Basics of Insulation and Cool Roofing

There are two main purposes for insulation. Insulation helps keep heat in during the winter and helps keep heat out during the summer. Whenever there is a temperature difference between the inside and outside of a building, heat tends to flow from the warmer to the cooler space. Insulation reduces or slows the heat transfer through the building envelope.

By understanding how heat moves, it is easier to understand how insulation works. There are three modes of heat transfer: conduction, convection, and radiation.

CONDUCTION is direct heat flow through matter. It is caused by fast moving molecules on the hot side colliding with and transferring energy to slower moving molecules on the cold side. It results from actual physical contact of one part of the same body with another part, or of one body with another. An example of conduction through contact is a cooking pot on the solid surface of a hot stove.

COVECTION is the transport of heat within air or liquid, caused by the actual flow of the material itself. Warm air rises and cold air falls to create a convection loop. The moving air either enters or exits a building during this process. Up to 45% of heat loss in winter happens through convection through the roof.

RADIATION is the transmission of electromagnetic rays through space. The radiant heat rays of the sun do not become heat until they strike an object such as the roof of a building. As the roof surface heats up, the heat energy is transferred by conduction throughout the rest of the roof mass. Infrared radiation from the sun is the source of 93% of the summer heat gain through a roof.

Thermal insulation does not stop the transfer of heat into or out of a building; it only slows down the transfer. R values are a means of showing the thermal value of an insulating material. R value is a measure of resistance to heat transfer by conduction and does not apply to other methods of heat transfer. Insulative materials act to hinder the flow of energy by using a gas and randomness of material to reduce direct contact (conduction) and air flow (convection).

R value has no utility to measure the reflective capability of a material. Highly reflective materials act to keep a surface cool by reducing the amount of the sun’s energy that is absorbed (radiation). The energy that is not reflected is either absorbed or emitted by the surface. The amount of radiation that is emitted is a function of the emissivity factor of the material. The most effective cool roofing materials then, are those with both high reflectivity (sun’s energy bounces off) and high emittance (easily sheds energy that is absorbed). A good cool roofing system combines reflective membrane with an optimum amount of insulation to reduce heat loss from convection in winter.

Selecting A Commercial Roofing System

Building owners, roofing contractors, and specifiers have many options when deciding which commercial roofing system is best for a specific project. When selecting a roofing system, there are many issues to investigate. A thorough investigation will assure you that your investment is the best long-term roofing decision.

1. History/Longevity:

How long has the roof product been on the market under one owner? Proven longevity is critical when selecting a roofing system or manufacturer.

2. Cost:

Up-front cost is often perceived as the key factor in choosing a roofing system. However, the life cycle cost is the more important financial aspect that needs to be investigated. Considerations should include: tear-off, maintenance expenses, energy savings, additional warranty cost, and fast, non-disruptive installations.

3. Installing Contractors:

The long-term success of any roofing system ultimately falls on the installing roofing contractor and their application quality. Building owners and specifiers need to investigate the roofing contractor thoroughly. Roofing contractors should be trained and authorized by the manufacturer to ensure that quality is kept at the highest level.

4. Warranty:

Roofing system warranties can occasionally be confusing. Many times, manufacturers don’t have a published warranty and in some situations, the manufacturer or roofing product has been on the market less than 10 years, with warranties ranging from 10-20 years.

Features you may want to consider for a commercial warranty are:

  • Exclusions for consequential damages
  • Additional cost for the warranty
  • Exclusions for ponding water
  • Whether it’s a “repair or replace” warranty
  • Whether the warranty is transferable

5. Type of Building Design:

The roofing system should be flexible and able to be designed to meet the needs of virtually any type of structure. Determine if the roofing system can be designed for:

  • Dead level, low-sloped, or steep-sloped roofs
  • Buildings that cannot handle additional weight
  • All types of decks
  • Retrofit applications
  • Small roofs to large facilities
  • The strictest wind or fire code requirements
  • Metal buildings

6. Prefabrication:

Prefabrication is very important when choosing a roofing system as it allows the manufacturer to construct a portion of the roof in ideal factory conditions. Many commercial roofs are completely “manufactured” by an installer on top of a building where heat, humidity, cold, wind, and poor labor decisions will affect the roof’s long-term performance.

7. A Complete System Supplier:

With respect to commercial roofing systems, it is important to select one that has single-source accountability. It is important to have complete system warranty coverage, not just a warranty for the materials supplied by the manufacturer.

8. Company Support:

Contractors especially should investigate this issue to make sure the company supplying and warranting the roofing system is a complete service provider. These support services should be provided to all contractors:

  • Sales
  • Marketing
  • Engineering
  • Quality Assurance
  • Manufacturing

9. Rooftop Environment:

  • Is there a lot of foot traffic on the roof?
  • Are there numerous penetrations on the roof?
  • Any rooftop emissions?
  • Are there extreme variations in the expansion and contraction of the building?

