Tuesday, August 20, 2013

A Few Words About Wet Insulation

John D’Annunzio
 August 20, 2013


Once the moisture source is eliminated insulation will physically dry out from normal building environmental elements – building heat rises through insulation. It may appear to be dry by sight – and in the case of some insulation materials – it may appear to be dry from the touch. Once wet no insulation material fully recovers its original structural and thermal capacity. Bottom line; just because it looks dry does not mean it is dry.

The only true way to determine if insulation is dry is through gravimetric testing. Gravimetric testing determines the percentage of moisture present in an insulation. Each insulation material has its own coefficient of acceptable moisture percentage. This is the point at which the insulations thermal and structural capacity diminish.

It should be pointed out the IBC code indicates that all wet insulation must be removed from an existing system for a roof recover application. The code also states that only one recover application is acceptable on a low-slope roof system. Furthermore, some States and local codes indicate that if over 25% of a roof area has wet insulation – the entire area requires removal.

Thursday, August 15, 2013

Service Life Predictability

John A. D'Annunzio
August 15, 2013

The most heated debate in the roofing industry centers on the issue of roof removal vs. roof repair.  It is not uncommon that 3 or 4 roof evaluators of a given roof installation would reach 3 or 4 different conclusions relative to the roofs condition, maintenance requirements, and service potential.  The evaluation of the sources of available maintenance options, and their economic benefits to the building owner, would likely yield additional varying conclusions.  Their condition exists because roof maintenance is often conducted in the absence of a standard set of measurements, values, or decision-making guidelines.

For example, a 2-inch high ‘ridge’ in the roofing membrane is an entirely different problem on a six-year old roof than it is on a twenty-one year old roof.  It is also different when it occurs within an organic felt system rather than a fiberglass felt system, and so on.  How many authorities or experts would agree on its ultimate impact on the serviceability of a roof system?

The standard of measurements and values referred to would establish the specific problems or potential problems existing within the roofs, their severity, their density, and their impact on the remaining serviceability of the system.  Depending on the defect type and membrane type, its age, and other considerations such as climate and building occupancy, a ‘decision tree’ process could guide the user to the most technically and economically sound course of action.

The intent of a program developed in this manner is to reduce costs, minimize maintenance requirements, and establish a level of quality assurance that would result in predictable and controllable roof service.  The program should be dynamic so that it can be upgraded, revised, or remolded to reflect changing roof technology, in house experience, or specific user requirements.

Developing a system to rate a roofs condition, estimate its service life, and to provide a basis to make decisions or select repair alternatives is a difficult task.  Ideally, the system would be based on the instrument-measured impact that each situation (such as a defect, weather) has on the roofs integrity and condition.  Each measurement would include combinations of problem type severity level, and identify the membrane type, the climate, test sample analysis, and thermal performance of the insulation component.  Such an approach would require both roof investigation and material forensic analysis in a laboratory.

Considering the complexity of roof systems, and the state-of-the-art in roofing technology, an empirical approach is necessary to establish a procedure that will provide a disciplined and effective management tool for optimizing the service life of a roof system.  Following are suggested procedures for instituting the rating and decision process.  This process eliminates the subjectivity of the evaluator and is based solely on objective analysis and evidence.

Forensic Analytical Serviceability Tracker (FAST)

The goal of the Forensic Analytical Serviceability Tracker (FAST) program is to remove all subjectivity from the formulation.  The service life prediction is based solely on objective evidence.  All roof system components should be analyzed, inspected, and tested.

In the Forensic Analytical Serviceability Tracker (FAST) procedure a service life prediction is established within the following parameters:

1.                  The age of the existing roof system

2.                  The industry average service life of the roof system
 
3.                  Roof Condition Evaluation:

a.                   Roof Inspection

b.                  The identified distress factors of the existing roof system

4.                  The on-site forensic analysis of the existing roof system, based on:

a.                   Moisture analysis

b.                  Attachment – bonding or wind uplift

5.                  Material Forensic Testing (Laboratory Analysis)

 

Forensic Analytical Serviceability Tracker (FAST) Calculation Factors


The following factors are used in the calculation of the FAST method of determining the existing serviceability of an existing roof system:

1.                  Provide the age of the existing roof system.


2.                  Identify the existing roof membrane system in the chart below and determine the industry average service life.  (The National Roofing Contractors Association (NRCA) developed the estimated service life chart).
                                   Roof Membrane System                                 Mean Life Years
Natural Slate                                                               60.3

Clay Tile                                                                      46.7

Metal Panels                                                                26.5

Coal-tar Organic BUR                                                23.0

Coal-tar Glass BUR                                                    11.2

Asphalt Glass Shingles                                               17.7

Asphalt Organic Shingles                                           17.5

Asphalt Glass BUR                                                    16.7

SBS Modified Asphalt                                               15.9

Asphalt Organic BUR                                                14.7

EPDM                                                                         14.2

PVC                                                                            13.8

APP Modified Asphalt                                               13.7

CSPE-CPE                                                                  12.8

EP-TPO                                                                       12.7

Polyisobutylene                                                           10.6

 
3.                  The roof condition investigation should determine the existing defects of the roof system.  All components of the roof system should be investigated: membrane, flashings, penetrations, and metal terminations.  All defects should be noted.

