Roof Synergy

FOAM ROOFING INSULATION
Vital foam-roof upgrades add comfort, lower
utility bills, and enhance your home's value

Why Quality Roof Insulation is Critical on an Eichler

One of the easiest ways to add value to an Eichler home to address one of the biggest problems an Eichler has: insulation loss through the roof. Adding insulation to the roof of an Eichler makes sense, because this large flat surface represents the single greatest point of failure in terms of insulating an Eichler.

Below:An SPF Foam roof is one of the easiest most effective ways to add insulation to an Eichler. The reflective cool roof coating, which keeps the roof surface temperature cooler, and the insulation of the spray foam provide a leak-proof barrier that can cut heating and cooling costs by as much as 40%.


Although windows are an important factor in the insulation of an Eichler, the roof itself is the largest surface of the Eichler exposed to the outdoor climate. As the air circulates inside an Eichler home, rising and falling, it inevitably rises to the ceiling. If the air near the ceiling is unusually cold or warm, it will continually add costs to respectively heat or cool that same air and bring it up or down to a temperate level. It is important to note that windows are a secondary point of failure in terms of insulation loss. Once a roof is well insulated, improving windows, for example moving from single pane to double pane, will then yield a greater benefit.

The fact remains, that the first place one should add insulation to an Eichler is on the largest exposed surface area: the roof. Adding insulation to the roof makes an Eichler home more valuable and improves quality of life, by both cutting energy costs and keeping the indoor climate more temperate. Fifty years ago, adding insulation was not as important as it is today, because energy costs were substantially lower. This is one of the reasons why Eichlers were not originally built with high levels of insulation.

The rising costs of electricity have outpaced the rise of inflation making homes more expensive to heat and cool today than fifty years ago. For example, in December 1955 Bob Johnson (an California Eichler owner) only paid $12 a month to heat his home. During this era, Eichlers had less than one inch of fiberglass, which performed poorly due to the compression caused by a heavy load of tar-paper and loose aggregate (gravel). For most, this poor level of insulation was insufficient; candles often melted due to summer heat and occupants breath steamed the frigid air on winter mornings. During this time period, energy costs were relatively cheap, so adding more insulation was not nearly as cost effective as it is in our day and age. And technology has now changed, so making an Eichler home both energy efficient and comfortable in both extreme heat and cold is now possible through improved ceiling insulation.


Below: SPF closed cell medium density (20 to 30lb) Foam is sprayed between basement joists, conforming to the wall cavity. Spray foam insulation traps air and vapor movement in addition to providing extremely high R-values. Although some contractors now offer cheaper hybrid insulation (spray foam with fiberglass), pure spray foam insulation is higher quality and a bit more expensive.

When is The Best Time to Install Roof Insulation?

The most cost effective time to add insulation to an Eichler is when re-roofing. The only practical place to add insulation on an Eichler in most cases, is on top of the roof surface. A roof surface must be removed or cleaned in order to add insulation, and this is something that must already be done when re-roofing. Therefore, adding insulation at this time saves otherwise unnecessary labor costs.

Polyurethane Foam is Superior to Traditional Roof Insulation

Most contractors have completely moved away from fiberglass batts and other more typical types of roof insulation because they are inferior in both R-value and air & moisture trapping when compared to polyurethane foam. Now most roofing systems, including BUR, modified bitumen, sprayed foam, torch down, and single ply now use polyurethane foam as the primary insulator. In the case of all roofs materials except sprayed foam, a board stock type of polyurethane foam is used underneath the roofing material to create insulation. Of course, in the case of sprayed polyurethane foam, the roof surface itself is the insulation.

Polyurethane Foam: High R-Value and Air Trapping

Mostly, the effectiveness of any insulation is measured in terms of R-value. An R-value of 1 represents about 1 inch of wood. So an R-value 19 would insulate as effectively as a 19 inch thick wood ceiling. An R-Value of 19 is ideal for an Eichler home, and adding insulation beyond this level would not create any noticeable difference. In fact, due to diminishing returns, insulation beyond this level is so ineffective that the costs could take decades to recover. When a polyurethane foam roof is installed on the building exterior, the first inch of foam represents 80 or 90% of the insulation benefit, and an incremental inch of foam can only add 10% to 20% more insulation benefit. Adding a sprayed foam roof to an Eichler which previously had poor roof insulation generally saves 25 to 40% on monthly heating and cooling costs.

