Advanced Insulation - Spray Foam Insulation

At Advanced Insulation we believe a state-of-the-art home built in an extremely hot climate should have an unvented attic with half-pound foam insulation installed on the underside of the roof sheathing. This technique is known as an unvented attic with cathedralized insulation. In this section, we will discuss half-pound foam insulation and unvented attics with cathedralized insulation in depth.

We believe that the underside of roof sheathing is where half-pound foam provides the best value. As a company, we also believe that foam is of questionable value when installed in conventional 2x4 or 2x6 exterior walls for a variety of reasons, which we will explore later in this article.

The problem with conventional attic insulation is that attic vents used in conjunction with recessed lighting fixtures and other penetrations through the sheetrock ceiling create an air leakage path from the inside of the house to the outside, and visa versa. These air leakage paths mean that dust, noise, hot attic air, insects … have a ready access path into the indoor environment. The other major shortcoming of insulating at the bottom chord of the truss is that the air distribution system, i.e. ductwork, is left in an extremely hot attic. We believe that in extreme climates insulating at the bottom chord of the truss with a vented attic is an outdated way of designing and building homes.

By insulating the underside of the roof sheathing, the air distribution system is brought inside the thermal pressure envelope, which means that this system is no longer exposed to extreme temperatures. Many people in the building industry make the mistake of over emphasizing attic R-value, while ignoring the fact that ductwork typically has an R-value of only 4. In the metropolitan Phoenix area, builders run 58ºF air in duct work with an R-value of 4 in an environment of summer time temperatures as high 135ºF. This is poor design.

By eliminating the need for attic vents and insulating on the underside of the roof sheathing we bring the ductwork into a conditioned space and almost eliminate heat gain through the air distribution system. A further advantage is that duct leakage becomes less critical since these leaks are now within the conditioned space of the building.

The unvented attic with cathedralized insulation is not a new technique. Pulte Homes of Phoenix and Las Vegas began incorporating this strategy in many of their subdivisions in the late 90’s. Pulte used wire-up batts and netted cellulose. They eventually gave up on the wired up batts due to performance issues. This strategy, coupled with the commitment to get the other basics of building science correct, provided Pulte Homes the confidence to guarantee the energy performance in their homes.

Advanced Insulation insulates many of metropolitan Phoenix’s finest homes. The builders of these homes know an unvented attic with cathedralized half-pound foam insulation is a superior building strategy. They have come to this conclusion through their first hand experience from both wiring-up batts and spraying half-pound foam as-well as feedback from satisfied customers.

In further discussion, we will attempt to answer key questions about half-pound foam insulation. We do not assume the view that half-pound foam is a panacea. We also take pride in our fiberglass and wall spray cellulose installations. We are more committed to total home performance than any single product and we have done our best to provide you with the most objective and accurate information.

Sprayed Foam Insulation

Spray foam insulation is usually defined by its density. There are three main types of spray foam that are installed in homes. Three-pound foam is installed on roofs. Occasionally, an inch of two-pound foam is installed in exterior walls, which then gets covered with other insulation products. Half-pound foam is the insulation you'll typically find installed at the underside of roof sheathing and in exterior walls.

The denser the foam the more expensive it is. Think of it this way, one cubic foot of three pound foam has six times more raw material than one cubic foot of half-pound foam. This is one of the principal advantages of half-pound foam; it simply costs less than denser sprayed-in foams. Foam is expensive to begin with, so using lighter density products makes sense.

One of the advantages of the denser foam is that the R-value per inch is greater. Instead of R-values ranging from R-3.6 to R-4.0 per inch for half-pound foam, the denser foams trap a denser gas than air and thus have aged R-values of approximately 6. We install both half-pound and two-pound foam, and in most cases we feel half-pound foam is a much better value because of the economics.

Another consideration is that half-pound foam has characteristics that permit the foam and roof assembly to dry in the event of a roof leak. A denser foam will trap moisture between the foam and the roof sheathing, which can create building durability problems. We believe that the greater the drying potential of a building assembly, the greater the building durability and building durability is a key component of our criterion for a high performance home.

