Frequently Asked Questions
R-value measures insulation's resistance to heat flow. It can also be referred to as "thermal resistance." The R-value of different insulating materials must be based on test methods established by the American Society of Testing and Materials (ASTM). Don't forget that R-values are determined by material type, thickness, and installed weight per square foot, not by thickness alone.
To the average person the higher the R-value number of your insulation, the warmer you should feel in the winter and cooler in the summer. The reality is something totally different as the R-value listed on insulation is not arrived at under real world conditions making them extremely misleading to the consumer. For instance, fiberglass insulation is generally assigned an R-value of approximately 3.5. It will only achieve that R-value if tested in an absolute zero wind and a zero moisture environment. Zero wind and zero moisture are not real-world. The average home with all its doors and windows closed has a combination of air leaks equal to the size of an open door, hence the reason why so many people feel that their homes are drafty. Even if you did a perfect job of installing Fiberglass or Cellulose insulation in your home and were to bring the air infiltration close to zero from one side of the wall to the other, you would still not stop air from moving vertically through fiber based insulation itself, in ceilings and walls. Water vapor from the atmosphere, showers, cooking, breathing, etc. constantly moves back and forth through walls and ceilings as well dropping Fiberglass or Celluloses insulation's R-value — as much as 50 percent or more as well.
By some estimates, 50-60% of your heat escapes through light fixtures, vents, and directly through your ceiling into the attic and out your ridge vent or soffits. This is why when considering insulation, addressing deficiencies in the attic can give you the biggest bang for your insulation dollar.
The only way to stop the moving of air and moisture within a building's structure is with an air and vapor barrier. One inch of spray Polyurethane foam insulation properly installed throughout the building structure can prevent more heat loss than all the fiber insulation that can be crammed into the structures walls.
The "stack effect" is when warm air moves upwards in a house. This happens in summer and winter. Warm air rises - because it's lighter than cold air. So when it rises, what happens? It escapes out of the upper levels of our homes through recessed lighting fixtures, fan fixtures, etc. But we can't create a vacuum in our homes so when air escapes new air has to come in to replace the air that escaped. Where does the new air enter the house? ...at the lower levels, through your floors above the crawl space, at your top plate, around windows, through under-insulated walls, vents and other leaks in the home envelope.
Spray Foam FAQs
Closed-Cell spray Polyurethane foam is highly dense and when sprayed expands up to 30 times its original liquid volume producing an R-value per inch of 6.4+. In Closed-Cell spray foam, cells or bubbles in the foam are compacted together, are not broken and each is filled with an inert gas selected to make the insulation value of the foam as high as possible. An example of Closed-Cell foam insulation that we benefit from every day would be the insulation found in your refrigerator and freezer.
The advantages of Closed-Cell foam include its strength, higher R-value, and greater resistance to the leakage of air or water vapor making it ideal for windy, damp and water prone locations, such as coastal areas, below grade, crawl spaces, or for the whole house. For many of our clients, Closed-Cell foam is the product of choice. While more expensive than Open-Cell foam because of its density, at 1 inch thickness Closed-Cell foam develops an air barrier and at 2 inches a moisture barrier. Closed-Cell Spray Foam is the only FEMA approved flood resistant insulation material.
Open-Cell spray Polyurethane foam is soft - like a foam cushion in a pillow and is an excellent air and sound insulator. Unlike Closed-Cell foam, Open-Cell foam is less dense, with each Cell in the foam being broken, thus allowing air to fill all of the spaces in the material. Upon spraying Open-Cell foam expands up to 150 times its original liquid volume, thereby filling all nooks and crannies in the wall cavity. When spraying is complete, the excess foam is shaved off the studs, leaving a flat surface over which dry wall or other material can be applied. With an R-value of 3.7+ per inch Open-Cell foam gives you an air barrier @ 5 inches of thickness. Uses for Open-Cell include spraying directly to all walls of a house, and as sound proofing for media rooms. Open-Cell foam may also be direct sprayed to roof decks.
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. Click here to view these R-value recommendations on a U.S. map or view these recommendations from the R-value calculator.
Be sure your new home complies with current building code requirements for insulation. These building codes establish minimum levels of insulation for ceilings, walls, floors, and basements for new residential construction.
Spray Polyurethane foam insulation is a two component, sprayed in place insulation designed to provide superior thermal performance on virtually any substrate (wood, masonry, metal studs and joists). When sprayed on the substrate, the foam expands allowing it to form a monolithic seal to the inside surface of exterior walls, to the underside of the roof deck, beneath floors, and in basements and crawl spaces. The result is that air can no longer penetrate your house making it less drafty and more comfortable.
