How to Measure or Calculate & Stop Building Heat Loss. Find
Drafts, Measure Insulation Values & Find Heating Cost Savings
How to measure or calculate heat loss (or gain) in a building
How to measure heat transmission in materials: definition of R-values, U-values, K-values, BTU, calorie, and rates of heat loss or gain
Building design temperatures & how to use a home energy audit or heat loss analysis
What insulation "R" values should be used in a building insulation?
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This article explains how to insulate a building and how much insulation is needed including how to measure or calculate heat loss in a building, defines thermal terms like BTU and calorie, provides measures of heat transmission in materials, gives desired building insulation design data, and shows how
to calculate the heat loss in a building with R values or U values.
Because no amount of insulation can keep a drafty building warm, also review ENERGY SAVINGS PRIORITIES. Also see HEAT LOSS INDICATORS (where is the building losing heat during the heating season, or gaining un-wanted heat during the cooling season),see HEAT LOSS DETECTION TOOLS for both tools and procedures, and see HEAT LOSS R U & K VALUE CALCULATION for a guide to calculating heat loss (or gain) rates for buildings and building insulation.
Formula-R™ and Owens Corning™ which may be visible in this photograph of pink Styrofoam™ insulation boards are registered trademarks of Owens Corning® and were photographed at a Home Depot® building supply center.
When we are evaluating the quality and effectiveness of insulation in a building or the adequacy of a building heating
or cooling system, we need to use measurements that permit us to describe the rate at which a building loses heat under
various conditions (such as outdoor temperature, wind velocity, how leaky the building is, the area of its windows and
perhaps doors, and the amount of insulation in the building walls, floors, and ceilings. A few of these critical definitions
is given just below, followed by some simple formulas used to calculate the heat loss in a building.
Definitions of BTUs, BTUH, and Calories
Definition of BTUs and BTUH: a BTU is one "British Thermal Unit" which is defined as the quantity of heat
that would be required to increase the temperature of one pound of water by one degree Fahrenheit.
A BTUH is defined as the number of BTU's lost (if we're talking about heat loss or air conditioning), or provided (if
we're talking about providing heat for a building) in one hour. You'll often see BTUH as a number on data plates on
air conditioners and on heating systems.
One BTU is also equal to 252 calories. So what's a calorie?
Definition of Calorie or Calories: a calorie is defined as the quantity of heat needed to raise
the temperature of one gram of water by one degree Centigrade.
How do we measure heat transmission or movement through a building wall, insulation, or any other material?
How do we measure and express how well a building is insulated? or How much heat loss is occurring at a specific building?
Many people have heard of using "R" values to describe "how good" a building's insulation is. Here we discuss three
measures of the flow of heat out of or into a building: R-values, K-values, and U-values. Each of these is defined below.
But before moving on to these basic concepts of building heat loss (or gain) theory, it is essential that this still
more basic point be considered:
How leaky is the building with respect to heat loss (in a heating climate) (or gain in a cooling climate)?
It doesn't matter much how wonderful the building insulation is, how thick it is, or what the insulating material's
"R" value is (see R defined below) if the building is leaky. If, for example, we're considering an older home with
leaky windows or doors, or if we're considering a tall building with poorly controlled heat in winter, such that
occupants of the upper floors are leaving windows open in winter then the heat flow out of these openings
will be so terrific that the amount of insulation won't matter much.
For details about actual heat loss calculations see HEAT LOSS R U & K VALUE CALCULATION. Continue reading this article series with the links shown just below.
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