Heat Migration in the Home 1 Energy Analysis and Comfort Solutions, Inc. Understanding Heat Migration in Your Home

Heat Migration in the Home 2 Simple truths about temperature –Heat always flows from “higher heat” to “lower heat”: like water in a stream – it flows from higher ground to lower ground. The greater the difference the faster the flow. –Insulation resists the flow of heat through the insulation: the thicker the insulation the less heat will conduct through the insulation – higher “R-values” = less heat conducted.

Heat Migration in the Home 3 Simple truths about sunlight. –Sunlight striking a solid object releases radiant energy or heat. Windows allow sunlight through, but hold radiant heat inside. –Solar heat increases can be large: on a summer day the temperature inside of a car can reach up to 165 F.

Heat Migration in the Home 4 Walls usually have more resistance to heat transfer than windows. Walls are opaque, do not allow sunlight to enter the house. Walls usually have a better insulation value, depending on the amount of insulation in between the walls. Windows are translucent and allow sunlight inside, which adds heat to the interior space. Windows also have an insulation value, “R-value”, which is much smaller than walls. The higher the R-values of the windows the less heat will escape during the winter. Windows with “coatings” resist heat gains by reflecting the radiant heat back outside, and holding more heat inside during the winter.

Heat Migration in the Home 5 The next few slides Look down into a home examining the effects of a typical summer day. –The sun rises in the east. The air is usually cooler in the morning than afternoon. –Sunlight strikes the east wall and heats it up. Sunlight enters windows and heat up the inside of the home. –If it is cooler outside, less radiant heat is conducted into the home through the walls.

Heat Migration in the Home 6

Heat Migration in the Home 7 –Late morning until early afternoon the sunlight shines on the south side of the house. –Sunlight strikes the south wall and heats it up. Sunlight enters windows and continues to heat up the inside of the home. –The warmer outside, the more radiant heat is conducted into the home through the walls. The heat flow into the home increases.

Heat Migration in the Home 8

Heat Migration in the Home 9 –Afternoon the sunlight shines on the west side of the house. –Sunlight strikes the west wall and heats it up. Sunlight enters windows and continues to heat up the inside of the home. –The hotter outside, the more radiant heat is conducted into the home through the walls. The heat flow into the home continues to increases.

Heat Migration in the Home 10

Heat Migration in the Home 11 Interior walls for rooms hold the additional heat in these rooms. The south and west side rooms have the highest additional heat during the afternoon. That is why these rooms are harder to maintain a comfortably cool temperature on a summer afternoon. Conversely, during the winter months, the north side of the house may be cooler than the rest of the house. This is because the higher temperature inside is being conducted outside through the walls and windows. Rooms with larger windows are more negatively effected, gain heat in the summer and loose more heat in the winter.

Heat Migration in the Home 12 The first step in controlling comfort in the home is to understand how and why temperature changes. Every building is different, therefore, each building must be analyzed individually. (See load calculations). The next step is to define the comfort parameters of the occupants, what temperatures are comfortable, and determine the average time schedules or routines. Next, HVAC systems should be designed to accommodate the unique requirements of the building, match the correct size of equipment to the loads, and distribute the proper amount of air to maintain comfort.