Each of these issues needs to be addressed when choosing a roofing system to purchase or install. Make sure that the roofing system you choose for your commercial application has the sales, marketing, quality assurance, engineering staff, and reputation to meet your needs.

Roof Dilemma: Maintain or Replace?

Is roof replacement a better option than maintaining it when the roof’s watertight integrity – its primary function – fails? In other words, at what point do roof leaks become intolerable, and it’s time to replace the roof?

Think about how roof leaks can affect the bottom line:

  • Interior damage: To ceiling tiles, carpet, computers, gymnasium floors that could cost $500,000 to replace.
  • Production downtime: Shutting a line down for a day could cost thousands of dollars in lost productivity.
  • Lost business: Roof leaks at a four-star hotel can make the priciest rooms unavailable for guests.

Delaying roof replacement can add costs to a new roof project once the decision to replace it is made. Ineffective and inconsistent patching and other maintenance can allow water to penetrate the membrane and cause irreparable damage to roof system components, including insulation and the roof deck itself. Here are some potential added-cost considerations:

  • Tear off – add $1-2 per square foot.
  • Roof deck replacement – add $2.50-6.00.
  • Asbestos removal (possible for some older facilities) – add 10% or more.

The roof contributes – on average – 5% to the construction cost of a building, but is the most litigated component of a commercial building.

Building owners/managers should use their experience to establish a projected average service life of roofs. Several factors will influence a roof’s service life: design quality, installation integrity, products, maintenance, roof use, and weather.

Here’s an example: If you manage a million square feet of roofing that has a projected life expectancy of 20-30 years, you might consider budgeting to replace 1/20 or 5% (50,000 square feet) per year. If the average installation cost is $5 per square foot, look to budget $250,000 each year.

So when you are deciding between maintaining or replacing, look at your annual maintenance costs and if they are exceeding what your annual new roof budget is, it may be time to replace.


Solar-Ready…and Moving Forward

This photovoltaic (PV) segment of the roofing industry continues to grow while most others decline. This trend is mainly due to rising energy costs and federal stimulus goals of making our country greener. Combine these factors with state and/or local incentives in many areas of the country and the return on a new roof and PV system investment can be less than ten years in some cases. The Database of State Incentives for Renewables & Efficiency (DSIRE) ( provides a “comprehensive source of information on state, local, utility, and federal incentives and policies that promote renewable energy and energy efficiency.”

As with any major building investment, there are number of considerations that must be addressed with a rooftop PV installation: how will the system be mounted on the roof – with penetrations, ballast, or adhesive? Can the building structure support the additional load? What about local codes and permits? How will the watertight integrity of the roof be ensured during and after installation?

When building owners are interested in solar, the roof system must be addressed. The PV system should be installed in an environment that will not require extensive roof maintenance or replacement for 20 to 30 years because the cost to remove and reinstall PV systems in order to (for example) find a leak source can be expensive. Another consideration: the incremental cost of a new roof will be minimal compared to the cost of the complete new PV system – a smart building owner will take care of both at the same time.

Although PV is an electrical application, roofing is the trade that owns the rooftop, and the majority of solar PV decisions/installations are controlled by roofing contractors. In California (where the use of PV is common) many roofing contractors have created in-house PV departments or have working relationship with solar integrators – the experts that design the systems for each specific building.

Solar technology will continue to show gains, both in efficiency and usage. Currently, it is widely accepted in only a few states because of the financial incentives available in those areas. Incentives will continue to expand to other parts of the country, and if the demand for rooftop PV has not hit your area yet, it will within a few years.


Roof Maintenance

Routine maintenance inspections of your roofing system should take place twice a year, once in the spring and again in the fall. The fall inspection of your roofing system is important to ensure that it is ready for the inclement weather of the winter months. The following are some areas that should be reviewed during the fall inspection.

