What is R-value?
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.
What is the R-value myth?
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. 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.
What is the Stack Effect?
The “stack effect” is when warm air moves vertically 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. This is what makes floors cold in the winter, the loss
of conditioned heated air though the vented attic.
In the Summer the stack effect is revered. Conditioned cold air falls to the bottom of your home and leaks out,
pulling the hot attic air down into your home and making the upper levels of a home hot and stuffy.
What is the difference between Closed-Cell and Open-Cell spray Polyurethane foam insulation?
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 6.8. 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, crawlspaces, 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 3.9 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 the underside of roof decks to create a highly efficent seal attic system.
Is Spray Polyurethane foam good for soundproofing?
Both Open-Cell and Closed-Cell spray Polyurethane foams are effective for reducing noise from outside sources by sealing cracks and gaps that allow sound to travel through the walls, floors and ceilings into the building.
Of the two, Open-Cell foam has the best soundproofing capabilities.
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.
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.
If you have more specific questions about how much insulation you need for your project contact us!
If you spray the underside of a roof deck with spray polyurethane foam insulation, should you vent the attic?
No. The application of spray polyurethane foam insulation to the underside of the roof deck eliminates the need to vent the attic. Venting of attics primarily came about as a way to eliminate condensation buildup on attic insulation resulting from temperature differences between the inside attic walls and the interior of the building.
Unfortunately, this venting also allows cold air into the attic in the winter and warm air in during the summer.
With spray Polyurethane foam insulation a thermal break and moisture gradient is provided allowing the space to become semi conditioned, within 10-15 degrees of the interior house temperature, thus preventing the development
of dew point conditions in the attic.
Should I be concerned with the temperature of my roof deck if closed-cell foam is sprayed directly against the deck?
Multiple studies have proven that non-ventilated roofs (spray foam applied directly to the underside of roof decks) do not significantly impact roof or roofing materials durability. Many manufactures to include Certainteed, Elk, and GAF now provide technical letters supporting the use of Polyurethane spray foam on the roof deck
(otherwise known as a hot roof system).
At what point in the construction of my house should spray polyurethane foam insulation be applied?
Spray polyurethane foam insulation is professionally installed at the same point in the construction cycle as other types of insulation. This typically occurs after the rough plumbing, electrical wiring, and heating and air conditioning ducts have been installed, but before the interior walls are completed in new home construction. In some cases spray polyurethane foam insulation can also be applied in older homes, to the inside of roofs and under floors after construction has been completed.
How does the spray polyurethane foam insulation seal my house?
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.
Won't sealing my house lead to indoor air quality problems?
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, crawlspace 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.
Can I use spray polyurethane foam to insulate an existing home?
Yes. Houston Bros. can spray polyurethane foam insulation on the underside of your roof deck, under crawl spaces, on basement walls, and into new additions or home renovation projects involving the removal of the existing drywall.
How does spray polyurethane foam insulation compare with fiberglass and cellulose?
While typically 3-4 more times expensive than fiberglass and blown-in cellulose, spray polyurethane foam insulation’s benefits allow it to provide a quick return on investment for the homeowner that continues indefinitely. Fiberglass in blown in form, batts and rolls, are not an air barrier and will not stop air leakage. Blown-in cellulose will slow down air leakage but is also not truly an air barrier. Spray polyurethane foam insulation will stop air leakage when sprayed to recommended thicknesses. Both fiberglass and blown-in cellulose have significantly lower R-values per inch of thickness than does spray polyurethane foam insulation. Both fiberglass and cellulose can sag, settle, and shift over time leaving sections in the wall cavity and attic un-insulated or under-insulated. Spray polyurethane foam insulation will completely adhere to the wood substrate and sheathing and is rigid; the result is a permanent barrier to heat loss and air entry that actually strengthens the structure. Fiberglass products and blown-in cellulose will do neither.
Will I save money if I insulate with spray polyurethane foam insulation?
