LEARNING OBJECTIVES:
- Interpret the Code Requirements for Building Envelope Design and Performance
- Learn About the Science Behind Thermal, Air and Moisture Control for Steel Stud Construction
- Discover How POLYISO Meets Requirements and Outperforms Traditional Methods for Optimum Control
- Understand Building Sustainability and Longevity
- Examine How Professionals are Looking to a Better Future
Continuous insulation, or c.i., is attached to building walls exterior to or interior to the structural framing, so the beams or studs don’t interrupt the insulation and allow heat loss, creating inefficiency.
- IECC: International Energy Conservation Code
- IBC: International Building Code
- ASHRAE: American Society of Heating, Refrigerating and Air-Conditionaing Engineers
2012 International Energy Conservation Code and ANSI / ASHRAE / IESNA Standard 90.1-2012 - Energy Standard for Buildings Except Low-Rise Residential Buildings, is a positive step forward in the efforts of the International Code Council (ICC) and the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) to increase the awareness and application of energy-efficient buildings.
The use of continuous insulation was mandated in 2009 for all jurisdictions except in Southern Florida and climate zones 1 and 2. It also depends on the type of occupancy and framing used. For steel-framed walls above grade, c.i. is mandatory in more than 90% of the United States today.
4 FACTORS AFFECTING BUILDING ENVELOPES
| 1. Temperature Gradients |
| 2. Control of Rain Penetration |
| 3. Air Leakage |
| 4. Air Flow |
BUILDING LIFE
This was proposed by Public Works & Government Services Canada, Real Property Services, A&ES, Technology and Environmental Services and illustrates the distinction between the terms ‘service life’ and ‘durability’. We need to ask if the actual service life is likely to meet or exceed the design service life. This answer will reflect a prediction of service life based on component and whole building durability factors under specific service conditions. None of the service life definitions deal with how long a building may actually stand, only with how long it will, or should, stand without unforeseen cost or disruption.
STEEL STUD WALL SYSTEMS
Steel stud wall systems for residential and commercial buildings are gaining in popularity. Very strong thermal bridges caused by highly conductive steel studs degrade the thermal performance of such walls. Several wall configurations have been developed to improve their thermal performance.
Very often, thermal performance of the steel stud wall is compared with wood stud wall. A reduction of the in-cavity R-value caused by the wood studs is about 10% in wood stud walls. In steel stud walls, thermal bridges generated by the steel components, reduce their thermal performance by up to 55%.
Relatively high R-values may be achieved by installing insulating sheathing, which is now widely recommended as the remedy for a weak thermal performance of steel stud walls.
POLYISOCYANURATE WALL INSULATION
WHY USE POLYISO WALL INSULATION?
- High R-value per inch
- Reflective R-value
- Thinner profile
- Fire resistance
- Thermoset material
- Permeability range
- Additional properties
- Easy to specify and install
Often referred to as “POLYISO”, it is a closed-cell, rigid insulation board consisting of a foam plastic core sandwiched between two facers.
The facers are composed of various inorganic and organic materials, usually aluminum foil, glass fiber or paper mats. The boards are typically manufactured in 4’x8’ panels, however, custom sizes are usually available.
- Achieves continuous insulation (c.i.) requirements
- Increase interior square footage with thinner profile (out to out)-or-More R-value on same square footage
- Wide range of thicknesses available
- Lightweight, nominally 2pcf
- Easy to cut & fit around openings/penetrations
- Various installation methods
- Governing Material Specification – ASTM C1289 Type I, Class 1
POLYISO is considered a thermoset material with a service temperature of up to 250F and will not soften or melt even at temperatures beyond this.
INSULATION COMPARISON
Insulation Comparison
c.i. R-Values
| Thickness | 1 1/2" | 2'" | 2 1/2" |
|---|---|---|---|
| EPS* | 6.0 | 8.0 | 10.0 |
| XPS* | 7.5 | 10.0 | 12.5 |
| Mineral Wool | 6.3 | 8.4 | 10.5 |
| POLYISO* | 9.6 | 13.1 | 16.7 |
*Approximate thicknesses, consult manufacturers for actual values
As a result, for POLYSIO the thicker it is, the more thermally efficient it gets. When comparing each of the materials, POLYISO has the greatest r value for each of the thicknesses stated. For example, when comparing XPS and POLYISO at a thickness of 2 inches, POLYISO will get 30% more r value. Overall, POLYISO is usually one of the top choices due to all of its benefits.
SUSTAINABILITY PRINCIPLES
Sustainability envisions the enduring prosperity of all living things.
Sustainable design seeks to create communities, buildings and products that contribute to this vision.
THE BUILDING
- Less energy usage
- Prolonged life of HVAC equipment
- Improved durability
- Reduced air infiltration
- Enhanced moisture control
- Smaller carbon footprint
THE OWNER/OCCUPANT
- Lower energy bills
- Enhanced occupant comfort
- Reduced building maintenance
- Improved indoor air quality with proper ventilation strategy
BUILDING CODES ASSISTANCE PROJECT (BCAP)
The U.S. Department of Energy's Building Energy Codes Program is an information resource on national model energy codes. The BCAP work with other government agencies, state and local jurisdictions, national code organizations, and industry to promote stronger building energy codes and help states adopt, implement, and enforce those codes.
The Program recognizes that energy codes maximize energy efficiency only when they are fully embraced by users and supported through education, implementation, and enforcement. The maps show the adaptation and implementation of the energy code in residential and commercial buildings for each state.
BEYOND THE CODE
Building codes play a major role in determining which products can be used in a building. Mandatory building codes set minimum performance thresholds for new construction and existing buildings including energy, air quality, fire protection and other areas to ensure safe and effective building operations. Energy codes determine minimum insulation levels.
The most effective approach to market transformation is to increase the “Pull". Recognize the urgency of the energy situation and the need for change. Some states and cities offer tax incentives for buildings that meet green building codes or become LEED certified.
MEET OUR EXPERT
Matt Stevens
RMAX Commercial Envelope Specialist
Matt received his Master's Degree in Architecture from Texas Tech University and has over 15 years in the building and construction industry. His experience includes architectural design, construction, consulting, training and development roles. As the Commercial Envelope Specialist at Rmax, he works directly with architects, owners, contactors and distributors to select the optimal insulation to meet the applicable building codes.