Attic Insulation and Attic Energy Solutions

-Attic Insulation-I've put a little information to help assist in explaining 'Attic Insulation for a Home'. I take a whole house approach to improve a Home's Energy Reduction Needs. The Attic Area and Attic insulation being just one area.  In the old days contractors just blew the insulation into the attic. Now, I suggest that any

• Air Infiltration areas be resolved before adding insulation- Stop the Air (Hot or Cold) From Entering or Leaving a Home.
  
  • This includes: proper attic ventilation, ceiling protrusions(Light Boxes / Ceiling Fan), access points, mechanical and electric points, Attic Knee Walls, Obtrusions, etc
  • Adding Radiant Barriers for Existing Buildings-in a nutshell this bounces the Exterior Temperature back outside.
  • Attached to the Underneath Side of Existing Rafters
  • Option 1:Double Reflective R-Values range from R-3.7 to R-17
  • Attic Add Insulation to meet Suggested Guidelines
  • When used in conjunction with a Radiant Barrier-Cost of Insulation is reduced and thickness / weight of insulation is reduced.
     
  • When we come over to perform an estimate. 
  • 1. We will inspect for the above mentioned problem areas. 
    2. Discuss the various solutions. 
    3. Next, I'll determine the Materials and Labor Needed to Complete and Fix the Areas Quoted in the Project. 
    4. I'll then submit a Project Proposal that will discuss project in detail. 
    5. Answer any Questions, Explain Procedures, and determine the least obtrusive time to Weatherize your Home.
    
    
  
  

  Looking forward to meeting you and discussing the ways I can help with Lowering your Energy Bills.

  
  

  Build Green,

  Scotty

  ps: Home Depot as Material Supplier

  
  
  

  Energy Star Government Suggestion for (Reference Links Below)

  w/ no insulation Add Insulation to achieve=R38 to R60

  If existing 3-4 inches Add Insulation to achieve=R38

  Suggested needed Rvalue of Insulation on Attic Floor=R25 to R30

   I will Save You $Money$!!!!  

• • Step One- Determine Installed Insulations R value
  
  
  
  
  
  Step Two - Calculate Your Need
  
  
  

  This is GreenFiber® Cellulose Loose-Fill Insulation click here to download coverage chart in PDF
  Application Coverage Chart				Product # INS551LD
  R-Value @75°F Mean Temp	Minimum Thickness (inches)		Maximum Net Coverage (No Adjustments for Framing)			Gross Coverage (Based on 2"x6" Framing, 16" on centers)
  To Obtain a Thermal Resistance (R) of:	Installed Insulation Should Not Be Less Than	Thickness After Settling	Maximum Square Feet per Bag	Minimum Bags per 1,000 Square Feet	Minimum Weight (lbs.) per Square Foot	Maximum Square Feet per Bag	Minimum Bags per 1,000 Square Feet
  R-13	4.1	3.7	55.4	18.0	0.407	61.1	16.4
  R-19	5.9	5.4	36.2	27.6	0.623	40.0	25.0
  R-22	6.9	6.2	30.7	32.6	0.734	33.5	29.8
  R-24	7.5	6.7	27.9	35.9	0.809	30.2	33.1
  R-25	7.8	7.0	26.6	37.6	0.847	28.7	34.8
  R-30	9.3	8.4	21.7	46.1	1.039	23.1	43.2
  R-38	11.7	10.5	16.6	60.1	1.355	17.5	57.1
  R-42	12.9	11.6	14.9	67.2	1.516	15.6	64.2
  R-49	15.0	13.5	12.5	79.9	1.802	13.0	76.8
  R-60	18.3	16.5	10.0	100.3	2.261	10.3	97.1
  The coverage chart is based on settled thickness, a nominal bag weight of 22.55 lbs and coverage based on the GreenFiber Monarch blowing machine. Settings are non adjustable. Use this chart for estimating purposes only. Job conditions, application techniques and settings on other equipment will influence actual coverage. Do not add water to this product.

  
  
  

  
  

  Referrence Materials:

  • http://www.ornl.gov/sci/roofs+walls/radiant/rb_fig2.html
  • http://www.ornl.gov/sci/roofs+walls/radiant/rb_02.html
  • http://www.ornl.gov/sci/roofs+walls/radiant/rb_tables.html#table1
  • http://www.ornl.gov/sci/roofs+walls/insulation/ins_07.html
  • http://www.greenfiber.com/step_one_-_calculate_your_need_how_to_install.html
  • http://www.homedepot.com/Building-Materials-Insulation-Radiant-Barrier/h_d1/N-5yc1vZ1xjlZbedf/R-100052556/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053
    
• 
  
Feel free to utilize the following information to Schedule a Free Green site evaluation- Scotty will Weatherize You Building Against the High Costs of the Summer Time Cooling Costs and Winter Time Heating Costs



CAD Design by Scotts Contracting, St Louis Renewable Energy



Scott's Contracting
scottscontracting@gmail.com
http://stlouisrenewableenergy.blogspot.com

Spray Foam: Open Cell VS Closed Cell

Scotty writes: In response to a prior questions:

Q:Which Spray Foam Insulation is Best, Open Cell or Closed Cell?

Open-Cell Vs. Closed-Cell

The real distinction between types of foam insulation focuses on whether they are open- or closed-cell. In general, both are made from the same materials and work in the same way, trapping air or gas in a plastic matrix. The differences start with the "blowing agents" used to create bubbles and end with both varied performance and cost.

Open-cell foam costs slightly less for the same thickness, but offers lower per-inch R-values than closed-cell products. In some instances, this is a disadvantage, but where thickness is less relevant, or where higher R-values are not needed, then open-cell can provide the better choice. It also has some green advantages over closed-cell: The blowing agent used to install open-cell insulation is water, which reacts with air to become CO2—while closed-cell products use HFCs.

Because CO2 expands quickly, the bubbles tend to burst before the plastic sets, and hence the "open cells," which produce a spongy, lightweight foam. The industry describes the foam as "half-pound" material, which simply means the foam has a mass that weighs 0.5 pounds per cubic foot. This density yields an R-value of approximately 3.6 per inch, equivalent to most traditional insulations. Because of the open cell structure, open-cell foam allows some vapor to pass through, making it a good choice in hot, humid climates, and under roof sheathing, such as in conditioned attics, where water vapor caught between insulation and sheathing could promote wood rot.

In short, open-cell foam, tested in accordance with ASTM E 283, provides an air barrier with vapor breathability. Water-blown solutions have less environmental impact than the current HFCs used for most closed-cell spray-foam insulation. And open-cell has about twice the noise reduction coefficient in normal frequency ranges as closed-cell foam. Because the blowing agent in open-cell insulation dissipates as it sets, instead of slowly over time, there is no degeneration of the R-value—a minor point given aged closed-cell R-values still trump open-cell R-values by a magnitude of nearly 100%.

