A home’s insulation – that barrier between your living space and the outside world – is where genuine “green building” exists. Reflective Insulation coupled with high-performance seaming tape are two tools that combine to create a superior, energy-saving surface. Here’s what you need to know.
What is Reflective Insulation?
Outside of recycling paper and reducing reliance on disposable plastics, your home represents one of the biggest opportunities to protect the environment and achieve an energy-efficient lifestyle. Indeed, a home’s building envelope—that barrier between your living space and the outside world—is where genuine “green building” exists. Reflective insulation (also known as foil insulation) is essentially a barrier usually made from aluminum foil or aluminized polyester. Much like other forms of insulation, reflective insulation may help reduce energy costs by blocking the heat that radiates from the sun, onto your roof, through your attic, and on into your living space. It is that natural transfer of heat from the outdoors that causes your systems to work harder and be less energy efficient. By blocking that heat gain in your attic, reflective insulation will also substantially reduce the air temperature surrounding your HVAC equipment and duct work.
Unlike insulation that is sprayed in or simply laid in place, reflective insulation typically requires a ¾ inch airspace to be most effective. The insulation sheets need room to “sag” along the surface to form little pockets between the insulation and space to properly reflect and deflect. It is most effective when kept clean and dust-free. The layer of still air itself gives it a degree of extra insulation—provided it is still, otherwise it will be taking heat away through convection.
Not only will building or retrofitting your attic with reflective insulation and high-performance seaming tape help improve energy efficiency, but it also increases HERS ratings, life expectancy of HVAC systems, and saleability.
Reflective Insulation vs. Radiant Barriers
Though used interchangeably, reflective insulation isn’t the same as a radiant barrier. Yes, they both reflect an average of 95-96% of the radiant heat that strikes their surfaces across and air space. And yes, each can increases the HERS rating and/or energy performance of a building.
However, a radiant barrier is a thin layer of aluminum placed in an airspace to block radiant heat transfer between a heat-radiating surface (such as a hot roof) and a heat-absorbing surface (such as conventional attic insulation). A quality radiant barrier has a reinforcement layer in the middle (typically referred to as a woven scrim) to make the product strong and tear-resistant.
A reflective insulation product is a thicker product with an “insulating” middle layer such as fiberglass, foam, or air bubbles. Because of the presence of the small insulating layer, a reflective insulation product by itself achieves a small R-Value typically around 1.0. While this R-Value is for the product only, when installed in certain applications with a dead air space (sealed cavity with no air movement) a much higher R-Value can be achieved. It’s the dead air space that provides the additional R-Value and the greater the dead air space, the greater the overall R-Value.
As a general rule of thumb for selecting the correct product:
- If you are looking to reflect or block radiant heat, use a radiant barrier.
- If you also need to achieve an R-Value (typically in order to meet specific building code regulations), OR need to control condensation such as in a metal or steel building, use a reflective insulation.
Where Should Reflective Insulation Be Used?
Reflective insulation or an aluminum foil radiant barrier blocks 95 percent of the heat radiated down by the roof so it can’t reach the insulation. Without a radiant barrier, your roof radiates solar-generated heat to the insulation below it. The insulation absorbs the heat and gradually transfers it to the material it touches, principally, the ceiling. This heat transfer makes your air conditioner run longer and consume more electricity. Reflective insulation can be used independently or in conjunction with mass insulation, like fiberglass. This increases the r-value of the bulk insulation by making it low-e (emittance). Thus, any structure using mass insulation can benefit from reflective technology. The benefit increases substantially the closer you get to the equator where radiant energy is more intense.
Furthermore, reflective insulation is ideal when there isn’t much space. Both bubble and board insulation are a fraction of the width of a bulk insulation system. In walls and other areas where space is limited, reflective insulation is often the best choice. The only thing reflective insulation needs to function is an adjacent air gap. The air absorbs the heat and acts as an insulator.
You may also find that radiant barriers can expand the use of space in your home. For instance, uninsulated, unconditioned spaces such as garages, porches, and workrooms can be more comfortable with radiant barriers.
