Improve Energy Efficiency and Air Sealing in Above-Grade Walls

Transcription

1 Improve Energy Efficiency and Air Sealing in Above-Grade Walls United States. Residential

2 Energy Efficiency Ranks Highest Second only to the mortgage, a family s home heating and cooling payments represent the largest portion of most household budgets. So it isn t surprising that 72 percent of homebuyers indicate that a home s energy efficiency features most influence their purchase decision. In fact, they would pay almost $9,000 up front to save on utility costs.* Many families are also combining the search for cost savings with a growing desire for greener homes that reduce a family s footprint or impact on the environment. With rigid and spray foam insulation, and integrated system components from Dow Building Solutions, homebuyers can benefit from value-added, proven, greener solutions that can help reduce energy loss and save money. And homebuilders and re-siding professionals can offer their customers enhanced energy efficiency. For example, STYROFOAM Brand Extruded Polystyrene Foam Insulation and polyisocyanurate insulation from Dow cover the entire exterior wall surface helping to alleviate conditions that can lead to energy loss, including: Air infiltration Moisture intrusion Thermal bridging through wood framing Air convection in the wall cavity Wood frame and mechanical detailing that reduce the amount of cavity insulation The Right Product for the Right Job Dow offers one of the broadest arrays of rigid foam insulation and other integrated building envelope solutions to fit the specific needs of above-grade applications, regardless of climate conditions. For new construction and re-siding applications, STYROFOAM Brand Extruded Polystyrene Foam Insulation combines exceptional moisture resistance with long-term, stable R-values (R-5.0 per 1"). Polyisocyanurate insulation from Dow offers a higher R-value (R-6.5), with special laminated facers that enhance its resistance to moisture and damage. STYROFOAM Brand Spray Polyurethane Foam (SPF) Insulation (RS Series)** creates a solid layer of thermal, air and moisture protection in stud cavities. For a tight build, it is crucial to consider the home as an overall system that should be insulated and sealed against air infiltration through major areas (walls and roofs) as well as gaps, cracks and penetrations. In addition to these key insulation products, a host of integrated system components from Dow work together to help protect the home from air and moisture intrusion: GREAT STUFF PRO Insulating Foam Sealants and FROTH-PAK Foam Insulation kits**, and WEATHERMATE Flashings, to name a few. Trademark of The Dow Chemical Company ( Dow ) or an affiliated company of Dow *Based on 2008 National Association of Home Builders Consumer Preferences Study **Consult the label/instructions and Material Safety Data Sheets carefully before use. 1

3 Basic Physics Three flows to remember when insulating and air sealing a home: 1. Heat moves from hot to cold. 2. Air moves from high pressure to low pressure even through the walls of a house. 3. Moisture moves from high concentration to low concentration including through the walls of a house. Air Infiltration Air infiltration accounts for percent of the energy used for heating and cooling a typical home. * Rigid foam sheathing, such as STYROFOAM SIS Brand Structural Insulated Sheathing directly over the studs, can reduce air leakage through walls three times better than housewrap typically installed over OSB sheathing (Figure 1). Figure 1: Air Leakage of Wall Assemblies Air at higher pressure tries to move to areas of lower air pressure. The wind outside and the operation of a home s mechanical heating/cooling equipment can create pressure differences, which cause air movement between the inside and outside of a home. Water vapor is similar moving from areas of high water vapor concentration to areas of low water vapor concentration. Since warm air holds more moisture, water vapor tends to move from warm areas to cooler areas. Air movement also carries water vapor along the air leakage paths in a wall. As it moves through the wall area, water vapor may meet a surface with a temperature lower than the vapor s dew point. Condensation can result and accumulate in the cavity compromising the cavity insulation s performance and causing (initially) unseen damage to drywall, wood framing, and OSB or plywood sheathing. Air infiltration Air exfiltration Based on ASTM E283 testing detailed in Tech Solutions 217.0: Air Barrier Performance of STYROFOAM SIS Brand Structural Insulated Sheathing vs. OSB and Housewrap available at Common Sources of Energy Loss ** Rigid and spray foam insulation products from Dow can reduce these flows to save heating and cooling costs and reduce moisture problems. Effective Solutions from Dow 13% through plumbing penetrations 15% through ducts Rigid Foam Insulation STYROFOAM Brand Spray Polyurethane Foam Insulation WEATHERMATE Housewrap WEATHERMATE Plus Housewrap FROTH-PAK Foam Sealant FROTH-PAK Foam Insulation GREAT STUFF PRO Gaps & Cracks Insulating Foam Sealant GREAT STUFF PRO Window & Door Insulating Foam Sealant 31% through ceilings, walls and floors 10% through windows 11% through doors Trademark of The Dow Chemical Company ( Dow ) or an affiliated company of Dow *Source: **Source: Energy Savers Booklet: Tips on Saving Energy & Money at Home, Oct