Unlike open-cell foam, closed-cell foam uses chemical blowing agents that come in liquid form and become gasses as they are applied. These gasses expand, but not as quickly as CO2, allowing the polyurethane plastic to set before the bubbles burst. This yields dense foam weighing nearly 2 pounds per cubic foot, and without the capillary characteristics of open-cell, it remains impermeable. The blowing agents used perform like the inert gasses between the panes of high-performance windows, adding to the insulating qualities of the foam. Unlike open-cell foam, closed-cell foam rarely requires any trimming, with little or no jobsite waste.

Closed-cell has more obvious advantages over open-cell, and a slightly higher price tag (20% to 30% for the same thickness). It provides both a vapor and air barrier and offers an aged R-value of a whopping 6.5 per inch. Because of its density and glue-like consistency, it remains very strong, providing both compressive and tensile strength to structure comparable to added sheathing, increasing the racking strength of walls by as much as 300%, according to the NAHB Research Center. Because water does not penetrate or degrade the product, FEMA recommends closed-cell foam as a suitable insulation material for flood regions.

The principle disadvantage of closed-cell foam comes with overkill. If you do not require the extra vapor barrier, structural strength, and R-value per inch, then you may be wasting money. As for the added wall strength, while real and substantial, it's not acknowledged by building codes currently, so you can't reduce the structural bracing as a tradeoff.
---------------
Information found at: http://www.ecohomemagazine.com

Spray Foam: Toxic Blowing Agents and Fire Proofing ecohomemagazine.com/green-products/expanding-options.aspx

--
Scott's Contracting
scottscontracting@gmail.com
http://stlouisrenewableenergy.blogspot.com
http://scottscontracting.wordpress.com
 

Which Kind Of Insulation Is Best?

Email: Scotts Contracting to Schedule a Green Proposal

for Your Next Project 

Scotts Contracting Offers Green Insulation Installs for the St Louis Area

Hempcrete and Hemp Fiber Insulation have not been mentioned in this old article.

Contents: Introduction Why Insulate Your House? How Insulation Works Which Kind of Insulation is Best? What Is an R-Value? Reading the Label Insulation Product Types Insulating a New House Where and How Much Air Sealing Moisture Control and Ventilation Installation Issues Precautions Attics Walls Design Options Crawlspaces and Slabs Advanced Wall Framing Metal Framing Insulating Concrete Forms Massive Walls Structural Insulated Panels External Insulation Finish System Attic Ventilation or a Cathedralized Attic Adding Insulation to an Existing House Where and How Much How Much Insulation Do I Already Have? Air Sealing Moisture Control and Ventilation Insulation Installation, the Retrofit Challenge Precautions Attics Walls Basement Walls Floors and Crawlspaces Resources and Links About This Fact Sheet

Which Kind Of Insulation Is Best? Based on our email, this is one of the most popular questions homeowners ask before buying insulation. The answer is that the 'best' type of insulation depends on: how much insulation is needed, the accessibility of the insulation location, the space available for the insulation, local availability and price of insulation, and other considerations unique to each purchaser. Whenever you compare insulation products, it is critical that you base your comparison on equal R-values. What Is an R-Value? Insulation is rated in terms of thermal resistance, called R-value, which indicates the resistance to heat flow. The higher the R-value, the greater the insulating effectiveness. The R-value of thermal insulation depends on the type of material, its thickness, and its density. In calculating the R-value of a multi-layered installation, the R-values of the individual layers are added. The effectiveness of an insulated ceiling, wall or floor depends on how and where the insulation is installed. Insulation which is compressed will not give you its full rated R-value. This can happen if you add denser insulation on top of lighter insulation in an attic. It also happens if you place batts rated for one thickness into a thinner cavity, such as placing R-19 insulation rated for 6 1/4 inches into a 5 1/2 inch wall cavity. Insulation placed between joists, rafters, and studs does not retard heat flow through those joists or studs. This heat flow is called thermal bridging. So, the overall R-value of a wall or ceiling will be somewhat different from the R-value of the insulation itself. That is why it is important that attic insulation cover the tops of the joists and that is also why we often recommend the use of insulative sheathing on walls. The short-circuiting through metal framing is much greater than that through wood-framed walls; sometimes the insulated metal wall's overall R-value can be as low as half the insulation's R-value. Reading the Label No matter what kind of insulation you buy, check the information on the product label to make sure that the product is suitable for the intended application. To protect consumers, the Federal Trade Commission has very clear rules about the R-value label that must be placed on all residential insulation products, whether they are installed by professionals, or whether they are purchased at a local supply store. These labels include a clearly stated R-value and information about health, safety, and fire-hazard issues. Take time to read the label BEFORE installing the insulation. Insist that any contractor installing insulation provide the product labels from EACH package (which will also tell you how many packages were used). Many special products have been developed to give higher R-values with less thickness. On the other hand, some materials require a greater initial thickness to offset eventual settling or to ensure that you get the rated R-value under a range of temperature conditions. Insulation Product Types Some types of insulation require professional installation, and others you can install yourself. You should consider the several forms of insulation available, their R-values, and the thickness needed. The type of insulation you use will be determined by the nature of the spaces in the house that you plan to insulate. For example, since you cannot conveniently "pour" insulation into an overhead space, blankets, spray-foam, board products, or reflective systems are used between the joists of an unfinished basement ceiling. The most economical way to fill closed cavities in finished walls is with blown-in insulation applied with pneumatic equipment or with sprayed-in-place foam insulation. The different forms of insulation can be used together. For example, you can add batt or roll insulation over loose-fill insulation, or vice-versa. Usually, material of higher density (weight per unit volume) should not be placed on top of lower density insulation that is easily compressed. Doing so will reduce the thickness of the material underneath and thereby lower its R-value. There is one exception to this general rule: When attic temperatures drop below 0°F, some low-density, fiberglass, loose-fill insulation installations may allow air to circulate between the top of your ceiling and the attic, decreasing the effectiveness of the insulation. You can eliminate this air circulation by covering the low-density, loose-fill insulation with a blanket insulation product or with a higher density loose-fill insulation. Blankets, in the form of batts or rolls, are flexible products made from mineral fibers, including fiberglass or rock wool. They are available in widths suited to standard spacings of wall studs and attic or floor joists. They must be hand-cut and trimmed to fit wherever the joist spacing is non-standard (such as near windows, doors, or corners), or where there are obstructions in the walls (such as wires, electrical outlet boxes, or pipes). Batts can be installed by homeowners or professionals. They are available with or without vapor-retarder facings. Batts with a special flame-resistant facing are available in various widths for basement walls where the insulation will be left exposed. Blown-in loose-fill insulation includes cellulose, fiberglass, or rock wool in the form of loose fibers or fiber pellets that are blown using pneumatic equipment, usually by professional installers. This form of insulation can be used in wall cavities. It is also appropriate for unfinished attic floors, for irregularly shaped areas, and for filling in around obstructions. In the open wall cavities of a new house, cellulose and fiberglass fibers can also be sprayed after mixing the fibers with an adhesive or foam to make them resistant to settling. Foam insulation can be applied by a professional using special equipment to meter, mix, and spray the foam into place. Polyisocyanurate and polyurethane foam insulation can be produced in two forms: open-cell and closed-cell. In general, open-celled foam allows water vapor to move through the material more easily than closed-cell foam. However, open-celled foams usually have a lower R-value for a given thickness compared to closed-cell foams. So, some of the closed-cell foams are able to provide a greater R-value where space is limited. Rigid insulation is made from fibrous materials or plastic foams and is produced in board-like forms and molded pipe coverings. These provide full coverage with few heat loss paths and are often able to provide a greater R-value where space is limited. Such boards may be faced with a reflective foil that reduces heat flow when next to an air space. Rigid insulation is often used for foundations and as an insulative wall sheathing. Reflective insulation systems are fabricated from aluminum foils with a variety of backings such as kraft paper, plastic film, polyethylene bubbles, or cardboard. The resistance to heat flow depends on the heat flow direction, and this type of insulation is most effective in reducing downward heat flow. Reflective systems are typically located between roof rafters, floor joists, or wall studs. If a single reflective surface is used alone and faces an open space, such as an attic, it is called a radiant barrier. Radiant barriers are installed in buildings to reduce summer heat gain and winter heat loss. In new buildings, you can select foil-faced wood products for your roof sheathing (installed with the foil facing down into the attic) or other locations to provide the radiant barrier as an integral part of the structure. For existing buildings, the radiant barrier is typically fastened across the bottom of joists, as shown in this drawing. All radiant barriers must have a low emittance (0.1 or less) and high reflectance (0.9 or more).