Yes! The installed cost of spray polyurethane foam insulation is somewhat higher than fiberglass and blown-in cellulose. However, the higher initial cost is partially offset because of the sustainability of the insulation
(it will not degrade over time like fiberglass and cellulose) and you may be able to downsize your heating and air conditioning equipment. Additionally, you will save in your heating and cooling bills. Studies suggest that homes insulated with spray polyurethane foam use up to 40 % less energy than homes insulated with conventional insulation. Your savings may be greater or less depending on your life style, appliances, house site, number and size
of windows, etc.
Will I smell the spray polyurethane foam insulation in my home?
Initially there will be a slight odor present. Usually within 24-48 hours the insulation is odorless. Polyurethane foam is common in most homes already. Chemically it is similar to the foam in couch cushions, mattresses, pillows, refrigerators, and freezers.
Can spray polyurethane foam insulation be applied directly to electrical wiring? What about installed electrical devices like recessed lights?
Yes. Spray polyurethane foam insulation can be applied directly to electrical wiring. Recessed lights or other fixtures may require a certain amount of air circulation around them for cooling purposes. In these cases, boxes are built of dry wall (gypsum wall board) and placed over the lighting fixtures prior to being sprayed directly with the foam insulation.
Does spray polyurethane foam insulation absorb moisture?
Closed-Cell spray polyurethane foam insulation does not absorb moisture which is why we recommend it for below grade applications, basements, crawlspaces, attics, or anywhere in the house. Open-Cell spray polyurethane foam, while an excellent insulation product, is susceptible to moisture which is why we do not recommend it for application in certain areas of the building structure that are moisture prone.
Will spray polyurethane insulation strengthen my house?
Yes. Closed-Cell spray polyurethane foam insulation is a rigid foam with superior adhesion to all substrates.
As a result, it provides exceptional performance in improving wall and roof deck racking strength, making it a top seller for windy locations or locations prone to tropical weather.
Does spray polyurethane foam insulation contain formaldehyde?
Is spray polyurethane foam insulation toxic?
No. Once installed and cured spray polyurethane foam is NOT toxic. Only briefly during the initial installation does SPF give off a gas that should not be inhaled. Usually within 24-48 hours of application and with proper ventilation there are no hazardous fumes present in the building.
Is spray polyurethane foam insulation a fire hazard?
No. Polyurethane spray foam is not a fire hazard. While foam technically can burn, it’s no more flammable than the wood in your structure. Polyurethane spray foam has recently been approved by the International Code Council (AC377) allowing the insulation foam to be installed in limited access attic assemblies and crawl spaces without an ignition barrier. Polyurethane spray foam is the only foam insulation currently approved on the market to be installed without an ignition barrier. Consult the building code to see if an ignition or thermal barrier is required for your application.
Does spray polyurethane foam insulation create a rodent or insect problem?
No. Spray polyurethane foam insulation is an inert substance and as such, is pest resistant. There is absolutely no food value in the insulation. In fact spray foam is a deterrent to most pest because it seals many of the cracks that allow pest into a structure.
Does spray polyurethane foam insulation adhere to metal or wood studs?
Yes. Spray polyurethane foam insulation adheres to almost any material, especially wood and metal studs and concrete which are commonly found in residential and commercial construction.
How long does spray polyurethane foam insulation last?
Indefinitely. As an inert, long lasting polymer, any residential or commercial structure using spray polyurethane foam insulation will retain its ability to reduce heat and cooling loss for years to come.
Is spray polyurethane foam insulation corrosive to metals?
No, spray polyurethane foam insulation is non-corrosive.
Does spray polyurethane foam insulation contain any VOCs or CFCs?
No. Spray polyurethane foam insulation does not contain any Volatile Organic Compounds, nor does it contain any formaldehyde, bleach, or any CFCs (Chloro Fluoro Carbons) or HCFCs (Hydro Chloro Fluoro Carbons).
Does spray polyurethane foam insulation have building code approvals?
Spray polyurethane foam insulation has the approval of all four major building codes in the United States, and Canada. Spray polyurethane foam insulation is not only recognized as a Thermal Insulation, it also meets the requirements of a Vapor Barrier, and an Air Barrier. In fact, it is one of the most extensively tested and highest performing insulation products ever.