4 Thermal Bridging Wood is a poor insulator. The wood framing in a home creates thermal bridges that allow heat to flow around insulation in stud cavities. In a typical home, thermal bridging through wood framing accounts for about 17 percent of energy loss.* Rigid foam insulation from Dow is the primary insulation layer for the home. It provides a complete, solid layer of insulation on the walls and covers all of the thermal bridges that cannot be insulated by cavity insulation reducing energy flow through the walls. And it significantly reduces air infiltration. Because it moderates the wall cavity temperature, rigid foam insulation reduces the potential for moisture condensation. Studs account for 25 percent of the wall surface. Left uninsulated, the wood framing contributes significantly to energy loss known as thermal bridging. Air Convection in Walls Hot air rises, and cold air drops. In the wall cavity, air near the warm side of the wall rises, while air near the cool side falls. This rising and falling of air within the wall cavity sets up a circular motion of air called convective looping (Figure 2). This does not involve air leakage into the wall just air movement within the hollow wall cavity. This circular motion of air in the wall cavity impacts energy efficiency. For instance, when the home is heated, convective looping moves cold air from behind the exterior sheathing to the back side of the drywall. Cold air from behind the drywall causes more heat to be lost through the wall, which causes the furnace to work harder. Convective looping steals heat from inside the house and releases it outside. In a wall insulated only with cavity insulation, heat moves easily through the studs and wood panel sheathing lowering the effective R-value of the wall system. Using rigid foam insulation from Dow closes thermal bridges to significantly improve R-value of the wall assembly as much as 32 percent. ** Inside Wood Stud Outside The air convection displaces air trapped in cavity insulation (like fiberglass batts or cellulose), lowering the R-value. But a layer of rigid foam insulation over the wall moderates the temperature inside the cavity. This reduces convection energy loss and increases the insulation value of the wall system. A layer of rigid foam insulation over the exterior of the wall warms the temperature inside the cavity and reduces the driving force for convective looping. This insulation layer: Reduces convection energy loss Increases the thermal performance of the wall system Increases the home s energy efficiency Reduces heating costs Figure 2: Convective Looping in a Wall Air movement within the stud cavity reduces the wall s thermal performance, contributing to energy loss. *Dow calculation based on estimated heat loss from typical house. **Wall assembly R-values calculated using parallel path from ASHRAE Handbook Fundamentals, pg

5 Wood Frame and Mechanical Challenges Cavity insulation is most effective when it is installed properly. Even so, several factors can limit the effectiveness of cavity insulation no matter how well it is installed: Structural requirements and wood framing Plumbing, electrical junctions and wiring HVAC ductwork In contrast, rigid foam insulation over the entire exterior wall surface covers the framing and augments cavity insulation for an energyefficient wall. Insulated sheathing provides a continuous layer of insulation for the building envelope and, in many cases, is the only layer of thermal protection. Structural requirements may necessitate wood framing more frequently than 16" or 24" on center. This extra framing restricts the use of cavity insulation. Insulated sheathing on the exterior reduces thermal bridging through these framing members. Plumbing and HVAC ductwork limit the use and effectiveness of batt insulation. Batt insulation must maintain its full loft to deliver its stated R-value. Insulation that is compressed into tight spaces will deliver a lower R-value. 4