Adding Insulation to an Existing House (Smart Approaches)

[Where and How Much] [How Much Insulation Do I Already Have?] [Air Sealing] [Moisture Control and Ventilation] [Insulation Installation, the Retrofit Challenge]
Does your home need more insulation? Unless your home was constructed with special attention to energy efficiency, adding insulation will probably reduce your utility bills. Much of the existing housing stock in the United States was not insulated to the levels used today. Older homes are likely to use more energy than newer homes, leading to higher heating and air-conditioning bills.

Where and How Much Adding more insulation where you already have some, such as in an attic, will save energy. You can save even greater amounts of energy if you install insulation into places in your home that have never been insulated. Figure 1 shows which building spaces should be insulated. These might include an uninsulated floor over a garage or crawlspace, or a wall that separates a room from the attic. Figure 3 can give you general guidance regarding the appropriate amount of insulation you should add to your home, and the rest of this page will provide more specific information.

A qualified home energy auditor will include an insulation check as a routine part of an energy audit. For information about home energy audits, call your local utility company. State energy offices are another valuable resource for information. An energy audit of your house will identify the amount of insulation you have and need, and will likely recommend other improvements as well. If you don't have someone inspect your home, you'll need to find out how much insulation you already have.

After you find out how much you have, you can use the ZipCode tool to find out how much you should add. This recommendation balances future utility bill savings against the current cost of installing insulation. So the amount of insulation you need depends on your climate and heating fuel(gas, oil, electricity), and whether or not you have an air conditioner. The program is called the ZipCode because it includes weather and cost information for local regions defined by the first three digits of each postal service zip code. The program also allows you to define your own local costs and to input certain facts about your house to improve the accuracy of the recommendations. However, some personal computer security systems won't allow Java programs to run properly. The recommended R-values table can be helpful in those cases, because it will provide recommendations based on insulation and energy costs for your local area.

How Much Insulation Do I Already Have?

 
Look into your attic. We start with the attic because it is usually easy to add insulation to an attic. This table will help you figure out what kind of insulation you have and what its R-value is.

Look into your walls. It is difficult to add insulation to existing walls unless:

• You are planning to add new siding to your house, or
• You plan to finish unfinished space (like a basement or bonus room).

If so, you need to know whether the exterior walls are already insulated or not. One method is to use an electrical outlet on the wall, but first be sure to turn off the power to the outlet. Then remove the cover plate and shine a flashlight into the crack around the outlet box. You should be able to see whether or not insulation is in the wall. Also, you should check separate outlets on the first and second floor, and in old and new parts of the house, because wall insulation in one wall doesn't necessarily mean that it's everywhere in the house. An alternative to checking through electrical outlets is to remove and then replace a small section of the exterior siding.

Look under your floors. Look at the underside of any floor over an unheated space like a garage, basement, or crawlspace. Inspect and measure the thickness of any insulation you find there. It will most likely be a fiberglass batt, so multiply the thickness in inches by 3.2 to find out the R-value (or the R-value might be visible on a product label). If the insulation is a foam board or sprayed-on foam, use any visible label information or multiply the thickness in inches by 5 to estimate the R-value.

Look at your ductwork. Don't overlook another area in your home where energy can be saved - the ductwork of the heating and air- conditioning system. If the ducts of your heating or air-conditioning system run through unheated or uncooled spaces in your home, such as attic or crawlspaces, then the ducts should be insulated. First check the ductwork for air leaks. Repair leaking joints first with mechanical fasteners, then seal any remaining leaks with water-soluble mastic and embedded fiber glass mesh. Never use gray cloth duct tape because it degrades, cracks, and loses its bond with age. If a joint has to be accessible for future maintenance, use pressure- or heat-sensitive aluminum foil tape. Then wrap the ducts with duct wrap insulation of R-6 with a vapor retarder facing on the outer side. All joints where sections of insulation meet should have overlapped facings and be tightly sealed with fiber glass tape; but avoid compressing the insulation, thus reducing its thickness and R-value.

Return air ducts are often located inside the heated portion of the house where they don't need to be insulated, but they should still be sealed off from air passageways that connect to unheated areas. Drywall- to-ductwork connections should be inspected because they are often poor (or nonexistent) and lead to unwanted air flows through wall cavities. If the return air ducts are located in an unconditioned part of the building, they should be insulated.

Look at your pipes. If water pipes run through unheated or uncooled spaces in your home, such as attic or crawlspaces, then the pipes should be insulated.

Air Sealing

 
Air sealing is important, not only because drafts are uncomfortable, but also because air leaks carry both moisture and energy, usually in the direction you don't want. For example, air leaks can carry hot humid outdoor air into your house in the summer, or can carry warm moist air from a bathroom into the attic in the winter.