There are a variety of manufactures of half-pound foam in the market. The most widely known is Icynene. Icynene is good foam, just like Demilec Foam, Biobased Foam, and North Carolina Foam. These foams are known as semi-open celled and semi-rigid when installed. They are water-blown foams, contain no formaldehyde, and emit no harmful VOC’s or CFCs. As mentioned, half-pound foams have R-values ranging from R-3.6 to R-4.0 per inch.

At Advanced Insulation we only use half-pound foams that are qualified by having an International Code Council (ICC) number or an ESR or NER report. We will not install foam products that do not have proper qualifications.

Installation of Foam

We strongly believe that our foam crew’s installations are the best in the Arizona. Simply ask any of our foam customers. For those who would like references, we will gladly provide a current list of builders and superintendents we've recently worked for. It is our company’s philosophy and commitment to getting the job done right that sets our installations apart from most other companies. We are proud of our culture and the quality of the insulation work we perform on a daily basis.

At Advanced Insulation we also believe that the installation of the foam is more important than the brand of foam, assuming the product meets the proper qualifications. Any product that is installed on a job site can be undermined by sloppy installation. This is true of framing materials, roof systems, sheetrock…foam is no different.

Foam insulation is not a panacea, as some foam manufactures and foam insulation contractors would like you to believe. We have inspected foam projects, where the foam was installed poorly. We found areas where the depth was too shallow and worse, areas where the pressure envelope was not sealed with foam to the outside thus undermining one of the big benefits of the foam.

Our philosophy is that workmanship and company culture are essential to achieving a quality job. Michael Uniacke, owner of Advanced Insulation, was featured as a consumer advocate and expert on a NBC Dateline expose’ on cheating in the insulation industry. Insulation doesn’t receive the same scrutiny as other building systems since the consequences of poor insulation are usually not safety concerns, but rather compromised comfort and high utility bills.

When we apply spray foam on an attic lid, we don’t tell our crews how much foam to spray. They simply know to spray enough foam until the job is done correctly. There is no incentive to skimp on material. We also go to great lengths to protect the building – covering windows, decorative beams, heating & cooling units, recessed cans … with plastic keeping them free of foam over spray. Pre-spraying preparation, or “prepping” as we commonly call this, is as important as the spraying itself.

How much R-value is Enough?

In unvented attics with cathedralized insulation, we recommend 6" of foam installed to the underside of roof sheathing having an R-value of 24. This is based on the excellent research done by Department of Energy (DOE) “Build America” program. Pulte Homes has insulated entire subdivisions having unvented attics with cathedralized insulation with an R-value of 21. As a result of the incorporation of this technique, Pulte was able to guarantee the energy costs in these homes.

To appreciate why 6” of foam is more than sufficient, consider that an unvented attic with cathedralized insulation places the air distribution system inside the thermal pressure envelope. These duct systems typically have an R-value of 4. By incorporating an unvented attic with cathedralized insulation the air distribution systems no longer sees extreme attic temperatures in the hot season and the heat gain through the duct work is eliminated.

Another major shortcoming in using R-value as a gage of insulation performance is that it does not factor in the foam’s ability to also act as an air barrier. Spray foam out performs fiberglass and cellulose since it creates its own air barrier. There is no air movement around and through the insulation. So, the foam only gets credit for its conductive properties in the R-value rating and not it’s air barrier properties, which is why the R-value is not a complete indicator of performance.

There are foam contractors in the marketplace using terms such as “effective R-value,” in order to get credit for the air sealing properties of the foam. We understand these contractors' frustration with traditional R-value measures, but their efforts often mislead consumers. Sometimes they intentionally mislead consumers, which is bad for the industry. For this reason, Advanced Insulation does not use terms like “effective R-value.”

The very same contractors who advertise “effective R-value” will also install less than 6” of foam on the underside of roof sheathing. Without proof, (from third party independent laboratories), supporting applications of less than 6”, we do not recommend R-values less than a 20.