Traditional insulation materials such as fiberglass, cellulose, and rock wool rely on trapping air to slow temperature changes. Just one inch of foam is substantially more effective than traditional types of insulation because billions of tiny closed cells completely block both moisture and air movement. Just a single cubic inch of polyurethane foam (the type used in roofing) has about 1 million cells. While manufactured foam boards insulate better than fiberglass, cellulose, and rock wool, polyurethane foam is superior to all of these. Both sprayed foam and foam boards have R-values superior to traditional insulation, although sprayed foam has R-values about 20% higher than foam board insulation. However, only polyurethane sprayed foam goes on to a roof in a single seamless, monolithic surface, effectively trapping air and vapor movement. This complements the high R-value of sprayed polyurethane foam roofing to create superior insulation.

Below: According to the U.S. Department of Energy (DOE) 40% insulation loss is caused by air infiltration. Spray foam insulation is the only insulation on the market that will conform the the shape of your home and truly prevent air infiltration. This air and moisture proof barrier provides ideal insulation. Although the home below is not an Eichler, it does provide a great example of how spray foam conforms to fit any structure.

Sprayed Foam Insulation is Superior to Foam Board Insulation

Foam boards are manufactured as 4x8 foot panels of varying depths. These boards are attached to the wood deck of a roof using long square head nails, screws, or adhesive. Boards shrink up to 4% with age, so its important they are attached securely to the roof surface. A membrane is then installed on top of the board such as BUR, single-ply, or modified bitumen.

Although foam boards provide high quality R-value, they are not nearly as effective as a seamless sprayed foam roof for trapping moisture and preventing air movement. It is well known that trapping air is critical to maximizing the effectiveness of any insulation. Various studys have been performed to determine just how much insulation is lost with a foam board vs sprayed foam. Generally, the rate of insulation loss appears to be about 25% due to the seams in the foam boards which fail to trap air and moisture movement. Research also shows that foam boards insulate best when taped together and when they are staggered in the case that multiple layers of boards are installed. Following these advised procedures however, is almost never done because they substantially increase labor costs as well as materials expenses without explicitly adding ‘r-value’. In other words, a non staggered series of foam boards, that are not taped together have the exact same R-value, despite the fact that the quality of insulation is 25% lower.

Foam boards have a further weakness beyond insulation loss at the seams. Foam boards must be carefully stored and protected until installed. Foam boards are not waterproof (nor were they designed or manufactured to be), so they will absorb water and moisture and warp if exposed to the elements. For example, leaving the boards outside for just one night can ruin them. Warped boards are no longer useable and must be thrown out.

Although not as effective as sprayed foam for building up low areas, foam boards can be used to some extent to correct ponding and build up low areas on a roof. Foam is light and durable and does not increase the weight load on a roof, so it is much safer and more effective to add than heavy membranes or loose aggregate (when building up a low area).

Another weakness of foam board insulation is that it often fails near overhang areas. The reason for this is that the foam board expands and contracts at a different rate than the roof membrane, causing undue stress on the membrane at the overhang where there is little or no insulation. A close look at the edge of a roof will show that the part of the roof with foam board under it sits at least one inch higher than the roof at the overhang. The hot/ cold differential caused by lack of insulation on the overhang causes added stress to the membrane. This part of the membrane either expands or contracts more than the rest of the roof which is held in place by the foam board insulation and the loose aggregate (tar and gravel) on the roof. This narrow inch of roofing membrane consistently takes more punishment than the rest of the roof, which is why it is usually the first part of the roof membrane to fail.

Below: Foam board insulation is installed on a roof. Although foam boards have high insulation ratings, generally the air infiltration at the seams causes foam board roofs to perform below their stated R-value. Taping the seams can improve insulation by as much as 20%, however most contractors are unwilling to do this because of the additional labor cost without any explicit improvement in the R-value of the roof (this also requires a higher upfront bid, so they risk losing the customer).


In contrast to foam boards, foam roofing is manufactured on site, and sprayed to seamlessly fit the existing roof. Foam is manufactured to be hard and rigid enough to walk on, but flexible enough to expand and contract with the rest of a building. There are many formulations of foam which are generally engineered for various climates and applications as required by contractors. Only closed cell polyurethane foam is used in roofing applications. The millions of tiny closed cells of plastic foam are inherently water repellant. Polyurethane foam for roofing is nothing like a foam cushion which you might find on a couch. Foam is lightweight, rigid, and strong, and feels similar to walking on a concrete sidewalk once installed on a roof.

Due to the fact that a spray foam roof is manufactured on site, it is critical to choose a contractor with a track record of success, because even one small unseen mistake could later lead to major roof issues or even failure. Sprayed foam requires no fasteners and adheres extremely well to a clean roof surface. Depending on the manufacturer and formulation foam varies in R-value from 6-8 per square inch. Foam is ideal for building up low areas of a sagging or ponding roof surface because it has no inherent drawbacks and forms seamlessly with the rest of the foam.