Most homeowners are aware that air leaks into and out of their houses through small openings around doors and window frames and through fireplaces and chimneys. Air also enters the living space from other unheated parts of the house, such as attics, basements, or crawlspaces. The air travels through:

• any openings or cracks where two walls meet, where the wall meets the ceiling, or near interior door frames;
• gaps around electrical outlets, switch boxes, and recessed fixtures;
• gaps behind recessed cabinets, and furred or false ceilings such as kitchen or bathroom soffits;
• gaps around attic access hatches and pull-down stairs;
• behind bath tubs and shower stall units;
• through floor cavities of finished attics adjacent to unconditioned attic spaces;
• utiltity chaseways for ducts, etc., and
• plumbing and electrical wiring penetrations.

These leaks between the living space and other parts of the house are often much greater than the obvious leaks around windows and doors. Since many of these leakage paths are driven by the tendency for warm air to rise and cool air to fall, the attic is often the best place to stop them. It's important to stop these leaks before adding attic insulation because the insulation may hide them and make them less accessible. Usually, the attic insulation itself will not stop these leaks and you won't save as much as you expect because of the air flowing through or around the insulation. There are many fact sheets that will help you stop these air leaks:

• Air sealing
• Air sealing an existing home
• Air Sealing Technology Fact Sheet
• Air Sealing in Occupied Homes (1995)

Moisture Control and Ventilation
We talk about moisture control in an insulation fact sheet because wet insulation doesn't work well. Also, insulation is an important part of your building envelope system, and all parts of that system must work together to keep moisture from causing damage to the structure or being health hazards to the occupants. For example, mold and mildew grow in moist areas, causing allergic reactions and damaging buildings.
When Is Moisture a Problem?

When moist air touches a cold surface, some of the moisture may leave the air and condense, or become liquid. If moisture condenses inside a wall, or in your attic, you will not be able to see the water, but it can cause a number of problems. Adding insulation can either cause or cure a moisture problem. When you insulate a wall, you change the temperature inside the wall. That can mean that a surface inside the wall, such as the sheathing behind your siding, will be much colder in the winter than it was before you insulated. This cold surface could become a place where water vapor traveling through the wall condenses and leads to trouble. The same thing can happen within your attic or under your house. On the other hand, the new temperature profile could prevent condensation and help keep your walls or attic drier than they would have been.

Four Things You Can Do to Avoid Moisture Problems:

1. Control liquid water. Rain coming through a wall, especially a basement or crawlspace wall, may be less apparent than a roof leak, especially if it is a relatively small leak and the water remains inside the wall cavity. Stop all rain-water paths into your home by:

• making sure your roof is in good condition,
• caulking around all your windows and doors, and
• keeping your gutters clean - and be sure the gutter drainage flows away from your house.
• If you replace your gutters, choose larger gutters and gutter guards to help keep rain from dripping onto the ground near the house.

Be sure that the condensate from your air conditioner is properly drained away from your house. You should also be careful that watering systems for your lawn or flower beds do not spray water on the side of your house or saturate the ground near the house. It is also a good idea to check the caulking around your tub or shower to make sure that water is not leaking into your walls or floors. You can place thick plastic sheets on the floor of your crawlspace to keep any moisture in the ground from getting into the crawlspace air, and then into your house.

2. Ventilate. You need to ventilate your home because you and your family generate moisture when you cook, shower, do laundry, and even when you breathe. More than 99% of the water used to water plants eventually enters the air. If you use an unvented natural gas, propane, or kerosene space heater, all the products of combustion, including water vapor, are exhausted directly into your living space. This water vapor can add 5 to 15 gallons of water per day to the air inside your home. If your clothes dryer is not vented to the outside, or if the outdoor vent is closed off or clogged, all that moisture will enter your living space. Just by breathing and perspiring, a typical family adds about 3 gallons of water per day to their indoor air. You especially need to vent your kitchen and bathrooms. Be sure that these vents go directly outside, and not to your attic, where the moisture can cause problems. Remember that a vent does not work unless you turn it on; so if you have a vent you are not using because it is too noisy, replace it with a quieter model. If your attic is ventilated, it is important that you never cover or block attic vents with insulation. Take care to prevent loose-fill insulation from clogging attic vents by using baffles or rafter vents. When you think about venting to remove moisture, you should also think about where the replacement air will come from, and how it will get into your house. When natural ventilation has been sharply reduced with extra air-sealing efforts, it may be necessary to provide fresh air ventilation to avoid build-up of stale air and indoor air pollutants. Special air-to-air heat exchangers, or heat- recovery ventilators, are available for this purpose. For more information about controlled ventilation, see the Whole-House Ventilation Systems Technology Fact Sheet.

3. Stop Air Leaks. It is very important to seal up all air-leakage paths between your living spaces and other parts of your building structure. Measurements have shown that air leaking into walls and attics carries significant amounts of moisture. Remember that if any air is leaking through electrical outlets or around plumbing connections into your wall cavities, moisture is carried along the same path. The same holds true for air moving through any leaks between your home and the attic, crawlspace, or garage. Even very small leaks in duct work can carry large amounts of moisture, because the airflow in your ducts is much greater than other airflows in your home. This is especially a problem if your ducts travel through a crawlspace or attic, so be sure to seal these ducts properly (and keep them sealed!). Return ducts are even more likely to be leaky, because they often involve joints between drywall and ductwork that may be poorly sealed, or even not sealed at all.

4. Plan a moisture escape path. Typical attic ventilation arrangements are one example of a planned escape path for moisture that has traveled from your home's interior into the attic space. Cold air almost always contains less water than hot air, so diffusion usually carries moisture from a warm place to a cold place. You can let moisture escape from a wall cavity to the dry outdoors during the winter, or to the dry indoors during the summer, by avoiding the use of vinyl wall coverings or low-perm paint. You can also use a dehumidifier to reduce moisture levels in your home, but it will increase your energy use and you must be sure to keep it clean to avoid mold growth. If you use a humidifier for comfort during the winter months, be sure that there are no closed-off rooms where the humidity level is too high.
Insulation Installation, the Retrofit Challenges

Whether you install the insulation yourself or have it done by a contractor, it is a good idea to educate yourself about proper installation methods because an improper installation can reduce your energy savings. Also, if your house is very old, you may want to have an electrician check to see if: the electrical insulation on your wiring is degraded, the wires are overloaded, or knob and tube wiring was used (often found in homes built before 1940). If any of these wiring situations exists in your house, it may be hazardous to add thermal insulation within a closed cavity around the wires because that could cause the wires to overheat. THIS IS FOR FIRE SAFETY. The National Electric Code forbids the installation of loose, rolled, or foam-in-place insulation around knob and tube wiring. Adding thermal insulation to the ceiling or walls of a mobile home is complex and usually requires installation by specialists. If adding insulation over existing insulation, do NOT use a vapor barrier between the two layers!

