Building Science 101
Building Science is the study of how buildings function under various environmental conditions. How does building science affect you? In today’s world of airtight homes, bacteria-free workplaces, and the latest and greatest synthetics building science is all around you. Words such as environmental allergies or sensitivity, asthma, chemical sensitivities have become a part of our vocabulary. Four performance principles interact to create either harmony or imbalance in our home. Understanding building science helps us understand how these factors affect the health of your home and those who live in it.
The moisture level in a home depends on a number of factors. It also is not simply determined by the climate and relative humidity in the area you live in. Living in a "dry" city does not mean you don't have to be worried about the moisture content in your home. Moisture is all around us. It moves and fluctuates with every single activity that takes place in the house. Cooking or using the shower, number of occupants, leaks, and ground or atmospheric moisture will change the moisture levels. In your home, water vapor moves from areas of high concentration to low concentration. For instance, as moisture levels increase in the summertime, simply opening your window will increase the humidity in your home as the increase concentration of water vapors outside diffuse into the cracks and openings in your home.
Moisture problems are the number one source of residential concerns. Moisture can wreak havoc on the home and its occupants. Excess moisture can result in mold, bacterial, and fungal growth which can exacerbate asthma, environmental sensitive and other respiratory diseases. To remedy this, you can lower the relative humidity by turning on your bathroom fan or some other ventilation system, use a dehumidifier, and ensure sources of humidity and moisture infiltration are corrected.
Did you ever wonder why condensation forms on your windows? Condensation in the form of water, frost, or ice forms on surfaces when there is excess moisture in the air. The amount of moisture in the air is measured by Dew Point. The higher the dew point, the higher the moisture content of the air at a given temperature. Dew point temperature is the temperature to which the air would have to cool in order to reach saturation (i.e. 100 percent relative humidity). As air comes into contact with a surface below this temperature, condensation will form on the surface. Excess moisture or humidity in the home in the winter will result in ice forming on your windows, a sure sign to turn down the humidifier in your house, or increase the ventilation to reduce the dew point.
Frequently, we hear homeowners complain about the draftiness of their homes, cold spots in certain areas of the house, or rising energy bills. This is caused by pressure changes and holes in the house, which can be a considerable annoyance for homeowners. Pressure can be caused by external conditions such as wind and temperature, and internal conditions, such as exhaust fans, chimneys, and clothes dryers. Pressure and holes can be beneficial or detrimental for the home. Holes are purposely added to the home in areas, such as air to air heat exchanger; to ensure an effective exchange and filtration of air other holes, such as gaps found in insulation, will allow cold air to penetrate into the home.
Air leakage through holes and pressure leaks in the house can account for as much as a third of your home's heat loss. As warm, moist air leaks out of the top of the house, it's replaced by cool, dry air from outside. An excessively leaky house will not only leave you feeling dry and uncomfortable, but can lead to upper respiratory disease, outdoor pollution, and pest invasion into the home. Controlling air leaks or negative pressure can be done by sealing cracks and holes, using the appropriate vapor barrier on walls, and providing pressure balance between rooms when forced air systems are used. Controlling air leakage can significantly improve the energy use of your home. However, as your house becomes more airtight, you must have a ventilation system to provide adequate air exchange.
The final factor in building science is Heat Flow, a concept that is familiar to all homeowners and the easiest to manage. Heat Flow, like moisture and pressure, will move from areas of higher temperature to areas of lower temperature. There are three types of heat flow:
Conduction is the transfer of heat between objects that are in contact (i.e. stovetop). Convection is the mechanism for heat transfer in gases and liquid (i.e. hair dryers). Radiation is the transfer of heat in the infrared spectrum (i.e. heat energy from the sun or heat lamps).
Heat can enter a home through purchased energy in the form of electricity; solar energy through windows and doors; transmission of heat through walls and roofs exposed to the sun; by internal heat derived from occupants, lights, and appliances. Basements, windows, and doors combined account for up to half the total heat loss of a house. Homeowners can control the heat flow in their homes by doing the following: using better construction materials and methods, properly insulating walls and plugging cracks and leaks in the home, using Low-e windows, controlling the natural light entering the home with window coverings, and using high energy efficiency appliances.
Developing an understanding of how moisture movement, dew point, pressure, and heat flow interact and affect each other can help homeowners create a healthy, comfortable home.
Building science 101 give you more reasons why you should consider using R-Valued Homes SIPs on your next project.