Air leakage can also introduce moisture into the wall cavity, resulting in wet insulation and mold and mildew. With the sealing effects of spray Polyurethane foam insulation moisture can be reduced to the point that this will not be a concern.
If you are sealing the entire building envelope we always recommend some form of fresh air ventilation. Most building design professionals will advise you to seal the building structure as tight as possible and provide the necessary ventilation through an air exchanger attached to your heating and air conditioning system. In the winter, this simple machine brings cold fresh air from the outside and passes it by the warm stale air being expelled. This allows the fresh air to pick up the heat from the stale air, maintaining energy efficiency while providing a continuous supply of fresh air. In the summer, the opposite occurs giving the same results. In this manner, you can build an extremely energy efficient exterior shell using spray Polyurethane foam insulation while still providing controlled and energy efficient ventilation.
If you are retrofitting parts of your home, such as the attic, crawl space, or basement walls, you will probably not need to worry about your house being sealed too tightly as air enters the building envelope every time we open the door as well as through windows and locations within the home that typically are not reachable because of drywall etc.
Our position in regards to insulating a new home is that you will get only one chance to do the whole house. If you under-insulate you will regret it. In the unlikely event that you over-insulate the situation can be remedied with low cost ventilation systems as previously mentioned.
Flash and Blatt System
The number one problem reported across the spray foam industry with the Flash and Batt method is the buildup of condensation between the inside face of the spray foam insulation and the Fiberglass Batt overlay. If left uncorrected, this can quickly lead to a mold and mildew problem. Upon inspection, what is usually found is that the insulation contractor sold the customer on the idea of doing a ¼ inch to a ½ inch of Closed-cell spray Polyurethane foam to get an air seal followed by an overlay of Kraft-faced Fiberglass to meet code. To the customer this sounds like an effective way to obtain the benefits of spray foam insulation without spray foams higher cost.
Unfortunately, what the latest industry research is showing, and what many customers do not realize is that such a thin layer of spray foam does not allow the foam to achieve the necessary exothermal reaction to create the proper cell structure within the foam. As a result, the foam that is sprayed does not retain the thermal benefits inherent to Closed-cell spray Polyurethane foam, and in effect becomes comparable to a piece of plastic. Consequently, because the foam is not providing any insulating ability, when the dew point is met, condensation can occur on the foam and lead to mold and mildew problems.
First, is the company's primary business installing traditional forms of installation, such as Fiberglass and Cellulose? While this in and of itself should not be interpreted as a condemnation of a traditional insulation contractors ability to install spray foam, it has been the experience of the spray foam industry that the majority of contractors who continue to push this substandard Flash and Batt are traditional insulation contractors.
Second, is the contractor proposing at least a 1 inch average thickness of Closed-cell spray Polyurethane foam (1.5 inch to 2 inch may be necessary north of Virginia or in higher/colder elevations)? If they propose anything less you should be deeply concerned and send them on their way. A reputable spray foam contractor will not propose anything less than 1 inch of foam. In fact, many are beginning to propose the application of more than 1 inch of Closed-cell spray Polyurethane foam or are not doing the Flash and Batt method altogether.
Third, have the contractor's personnel been through a foam manufacturer's training program and become knowledgeable about the product's properties, and have they been certified in the use of the equipment and application of the product? At Virginia Foam Insulators spray foam is our specialty. All of our sprayers are licensed applicators and certified.
And lastly, something to keep in mind when choosing a spray foam contractor is that spraying foam insulation is a complex undertaking with many factors contributing to the successful application and performance of the product. The quality of the job that you receive in many respects will be dependent upon the knowledge of the individuals prepping and spraying the job.
A down spray is an insulation method that utilizes Closed-Cell Polyurethane Spray Foam. Spray Polyurethane foam is directly sprayed down onto the floor of the attic as opposed to the roof deck and is typically overlaid with blown-in Cellulose or Fiberglass so as to meet local R-value requirements. When using this method, the installer will cover all light fixtures, fans, vents etc. with protective boxes.
The primary benefit to doing a Down Spray is that it is significantly cheaper in cost as compared to spraying the roof deck. This is because there is less square footage in your attic than in the two or more sides of your roof. For example a 2,000 sq. ft. ranch house would typically have about 2,000 sq. ft. of floor space or attic space. If you were to spray the roof deck, depending on the pitch of the roof, you could be looking at 3,000-3,500 sq. ft. or more. The drawbacks to doing a Down Spray are that most homes contain duct work and an HVAC system in the attic. According to some DOE estimates, as much as 25% of your air-conditioning and heat escapes through improperly sealed ductwork. Additionally, these same escape points for air can also be used to pull in pollutants from your attic. When you seal the roof deck the attic becomes semi-conditioned space thus allowing your HVAC system and duct work to operate in an environment no more than 10-15 degrees different than your internal home temperature.