Presentation on theme: "Chapter 5: Designing for Heating and Cooling 5.1 Organizing the problem a) Fenestration How much is optimum for the building? What should the form of the."— Presentation transcript:
Chapter 5: Designing for Heating and Cooling 5.1 Organizing the problem a) Fenestration How much is optimum for the building? What should the form of the building be? internal load dominated skin load dominated Daylighting issues side lighting vs top lighting role of direct sunlight, solar gain vs. glare seasonal adjustments to daylight openings daily daylight control daylight distribution
Chapter 5: Designing for Heating and Cooling cont’d 5.1 Heating issues can the sun be used to heat spaces? South wall design. openings to other orientations? U-value relationship to daylighting how to minimize cooling effects of large glass surfaces? how can incoming fresh air be warmed? is there surplus heat in the building that can be used at perimeter? Cooling issues Which strategy… Open the building to breezes or close it to retain coolth? How to keep out direct sunlight? How to allow daylighting in winter without overheating in summer? When can cooling be provided by outside air rather than refrigeration? Can use of refrigeration be confined to off peak times? How can incoming fresh air be cooled? Can the structure of the building be used to absorb daytime heat and flush it out at night?
Chapter 5: Designing for Heating and Cooling 5.2 Zoning your building based on function, schedule, orientation fig. 5.3 5.3 Daylighting guidelines (calculations optional) daylight factor def’n: indoor illumination from daylight x 100% outdoor illumination Fig. 5.4 Design diagrams - one way structure → high windows Table 5.2 Recommended daylight factors Fig. 5.7 EPUD building
Chapter 5: Designing for Heating and Cooling 5.4 Passive Solar Heating Guidelines Incorporates sun collection and storage as part of a building’s wall, floors or ceilings. “Insulate before you isolate” Principle of whole building heat loss. Relative to conventional buildings, passively solar-heated buildings usually conserve purchased energy, yet buildings that aim at very high percentages of solar heating can use more total heating energy than is used by buildings with smaller window areas. Designers interested primarily in saving purchased energy may aim at lower solar percentages and more insulation; designers interested in buildings that closely relate to climate and climatic changes may aim at higher solar percentages (and more daylighting) along with higher thermal masses and probably greater ranges of indoor temperature.
Chapter 5: Designing for Heating and Cooling 5.4 b) Solar Savings Fraction a measure of the solar building’s conservation advantage (not the percentage of solar energy used) c) Thermal mass (calculations optional) phase change materials d) Orientation best within 30˚ of south. figures 5.12 and 5.13 e) Roof ponds not recommended for climates with snow since they require moving insulating panels f) Active Solar Heating Uses mechanical equipment to collect and store solar energy
Chapter 5: Designing for Heating and Cooling 5.6 Passive Cooling Guidelines a) Cross ventilation provides air movement and fresh air indoor temperature will be slightly above outdoor temperature difficult to quantify b) Stack ventilation also maintains slightly above outdoor air temperature c) Night Ventilation of Thermal Mass Maintains a building at temperatures lower than outside by day and flushes the building with plentiful fresh air by night. Example 5.3 describes how to calculate appropriateness of system with respect to climate
Chapter 5: Designing for Heating and Cooling 5.6 Passive Cooling Guidelines d) Evaporative cooling calculations optional e) Cool towers passive approach to evaporative cooling Figure 21 f) Roof Ponds calculations optional g) Earth Tubes feasible if trenches already required.
Chapter 5: Designing for Heating and Cooling 5.9 b) Degree Days def’n 5.10 Passive Solar Heating Performance figure 5.13 Passive Solar Heating Systems compared a) glazing performance the issue of nighttime insulation
Chapter 5: Designing for Heating and Cooling b) Direct Gain Systems Problems: possible overheating on sunny winter days inadequate area of thermal mass Thermal mass should be widely distributed around the room so that direct sun can strike the mass surface or be reflected onto it as soon as possible upon entering the window. Figure 3.6
Chapter 5: Designing for Heating and Cooling c) Sunspaces Problem: Expectation that the sunspace will be a greenhouse. Comfortable temperatures in the main spaces are achieved at the expense of very wide temperature swings in the sunspace. Wall between sunspace and main space should be vented masonry or contain water containers. All sunspace systems are assumed to have a thermally massive perimeter insulated floor slab on grade. Figure 5.26
Chapter 5: Designing for Heating and Cooling d) Trombe Walls The main advantages of the Trombe wall systems: Thermal stability. The diurnal temperature swings are less than with most other passive systems. They deliver a large portion of their heat by radiation to the space. The main disadvantages: The loss of view and daylight Keeping the air space clean between the Trombe wall mass wall and the glass. Vented walls use the stack effect to circulate warm air to the main space. Deliver warm air sooner, but introduce dust into the space behind the glass. Unvented spaces deliver heat quite late and are somewhat less efficient than vented spaces. Figure 5.27
Chapter 5: Designing for Heating and Cooling e) Water Walls Water phobia? A real water wall is not transparent but opaque. Black selective paint (excellent absorber of short-wave solar radiation, poor emitter of long- wave radiation from the heated black surface) behind double glazed unit. Leave airspace for water expansion due to temperature, also rust inhibitor. Figure 5.28
Chapter 5: Designing for Heating and Cooling 5.11 Calculating heat gain (cooling load) Be aware of the factors involved in heat gain; calculations optional. roof and walls q = U x A x DEDT glass outdoor air (infiltration, mechanical ventilation) people lights equipment latent heat gain (varies with occupancy)
Chapter 5: Designing for Heating and Cooling 5.14 Passive cooling calculation procedures Read through the UK pavilion at the Seville Expo 1992. Look at figures 5.48 5.59