere 2005 Building Science CorporationPR-0510a: BuildBoston 2005—Building Science for Architects IntroductionPage 21 of 24
The Rules1. Heat Flow is From Warm to Cold2. Air Flow is From a Higher Pressure to a Lower Pressure3. Moisture Flow is From Warm to Cold4. Moisture Flow is From More to Less5. Gravity is Always Down the earth “sucks” 2005 Building Science CorporationPR-0510a: BuildBoston 2005—Building Science for Architects IntroductionPage 22 of 24
Climate Dependence of Building Design Buildings should be suited to their environment. It is not desirable to construct the same manner of building inMontreal, Memphis, Mojave and Miami. It is cold in Montreal, it’s humid in Memphis, it’s hot and dry in Mojaveand it’s hot and wet in Miami. And that’s just the outside environment. It is also not desirable to construct the same manner of building toenclose a warehouse, house, school, office, health club with aswimming pool, hospital or museum. The interior environment also clearly matters. 2005 Building Science CorporationPR-0510a: BuildBoston 2005—Building Science for Architects IntroductionPage 23 of 24
Firmness Commodity DelightThese are properly designed, when due regard is had tothe country and climate in which they are erected. For themethod of building which is suited to Egypt would bevery improper in Spain, and that in use in Pontuswould be absurd at Rome: so in other parts of the worlda style suitable to one climate, would be very unsuitable toanother: for one part of the world is under the sun'scourse, another is distant from it, and another, betweenthe two, is temperate.Marcus Vitruvius Pollioc. 90 – 20 B.C.E. 2005 Building Science CorporationPR-0510a: BuildBoston 2005—Building Science for Architects IntroductionPage 24 of 24
2005 Building Science Corporation At the most basic level a building provides shelter -
