What is home air sealing?
Home air sealing consists of sealing all cracks and penetrations in your home envelope, usually with elastomeric water-based sealants in order to bring your house to a desirable air changes per hour. Uncontrolled air infiltration through cracks and openings can affect heating and cooling costs, building durability and interior air quality.
What are air changes per hour?
Air changes per hour (ACH/hr) represents how many times the air in your house is replaced per hour. There are standards set by the American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRE), that established the minimum ventilation rates. We measure ACH/hr before and after we seal the air in a home in order to measure the improvement.
What is insulation?
In our context the term Insulation means “thermal building insulation” and we refer to the materials, methods and physics involved in the process used to reduce heat transfer in buildings.
According with the US Department of Energy (DOE) heating and cooling account for 50 to 70% of the energy used in the average American home. Inappropriate insulation and air infiltration are leading causes of energy waste in most homes. The benefits of insulation are:
- Reduces your home heating and cooling costs
- Makes your house more comfortable by helping to maintain a uniform temperature throughout the house
- Helps to reduce sound transmission through walls and ceilings and floors
- Reduces Greenhouse gas emissions
- Save our nation’s energy resources
Which factors determine your home energy savings?
Several factors determine the energy savings:
- Size, shape, orientation and construction materials of your home.
- Local climate
- Type and efficiency of your heating and cooling system.
- Fuel you use.
- The living habits of the residents of the house.
In order to optimize energy savings you can modify some of those factors, we recommend these two steps:
- Home energy assessment.
- Apply the cost effective energy improvements.
How Insulation works?
The motion of atoms and molecules is a form of energy called heat. Heat flows naturally from a higher temperature space to a cooler temperature space through an element of the building envelope (floor, wall, roof/ceiling, door and window), this transfer cannot be stopped but its rate can be restrained. This is the job of building insulation: restrain the heat flow the through buildings envelope. In order to minimize unwanted heat transfer in a home we need to understand the physics of heat transfer. There are three basic mechanism of heat transfer:
Is the transfer of thermal energy (molecular movement) within an object toward different object in contact. For example the thermal energy of the hot mass of air enclosed in your attic in summer days will be “conducted” through the ceiling material into the living space, that may cause your A/C unit to work overloaded, that extra work will be reflected increasing your electric bill. A good ceiling insulation is the appropriate prescription to mitigate this situation.
Is the transfer of thermal energy due to the movement of molecules within fluids (liquids and gases). Natural convection occurs for example within a stud cavity wall when the flow of more dense cool air moves downwards while the less dense hot air moves upwards, this convection loop inside the stud wall can create condensation with consequences such as structural deterioration and mold. A well installed insulation can stop these pernicious convection loops.
Is the transfer of energy by means of electromagnetic waves. All objects radiate energy accordingly with their temperature. The energy that our planet receives from the sun comes in form of radiation, the light, the U-V rays, the infrared rays and others are electromagnetic waves that travel in a straight line through the empty space that collide and energize the earth. We can feel Infrared radiation as a heat; heat can pass through air and glass and is absorbed when hits an object. A good example of heat transfer by radiation and how a good insulation works is a Florida home in summer. The sun’s electromagnetic waves will strike the home’s roof raising the temperature more than 160°; the roof will radiate energy into the attic space where the temperature could rise up to 130° while the temperature in the living space of a house could be 77°. The difference of temperature will trigger the heat transfer from the attic to the living space through the ceiling by conduction, that heat flow could be mitigated by any thermal insulation like fiber glass. Installing radiant barrier stapled to the bottom of the roof rafters in the attic space can block up to 97% of the infrared waves radiated by roof, this plunge in energy input in the attic space will cause that the average attic temperature will decrease by almost 30°, reducing the temperature difference and heat flow between attic and living spaces will reduce the A/C load and by consequence your electric bill.
What is R-value?
R-value measures insulation’s resistance to heat flow. It can also be referred to as “thermal resistance.” The higher the R-value, the greater the insulating power. All materials having the same R-value, regardless of type, thickness, or weight, are equal in insulating power.
Types of insulation
- Fiberglass is made from molten sand or recycled glass and other inorganic materials under highly controlled conditions. Fiberglass is produced in batt, blanket, and loose-fill forms. Fiber glass works by limiting air movement; the still air trap in between the fibers is an effective insulator because it eliminates convection and has low conduction.
- Rock and slag wool are manufactured and work similarly than fiberglass, but use natural rock and blast furnace slag as its raw material. Typical forms are loose-fill, blanket, or board types.
- Cellulose is a loose-fill insulation made from recycled newspaper using grinding and dust removing machines to which flame retardants are added. Cellulose insulation has low thermal conductivity. It is used in walls and roofs cavities to separate the inside and outside of the building thermally and acoustically.
- Rigid foam insulation is available as rigid boards or foamed-in-place materials that can fill and seal blocks or building cavity spaces. Foams are also used in air sealing to fill gaps, cracks, or openings.
- Reflective materials are fabricated from aluminum foils with a variety of backings such as polyethylene bubbles, paper and plastic film. Some forms of reflective insulation also divide a space up into small regions to reduce air movement, or convection, but not to the same extent as batts, blankets, loose-fill, and foam.
- Radiant Barriers consist of a highly reflective material installed usually in attics primarily to reduce summer heat gain. Radiant barriers are particularly effective in homes with air-conditioning duct-work in the attic in climate zones with high impact of solar energy like in the state of Florida.
- Spray Foam Insulation consists in polyurethane spray-applied foam insulation system designed for insulates walls, ceilings and everywhere else one would expect insulation. Spry foam insulation can create an air tight barrier that conserves energy, blocks moisture, decreases noise, and reduces the influx of outdoor pollutants and allergens environment.
How much will I save by adding insulation to, my home?
DOE statistics show that typically more than 40% of a homeowner’s utility bill goes for heating and cooling costs. DOE states that homeowners may be able to reduce their energy bills from 10% to 50% by taking certain steps. One of the major steps is increasing the amount of thermal insulation in their existing homes or purchasing additional insulation when buying new homes.
How much insulation should my house have?
The U.S. Department of Energy recommends home insulation R-values based on where you live. These recommendations are detailed for various sections of the home including walls, ceilings, and basements. For Florida homes usually the recommended level of attic insulation is between R-30 to R-49. In order to install the appropriate amount of insulation to a home, there are several factors to be considered like, air conditioned space area, air conditioning units, house orientation, windows, etc; even your budget must be considered, all under the umbrella of Florida Energy Code.
Which is the best insulation for my home?
To retrofit your attic, blown in fiber glass insulation is recommendable. For a leaky wood floor over a crawl space, closed cell spray foam insulation could be a good option. For sound insulation in an office, blown in cellulose in walls cavities will improve significantly the walls sound transmission coefficient. Ask our home energy expert, he has a whole house vision that allows him to see beyond insulation and will give you the best advice to solve your energy concerns.