MU-KFTS04
渗透是指室外空气通过墙壁、门窗周围的裂缝以及由于室内和室外空气压力差而打开的门进入建筑物的过程。压差是由风机运行引起的温差和进气或排气引起的。渗透导致的热损失是温差和移动空气量的函数。渗出是空气离开建筑物（例如，穿过墙壁和门窗周围的裂缝）并带走热量的过程。渗透和渗出可能同时发生。通风带来可能需要加热的新鲜室外空气。与渗透和渗出热损失一样，通风热损失是温差和进入建筑物或排出的空气量的函数。加热设备选择合适的加热设备取决于许多因素，包括燃料的成本和可用性、建筑尺寸和用途、气候以及初始和运营成本权衡。主要热源包括天然气、石油、木材、煤炭、电力和太阳能。有时，多种来源的组合是经济的。锅炉通常以天然气为燃料，在需求旺盛的时期，可以选择改用石油。太阳能可以作为任何类型燃料的替代或补充来源。

Infiltration is the process by which outdoor air enters a building through walls, cracks around doors and windows, and open doors due to the difference between indoor and outdoor air pressures. The pressure differential is the result of temperature difference and air intake or exhaust caused by fan operation. Heat loss due to infiltration is a function of temperature difference and volume of air moved. Exfiltration is the process by which air leaves a building (e.g., through walls and cracks around doors and windows) and carries heat with it. Infiltration and exfiltration can occur at the same time. Ventilation brings in fresh outdoor air that may require heating. As with heat loss from infiltration and exfiltration, heat loss from ventilation is a function of the temperature difference and the volume of air brought into the building or exhausted. HEATING EQUIPMENT Selecting the proper heating equipment depends on many factors, including cost and availability of fuels, building size and use, climate, and initial and operating cost trade-offs. Primary sources of heat include gas, oil, wood, coal, electrical, and solar energy. Sometimes a combination of sources is most economical. Boilers are typically fueled by gas and may have the option of switching to oil during periods of high demand. Solar heat can be used as an alternate or supplementary source with any type of fuel.