Attics
On unfinished attic floors, work from the perimeter toward the attic door. Be careful about where you step in the attic. Walk only on the joists so that you won't fall through the drywall ceiling. You may need to place walking boards across the tops of the joists to make the job easier. Remember that it is important to seal up air leaks between your living space and the attic before adding insulation in your attic.
Installing batts and rolls in attics is fairly easy, but doing it right is very important. Use unfaced batts, especially if reinsulating over existing insulation. If there is not any insulation in your attic, fit the insulation between the joists. If the existing insulation is near or above the top of the joists, it is a good idea to place the new batts perpendicular to the old ones because that will help to cover the tops of the joists themselves and reduce thermal bridging through the frame. Also, be sure to insulate the trap or access door. Although the area of the door is small, an uninsulated attic door will reduce energy savings substantially.

In some houses, it is easier to get complete coverage of the attic floor with blown-in loose-fill insulation. It is best to hire an insulation contractor for this job. Loose-fill insulation must be prevented from shifting into vents or from contacting heat-producing equipment (such as recessed lighting fixtures). Block off those areas with baffles or retainers to hold the loose-fill insulation in place. When you stack new insulation on top of existing attic insulation, the existing insulation is compressed a small amount. This will slightly decrease the R-value of the existing insulation. This effect is most important if the new insulation is more dense than the old insulation. You can compensate for this stacking effect and achieve the desired total R-value by adding about one extra inch of insulation if the old insulation is fiber glass, or about 1/2 inch if the old insulation is rock wool or cellulose.

Reflective Systems are installed in a manner similar to placing batts and blankets. Proper installation is very important if the insulation is to be effective. Study and follow the manufacturer's instructions. Often, reflective insulation materials have flanges that are to be stapled to joists. Since reflective foil will conduct electricity, avoid making contact with any bare electrical wiring.

Radiant barriers may be installed in attics in several configurations. The radiant barrier is most often attached near the roof, to the bottom surface of the attic truss chords or to the rafter framing. Do not lay a radiant barrier on top of your insulation or on the attic floor because it will soon be covered with dust and will not work. A separate DOE fact sheet is available for radiant barriers to show which parts of the country are most likely to benefit from this type of system.

If your attic has NO insulation, you may decide to insulate the underside of the roof instead of the attic floor. (This option is more often used in new houses and is described in Design Option: ATTIC VENTILATION OR A CATHEDRALIZED ATTIC). If you choose the cathedralized attic approach, all attic vents must be sealed. Spray-foam is then often used to insulate the underside of the roof sheathing. If batts are used for this purpose, they must be secured in a manner similar to that described below for insulating under floors. It is best to hire an insulation contractor with experience in this type of installation for this job.

Walls

Installing insulation in the cavity of exterior walls is difficult. However, when new siding is to be installed, it is a good idea to consider adding thermal insulation under the new siding. The Retrofit Best Practices Guide provides useful information about adding insulation when you remodel the outside of your house. It usually requires the services of a contractor who has special equipment for blowing loose-fill insulation into the cavity through small holes cut through the sidewall, which later are closed. It is sometimes feasible to install rigid insulation on the outdoor side of masonry sidewalls such as concrete block or poured concrete. However, if that is not an option, you can use rigid insulation boards or batts to insulate the interior of masonry walls. To install boards, wood furring strips should be fastened to the wall first. These strips provide a nailing base for attaching interior finishes over the insulation. Fire safety codes require that a gypsum board finish, at least 1/2 inch thick, be placed over plastic foam insulation. The gypsum board must be attached to the wood furring strips or underlying masonry using nails or screws. The first-floor band joist may be accessible from the basement or crawlspace. Make sure it is properly insulated as shown in Figure 1. More detailed drawings and insulation techniques for the band joist are shown in the Wall Insulation Technology Fact Sheet.

Basement Walls
When using batt or rigid insulation to insulate the inside of concrete basement walls, it is necessary to attach wood furring strips to the walls by nailing or bonding, or to build an interior stud-wall assembly on which the interior finish can be attached after the insulation is installed. The cavity created by the added framing should be thick enough for the desired insulation R-value.

The kraft paper or standard foil vapor retarder facings on many blanket insulation products must be covered with gypsum or interior paneling because of fire considerations. Some blanket products are available without these facings or with a special flame resistant facing (labeled FS25 - or flame spread index 25) for places where the facing would not be covered. Sometimes the flame-resistant cover can be purchased separately from the insulation. Also, there are special fiber glass blanket products available for basement walls that require less framing and can be left exposed. These blankets have a flame-resistant facing and are labeled to show that they comply with ASTM C 665, Type II, Class A.



Floors and Crawlspaces
If you have a floor over a crawlspace, you can EITHER:

• Insulate the underside of the floor and ventilate the crawlspace, OR
• Leave the floor uninsulated and insulate the walls of an unventilated crawlspace.

When batts or rolls are used on the underside of a floor above an unheated crawlspace or basement, fit the insulation between the beams or joists and push it up against the floor overhead as securely as possible without excessive compaction of the insulation. The insulation can be held in place, either by tacking chicken wire (poultry netting) to the edges of the joist, or with snap-in wire holders. Batts and rolls must be cut and fit around cross-bracing between floor joists or any other obstructions. Strips of insulation may be cut off and stuffed into tight spaces by hand. Don't forget to place insulation against the perimeter that rests on the sill plate. If you insulate above an unheated crawlspace or basement, you will also need to insulate any ducts or pipes running through this space. Otherwise, pipes could freeze and burst during cold weather.

Reflective Systems are installed in a manner similar to placing batts. Proper installation is very important if the insulation is to be effective. Study and follow the manufacturer's instructions. Often, reflective insulation materials have flanges that are to be stapled to floor joists. Since reflective foil will conduct electricity, one must avoid making contact with any bare electrical wiring.

Spray-foam can be used to insulate the underside of a floor. The spray foam can do a good job of filling in the space around wires and other obstructions and in filling any oddly-shaped areas. It is best to hire an insulation contractor with experience in this type of installation.

When a fiberglass blanket is used to insulate the walls of an unventilated crawlspace, it is sometimes necessary to attach wood furring strips to the walls by nailing or bonding. The insulation can then be stapled or tacked into place. Alternatively, the insulation can be fastened to the sill plate and draped down the wall. You should continue the insulation over the floor of the crawl space for about two feet on top of the required ground vapor retarder. Because the insulation will be exposed, be sure to use either an unfaced product or one with the appropriate flame spread rating. When rigid foam insulation boards are used to insulate the walls of an unventilated crawlspace, they can be bonded to the wall using recommended adhesives. Because the insulation will be exposed, be sure to check the local fire codes and the flame-spread rating of the insulation product. If you live in an area prone to termite damage, check with a pest control professional to see if you need to provide for termite inspections.

