Control Your Energy Costs with Radiant Barrier Home Insullation

Radiant Barrier Products: BUY ONLINE

Radiant barriers are installed in homes (attics, walls, roof decking, flooring) and have been proven effective to reduce energy usage and cost by reducing summer heat gain and winter heat loss. Most newly constructed homes contain some type of radiant barrier in the construction process. Installing a radiant barrier in your home may be the lowest cost, single best improvement possible to produce the greatest overall reduction in energy usage and expense.

Radiant barrier technology like other technologies has experienced dramatic improvements over the years. Today’s barriers are lighter and stronger yet preform better than older versions. The barriers being sold today are typically not a “foil” at all but rather a highly reflective metalized film material that reflects (or more specifically, re-emits) radiant heat rather than absorbing it. Effort should be made to compare products and specifications prior to selecting a radiant barrier to install in your home. Price should not be the deciding factor when considering which barrier to purchase. As with most things a little research may yield a greater benefit over time.

It is important to note that many older versions of radiant barrier have ASTM E84 tests stating those products are Class A / Class 1 fire rated products, however these tests have been run using older methods of mounting the product for the test. You may see a test report that is listed as E84-05 Class A / Class 1 fire rated. These products will no longer pass the more stringent testing methods. Only tests that are listed as E84-10 using E2599 mounting methods will pass the new codes.

The new “test” mounting method is listed as (ASTM E2599) for fire testing. The new mounting method is designed to allow the products to be tested more closely on how these products are installed in standard building applications.

Section 719 of the International Building Code states that if radiant barrier is installed in any attic space accessible from the interior of the home the radiant barrier product must have a Class A / Class 1 fire rating as per ASTM E84-10 using the new E2599 mounting method (2011).

How They Work

Heat travels from a warm area to a cool area by a combination of conduction, convection, and radiation. Heat flows by conduction from a hotter location within a material or assembly to a colder location. Heat transfer by convection occurs when a liquid or gas is heated by a surface, becomes less dense, and rises (natural convection), or when a moving stream of air absorbs heat from a warmer surface (forced convection). Radiant heat travels in a straight line away from any surface and heats anything solid that absorbs the incident energy. Radiant heat transfer occurs because warmer surfaces emit more radiation than cooler surfaces.

When the sun heats a roof, it’s primarily the sun’s radiant energy that makes the roof hot. A large portion of this heat travels by conduction through the roofing materials to the attic side of the roof. The hot roof material then radiates its gained heat energy onto the cooler attic surfaces, including the air ducts and the attic floor. A radiant barrier reduces the radiant heat transfer from the underside of the roof to the other surfaces in the attic.

A radiant barrier’s performance is determined by three factors:

• Emissivity (or emittance) â€" the ratio of the radiant energy (heat) leaving (being emitted by) a surface to that of a black body at the same temperature and with the same area. It’s expressed as a number a between 0 and 1. The higher the number, the greater the emitted radiation.
• Reflectivity (or reflectance) â€" a measure of how much radiant heat is reflected by a material. It’s also expressed as a number between 0 and 1 (sometimes, it is given as a percentage between 0 and 100%). The higher the number, the greater the reflectivity.
• The angle the incident radiation strikes the surfaceâ€"a right angle (perpendicular) usually works best.

All radiant barriers must have a low emissivity (0.1 or less) and high reflectivity (0.9 or more). From one brand of radiant barrier to another, the reflectivity and emissivity may appear similar however, even small differences will impact the performance of the barrier as a whole. The difference between products with emissivity values of 0.04 and 0.05, respectively, may appear to be minimal – in reality, the radiant barrier with the emissivity value of 0.05 emits 25% more radiant heat! This is a HUGE difference when it comes to keeping a home cool during summer months.

Radiant barriers are typically seen more often in hot climates than in cool climates although they can be used in either. Some studies have show that radiant barriers may lower cooling & heating costs up to 20% depending on the amount of insulation the home contains prior to the addition of a radiant barrier. Radiant barriers are also effective in cool climates when used in addition with recommended levels of thermal insulation.

Types of Radiant Barriers

Radiant barriers come in a variety of forms, metalized film, reflective foil, reflective metal roof shingles, reflective laminated roof sheathing, and even reflective chips, which can be applied over loose-fill insulation. Laminated radiant barriers utilize a reflective material, usually aluminum, applied to one or both sides of a number of substrate materials. Substrate materials include kraft paper, plastic films, cardboard, oriented strand board, and air infiltration barrier material. Some products are fiber-reinforced to increase the durability and ease of handling. Today, a more advanced non-laminated, recycleable radiant barrier material is made in the USA and designed for maximum strength and durability making them ideal for the most demanding retrofit installations. Strength and durability also make this non-laminated product work well in both “nail-up” and “lay-down” installation methods.

Installation

A radiant barrier’s effectiveness depends on proper installation. Therefore, it’s best to have a certified installer do it.

If you want to install a radiant barrier yourself, obtain instructions and safety precautions from the manufacturer. Carefully study and follow these directions. You should also check your local building and fire codes.

Radiant barriers can be installed between the roof sheathing and attic floor insulation, in cavity walls, and around door openings, water heaters, and pipes. Although it may be easier to incorporate radiant barriers into a new home, retrofitting existing homes typically reap a greater benefit due to the fact that most older homes may not be overall as energy efficient.

An installer typically drapes a rolled-foil radiant barrier foil-face down between the roof rafters to minimize dust accumulation on the reflective faces (double-faced radiant barriers are available). This is generally done just before the roof sheathing goes on if it’s not too windy, but it can also be done afterwards from inside the attic by stapling it to the bottom of the rafters.

When installing a foil-type barrier, it’s important to allow the material to “droop” between the attachment points to make at least a 1.0 inch (2.5 cm) air space between it and the bottom of the roof. This air space has mainly two functions: it creates an air channel for the soffit and ridge ventilation system to work more effectively, and it acts as a second reflector since there are two shiny sides (one facing up/ one facing down.)

Some builders attach the radiant barrier directly onto the roof sheathing prior to their installation on the roof rafters. However, without the air space this method is not very effective. There are also metal roof shingles that have a reflective underside. If you need roof shingles, these are a practical option, but the cost of this type of radiant barrier is considerably higher than other types.

A radiant barrier installed on top of attic floor insulation may be more susceptible to dust accumulation however, with the advent of double side barriers this concern may not create a significant reduction in performance. This installation method may also trap moisture in fiber insulation during cold weather. To reduce the potential of moisture it is best to use a “perforated” radiant barrier and when installing simply lay the barrier “lightly” on top of the existing insulation “overlapping” the material as it is rolled out.