The anecdotal evidence we have gotten from our past half-pound foam customers has been truly remarkable. We have customers who now will only use foam in their attics. This evidence coupled with the infrared scanning we have done, supports our belief in the half-pound foam.

Foam versus Fiberglass Batts and Dense Pack Cellulose

It is possible to wire-up batts to the underside of the roof sheathing or to install netting between the top chords of the trusses and then blow in cellulose insulation. Through first-hand experience from spraying half-pound foams, wiring up fiberglass batts, and doing dense pack insulation, we have concluded spraying foam is, by far, a superior method. We routinely see houses that have attics in which the framing is so complex that the attic can not be properly sealed without the benefit of foam.

When specified our company does an excellent job of wiring-up batts to the underside of roof sheathing. Having said this, careful examination of our work, as well as that of any of our competitors, shows a multitude of gaps and voids that occur because of the webs of trusses, cuts due to hip roofs, decorative framing details, and more. If the top chord of the truss is a 2x6 framing member then the fiberglass batts often will not touch, creating gaps that undermine the R-value.

During the summer of 2005 we performed infrared scanning analysis in several attics with both wired up batts and foam. We also took numerous temperature readings in order to observe where the insulation was failing and to determine where the thermal defects occurred.

Scanning attics with wired up batts that are failing within three years of installation.

Heat created by these gaps seen through the infrared camera.

Thermal defects and wired up fiberglass batts

What was most disturbing was that we observed wires starting to fail in attics with wired-up batts. We have surmised that heat transmitted through the truss web is transferred into the wire, which begins a series of expansions and contractions, thus weakening the wire.

We also know that some custom homes with complicated ceilings have many areas that are impossible to seal and insulate correctly unless foam is used. We have customers who will have wired-up batts in the field and foam the more complex areas in order to maintain the integrity of the thermal / pressure envelope.

If you combine the air sealing qualities of foam and the reduction of thermal defects due to the inherent quality of the sprayed-in process, you have a superior system. We genuinely believe that 6” of half-pound foam will outperform wired-up R-38 fiberglass batts.

Half-Pound Foam in 2x4 or 2x6 Exterior Walls

At advanced Insulation we are energy pragmatists and not energy purists. We realize no one product makes the home and that budgets often drive the decision making process. This is why we advocate the use of foam on the underside of roof sheathing and not necessarily on 2x4 or 2x6 exterior walls.

We have learned by blower door testing of homes that it is the roof and not the exterior walls where we need to concentrate on air sealing. Between the attic vents and penetrations in the ceiling, i.e. recessed cans, sprinkler heads, duct leaks - the ceiling is where most air leaks occur.

We also have conducted thermal analysis (Manual J Heat Gain Calculations) of homes in the desert and know that an exterior wall with an inch of rigid foam on the outside is not a major contributor to heat gain. This is especially true if the walls have porches – they are shaded and thus not in direct sunlight. The majority of stucco homes have one inch of rigid insulation on the exterior, which makes a huge difference in reducing thermal bridging and sealing the pressure envelope.

One could argue that one-inch of foam on a stucco house is a better value than sprayed half- pound foam between the framing cavities. Approximately 20-25% of a wall is wood framing with wood having an R-value of only 1 per inch. When sprayed between studs, foam doesn’t deal with this thermal bridging, whereas the foam on the exterior of the building does.

Cutting the foam flush with the face of a 2x4 or 2x6 generates a phenomenal amount of waste. This is due to the rapid expansion rate of the foam. It is virtually impossible to fill a cavity flush and not generate waste.

We believe that the energy savings do not warrant the investment of foam in conventional exterior walls. For walls greater than 2x6, the spraying of foam does not generate nearly as much waste therefore the labor is dramatically reduced, thus making the foam much more economically attractive. For those who can benefit from foam in exterior walls but can't afford the cost, a great compromise is our hybrid systems.