All roof membrane systems have defects that decrease the service life of the roof system.  The major defects that have a direct influence on the service life of the roof system should be identified.

4.                  The on-site forensic analysis of the existing roof system:

a.       Moisture Analysis: Proper analysis includes a combination of both non-destructive and destructive methods of testing.  Investigations completed using only one of these methods are insufficient and lack creditability.  The equipment used to conduct non-destructive tests provides analysis (a snapshot) of the overall roof conditions of large expansive areas in a quick and efficient manner.  Destructive testing – coupled with gravimetric tests – are required to verify the conditions observed by the moisture analysis equipment.

There are three types of non-destructive testing equipment:

  1. Impedance or Capacitance
  2. Infrared
  3. Nuclear 

b.      Attachment: System attachment is the most critical element of roof application.  Improper attachment results in the increased probability of wind blow-offs and contributes to membrane strain created by differential movement of the system components.  Testing can be conducted with bonded pull test or wind uplift (dome) tests in compliance with  

5.                  Material Forensic Analysis of the existing system (Laboratory Testing):

a.                   Insulation:  determine the condition of the existing insulation by completing the following tests:

·                     Gravimetric Moisture Content

·                     Volumetric Moisture Content

b.                  Membrane: determine the condition of the existing membrane by completing the following tests:

Built-Up Roof System and Modified Bitumen:

·                     ASTM D 2829 Standard Practice for Sampling and Analysis of Built-up Roofs

·                     ASTM D 4 Standard Test for Bitumen Content

·                     ASTM D 1670 Standard Test Failure End Point in Accelerated and Outdoor Weathering of Bituminous Materials

·                     ASTM D 2523 Standard Practice for Testing Load Strain Properties of Roofing Membranes

·                     Microscopic Examination

Thermoset Membrane Systems (EPDM):

·                     ASTM D 4637 Standard Specification of EPDM Sheet used in Single Ply Roof Membrane, to include

·                     ASTM D412 Tensile strength

·                     ASTM D412 Elongation

·                     ASTM D816 Factory Seam Strength

·                     Mil thickness of existing membrane

·                     Seam strength

·                     Microscopic Examination

 
Thermoplastic Membrane Systems:

·                     ASTM D 4434 Standard Specification for Poly (Vinyl Chloride) Sheet Roofing, to include;

·                     ASTM D638 Tensile strength at Break

·                     ASTM D638 Elongation at break

·                     ASTM D638 Seam Strength

·                     ASTM D638 Overall Thickness

·                     Seam strength

·                     Microscopic Examination

Friday, August 9, 2013

Forensic Testing Used to Investigate Building Exterior Components

John A. D’Annunzio
August 9, 2013

Introduction to Forensic Testing

Forensic testing is playing an increasingly larger role in determining the cause of building exterior failures.  The most important attribute of properly completed forensics testing is that it eliminates subjective thought and presents objective analysis based on factual evidence. This is critical, particularly when you have participants that have a vested interest in the cause of a premature failure, such as contractors or material manufacturers. 

In building exterior investigations forensics testing can be employed through two investigative methods:

1.      on-site analysis, and

2.      material testing in an off-site laboratory. 

These methods can be conducted at all building envelope components from below-grade waterproofing, exterior walls, sealants, to roofs.  The most effective conclusions are drawn when both methods are applied in tandem to analyze a problem.  On-site analysis performed independently may provide only subjective conclusions.

On-Site Analysis

On-site analysis is completed through a thorough inspection of the required component.  In some respects this analysis is comparable to a crime scene investigation.  All aspects of the component are investigated to determine the cause of the problem.  Analysis can be conducted by visual observation, non-destructive testing using various moisture meters, gages and specialized testing equipment and through the collection of physical material samples that are extracted from the component. Material samples collected from the site are transported to an off-site testing laboratory for analysis.

Material Sample Testing

Material sample testing is the primary element in forensics testing.  Material testing identifies the types of materials applied in the construction of the building exterior component and, more importantly, it identifies the quantities of materials applied in construction.  In the United States construction material testing is conducted in accordance with the testing procedures established by the American Society of Testing Materials (ASTM).  ASTM is comprised of several sub-committees that work within each building component discipline to develop and update testing standards and procedures for all materials.  The sub-committees are comprised of industry professionals, primarily manufacturers, who work on these efforts on a volunteer (non-paying) basis.

Wednesday, August 7, 2013

Can Hail Damage a Roof System? Hail Yes!

John A. D’Annunzio
August 7, 2013

How to Inspect for Hail Damage


Hail force damage is often difficult to find because it is not easily detectable in all roof membranes.  It is often only visible within or below the roof surface.  Typically, the use of magnifying instrumentation or microscopic analysis is required to clearly identify the damage.  Damage to single ply membranes is often illustrated through fractures that occur at the bottom of the sheets.  Damage to built-up roof membranes may occur in the interply layers, and damage to some systems - such as SPF and PVC - can be identified at the surface layer in severely damaged conditions.