 Article Provided by: http://www.ornl.gov/sci/roofs+walls/insulation/ins_06.html
--
Scott's Contracting
scottscontracting@gmail.com
http://stlouisrenewableenergy.blogspot.com

Wall RValue, Configuring Wall RValues, Wall RValue Testing

Wall R-Values that Tell It Like It Is

---

by Jeffrey E. Christian and Jan Kosny
Jeffrey E. Christian is the manager of the DOE Building Envelope Systems and Materials Program at the Oak Ridge National Laboratory, Oak Ridge, Tennessee, and Jan Kosny is a research engineer at the University of Tennessee in Knoxville.

---

There's a lot more to most walls than meets the eye, and the R-value of a whole wall can be considerably lower than the R-value of the insulation that fills it. At DOE's Buildings Technology Center, scientists have developed a system for measuring whole-wall R-value, and have already tested several types of wall system.

---

DOE's rotatable guarded hot box is the workhorse behind the whole-wall rating label system. Sample wall sections are placed in the box, where their thermal properties can be tested in a controlled environment.

Several new wall systems are gaining popularity, due to increasing interest in energy efficiency, alternatives to dimensional wood framing, and building sustainable structures. Steel framing, insulating concrete forms, autoclave cellular concretes, structural insulated core panels, engineered wood wall framing, and a variety of hybrid wall systems are a few of the new types. But accurately comparing the thermal performance of these systems has been difficult.

How Wall R-Value Is Usually Calculated

Currently, most wall R-value calculation procedures are based on calculations developed for conventional wood frame construction, and they don't factor in all of the effects of additional structural members at windows, doors, and exterior wall corners. Thus they tend to overestimate the actual field thermal performance of the whole wall system.
In these common procedures, the user enters a framing factor (ratio of stud area to whole opaque exterior wall area). The framing factor is usually estimated, is seldom verified against actual site construction, and is frequently underestimated (see "Is an R-19 Wall Really R-19?" HE Mar/Apr '95, p. 5). Framing factors range from 15% to 40% of the opaque exterior wall area, yet lower values are commonly used. Unfortunately, the wall's energy efficiency is usually marketed solely by the misleading clear-wall R-value (Rcw).

Clear-wall R-value accounts for the exterior wall area that contains only insulation and necessary framing materials for a clear section. This means a section with no windows, doors, corners, or connections with roofs and foundations. Even worse is the center-of-cavity R-value, an R-value estimation at the point in the wall containing the most insulation. This converts to a 0% framing factor and does not account for any of the thermal short circuits through the framing.

The consequences of poorly selected connections between envelope components are severe. These interface details can affect more than half of the overall opaque wall area (see Figure 1). For some conventional wall systems, the whole-wall R-value (Rww) is as much as 40% less than the clear-wall value. Poor interface details may also cause excessive moisture condensation and lead to stains and dust markings on the interior finish, which reveal envelope thermal shorts in an unsightly manner. This moist surface area can encourage the growth of molds and mildews, leading to poor indoor air quality.

Metal-framed walls are particularly vulnerable to thermal shorts. Unfortunately, builders often attempt to solve metal wall problems by making thicker walls and adding more insulation in the cavity between the metal studs. In fact, the thicker walls have an even higher percentage difference between clear-wall and whole-wall R-value.

Figure 1. Interface details for metal and wood framing.

Measuring Whole-Wall R-values

To compare wall systems more accurately, we have developed a procedure for estimating the Rww for various system types and construction materials (see "Wall R-Value Terms"). The methodology is based on laboratory measurements and simulations of heat flow in a variety of wood, metal, and masonry systems (see "How We Evaluate Wall Performance"). The whole-wall R-value includes the thermal performance not only of the clear-wall area, with its insulation and structural elements, but also of typical envelope interface details. These details include wall/wall (corner), wall/roof, wall/floor, wall/door, and wall/window connections.

Table 1. Clear-Wall and Whole-Wall R-Values for Tested Wall Systems
No.	System Description	Clear Wall R-Value (Rcw)	Whole Wall R-Value (Rww)	(Rww/Rcw) x 100%
1.	12-in two-core insulating units concrete 120lb/ft3, EPS inserts 1 7/8-in thick, grout fillings 24 in o.c.	3.7	3.6	97%
2.	12-in two-core insulating units wood concrete 40lb/ft3, EPS inserts 1 7/8-in thick, grout fillings 24 in o.c.	9.4	8.6	92%
3.	12-in cut-web insulating units concrete 120lb/ft3, EPS inserts 2 1/2 in thick, grout fillings 16 in o.c.	4.7	4.1	88%
4.	12-in cut-web insulating units wood concrete 40lb/ft3, EPS inserts 2 1/2 in thick, grout fillings 16 in o.c.	10.7	9.2	86%
5.	12-in multicore insulating units polystyrene beads concrete 30lb/ft3, EPS inserts in all cores	19.2	14.7	77%
6.	EPS block forms poured in place with concrete, block walls 1 7/8 in thick	15.2	15.7	103%
7.	2 x 4 wood stud wall 16 in o.c., R-11 batts, 1/2-in plywood exterior, 1/2-in gypsum board interior	10.6	9.6	91%
8.	2 x 4 wood stud wall 24 in o.c., R-11 batts, 1/2-in plywood exterior, 1/2-in gypsum board interior	10.8	9.9	91%
9.	2 x 6 wood stud wall 24 in o.c., R-19 batts, 1/2-in plywood exterior, 1/2-in gypsum board interior	16.4	13.7	84%
10.	Larsen truss walls 2 x 4 wood stud wall 16 in o.c., R-11 batts + 8-in-thick Larsen trusses insulated by 8-in-thick batts, 1/2-in plywood exterior, 1/2-in gypsum board interior	40.4	38.5	95%
11.	Stressed-skin panel wall, 6-in-thick foam core + 1/2-in oriented strand board (OSB) boards, 1/2-in plywood exterior, 1/2-in gypsum board interior	24.7	21.6	88%
12.	4-in metal stud wall 24 in o.c., R-11 batts, 1/2-in plywood exterior + 1-in EPS sheathing + 1/2-in wood siding, 1/2-in gypsum board interior. NAHB Energy Conservation House Details.	14.8	10.9	74%
13.	3 1/2-in metal stud wall 16 in o.c., R-11 batts, 1/2-in plywood exterior + 1/2-in wood siding, 1/2-in gypsum board interior	7.4	6.1	83%
14.	3 1/2-in metal stud wall 16 in o.c., R-11 batts, 1/2-in plywood exterior + 1/2-in EPS sheathing + 1/2-in wood siding, 1/2-in gypsum board interior. AISI Manual details	9.9	8.0	81%
15.	3 1/2-in metal stud wall 16 in o.c., R-11 batts, 1/2-in plywood exterior + 1-in EPS sheathing + 1/2-in wood siding, 1/2-in gypsum board interior. AISI Manual details	11.8	9.5	81%
16.	3 1/2-in metal stud wall 24 in o.c., R-11 batts, 1/2-in plywood exterior + 1/2-in wood siding, 1/2-in gypsum board interior. AISI Manual details	9.4	7.1	75%
17.	3 1/2-in metal stud wall 24 in o.c., R-11 batts, 1/2-in plywood exterior + 1/2-in EPS sheathing + 1/2-in wood siding, 1/2-in gypsum board interior. AISI Manual details	11.8	8.9	76%
18.	3 1/2-in metal stud wall 24 in o.c., R-11 batts, 1/2-in plywood exterior + 1-in EPS sheathing + 1/2-in wood siding, 1/2-in gypsum board interior. AISI Manual details	13.3	10.2	77%