Hybrid Wall and Roof Systems

For our customers who have major budgetary constraints, Advanced Insulation offers a “hybrid solution” to controlling the insulation budget. Where the project budget does not permit the use of foam exclusively, we install foam where we get the most benefit, and wired-up batts or wall spray cellulose where it will perform the best. We know that the construction process is fraught with compromise, and we believe that with our “Advanced Hybrid Systems” we get optimum performance at the lowest possible price.

We can insulate exterior walls with foam / fiberglass batt or foam / walls spray cellulose insulation combination. This means we insulate approximately 3% to 6% of the walls with foam and the balance with the other materials. We spray the foam in areas that would be hard to insulate with conventional insulation. These are typically areas where efficient framing techniques were not utilized.

Truss webs create thermal short circuits, whereas the foam completely envelops the framing members.

Hybrid - Foam/Fiberglass

This combination with an inch of foam on the exterior provides the best value. A square foot of R-19 unfaced batts costs five times less than a square foot of foam installed. The foam on the exterior of the building eliminates thermal bridging.

Our wall spray cellulose / foam or fiberglass / foam hybrid is a much better value in exterior walls than an all foam installation. A good example of a hybrid system is where we insulate the roof with foam and spot-foam portions of the exterior walls that are difficult, if not impossible, and complete the job with conventional insulation. This way our customers get all the benefit of foam and use fiberglass or cellulose wall spray where it makes the most sense.

A component of any house insulated with foam should be a ventilation system. We would rather see the money our customers save by not using foam in the exterior walls spent on a Venmar Hepa 3000. This ventilation and filtration system introduces fresh air into the tightly sealed home in an energy efficient manner, thus addressing indoor air quality concerns.

Garage Separation Wall

A half-pound insulation quote from Advanced Insulation will include a wall separating the house attic from the garage attic. This is also true if we insulate the garage attic with foam. This wall is created to make sure that, while engines are running in the garage, none of the exhaust gasses get drawn into the house. Although the risk of this is not that significant, we recognize that when homeowners run kitchen fans, dryers, and bathroom fans they put the house under a slight negative pressure. Make-up air for these appliances could draw air from the garage and this is why we establish an air barrier between the house and the garage.

The Codes

An unvented attic with cathedralized foam insulation is a relatively new building technique, so we advise our customers that it may be wise to be proactive and work with their building inspectors in advance to gain approval for this technique. When assisting our customers in providing inspectors with the information they need, Advanced Insulation has experienced few objections from municipal building departments while getting approval for unvented attics and foam insulation.

The acceptance of unvented attics is gaining momentum. The work done by the DOE program “Build America” and Pulte Homes has helped to pave the way towards acceptance. The International Energy Conservation Code Council accepts unvented attics with cathedralized insulation. See Item 11.F Section R806.4.

One concern with foam insulation is its burn characteristics. Like wood, foam will burn when exposed to a constant ignition source. All half-pound foams should have a Class One Certifications since they are treated with a fire retardant package. The Demilec Foam we spray frequently, Sealection™ 500, has a flame spread index of 21 and smoke development of 216, which satisfies the 2003 International Residential Code (section R316). These are the key numbers building officials want to see.

To place the safety of foam insulation in an attic in context, there are many products in a home that contain foam, including carpet pads, sofa's, and mattresses, just to name a few. The vast majority of fires start inside the house and not in attics. The foam we are installing is also separated from livable areas, people and ignition sources by sheet rock.

The codes intention is designed to keep people and ignition sources away from the foam. To keep people away from the foam, the attic space must not have a walk in door and storage areas. In an attic there must not be any open source flame appliances such as an eighty-percent efficient furnace. We tell our customers, who are using gas heating, to only use sealed combustion 90% efficient or better furnaces.

Unvented Attics in Cold Climates

In cold climates unvented attics with cathedralized insulation require special attention to detail with the insulation due to the risk of moisture condensation. Insulation defects can create cold spots, and cold spots can lead to moisture condensation if the relative humidity in the building is not properly controlled. Warm moisture laden air will rise into an attic space and if there are any surface temperatures in the attic that are too low due to insulation defects, condensation will occur.