It’s also worth noting that reflective insulation is a smart choice for metal building applications. It provides superior thermal performance against radiant heat transfer—the primary mode of heat gain/loss in any metal building system. Plus, it reduces energy usage and lower heating/cooling costs; prevents interior condensation and mold; and can easily be used to retrofit existing metal buildings. Plus, according to Metal Construction News: It has a Class 1/A Fire Rating (ASTM E84-09 and ASTM C2599), passes NFPA-286 Full Room Burn Test and passes ASTM G-155 (long-term weatherization/oxidation)
How Do You Install Reflective Insulation?
When installing foil insulation, there are a few important considerations. The first is the location. Research indicates that foil insulation works best when it is placed near the heat source. This means that stapling it to the inside of the roof trusses or rafters is the best way to keep heat out in summer. It can also be used as a house wrap to stop heat from radiating outward through the walls, as well as beneath the floor, which is more important in winter applications. Remember: Unless it has an air space it won’t save energy.
Another consideration is moisture, which can affect the insulation’s performance. When installed in the attic, foil insulation should be perforated so that moisture cannot build up, causing condensation and even freezing in the winter.
The third consideration when installing foil insulation is getting a tight seal. When properly installed as a house wrap using a high-quality seaming tape, reflective insulation can act as a barrier against air transfer, drastically reducing drafting in your house.
Don’t forget: Radiant barriers require a dead airspace! In order for a radiant barrier to be effective, it requires a dead airspace on at least 1 side of the product. If you sandwich a radiant barrier between two solid materials, then heat will just conduct through it, rendering it ineffective. The ever-popular stainless insulated cups that work so well to keep your drink hot or cold for extended periods, use an airspace or vaccuum between layers to keep radiant heat from penetrating through it. Radiant barriers work on this same principle when they have a dead air space on one side. This allows the radiant barrier to reflect 96% of the radiant heat away from it and only allow 4% through it, making the product a no brainer to use in many applications.
Advantages of Reflective Insulation
- It is very effective in warm climates where it is useful in keeping buildings cool.
- Unlike other insulation, it does not degrade over time due to compacting, disintegration, or absorbing moisture.
- It is thin and fairly lightweight and much less bulky than other forms, making it easy to work with and fit.
- It can also be used as a vapor barrier, as it is relatively waterproof and unaffected by moisture.
- Unlike other forms of insulation, it is also non-toxic and non-carcinogenic, making it safer and easy to install with the use of less safety equipment.
Radiant Barrier Insulation Benefits
- Works to keep warm air in during the winter and solar radiant heat out during the summer.
- Prevents up to 97% of solar radiation.
- Reduces attic temperatures by up to 30ºF
- Improves energy efficiency and lowers utility costs, especially if HVAC and duct systems are located in the attic.
- Provides faster heating and cooling with fewer cycle times. This reduces the need for repairs and extends the lifespan of your HVAC equipment.
- Greater control over heating, air conditioning, and humidity.
- More comfortable, more precise heating and air conditioning.
- No maintenance required.
Disadvantages of Reflective Insulation
- It is generally more expensive due to being a metal-based product.
- Though effective in warmer climates, it will require being combined with other forms of insulation in colder climates. This is in order to prevent heat loss in cold weather from convection.
- There is the potential of reflective insulation becoming an electrical hazard should a wiring fault occur. After all, it is a metal and conducts electricity.
- It also relies on being clean and free of dust and debris, both when fitted and when in use. This means in some areas, such as roofs, it may require being cleaned of dust from time to time to ensure maximum efficiency.
Your home is not only most likely your biggest personal investment, it is the structure that will allow you to make the biggest environmental impact. Go the extra mile and install reflective insulation and/or a radiant barrier. And for maximum efficiency, be sure to seam it with PE-M4535. Engineered to adhere to a wide range of building materials and surfaces including house wrap, exterior, and rigid insulation, sheathing, vapor barriers, and a variety of underlayments.
Not sure which seaming product is right for you? Contact our adhesive professionals for help with your specific needs.