The need for foil insulation

When installed correctly, insulation reduces heat transfer through a building envelope. Whenever there is a difference in temperature, heat naturally flows from a warmer space to a cooler space. To maintain comfort in winter, the heat lost must be replaced by the heating system: and in summer, the heat gained must be removed by the cooling system. Statistics show that 50% to 70% of the energy used in the average UK home is for heating and cooling. It makes sense to use thermal insulation to reduce this energy consumption, while increasing comfort and saving money. Naturally, less consumption of fossil fuels and the energy produced from them eases the burden on our ecosystem.

In summary, insulating the conditioned space envelope of a building yields these key points:

• It provides a much more comfortable, productive and deliverable structure. Also, the effects of moisture condensation and air movement are minimized in well-insulated buildings. This results in lower maintenance costs and increased longevity of the building structure.
• Reduces energy requirements, which lowers utility bills.
• Supports economic, environmental, and energy conservation goals. This is demonstrated by the numerous studies sponsored by the energy commission.

Heat moves through wall cavities or between ceilings and attic floors by radiation, conduction, and convection, with radiation being the dominant method of heat transfer. A reflective insulation is an effective barrier against radiant heat transfer because it reflects almost all of the infrared radiation that strikes its surface and emits very little heat that is conducted through it. By virtue of its impermeable surface, reflective insulation also reduces convective heat transfer. Mass insulation such as fiberglass, polyisocyanurate (pyr) insulation board, or rock wool primarily slows down the flow of heat by eliminating convection and reducing some of the radiation. Reflective insulation provides a drastic reduction in radiative heat flow, as well as some convection. Polyisocyanurate plates and spray foam can provide increased resistance to conductive transfer until cell gas is lost or diluted in air typically over a period of 15 years.

What is reflective radiant barrier insulation? Radiant barrier insulation is a reflective insulation system that offers a permanent way to reduce energy costs. Radiant barrier insulation systems reflect radiant heat energy instead of trying to absorb it. A pure aluminum radiant barrier reflective insulation is unaffected by moisture and will continue to perform at a constant level no matter how humid it is. A radiant barrier insulation system is a sheet layer that faces an airspace and is installed in a building envelope.

Most people are familiar with traditional insulation materials such as fiberglass, cellulose, polycyanurate board, Styrofoam, and rock wool. These products use their ability to absorb or resist (slow down) conductive and convective heat transfer to insulate (R-value). There is a third, rarely discussed but dominant form of heat transfer: radiant heat transfer. What are the differences between the three forms of heat transfer? Conductive: Direct contact. If you touch a pot on the stove, it is conductive heat transfer. Convective: Steam, moisture. If you put your hand over a boiling pot, you will feel heat in the form of steam. This is convective heat transfer.

Radiant: Electromagnetic. Go outside on a sunny day and feel the sun’s rays on your face. You are feeling the radiant heat transfer. All objects above absolute zero (-459.7 degrees F.) emit infrared rays in straight lines in all directions.

A radiant barrier reflects radiant heat energy instead of trying to absorb it. What does this mean in your home or business? During winter, 50-75% of heat loss through the ceiling/roof system and 65-80% of heat loss through walls is by radiation. In the summer, up to 93% of the heat gain is radiant. If you rely solely on R-value (resistance) to insulate against heat gain and loss, remember that traditional forms of insulation are virtually transparent to radiant energy and are affected by changes in humidity (humidity levels). A 1-1/2% change in moisture content of fiberglass insulation will result in a 36% decrease in performance (referenced in HVAC Manual 10.6; McGraw-Hill). A pure aluminum radiant barrier is not affected by moisture and will continue to perform at a constant level no matter how wet it is.

reflective insulation concept

Different types of insulation products reduce conductive, convective, and radiant heat transfer to varying degrees. As a result, each provides different thermal performance and corresponding “R” values. The primary function of reflective insulation is to reduce radiant heat transfer through open spaces, which contributes significantly to heat gain in summer and heat loss in winter. The low emittance metallic fe surface of the product blocks up to 97% of the radiation and therefore a significant part of the heat transfer. There are many types of materials that reduce heat gain and loss. Some materials offer greater resistance than others, depending on the mode of heat transfer: convection or radiation. Most insulating materials work on the principle of trapped air, with gas being a good insulator. Mass insulation such as fiberglass, foam, and cellulose use layers of fiberglass, plastic, and wood fiber, respectively, to reduce convection and therefore decrease heat transfer. These materials also reduce conductive heat transfer due to the presence of entrapped air. (However, these products, like most building materials, have very high radiant transfer rates.) Radiant heat flux has caught the public eye with high efficiency windows that commonly use the term “low E” to advertise the highest performance. ratings This value is measured in emittance or “e” values ​​ranging from 0 to 1 (lower “E” value indicates better performance). Most construction materials, including fiberglass, foam, and cellulose, have “E” values ​​greater than 0.70. Reflective insulation typically has “E” values ​​of 0.03 (again, lower is better). Therefore, reflective insulation is superior to other types of insulating materials in reducing radiative heat flux. The term reflective insulation, in a way, is a bit of a misnomer because aluminum or polyester work by reflecting heat (0.97 reflectance) or not radiating heat (0.03 emittance), whether stated as reflectivity or emittance, performance (heat transfer) is the same. When reflective insulation is installed in the wall cavity, it traps air (like other insulation materials) and therefore reduces convective heat flow, thus addressing both modes of heat transfer. In all cases, the reflective material must be adjacent to an air gap. Foil, when sandwiched between two pieces of plywood, for example, will conduct heat at a high rate.

In the UK we are required by current regulations to provide insulation that will achieve an au value of 0.16, this can be achieved by using several of our aluminum materials together with glass wool or polyisocyanurate (PIR) board. . Please note check with your local building control on what specs they require as we have seen many councils differ on specs. We recommend the following specification and have received many excellent reports of work completed in the UK and France. If it is to gain more insulation and create a warm ceiling, a DIY job, I would use 70mm polyisocyanurate board or 100mm glass wool between the joists, then cover the face of the joists with a padding sheet, we recommend Actis super 10, Superfoil 19, Alumaflex or Aluthermo quatro. all of these materials are in stock for instant shipping. If you use the sheet on its own, you’ll get a u-value of between 0.18 and 0.20, which is quite acceptable in a renovation project. If the roof shingles have been removed, I would place the foil insulation on top of the joists and a buttress pattern and membrane would be applied to cover these battens and shingles. The most important aspect with any foil insulation is to have a 25mm air gap between the foil and any covering material, this will allow heat transmission to occur, without this you are removing the benefit of face reflection of the sheet Bubble foil is also a great way to insulate your home at a low cost, very popular in the US and known as house wrap, inexpensive and very effective, great for keeping your home cool in the summer months and to retain heat in the winter.