Building codes now require us to insulate at the underside of roof sheathing in commercial buildings over five thousand square feet because of the requirement for a sprinkler system in the attic. To prevent the fire sprinkler systems from freezing, it must be insulated at the underside of the roof sheathing. Based on our recent research, we believe it is a mistake to insulate these attics in cold climates with wired-up batts.

As we stated earlier, it is almost impossible to eliminate all of the defects in thermal pressure envelope in an attic with wired-up fiberglass batts. Even though we are proud of our work at Advanced Insulation, in cold climates, we do not believe this method satisfactorily reduces the potential for condensation to a low enough level.

A recent article titled Roofs, stipulated “if any insulation other than foam is used, it will be required that one inch of rigid insulation be installed on top of the roof in order to reduce the risk of condensation in the attic space. In extremely cold climates a vapor barrier paint will have to be sprayed over the half-pound foam.”

Roofing Issues

When insulation is installed at the underside of roof sheathing, the roofing material and roof sheathing will experience slightly higher operating temperatures. In extremely hot climates this impacts the choice of products that can be installed on the roof. Roofs that have tiles, cement shingles, or three-pound roofing foam on the roof are not a concern. Asphalt shingles and metal roofs have special requirements.

Tile, cement shingles and three-pound foam are all acceptable, since the tile is back vented so there is a reduced conduction path into the roof sheathing and a flat roof with three-pound roofing foam prevents conduction. These types of roofing systems protect the roof sheathing of extreme temperatures.

There are also different types of metal roofs. In extremely hot climates like the Phoenix metropolitan market, we only want to install half-pound foam on backvented metal roofs, since the airspace breaks the conduction path between the metal and roof sheathing. In other words we do not want to see metal roofs in which the metal sits directly on top of the roof sheathing.

We only recommend asphalt shingles that are guaranteed by the shingle manufacture for unvented roofs with cathedralized insulation. Elk Corporation has provided a guarantee for their premium roofing shingles as long as they are installed correctly.

Foam Costs More

When you make the choice to go to an unvented attic with cathedralized insulation you will pay more for insulation than you would have with a more conventional insulation package. The same holds true when you upgrade your window package from aluminum frame to wood frame. You pay considerably more for the superior product.

Foam insulation costs more for a variety of reasons. Installation labor and the material costs for traditional blown-in attic are considerably less than wired-up batts or foam. Foam insulation is a highly refined petro-chemical based product while cellulose is recycled newsprint treated with a fire retardant.

The minute you go from insulating at the ceiling, where the sheet rock is installed, to installing insulation at the underside of the roof sheathing, the area you need to insulate increases and so does the cost to insulate regardless of the type of insulation you select. The area increases due to the slope of the roof and separation walls that must be sprayed when trusses extend out over porches.

So the question that needs to be asked, is do the benefits of the foam outweigh the additional expense? We believe so, when you consider the lower utility bills, increased comfort reduced amount of dust being driven through attic vents and into the house, and a healthier home.

Summary

Advanced Insulation is committed to installing half-pound foam insulation on the underside of roof sheathing (cathedralized insulation) because it represents the future of insulation in attics in the Southwest. Our commitment to foam is based on our experience installing both fiberglass and cellulose to the underside of roof sheathing and realizing their shortcomings. Our perspective has been enhanced because we have the benefit of performing infrared scanning and blower door testing on homes insulated with foam versus conventional insulation. Based on these experiences coupled with anecdotal feedback from customers, we know that foam does a superior job.

The benefits of eliminating attic vents, bringing the ductwork into the thermal pressure envelope are too significant to ignore. It makes no sense to run conditioned air through the hottest part of the house in ductwork that only has an R-value of 4.

When you opt to incorporate an unvented attic with cathedralized insulation into your building design, we hope you will consider using Advanced Insulation. Foam insulation will only be as good as the products used and the installation itself. Advanced Insulation has an outstanding reputation for doing the highest quality insulation work in the State. Our prices are competitive and our commitment to quality is unparalleled.

Unvented Attics with Cathedralized Half-Pound Foam Insulation