We estimated whole-wall R-values for 18 wall systems, using a computer model. We validated the accuracy of the modeling using the results of 28 experimental tests on masonry, wood frame, and metal stud walls. The model was sufficiently accurate at reproducing the experimental data.
The whole-wall R-values estimated for the 18 wall systems are shown in Table 1 along with the clear-wall R-values. A reference building was used to establish the location and area weighing of all the interface details. The comparison of these two values gives a good overall perspective of the importance of wall interface details for conventional wood, metal, masonry, and several high-performance wall systems.
In general, construction details for the wall systems chosen come from the ASHRAE Handbook and from the respective manufacturers. In the case of the metal frame systems, the details come from the American Iron and Steel Institute and other common sources.
A wall's thermal performance is often simply described at the point of sale as the clear-wall value. The results shown in Table 1 indicate that the whole-wall value could be overstated by up to 26% for these systems. These differences can be even greater with interface details that are easier to construct but that may have more thermal shorts.

Whole-Wall versus Clear-Wall
Interesting comparisons can be made using the data in Table 1 to illustrate the importance of using a whole-wall value to select the most energy-efficient wall system. It could be argued that the difference between the clear wall and whole-wall R-value represents the energy savings potential of adopting the rating procedure proposed in this paper. Most building owners assume that they have the higher clear-wall value, rather than the more realistic whole-wall value.

An insulating concrete form with metal ties is prepared for testing at the Buildings Technology Center. Its whole-wall R-value and thermal mass will be measured.

Knowing whole-wall R-value could affect consumer choices. Systems 5 and 6 in Table 1 show two different high-performance masonry units. If one used the clear-wall data to choose the unit with the highest R-value, one would pick System 5, the low-density concrete multicore insulation unit, because its clear-wall value is 19.2 compared to 15.2 for System 6, expanded polystyrene (EPS) block forms. However, if one used the whole-wall data, one would choose just the opposite, because System 6 has the higher value--15.7 compared to 14.7 for System 5. Also, the whole-wall value of the foam form system is actually higher than the clear-wall value by more than 3%. This illustrates the effect of the high thermal resistance of the interface details.
Systems 7, 8, and 9 are all conventional wood frame systems. Note that the details affect the whole-wall R-value more for 2 x 6 walls than for 2 x 4 walls. The ratio of Rww to Rcw is about 90% for the 2 x 4 walls and 84% for the 2 x 6 wall.

Comparing System 11, the 6-inch stressed-skin panel wall, to System 9, the conventional 2 x 6 wood frame wall, shows that the Rcw for the former (R-24.7) is 51% higher than that for the latter (R-16.4). However, the figures for the Rww are R-21.6 to R-13.7 respectively, an improvement of 58%. As this example shows, advanced systems will generally benefit from a performance criterion that reflects whole-wall rather than clear-wall values.

How We Evaluate Wall Performance To determine whole-wall R-value, we test a clear-wall section, 8 ft x 8 ft, in a guarded hot box. We compare experimental results with sophisticated heat conduction model predictions to get a calibrated model. Next, we make simulations of the clear-wall area with insulation, structural elements, and eight interface details--corner, wall/roof, wall/foundation, window header, windowsill, doorjamb, door header, and window jamb--that make up a representative residential whole-wall elevation. Results from these detailed computer simulations are combined into a single whole-wall steady-state R-value estimation. This estimation is compared with simplified calculation procedures and results from other wall systems. The user defines a reference wall elevation to weigh the impact of each interface detail. For each wall system for which the whole-wall R-value is to be determined, all details commonly used and recommended (outside corner, wall/floor, wall/flat ceiling, wall/cathedral ceiling, doorjamb, window jamb, windowsill, and door header) must be included. The detail descriptions include drawings, with all physical dimensions, and thermal property data for all material components contained in the details.

Beyond R-Value The R-value is only the first of five elements that are needed to compare whole-wall performance. The other four elements are thermal mass, airtightness, moisture tolerance, and sustainability. We are working on standard ways to measure thermal mass, airtightness, and moisture tolerance. For some systems all five factors are important; for others, only whole-wall R-value is relevant. Thermal Mass Benefit Wall systems with significant thermal mass have the potential--depending on the climate--to reduce annual heating and cooling energy requirements below those required by standard wood frame construction with similar steady-state R-value. The thermal mass benefit is a function of climate. Effective R-values for massive walls are obtained by comparing the massive wall to light-weight wood frame walls. However this effective R-value is only a way to determine the link between the thermal mass of the wall and annual space heating and cooling loads, or a way to answer the question "what R-value would an identical house with wood frame walls need to obtain the same space heating and cooling loads as the massive walled house?" The term cannot be generally applied to a given wall type. A procedure to account for thermal mass was used to create the generic tables found in the Model Energy Code (MEC) for all thermal mass walls with more than 6.0 Btu/ft2 of wall thermal capacitance. The tables have been in use since 1988. Customized tables can be used to show code compliance with the prescriptive Uw requirements in the MEC that are based on wood frame construction. Airtightness Users of the DOE Buildings Technology Center follow a combination of ASTM Standards C236 or C976 (ASTM 1989) or E1424 and E283 (ASTM 1995) to measure air leakage and heat loss through clear-wall assemblies under simulated wind conditions ranging from 0 to 15 mph. Varying the differential pressures from 0 to 25-50 Pascals (Pa) simulates the extremes to which a wall is exposed in a real building. The test specimens contain one light switch and one duplex outlet connected with 14-gauge wiring that spans the width of the wall. Because heat loss in a building can be as high as 40% due to infiltration, it is important to include this performance parameter, but the quality of workmanship on the construction site, as compared to a laboratory specimen, must be considered. A second complicating factor is that materials may shrink or crack over time, and this will change the leakage. We will never completely predict the impact of workmanship on energy loss in buildings. What is important is to establish a uniform baseline for all wall systems. Moisture Tolerance The wall's moisture behavior, like the benefit of thermal mass, is a function of climate and building operation. Annual moisture accumulation due to vapor diffusion of a particular wall system can be estimated by computer simulation. It is harder to estimate moisture accumulation due to air flow into the wall. It is important, in a long-lasting wall assembly, that the wall have the ability to dry itself out if it is built wet or picks up moisture due to a leak. The drying rate can be modeled and measured in the laboratory. The potential for moisture accumulation over specific full annual climatic cycles can also be modeled by heat and mass transfer codes such as MOIST (available from the National Institute of Standards and Technology, Special Publications 853, Release 2.1) and MATCH (available from Carston Rode, Technical University of Denmark, Department of Buildings and Energy, Building 188, DK-2800, Lyngby).

