Energy & Its Impact on Global Society Jerome K. Williams, Ph.D. Saint Leo University Dept. Mathematics & Sciences

Chapter 5: Home Energy Conservation and Heat Transfer Control Home Design Activity Building Materials Site Selection of Home Energy Conservation Measures Heating & Cooling Home

Home Design Activity If money were not a concern, what would be the most effective design to heat and cool a home?

Home Design Activity Since we live in the “real world”, what can one do to control heating and cooling costs? Choice of home design Retrofitting an older house Energy efficient appliances Addition of solar energy features

Home Design Activity Ultimate Goal: Zero-Energy House (ZEH) Idea is to make house livable on nearly no net commercial energy input Run the meter “backwards” thereby having power company pay the homeowner money for unused energy

Building Materials Choice of materials is important Metals are good conductors of heat and electricity Fiberglass or Styrofoam are insulators; these will slow down the flow of heat between objects. Color of material does have impact on heat transfer by radiation

Building Materials Increased insulation is one of easiest, most cost-effective means of reducing energy consumption Can save up to 50% on heating & cooling bills Rate Heat Flow= (Q/t) = (1/R) x A x ΔT Tables 5.1 & 5.2

Building Materials A measure of material’s resistance to heat flow is thermal resistance R, also called R-value The higher the R value, the better the insulating properties of the material For composite materials, add up all R values for mixture

Example Problem Calculate the total heat transfer for 12 hours through an insulated window (two glass panes with an air gap of ¼ in.) that measures 4 ft. by 7 ft. when the outside temperature is 5 oF and the inside temperature is 65oF. Answer 13,100 Btu

Building Materials R values include effects of conduction and convection Convection can be reduced by planting trees and shrubs near a house to reduce wind Inside convection loss around windows can be reduced by using floor drapes and valence

Building Materials Windows: important source of heat loss (35% of energy requirements for insulated home) Solutions to Problem Double Pane Windows (Required New Homes) Plastic Storm Windows (Cheaper; Replace often) Weather Stripping & Caulking (Easy; Cheap)

Site Selection of Home Location, Location, Location Use Wind to cool in summer but not freeze in winter Path of Sun: Solar energy panels face south to capture energy in winter

Heating & Cooling Home Air Conditioning vs. Passive Cooling Systems Heating Options Gas Furnace Heat Pump System Electrical Resistance Heating System

Energy Conservation Measures Home Energy Audit http://energy.gov/public-services/homes/home-weatherization/home-energy-audits

Problems 3, 5, 7, 8