6 Control Moisture It takes only a small amount of consistent moisture to create problems in a wall. Moisture from wind-driven rain on the outside and dew point condensation on the inside can compromise the R-value of cavity insulation and lead to mold, deterioration and wood rot. Insulated sheathing on the exterior can help protect the home from these moisture sources. Rigid foam sheathings from Dow are closed-cell, and some have special laminated facers for exceptional moisture resistance. They qualify as code-prescribed, water-resistive barriers when installed according to Dow installation instructions for this application. See ICC ESR STYROFOAM Brand Extruded Polystyrene Foam Insulation is inherently moisture-resistant helping to shed bulk water and defend against moisture penetration. It can also qualify as a water-resistive barrier. Enhance building envelope resistance to moisture intrusion with WEATHERMATE Construction Tape over insulation board joints and housewrap seams, as well as other penetrations. Wind-Driven Rain All brick and exterior sidings leak. Behind siding or brick, a moisture-resistant product is needed to manage winddriven rain and other sources of exterior bulk water. When bulk water gets behind the exterior sheathing, it can penetrate the wall cavity. Pressure differentials and capillary forces compound the penetration of water into a wall system. Insulated sheathing from Dow, installed over the studs, not only insulates the entire wall surface and moderates the stud cavity temperature to reduce convection, it also can qualify as a waterresistive barrier without the additional cost and labor of housewrap. Wood panel sheathing, like OSB, can allow moisture to move into the wall cavity. Adding housewrap to the wood panel sheathing will provide a drainage plane that helps protect the wall cavity from bulk water intrusion. Building with insulated sheathing instead of wood panel sheathing and housewrap not only provides a drainage plane to help protect the wall cavity, it also adds insulating value. Moisture management solutions for windows include WEATHERMATE Flexible Flashing, WEATHERMATE Straight Flashing and WEATHERMATE Sill Pan. Trademark of The Dow Chemical Company ( Dow ) or an affiliated company of Dow 5

7 Dew Point Condensation Dew point temperature is determined by relative humidity of the air. Relative humidity is determined by the amount of water vapor in the air at a given temperature. When water vapor in the air meets a surface that is cooler than the dew point temperature, water vapor condenses into liquid. It is common during the year for some surfaces in the wall to be cooler than the dew point temperature. Therefore, it is not unusual for some condensation to occur on surfaces in a wall. Condensation leads to damage when the surface that is wet supports the growth of mold or decay organisms, and it stays wet long enough at the right temperature for the organisms to grow. For moisture to cause damage, three conditions must exist: 1. Prolonged exposure to wetness 2. Material that supports mold/decay organisms 3. Temperature that allows the growth of mold/decay organisms Take away any one condition and mold/decay cannot occur. Insulated sheathing can take away two of the conditions for mold/decay. First, insulated sheathing can reduce the potential for condensation, which reduces moisture in the wall assembly. Second, insulated sheathing is made from water-resistant materials that do not support mold growth. Your Dow representative can help you determine the right thickness of insulated sheathing based on a dew point analysis. If either surface of the wall is colder than the dew point temperature, water vapor in the wall cavity will condense into liquid. Over structural sheathing, rigid foam from Dow adds insulation value and protects against moisture. Installing rigid foam insulation over wood panel sheathing reduces air leakage and wind-driven moisture from affecting vulnerable wood components. It also creates an even temperature within the wall so condensation is minimized something housewrap alone cannot do. Maximize Your Investment When you add a layer of rigid foam insulation to the studs or over wood panel sheathings such as OSB or plywood, you can make the most of your investment. STYROFOAM SIS Brand Structural Insulated Sheathing provides three functions in one product: wall bracing, insulation and a water-resistive barrier. Alternatively, rigid foam insulation from Dow is easy to install directly over studs using let-in bracing or metal strapping to provide the code-required lateral bracing. (Refer to 2009 International Residential Code, Table R ) Because it helps save energy costs, rigid foam insulation from Dow can pay for itself in the first two years. To add value to your investment, insulate the walls and entire building envelope with Dow Building Solutions products. Installing insulated sheathing from Dow directly over the studs maximizes the wall s insulation value and provides a level, even surface for the exterior finish. A layer of STYROFOAM Brand XPS Foam Insulation or polyisocyanurate insulation from Dow helps reduce the potential for condensation. Trademark of The Dow Chemical Company ( Dow ) or an affiliated company of Dow 6

