During the spring of 2020, low interest rates and a sharp increase in single-family housing starts led to a boom in the residential housing market, resulting in an upsurge in demand for lumber but a decrease in supply due to pandemic-related factors. These problems have culminated in soaring lumber prices, hurting both builders’ and home buyers’ pockets. According to an April 2021 analysis by NAHB, lumber prices have tripled over the past year, “causing the price of an average new single-family home to increase by $35,872.”
With lumber prices continuing to soar, there is a proven method for builders to build a more energy-efficient home while saving money by replacing OSB sheathing with polyisocyanurate (polyiso) continuous insulation and alternative bracing methods.
The Polyiso Advantage
Depending on the size and shape of the home, much of the OSB sheathing can be eliminated and replaced with polyiso continuous insulation and pairing with code-approved alternative bracing methods. Currently, 1/2-inch polyiso is a less expensive alternative and provides additional benefits, including increased R-value, reduced thermal bridging and integrated moisture control.
Exploring the Benefits
Cost: According to Random Lengths data and NAHB calculations, the average price of 1/2-inch OSB sheathing is currently $1,226 per thousand square feet. Polyiso insulation is currently under $450 per thousand square feet for 1/2-inch thickness.
Availability: Polyiso insulation has optimal supply availability, meaning builders and contractors can expect to receive orders on time to help keep construction schedules moving forward. Consistent availability of polyiso makes it easier for developers and builders to predict costs and profit margins.
R-value: A 2020 NAHB survey found that of the many benefits available to home owners, energy efficiency ranks highest on their list of most desired features. One of the most significant contributors to energy efficiency is continuous insulation. Polyiso insulation achieves a higher effective R-value with minimal material thickness and significantly reduces thermal bridging, meaning home owners can have a more energy-efficient home without sacrificing interior living space.
Weather-Resistant Barrier (WRB): Polyiso insulation is an approved WRB in place of additional, traditional membrane. When detailed properly, polyiso insulation functions as the WRB and drainage plane, preventing water intrusion at the outermost surface, and can serve as the air barrier. It is important to follow IRC requirements per Section R703.2 and the manufacturer’s installation instructions.
Bracing for Change
Common and approved methods of bracing can be found in The International Residential Code (IRC 2018) and are based on equivalent performance. This means the structural performance of using alternative bracing with polyiso can be just as strong as using wood sheathing, as long as the minimum requirements are met. However, always check local building codes to ensure you are properly addressing all requisites. This solution may not be applicable in seismic regions or those prone to high winds like coastal hurricane areas experiencing wind speeds of greater than 120 miles per hour.
The Advanced Alternative
By making straightforward adjustments to building plans in replacing wood sheathing with polyiso and bracing methods, builders can save significant time and money. When combined with the added benefits of polyiso insulation, including higher R-values and WRB capabilities, the advantages are clear.
Sponsored post by Jen Frey, Senior Product Manager – EnergyShield Wall Insulation, Atlas Roofing Corporation. Atlas Roofing Corporation is a leading manufacturer of polyiso roof and wall insulation. Polyiso is a safe, cost-effective, sustainable and energy efficient building material.