ASHRAE Journal - August 2011 - 67

make it are predominantly (75% to 85%) recycled, the cost of raw materials is low. Cellulose insulation comes in many forms and is thus applicable to walls, ceilings and roofs, and floors.14 Like fiberglass, mineral wool is another form of insulation that is available in blanket and loose-fill forms. There are varying types of mineral wools based on the material base: rock wool is made from basalt or diabase, while slag wool is made from furnace slag. Mineral wools are usually made from a mixture of various natural and recycled materials. On average, mineral wool is comprised of 75% recycled materials, with at most 90% recycled materials.15 Though it has R-values between 3.5/in. to 5.5/in., superior fire resistance (can withstand temperatures above 2,000°F [1093°C] before melting), and resistance to insects and rodents, it is not commonly used in U.S. residential construction. However, it is prevalent in U.S. commercial and industrial construction, as well as in all types of European construction.7 Exterior insulation is one of the key ways in which superinsulated buildings are achieved through retrofit and new construction. Without exterior insulation, the exterior wall cavities of a home would need to be significantly thicker than normally constructed, significantly intruding on interior floor space. Polystyrene and polyurethane components comprise the majority of exterior foam board options. Polystyrene is a thermoplastic that is manufactured by fusing small beads of the material (expanded polystyrene [EPS]) or is formed from shaping molten material (extruded polystyrene [XPS]).9 Polyurethane insulation is a closed-cell foam with trapped low conductivity gas pockets; these gas pockets give the foam its high R-value by reducing heat transfer. Polyurethane foams can be either petroleum or soy based. As rigid foam sheets with a foil facing, the foam maintains its R-value for at least a decade. Polyurethane foam can also be sprayed into wall cavities. As the material settles and the gas is replaced by air the R value decreases or settles over time.11

Alternative insulation types
Aerogel insulation has a high R-value, but is expensive and therefore rarely used. It provides the highest R-value per inch because it is composed of silica (silicon dioxide) that is processed such that the end product is 95.7% to 99.8% air, with 20 nm pores. Aerogel insulation protects against all modes of heat transfer—convection, conduction, and radiation: • The pore size eliminates airflow, preventing convection. • Silica aerogels absorb IR radiation, and when impregnated with carbon, they can absorb a greater amount of IR radiation, overall reducing radiation heat flow.* • Silica is a poor heat conductor.16 Sheep’s wool insulation is environment-friendly and as insulating as more conventional insulating materials.
* Carbon-impregnated aerogels are more pertinent to high-temperature applications

The production of wool batts requires 14% of the energy used to make glass fiber insulation. Eighty-five percent of the batt is sheep’s wool, the remaining 15% is polyester. Sheep’s wool is hygroscopic; in cold weather, heat is absorbed from moisture in the air, and in warm weather the release of moisture cools the batt. These properties protect the insulation from condensation buildup, as well as help maintain internal house temperature.17 It is considerably more expensive than conventional insulating materials. Superinsulated construction incorporates more insulation as well as modified wall structures. The walls are designed to hold the increased insulation and to minimize or even eliminate thermal bridging. This is accomplished through exterior insulation, aerogel stud strips, or double-stud walls. Conventional means are used cooperatively to achieve the highest performance possible. When constructing or installing superinsulating walls, the air barrier is placed behind enough of the insulation to minimize the potential creation of a condensation plane. By keeping the barrier significantly insulated, it stays consistently warm enough to prevent condensation. As the superinsulated home is designed to be airtight, air exchanges are achieved through a mechanical (fan-forced) ventilation system. Heat recovery or energy recovery ventilators are most commonly used. A heat recovery ventilator uses exhaust air to preheat the entering fresh air by running the two airstreams through a counterflow or cross-flow heat exchanger. An energy recovery ventilator, in addition to preheating the fresh air with exhaust air, also recovers moisture, thereby controlling indoor relative humidity. The indoor moisture content indicates the effectiveness of the ventilation system as designed. In cold weather, condensation on window panes and other surfaces indicates too few air changes. With the home sealed to be airtight, it is necessary to design any combustion-based heating equipment to be sealed from the house, using only outdoor air as combustion air. By doing this, flue gas backflow is prevented from entering the residence, which could cause harmful indoor air contamination.1 Heat is generated in the home via nonconventional sources (intrinsic sources), such as appliance waste heat; body heat; solar radiation; and backup heat sources such as wood-burning stoves, downsized natural gas furnaces, ground- or air-source heat pumps, or electrical resistance heaters. The rate of heat loss is so low that it has been possible for one superinsulated house to maintain an internal temperature between 64°F and 68°F (18°C and 20°C) during Madison, Wis., winter months without any conventional backup heat.18 Superinsulated homes are versatile. As they are designed to be thermally efficient, they can both keep heat outside (in warm weather) or inside (in cold weather), making them suitable for varying climates.
ASHRAE Journal 67