  • Sealants
    • All edge terminations, pitch pans, stacks, and curbs should be inspected for proper adhesion and visible signs of cracking or wear.
  • Drainage
    • Drains must be kept free of debris such as bottles, sticks, and leaves. A proper-sized leaf grate will help prevent clogs. Commercial grade push brooms can be used to sweep leaves and other debris away from drainage paths: these materials should be removed from the roof. Additional inspections of the drains may be needed in areas with heavy foliage to keep the drains cleared throughout the year.
  • Parapet Walls
    • Parapets should be inspected for deteriorated coping, cracked or missing mortar joints, and any signs of deterioration. Always remember to practice safe inspection routines near any roof edge. Keep in mind that some roofing systems can be slippery due to frost, morning dew, rain, snow, etc.
  • Tie-Ins
    • Roof tie-ins should be inspected for proper adhesion between the roofing systems. The sealants used for completing the tie-in should be examined for cracks, splits, or gaps which could allow water infiltration.
  • HVAC
    • Rooftop units should be inspected for missing or unfastened panels and properly functioning condensate lines. These situations can produce moisture that is commonly and mistakenly believed to come from roof leaks, which can lead to unnecessary costs and aggravation.
  • Debris/Snow and Ice Removal
    • All debris that could lead to damage to the roofing system such as nails, screws, broken bottles, etc. should be removed from the roofing system. If at any time a shovel is needed for removing debris or snow, it is recommended that a plastic scoop shovel be utilized to minimize the risk of damage to the roof. A metal shovel or plastic with a metal edge, has sharp edges that can snag on plates/fasteners, seams, etc, and create a hole in roofing membranes. If removing ice from the roof, it is recommended that you use an ice melting product (such as salt) rather than chopping or trying to break up the ice, which could possibly damage the roof.

Frequently Asked Questions about PVC Roofing Systems. Part 3

Q: What makes PVC systems more cost-effective in the long run?

A: Life Cycle Cost analyses have proven that PVC roofing systems are among the least costly over time for two major reasons: long service life and energy efficiency. The longer a roof lasts without major problems, the less costly it is on an annual basis. Energy savings of up to 40 percent every year due to the reflective properties of white PVC roofs can add up to tens of thousands of dollars during a 20- or 30-year life-span. Custom prefabricated PVC roofing systems also contribute to cost-effectiveness because they generate less waste, require less time and labor to install, and reduce the potential for rooftop human error, because up to 85 percent of membrane seaming can be completed in a controlled factory environment.

Q: Environmental groups seem to think that PVC is one of the most hazardous products ever created – dangerous to human health and the environment. How do you answer that?

A: During the last 35 years, there have been literally dozens of scientific studies and more than 26 full-scale LCAs relating to the safety and environmental impact of vinyl production, use and disposal. Study after study by a wide range of scientific, governmental, academic, and industry groups has confirmed that vinyl production in the United States today is very safe, and that finished vinyl products, including PVC roofing membranes, are inert, posing no risk to human health and with very little impact on the environment. In fact, many PVC products – including reflective PVC roofing systems – often make a decidedly positive contribution toward sustainability. According to Dr. Patrick Moore, a co-founder of Greenpeace in 1971 and current chairman and chief scientist of Greenspirit Strategies:

“It’s completely unacceptable for activists to call PVC ‘toxic’ when PVC’s effects on health and the environment have been investigated at every stage from manufacture through use and on to final disposal – in all cases vinyl has been shown to be safe and environmentally sound.”

The Art Of Specifying A New Or Replacement Roofing System

Putting a new roof on a building is a major undertaking. Assembling the right team to plan and carry out the project can help ensure that the job proceeds smoothly, and that the finished product looks and performs up to expectations.

Who’s Involved?

An important first step is determining who to include in the decision-making process. While the exact titles will vary with each project, two individuals or groups are key. One is the employee most familiar with the current roof, any problems it’s been experiencing, and the solutions that have been used.

Not surprisingly, it’s also helpful to include the individual who will have final approval over the decisions to install the roof and the amount to be spent. Depending on the company, this individual may be the facility manager, building owner, purchasing manager, company owner, or head of finance.

In addition, roofing systems slated for installation on new construction often require the input of an architect or designer. Including them early on in the process helps ensure that all concerns are addressed up-front.

Another key member of the roofing team is, of course, the contractor chosen to install the roof. Facilities professionals evaluating contractors should consider the experience each contractor has with different roofing systems.

The Contractor’s and Manufacturer’s Roles

Before re-roofing begins, the contractor should complete a thorough investigation of the current roof and determine what, if any, problems have arisen.

The contractor also should ask the building owner or manager about any constraints the installers might face, such as, if there are times during which the noise that accompanies a roofing job would interfere with building operations.

Building owners and managers should also stay in contact with the manufacturer of the roofing system. If the contractor that installed the roof retires, for example, the manufacturer should be able to help the building owner locate another one.

Other Considerations

When a new roof is installed, the initial cost typically is top of mind for most building owners and managers. However, there are other costs that facilities managers should factor into roofing decisions. The warranty also plays a key role in the overall costs of the roof. What does it cover and what does it exclude? Some warranties cover damage to a building’s interior that results from a leaking roof, while others don’t.

Equally important to consider are the ongoing roof maintenance costs and its expected life. The less it costs to maintain a roof and the longer it lasts, of course, the lower the overall cost will be.