8 Achieve a Tight Seal FROTH-PAK Foam Insulation is a two-component, quickcure polyurethane foam that fills cavities, such as rim or band joists, for insulation and air sealing. The Class-A rating (flame spread of 25 or less) allows its use in residential wall and crawl space applications. Designed to fill gaps up to 3", GREAT STUFF PRO Gaps & Cracks Insulating Foam Sealant forms a permanent, airtight and water-resistant bond when applied properly. It expands to take the shape of cracks and voids, forming a permanent, airtight and water-resistant bond to vinyl, wood and metal surfaces. GREAT STUFF PRO Window & Door Insulating Foam Sealant is a one-component, minimal-expanding, flexible polyurethane foam. It is exclusively formulated to air seal the gap between a window or door frame and its rough opening. For high-grade, above-grade wall insulation and more, call BLUE (2583). THE DOW CHEMICAL COMPANY Dow Building Solutions 200 Larkin Midland, MI For Technical Information: BLUE (2583) For Sales Information: NOTICE: No freedom from any patent owned by Dow or others is to be inferred. Because use conditions and applicable laws may differ from one location to another and may change with time, Customer is responsible for determining whether products and the information in this document are appropriate for Customer s use and for ensuring that Customer s workplace and disposal practices are in compliance with applicable laws and other government enactments. The product shown in this literature may not be available for sale and/or available in all geographies where Dow is represented. The claims made may not have been approved for use in all countries or regions. Dow assumes no obligation or liability for the information in this document. References to Dow or the Company mean The Dow Chemical Company and its consolidated subsidiaries unless otherwise expressly noted. NO WARRANTIES ARE GIVEN; ALL IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE ARE EXPRESSLY EXCLUDED. NOTICE: Changes to the International Residential Code require the installation of a water-resistive barrier (WRB) within most exterior wall assemblies in residential construction. The following Dow insulated sheathing products qualify as a WRB when installed according to the installation instructions developed for installation of foam sheathing as a weather-resistive barrier : STYROFOAM DURAMATE Plus, STYROFOAM Residential Sheathing, STYROFOAM Tongue and Groove, STYROFOAM SIS, STYROFOAM Square Edge, STYROFOAM Residing Board, DOW High Performance Underlayment, THERMAX Sheathing, TUFF-R and Super TUFF-R and therefore do not require the use of a building paper or a housewrap as a WRB. When a WRB is not needed, these Dow foam sheathings may be installed according to standard installation instructions for foam sheathing from Dow. Be sure products and installation instructions meet code requirements for your particular location. Note: WEATHERMATE and WEATHERMATE Plus Housewraps have already qualified as water-resistive alternatives to the prescribed felt (see Evaluation Reports NER-593 and NER-640 for approved alternative). STYROFOAM Brand Extruded Polystyrene Foam Insulation CAUTION: This product is combustible. Protect from high heat sources. A protective barrier or thermal barrier may be required as specified in the appropriate building code. For more information, consult MSDS, call Dow at BLUE (2583) or contact your local building inspector. In an emergency, call Dow Polyisocyanurate Insulation CAUTION: This product is combustible and shall only be used as specified by the local building code with respect to flame spread classification and to the use of a suitable thermal barrier. For more information, consult MSDS, call Dow at BLUE (2583) or contact your local building inspector. In an emergency, call WARNING: Rigid foam insulation does not constitute a working walkable surface or qualify as a fall protection product. Dow Polyurethane Foam Insulation and Sealants CAUTION: These products are combustible and will burn if exposed to open flame or sparks from high-energy sources. Do not expose to temperatures above 240 F. For more information, consult MSDS, call Dow at BLUE (2583) or contact your local building inspector. In an emergency, call STYROFOAM Brand Spray Polyurethane Foam contains isocyanate, hydrofluorocarbon blowing agent and polyol. Read the instructions and Material Safety Data Sheets carefully before use. Wear protective clothing (including long sleeves), gloves, goggles and proper respiratory protection. Supplied air or an approved air-purifying respirator equipped with an organic vapor sorbent and a P100 particulate filter is required to maintain exposure levels below ACGIH, OSHA, WEEL or other applicable limits. Provide adequate ventilation. Contents under pressure. STYROFOAM Brand SPF should be installed by a trained SPF applicator. FROTH-PAK Polyurethane Spray Foam contains isocyanate, hydrofluorocarbon blowing agent and polyol. Read the instructions and Material Safety Data Sheets carefully before use. Wear protective clothing (including long sleeves), gloves, goggles or safety glasses, and proper respiratory protection. Supplied air or an approved air-purifying respirator equipped with an organic vapor sorbent and a P100 particulate filter may be required to maintain exposure levels below ACGIH, OSHA, WEEL or other applicable limits. Provide adequate ventilation. Contents under pressure. GREAT STUFF PRO Insulating Foam Sealants contain isocyanate and a flammable blowing agent. Read the label and Material Safety Data Sheet carefully before use. Eliminate all sources of ignition before use. Wear long sleeves, gloves, and goggles or safety glasses. Provide adequate ventilation or wear proper respiratory protection. Contents under pressure. Building and/or construction practices unrelated to building materials could greatly affect moisture and the potential for mold formation. No material supplier including Dow can give assurance that mold will not develop in any specific system. Printed in U.S.A. Trademark of The Dow Chemical Company ( Dow ) or an affiliated company of Dow Habitat for Humanity is a registered service mark owned by Habitat for Humanity International Form No X-0710P&M