Chapter 7 – Thermal and Moisture Protection Book NotesSustainability Considerations- Materialso Some cellulose products contain as much as 85% recycled materialso The energy needed to produce a pound of cellulose insulation is only a small fraction of the energy required to produce a pound of glass wool, mineral wool, orfoam insulation- Designo Roof overhangs can be used to reduce the amount of sunlight falling on walls and thereby reduce the cooling loado The color of the roofing can affect heating and cooling loads Lighter shades reflect sunlight and reduce cooling loads Darker roofing increases absorption and reduces heating loads Selection of roof coloring is influenced by location- In southern areas where cooling is the major problem, lighter shades are better- In northern areas where heating is the major problem, darker shades are better Some roofing manufactures make dark colored shingles containing a product that reduces the heat absorption of the shingleso Properly oriented roofs can act as a platform for solar collectorso Green roofs that reduce stormwater runoff, reduce noise, and reduce energy consumption Downside is that they need to maintain the vegetation more ofteno A roof can be designed to capture and hold rainwater for eventual distribution to aholding pond on the site or into a storm drainage system to control the quantity of water that is introduced into the drainage system at one timeo Roofs should be designed to sustain long-time performance Defined as a 30-year minimum standard, but longer term performance can be achievedMasterFormat- 07 10 00 – Dampproofing and Waterproofing- 07 20 00 – Thermal Protection - 07 30 00 – Steep Slope Roofing- 07 40 00 – Roofing and Sliding Panels- 07 50 00 – Membrane Roofing- 07 60 00 – Flashing and Sheet Metal- 07 61 00 – Sheet Metal Roofing- 07 62 00 – Sheet Metal Flashing and Trim- 07 63 00 – Sheet Metal Roofing Specialties- 07 65 00 – Flexible Flashing- 07 70 00 – Roof and Wall Specialties and Accessories- 07 80 00 – Fire and Smoke Protection - 07 90 00 – Joint ProtectionMoisture Control - Introductiono Many designers do not give adequate consideration to preventing water penetrationo More than half of the lawsuits involving architects are related to water leakso As absorbed water, moisture is present in most construction materials and affects their properties, especially dimensional stabilityo Moisture is not damaging to construction in its vapor form, however, it becomes dangerous as it condenses/thaws (liquefies) or freezes (solidifies)o Condensation and freezing may occur as a result of either a temperature drop or the migration of water vapor to areas of lower temperature In cold climates in heated occupied buildings, which generate substantial amounts of water vapor In warm, humid climates in cooled buildings- Water Vapor Movemento Water vapor becomes a hazard when it condenses (thaws) inside the structural cavity of a floor, wall, or roof assembly Here it can reduce the effectiveness of insulating materials and cause organic material to decay, metals to corrode, and protective coatings to deteriorateo Air with more vapor has a higher vapor pressureo Vapor moves through air by diffusion from regions of high vapor pressure to regions of lower pressure without relying on air circulation to carry it o Vapor pressure is commonly expressed in inches of mercury (Hg)o During cold weather, the difference in pressure between inside (higher pressure) and outside environments (lower pressure) causes vapor to move out through every available crack and directly through permeable materials- Adsorption and Absorptiono Adsorption – Accumulation (steadily increasing until reaching equilibrium) of the species at the surface rather than in the bulk of the solid or liquid  The process in which atoms, ions or molecules from a substance adhere to a surface of the adsorbent Film of water molecules that gets thicker as humidity rises Molecules will stick to the surface of an object and will accumulate on ito Absorption – Assimilation (occurring at a uniform rate) of molecular species throughout the bulk of a solid or liquid  The process in which a fluid is dissolved by a liquid or solid Molecules will actually pass through the surface of an object as they get toits surface without sticking to it like in adsorption o Hygroscopic materials – materials that tend to absorb moisture from the air Fibrous materials such as wood, plywood, and fiberboards present very large surface areas to water molecules, so that the amount of water held onthe surface, and subsequently absorbed into these materials through surface pores, is relatively large even at moderate humidities Materials that present relatively small surfaces, such as most metals, are not penetrated by water molecules and take only small amounts of water as surface filmo Problems that arise from Adsorption and Absorption  Dimensional Instability- When a material does not maintain its essential or original dimensions while being used for its intended purpose- Changes in moisture content can cause significant dimensional changes in construction materialso When wood is dried from an air-dry condition (12% or 25% moisture content) to an oven-dry condition (0% moisture content) it shrinks about 0.1% longitudinally, 2% radially, and 4% tangentially- The continuous movement of dimensionally unstable materials must be carefully considered in building design and detailing Deterioration of Materials- Moisture can cause or contribute to the breakdown of materialso Chemical changes such as the rusting of steelo Physical changes such as masonry spalling by frost action o Biological process such as wood decay- Measures to control liquid water (other than water vapor) include dampproofing and waterproofing, flashing, and storm drainage Condensation Tolerance of Materials- Some materials are able to tolerate condensation with little damage; others are noto Metal panels in refrigerated storage boxes almost contain a frost coating with no resulting damage- Some materials can store condensation with little or no effecto Concrete Masonry Units (CMU) can easily have their saturation level raised from 40% to 50% by absorbing condensation without being noticeableo Metal panels absorb little moisture, but can rapidly release collected moisture or frost though evaporation when weather conditions change Effect on Heat