Small hailstones should not damage the membrane.  However, it has happened.  The best way to determine the size of the hail is by inspecting the metal components of rooftop equipment or copings.  Indentations from hail over the metal coverings can be measured to determine the actual hail size.  It is also a good idea to investigate adjoining roof areas or surrounding buildings to determine if the same storm produced similar damage. 

Certain roof membranes are negatively affected by cold weather conditions.  A combination of cold weather and rain can significantly cool the membrane surface and make it brittle, which makes it more susceptible to damage from the force of hail.

The Effects of Hail on Low-Slope Membranes:

Water in the form of hail could have negative effects on all roof systems.  Depending on the type of membrane and the size of the hail, roof damage can be sustained in the form of punctures or holes.  The roof area should be inspected after every hailstorm to insure that no damage has occurred.  All commercial low-slope roof membranes can be damaged by hail to some extent.  Damage can occur from improper installation or material defects. 

Hail damage to built-up roof systems typically occurs due to improper application of surfacing aggregate.  Aggregate that is not evenly distributed throughout the roof area (bare spots) or is applied in inadequate amounts renders the membrane vulnerable to hail force damage.  As previously noted, the damage typically occurs at the interplies due to the force of the impact. 

Hail damage to Sprayed Polyurethane Foam roofs largely results from improper application.  In consistent application, which results in uneven distribution of foam throughout the roof area, creates vulnerable points in the system for hail impact damage.  Properly applied (thicker) areas are more likely to restrict impact than the improperly (thinner) areas.  The lower density of foam in the inadequately applied areas reduces the compressive strength of the material and increases the probability of damage from hail force impact.

The most vulnerable roof systems to hail force damage are single ply membranes.  These types of membranes are susceptible because they typically do not employ protective surfacing components or the redundancy of materials that other conventional low-slope roof systems provide.  Impact resistance is limited to a single membrane layer.  Premature deterioration of the material can also contribute to hail force damage many single ply membranes – particularly Thermoplastics – have a tendency to harden and become brittle in colder temperatures.  This type of material deterioration can be identified by taking samples from exposed field areas and from unexposed laps at covered seams.  Comparative studies of these samples will indicate the differences in the physical properties of the membrane.  The vulnerability of unreinforced PVC in colder temperatures is well documented in this industry.

How to Avoid Hail Damage  


The best way to avoid hail impact damage on low-slope roofs is by installing adequately manufactured materials in accordance with proper application procedures.  The durability and puncture (impact) resistance of a membrane material is an important criterion of membrane selection, particularly in hail-laden regions.  The impact resistance standards for membranes that are currently enforced in the Southern Florida Building Code may soon be enacted in all hurricane regions, due to significant membrane damage from projectiles during these windstorms.  Similar codes may be considered in hail-laden regions.  It is very likely that that the insurance companies that are paying millions of dollars in hail force damage on an annual basis will lobby for these types of requirements.

Some hail force damage may occur due to the inherent tendencies of the applied membrane.  The only defense against these situations is a combination of proper application procedures and the addition of protective surfacing components over vulnerable membranes.  Proper application procedures include accurate and even distribution of aggregate on built-up roof systems and proper foam distribution in SPF systems.  On single ply applications it is critical that a durable (higher mil thickness), impact resistant (reinforced) membrane is installed.  In hail laden regions additional surfacing components, such as pavers or ballast, may be considered to provide further protection.

Monday, August 5, 2013

Problems With Roof Membrane Can Lead to Leaks

John A. D'Annunzio


The roof membrane can also be compromised, potentially causing roof leaks and other problems.  The building owner or maintenance supervisor should first make sure that the roof system has been applied properly by a licensed, qualified roofing contractor. However, even when the roof system is applied properly, the membrane can fail due to the following circumstances:

· Blisters, ridges or bare areas in the roof membrane can compromise the roof system’s performance. Cracks in the membrane can often occur as a result, allowing moisture into the system and the facility.
· Ponding areas or excessive wear in certain areas, can lead to structural damage to the roof system and leaks. 
· Plant growth on the roof surface, which sometimes occurs in the areas of chronic ponding conditions and accumulation of dust and organic air-borne contaminants, can also cause damage to the membrane.
· Punctures in the membrane, which may be caused by broken blisters, fasteners backing out of the substrate, dropped tools or other dropped objects, hail, lack of proper membrane support, or by mechanical abuse, allow for the moisture intrusion into the membrane and the facility.
· Plugged drains caused by debris, abuse, incorrect or marginal design, or insufficient maintenance, can lead to improper drainage and chronic ponding problems.

While some of the roof-related problems can be easily fixed, such as flashing around HVAC units or removing debris from drains, others may require professional assistance.  If the problems are the result of a faulty application or material failure, the building owner or maintenance supervisor should contact the roofing contractor who performed the original work. 

You may also want a professional roofing consultant to inspect your roof to get an unbiased opinion of your roof system’s potential problems. 

Either way, a little regular inspection and maintenance of a buildings roof will help to eliminate major problems, and the costs associated with those problems.