August 2011



ASHRAE Journal - August 2011

Table of Contents for the Digital Edition of ASHRAE Journal - August 2011

ASHRAE Journal - August 2011
Contents
Commentary
Industry News
Letters
Meetings and Shows
Feature Articles
2011–12 Presidential Address: Sustaining ASHRAE Through Leadership
Retrocommissioning Older Buildings
Liquid Refrigerant Pumping in Industrial Refrigeration Systems
Technology Award Case Studies:
Hospital Upgrade: Heat Recovery, Geothermal Save Energy
Cool Weather Savings: Using Hybrid Refrigeration Systems for Chiller Retrofit
Special Section
InfoCenter
Standing Columns
Solar NZEB Project
Emerging Technologies
Special Products
IAQ Applications
Washington Report
People
Products
Classified Advertising
Advertisers Index
ASHRAE Journal - August 2011 - Intro
ASHRAE Journal - August 2011 - ASHRAE Journal - August 2011
ASHRAE Journal - August 2011 - Cover2
ASHRAE Journal - August 2011 - 1
ASHRAE Journal - August 2011 - 2
ASHRAE Journal - August 2011 - Contents
ASHRAE Journal - August 2011 - Commentary
ASHRAE Journal - August 2011 - 5
ASHRAE Journal - August 2011 - Industry News
ASHRAE Journal - August 2011 - 7
ASHRAE Journal - August 2011 - 8
ASHRAE Journal - August 2011 - 9
ASHRAE Journal - August 2011 - Letters
ASHRAE Journal - August 2011 - 11
ASHRAE Journal - August 2011 - 12
ASHRAE Journal - August 2011 - 13
ASHRAE Journal - August 2011 - 14
ASHRAE Journal - August 2011 - 15
ASHRAE Journal - August 2011 - Meetings and Shows
ASHRAE Journal - August 2011 - 17
ASHRAE Journal - August 2011 - 2011–12 Presidential Address: Sustaining ASHRAE Through Leadership
ASHRAE Journal - August 2011 - 19
ASHRAE Journal - August 2011 - 20
ASHRAE Journal - August 2011 - 21
ASHRAE Journal - August 2011 - 22
ASHRAE Journal - August 2011 - 23
ASHRAE Journal - August 2011 - 24
ASHRAE Journal - August 2011 - 25
ASHRAE Journal - August 2011 - Retrocommissioning Older Buildings
ASHRAE Journal - August 2011 - 27
ASHRAE Journal - August 2011 - 28
ASHRAE Journal - August 2011 - 29
ASHRAE Journal - August 2011 - 30
ASHRAE Journal - August 2011 - 31
ASHRAE Journal - August 2011 - 32
ASHRAE Journal - August 2011 - 33
ASHRAE Journal - August 2011 - 34
ASHRAE Journal - August 2011 - 35
ASHRAE Journal - August 2011 - Liquid Refrigerant Pumping in Industrial Refrigeration Systems
ASHRAE Journal - August 2011 - 37
ASHRAE Journal - August 2011 - 38
ASHRAE Journal - August 2011 - 39
ASHRAE Journal - August 2011 - 40
ASHRAE Journal - August 2011 - 41
ASHRAE Journal - August 2011 - 42
ASHRAE Journal - August 2011 - 43
ASHRAE Journal - August 2011 - Hospital Upgrade: Heat Recovery, Geothermal Save Energy
ASHRAE Journal - August 2011 - 45
ASHRAE Journal - August 2011 - 46
ASHRAE Journal - August 2011 - 47
ASHRAE Journal - August 2011 - Cool Weather Savings: Using Hybrid Refrigeration Systems for Chiller Retrofit
ASHRAE Journal - August 2011 - 49
ASHRAE Journal - August 2011 - 50
ASHRAE Journal - August 2011 - 51
ASHRAE Journal - August 2011 - InfoCenter
ASHRAE Journal - August 2011 - 53
ASHRAE Journal - August 2011 - 54
ASHRAE Journal - August 2011 - 55
ASHRAE Journal - August 2011 - 56
ASHRAE Journal - August 2011 - 57
ASHRAE Journal - August 2011 - 58
ASHRAE Journal - August 2011 - 59
ASHRAE Journal - August 2011 - 60
ASHRAE Journal - August 2011 - Solar NZEB Project
ASHRAE Journal - August 2011 - 62
ASHRAE Journal - August 2011 - 63
ASHRAE Journal - August 2011 - 64
ASHRAE Journal - August 2011 - 65
ASHRAE Journal - August 2011 - Emerging Technologies
ASHRAE Journal - August 2011 - 67
ASHRAE Journal - August 2011 - 68
ASHRAE Journal - August 2011 - 69
ASHRAE Journal - August 2011 - 70
ASHRAE Journal - August 2011 - 71
ASHRAE Journal - August 2011 - 72
ASHRAE Journal - August 2011 - 73
ASHRAE Journal - August 2011 - 74
ASHRAE Journal - August 2011 - Special Products
ASHRAE Journal - August 2011 - IAQ Applications
ASHRAE Journal - August 2011 - 77
ASHRAE Journal - August 2011 - 78
ASHRAE Journal - August 2011 - 79
ASHRAE Journal - August 2011 - Washington Report
ASHRAE Journal - August 2011 - 81
ASHRAE Journal - August 2011 - People
ASHRAE Journal - August 2011 - 83
ASHRAE Journal - August 2011 - Products
ASHRAE Journal - August 2011 - 85
ASHRAE Journal - August 2011 - Classified Advertising
ASHRAE Journal - August 2011 - 87
ASHRAE Journal - August 2011 - Advertisers Index
ASHRAE Journal - August 2011 - Cover3
ASHRAE Journal - August 2011 - Cover4
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