Systems 12 through 18 are all metal-framed. On average, the whole-wall value for these seven systems is 22% less than the clear-wall value. Metal can be used to build energy-efficient envelopes, but not by using techniques common to wood frame construction. The conventional metal residential systems reflected in Table 1 do not fare as well, compared to the other systems, when the whole-wall value is used as the reference. For example, if one is considering either System 6 (EPS block forms) or System 12 (a 4-inch metal stud wall), the clear-wall R-value is about the same--R-15. However, if the comparison is made using the whole-wall R-value, the EPS block form system has a 45% higher value--R-15.7 compared to R-10.9.

A standard metal frame wall section before insulation and drywall is installed.

Whole-Wall versus Center-of-Cavity
We also compared whole-wall R-values to center-of-cavity R-values. When a real estate agent or contractor states the R-value of insulation across the cavity to a potential home buyer, the implied whole-wall R-value is often overstated by 27% to 58%. If one compared metal (System 13) and wood (System 7) frames using center-of-cavity R-values, one would conclude that there was no difference, since both have center-of-cavity values of about R-14. However, the whole-wall value of the 2 x 4 wood wall system is 56% better than the whole-wall value for the metal system -- R-9.6 compared to R-6.1.

These comparisons are not meant to imply that one type of construction is always better than another. They are all based on representative details. Whole-wall R-values could change if certain key interface details were changed. The purpose of making these sample comparisons is simply to show the importance of having the whole-wall value available in the marketplace, to guide designers, manufacturers, and buyers to more energy-efficient systems.

An autoclave concrete wall is stuccoed in preparation for the hot box test.

Coming Soon: A Wall Rating Label?

A number of innovative wall systems offer advantages that will continue to gain acceptance as the cost of dimensional lumber rises, the quality of framing lumber declines, availability fluctuates, and consumers remain concerned about the environmental impact of the nonsustainable harvesting of wood. For instance, while common dimensional lumber systems historically represent about 90% of the market, metal framing manufacturers anticipate attaining 25% of the residential wall market by the year 2000. This projection may be a bit optimistic, but it is clear that cold form steel is set to make major inroads into the residential market.
Now that a growing wall database and an evaluation procedure are available, the building industry can develop a national whole-wall thermal performance rating label. This would establish in the marketplace a more realistic energy savings indicator for builders and homeowners faced with selecting a wall system for their buildings.

Labels could also help specific systems to gain the acceptance of code officials, building designers, builders, and building energy-rating programs such as Home Energy Rating Systems (HERS) and EPA Energy Star Buildings. The whole-wall R-value procedure has been proposed for adoption in the ASHRAE Standard 90.2, the Council of American Building Officials Model Energy Code, and U.S. Department of Energy's national voluntary guidelines for HERS. Many of the documents that are available to show builders how to comply with applicable codes, standards, and energy efficiency incentive programs would benefit by using the whole-wall R-value comparison procedure.
Ultimately, wall comparisons should include five elements: whole-wall R-value, thermal mass benefits, airtightness, moisture tolerance, and sustainability (see "Beyond R-Value"). Publication of this article was supported by the U.S. Department of Energy's Office of State and Community Programs, Energy Efficiency and Renewable Energy.

Wall R-Value Terms Center-of-cavity R-value: R-value estimation at the point in the wall that contains the most insulation. Clear-wall R-value (Rcw): R-value estimation for the exterior wall area that contains only insulation and necessary framing materials for a clear section, with no windows, doors, corners, or connections between other envelope elements, such as roofs and foundations. Interface details: A set of common structural connections between the exterior wall and other envelope components--such as wall/wall (corners), wall/roof, wall/floor, window header, windowsill, doorjamb, door header, and window jamb--that make up a representative residential whole-wall elevation. Whole-wall R-value (Rww): R-value estimation for the whole opaque wall, including the thermal performance of both the "clear wall" area and typical interface details. Opaque wall area: The total wall area, not including windows and doors.

Continuing research is being cofunded by DOE's Office of Buildings Technology and Community Programs and by private industry to add more advanced wall systems to the database, and to address not only thermal shorts, but thermal mass benefits, airtightness, and moisture tolerance. Industry participants so far include American Polysteel, Integrated Building and Construction Solutions (IBACOS), Icynene Incorporated, Society for the Plastics Industry Spray Foam Contractors, Hebel USA L.P., Composite Technologies, Structural Insulated Panel Systems Association, LeRoy Landers Incorporated, Florida Solar Energy Center, American Society of Heating, Refrigerating and Air-Conditioning Engineers and Enermodal.

The database of advanced wall systems is available on the Internet (http://www.cad.ornl.gov/kch/demo.html). For more information, contact Jeffrey E. Christian at Oak Ridge National Laboratory, P. O. Box 2008, MS 6070 Oak Ridge, TN 37831-6070. Tel:(423) 574-4345; Fax:(423)574-9338; E-mail: jef@ornl.gov.

Further Reading

Kosny, J., and A. O. Desjarlais. "Influence of Architectural Details on the Overall Thermal Performance of Residential Wall Systems." Journal of Thermal Insulation and Building Envelopes Vol. 18 (July 1994) pp. 53-69.
Kosny, J., and J. E. Christian. "Thermal Evaluation of Several Configurations of Insulation and Structural Materials for Some Metal Stud Walls." Energy and Buildings, Summer 1995, pp. 157-163.
Christian, J. E. "Thermal Mass Credits Relating to Building Envelope Energy Standards." ASHRAE Transactions 1991, Vol. 97, pt. 2.
Kosny, Jan and Jeffrey E. Christian. "Reducing the Uncertainties Associated with Using the ASHRAE ZONE Method for R-Value Calculations of Metal Frame Walls." ASHRAE Transactions 1995, Vol. 101, pt. 2.
Christian, J.E., and J. Kosny. "Toward a National Opaque Wall Rating Label." Proceedings from Thermal Performance of the Exterior Envelopes VI conference, December 1995.

---

Publication of this article was supported by the U.S. Department of Energy's Office of State and Community Programs, Energy Efficiency and Renewable Energy.

---

Back to Contents Page Home Energy Index About Home Energy Home Energy Home Page Back Issues of Home Energy

-- Scott's Contracting scottscontracting@gmail.com