Assembling the right team, keeping the lines of communication open, and considering both the initial and long-term costs of different roofing systems help ensure a successful roofing project.

Frequently Asked Questions about PVC Roofing Systems: Part 2

Q: How are PVC roofing systems sustainable?

A: More than 26 Life Cycle Assessments (LCAs) confirm that PVC roofing membranes are an outstanding sustainable choice for many reasons:

  1. Energy efficiency.
  2. Mitigation of urban heat islands that cause elevated levels of air pollution.
  3. Waste reduction throughout their life cycle: production, shipment, installation, post-consumer disposal.
  • Only 43 percent of PVC membrane composition is derived from nonrenewable fossil fuel feedstocks, compared with other single-ply and built-up systems that contain a much higher percentage.
  • PCV requires less energy to produce than competitive products.
  • They typically last for 20 to 30 years, reducing the rate of waste flow into landfills.
  • There is virtually no scrap in PVC roof manufacturing or installation.
  • PVC roofs can often be installed directly over old roofs.
  • Many PVC roof manufacturers have post-use recycling programs.
  • PVC roofing membranes are inherently recyclable, and are the only roofing material that can be recycled back into roofing products.
  1. Extremely low contribution to greenhouse gases and hazardous emissions, due to closed-loop manufacturing.
  2. There are at least 10 categories in which white PVC roofing systems can help earn points under the LEED® rating systems.

Q: Why do PVC roofing systems last so long?

A: Among the reasons that PVC roofing systems typically last between 20 and 30 years with very little maintenance are the following:

  1. Reflective properties extend the useful life of the roof substrate materials by reducing the rate of deterioration by as much as 75 percent.
  2. Waterproof characteristics that prevent PVC from rotting, rusting or corroding.
  3. Custom prefabricated systems from some manufacturers that help ensure optimal installation and long-term performance.
  4. Heat-welding properties that create seams that are stronger than the membrane itself while eliminating the need for chemicals, torches or other hazardous installation methods.
  5. Inherent flame resistance strengthened by the addition of flame retardant additives, which facilitates Underwriters Laboratories Class A ratings and Factory Mutual Class 1 ratings.
  6. High resistance to chemicals, grease, and other harmful substances that is common on rooftops.
  7. Simple repair procedures normally accomplished by heat-welded patches or seams.

Warranty Considerations

Twenty-, thirty-, and even fifty-year warranties – the range of commercial roofing warranties available has increased significantly over the past few years. Does that mean a longer coverage period is automatically better?

Of course, you want a warranty that covers a reasonable period of time. Roofing systems are expensive. If the roof should fail, you should know whether the manufacturer will stand behind it.

However, that doesn’t necessarily mean that a longer warranty is the one to choose. You need to evaluate the conditions the warranty covers and the steps you’re required to take to ensure that it remains in force. Some longer manufacturers’ warranties sound good, but as they say, the devil is in the details.

As a starting point, you’ll want to know whether the roofing installation must pass an inspection, often conducted by the manufacturer or an independent third part, before the manufacturer will issue the warranty. There is nothing wrong with having a newly installed roof inspected. However, you should know before the installation process begins if this is required in order to activate the warranty.

Some manufacturers require the building owner to conduct regular roofing inspections, and then to submit reports showing that the roof has passed the inspections. Virtually all manufacturers require roofing inspections and extra payments for warranty protection beyond the standard coverage period.

Other warranties require an initial payment from the building owner. While there’s nothing inherently wrong with this, it helps to know this before you decide to use that manufacturer’s product.

Many warranties limit the amount to be paid if the roof fails. For instance, they may cover the replacement materials needed, but not the labor required to install the new roofing system. Contrary to conventional wisdom, many warranties do not cover the damage a building’s contents might sustain due to a roof failure.

In addition, damage caused by “acts of God,” such as hail storms or hurricanes, may not be covered under the warranty.

Building owners should also know whether they can transfer ownership of the roofing warranty if they sell their building.

Before purchasing a roofing system, building owners should be sure that the warranty offers a reasonable amount of coverage for a reasonable period of time. When the choice is between a highly restrictive longer warranty, and a shorter one that offers better coverage, the shorter warranty probably will be a better value.

What We Mean When We Say Green

The term “green roof” has become narrowly defined in recent years to refer to “vegetative roof.” But “green roof” can also mean “sustainable roof” – one that provides long-term environmental benefits that building owners want roofing systems to deliver for their high-performance facilities: high reflectivity; recyclability; able to accommodate photovoltaic systems; able to help facilities obtain LEED credits; etc. This brief video discusses these benefits and more. For additional information about green roofing, visit