Easy Foil Insulation Installation Guide and Recommended Materials to Achieve a 0.16 U-Value

The need for foil insulation

When installed correctly, insulation reduces heat transfer through a building envelope. Whenever there is a temperature difference, 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 an 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, the lower consumption of fossil fuels and the energy produced from them eases the burden on our ecosystem.

In summary, isolating the envelope of a building’s conditioned space yields these key points:

• It provides a much more comfortable, productive and deliverable structure. Additionally, 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 fabric.
• Reduces power 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 hits its surface and emits very little heat that is conducted through it. By virtue of its impervious surface, reflective insulation also reduces convective heat transfer. Massive insulation such as fiberglass, polyisocyanurate (pir) insulation board, or rock wool primarily slows heat flow by eliminating convection and reducing some of the radiation. Reflective insulation provides a drastic reduction in heat flow by radiation as well as some convection. Polyisocyanurate plates and spray foam can provide increased resistance to conductive transfer until the cell gas is lost or diluted in air normally over a 15 year period.

What is radiant barrier reflective insulation? Radiant barrier insulation is a reflective insulation system that offers a permanent way to reduce energy costs. Radiant barrier insulation systems reflect radiant thermal energy rather than 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 wet it is. A radiant barrier insulation system is a sheet layer that faces an air space 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) convective and conductive 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 heat transfer by conduction. Convective: Steam, humidity. If you put your hand on a boiling pot, you will feel heat in the form of steam. This is heat transfer by convection.

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 a straight line in all directions.

A radiant barrier reflects radiant thermal energy rather than trying to absorb it. What does this mean in your home or business? During winter, 50-75% of heat loss through the ceiling/roofing 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 the 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 unaffected 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 heat transferred by conduction, convection, and radiation 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 summer heat gain and winter heat loss. The product’s low-emitting fe metal surface blocks up to 97% of radiation and thus a significant portion of 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. Massive insulation such as fiberglass, foam, and cellulose use layers of fiberglass, plastic, and wood fiber, respectively, to reduce convection and thus decrease heat transfer. These materials also reduce conductive heat transfer due to the presence of trapped air. (However, these products, like most building materials, have very high radiant transfer rates.) Radiant heat flux has come to the public’s attention with high-efficiency windows that commonly use the term “low E” to advertise higher efficiency. ratings This value is measured in emittance or “e” values ​​ranging from 0 to 1 (a lower “E” value indicates better performance). Most building materials, including fiberglass, foam, and cellulose, have “E” values ​​greater than 0.70. Reflective insulation typically has “E” values ​​of 0.03 (again, the lower the 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 misnomer because aluminum or polyester function by reflecting heat (reflectance of 0.97) or not radiating heat (emitance of 0.03), whether stated as reflectivity or emittance, the performance (heat transfer) is the same. When reflective insulation is installed in the wall cavity, it traps air (like other insulation materials) and thus 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 current regulations require us to provide insulation that will achieve an au value of 0.16, this can be achieved by using a number of our aluminum materials in conjunction with glass wool or polyisocyanurate (PIR) board. . Please note to check with your local building control as to what specifications they require as we have seen many councils differ on specifications. 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. We have all these materials in stock for instant shipping. Using the sheeting on its own will give you a u-value of between 0.18 and 0.20, which is quite acceptable on a renovation project. If the roof tiles have been removed, I would put the foil insulation on top of the joists and put a buttress and membrane to cover these battens and tiles. 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 take place, without this you will be removing the benefit of face reflection of the sheet. Bubble wrap 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.