Spray Foam Roofing Helps Divert Landfill Waste

Due to foams light weight it can also be installed over existing roof membranes, effectively diverting large amounts of thousands of pounds of landfill waste. This can be safely done without significantly increasing the weight or load on an existing roof. In fact, removing hundreds of thousands of pounds of loose aggregate and cleaning a roof then adding sprayed foam roof usually results in a decrease in the load on a roof surface. Gravel (also called loose aggregate) removed from a foam roof can be cleaned and recycled for use on other roofs. Any underlying foam board or fiberglass insulation can be left in place to add incremental insulation to a roof.

Below: Generally, due to the light weight of Foam Roofing, it can be installed over an existing substrate. This diverts many tons of unnecessary landfill waste.

Reflective Coatings Enhance Roof Performance

On a 90 degree day the surface of a non-reflective Eichler roof may reach temperatures of 160 degrees or more! The net effect of many non reflective roof surfaces, black asphalt streets, vehicle and other motor exhaust emissions and air trapping due to crowded buildings and structures is called the ‘urban heat island’ effect. Scientific studies have shown that the temperature in a city is often 10 degree hotter than the area immediately outside of a city. This often has negative consequences on weather patterns and increases the usage of fossil fuels in a city area due to the increased need for air conditioning during summers. Non reflective, heat absorbent roofs contribute to the urban heat island problem, in addition to the negative immediate consequences of increased cooling bills or reduced living quality.

Cool roof coatings do more than just improve the comfort of building occupants. The extremely high temperatures caused by non-reflective roof surfaces heat up roof materials to extremely high levels, effectively aging the roof system prematurely. In contrast, cool roof coatings may reduce the surface temperature of a roof by as much as 50 degrees vs a non reflective roof on a 90 degree summer day (110 degrees vs 160 degrees respectively). By keeping the roof cooler, the building stays cooler, and by reflecting most of the suns rays, the roof surface is preserved, extending roof life..

Below: To comply with title 24 in California, cool roof coating was installed on this Los Angeles building. Depending on the level of direct sunlight a building receives, some studies claim cool roof coatings can reduce air conditioning costs by as much as 50% due to lower roof surface temperatures and less absorbed heat.


Energy star, the international standard for energy efficiency, recommends reflective roof coatings to reduce roof surface temperatures. This leads to increased building efficiency and helps counteract the urban heat island effect. The importance of reflective roof coatings has been recognized by state, local, and national government agencies. In fact, in 2005 the state of California passed title 24, which required new roof installations to use reflective coatings. This required no changes for foam roofing contractors since cool roof coatings were already in use which exceeded energy star standards.

Conclusion

The best time to install roof insulation is when re-roofing, and the best type of insulation to install is sprayed foam roofing, especially on Eichlers. The best type of insulation is polyurethane foam.

Although polyurethane foam boards can be beneficial for increasing insulation with a more traditional BUR, torch down, or single ply roof, these boards inherently have about 20% less R-value than polyurethane sprayed foam, which creates a single monolithic and seamless barrier. Furthermore, foam boards have seams which cause about 25% insulation loss. Although this can be counteracted to some extent with staggering (multiple layers of boards) or by taping seams, generally contractors are unwilling to do this because it does not explicitly increase the R-value and increased labor costs are substantial.

Polyurethane sprayed foam roofing is ideal for Eichlers for several reasons including: high R-value, air trapping, seamless barrier, waterproof closed cells, and cool roof coatings.

It's really amazing that a home like an Eichler--with a flat roof and giant windows, often the size of entire walls can actually be energy efficient. Its greats news as well that an Eichler owner can cut heating and cooling costs by 25% to 40% simply by adding a polyurethane spray foam roof. It does make sense that the roof is often the single biggest point of failure in insulating an Eichler home. The roof is the single largest surface area exposed to the outer elements, and most Eichlers have very poor roof insulation.

Its great that the government has recognized the importance of cool roof coatings as well. Hopefully, our cities will start making 'green' roofs, such as those with foam roofing, or solar power, their roof of choice.

Find a local Foam Roofing contractor.

hey, thanks for putting lots of work into this article.

i have heard about foam roofing insulation--i guess i didn't realize there was such a big difference in the effectiveness of this kind of insulation (vs cellulose or fiberglass).

it's also good to know or understand what R-value is and how vapor trapping or performance at extreme temperatures makes a big difference.

SPF foam is the highest quality insulation, but it is also a bit more expensive.