The Need For Foil Insulation
When installed correctly, insulation reduces the heat move by the envelope of a building. When ever there is a temperature difference, heat flows naturally from a warmer space to a cooler space. To continue comfort in winter, the heat lost must be replaced by the heating system: and in summer, the heat attained must be removed by the cooling system. Statistics show that 50% to 70% of the energy used in the average home in the U.K. 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 relieves the burden our eco-system must bear.
To summarise, insulating the envelope of a building`s conditioned space yields these meaningful points:
- Provides a much more comfortable, productive and livable structure. In addition, the effects of moisture condensation and air movement are reduced in well-insulated buildings. This results in lower maintenance costs and increased longitivity of the building structure.
- Reduces energy requirements, which lower utility bills.
- Supports economic, environmental and energy conservation goals. This is evidenced by the numerous studies sponsored by the energy commission.
Heat moves by wall cavities or between roofs and attic floors by radiation, conduction, and convection with radiation the principal method of heat move. A reflective insulation is an effective v obstacle against radiant heat move because it reflects almost all of the infrared radiation strickeing its surface and emits very little heat conducted by it. By virtue of its impermeable surface, reflective insulation also reduces convective heat move. Mass insulation like fibre Glass, polyisocyanurate (pir) insulation board or rock wool, chiefly slow heat flow by eliminating convection and reducing some radiation. Reflective insulation provides a emotional reduction in radiation heat flow in addition as some convection. Polyisocyanurate boards and Spray Foam can provide increased resistance to conductive move until the cell gas is lost or diluted by air typically over a period of 15 years.
What Is Radiant obstacle Reflective Insulation? Radiant obstacle insulation is a reflective insulation system that offers a long-lasting way to reduce energy costs. Radiant obstacle insulation systems mirror radiant heat energy instead of trying to absorb it. A pure aluminum radiant obstacle reflective insulation is unaffected by humidity and will continue to perform at a consistent level no matter how humid it may be. A radiant obstacle insulation system is a inner of foil facing an airspace and is installed in the envelope of a building.
Most people are familiar with traditional insulating materials such as fiberglass, cellulose, Polyiscyanurate boards, Styrofoam, and rock wool. These products use their ability to absorb or resist (slow down) convective and conductive heat move to insulate (R-value). A third, seldom discussed but principal form of heat move exists: radiant heat move. What are the differences among the three forms of heat move? Conductive: Direct contact. If you touch a pot on the stove, this is conductive heat move. Convective: Steam, moisture. If you put your hand above a boiling pot, you will feel heat in the form of steam. This is convective heat move.
Radiant: Electromagnetic. Step outside on a sunny day and feel the sun’s rays on your confront. You are feeling radiant heat move. All objects above absolute zero (-459.7 degrees F.) release infrared rays in a straight line in all directions.
A radiant obstacle reflects radiant heat energy instead of trying to absorb it. What does this average in your home or business? During the winter, 50-75% of heat loss by the ceiling/roofing system and 65-80% of heat loss by walls is radiant. In the summer, up to 93% of heat gain is radiant. If you are depending on R-value (resistance) alone 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 (moisture levels). A 1-1/2% change in the moisture content of fiberglass insulation will consequence in a 36% decline in performance (referenced from HVAC Manual 10.6; McGraw-Hill). A pure aluminum radiant obstacle is unaffected by humidity and will continue to perform at a consistent level no matter how humid it may be.
Concept of Reflective Insulation
Different types of insulation products reduce the heat transferred by conduction, convection and radiation to varying degrees. As a consequence, each provides different thermal performance and corresponding “R” values. The dominant function of reflective insulation is to reduce the radiant heat move across open spaces, which meaningful contributor to heat gain in summer and heat loss in winter. The low emittance metal foi surface of the product blocks up to 97% of the radiation and consequently a meaningful part of heat move. There are many types of material that reduce heat gain and heat loss. Some materials provide greater resistance than other, depending on the mode of heat move: convection, or radiation. Most insulating materials work on the rule of retained air, gas being a good insulator. Mass insulation like fibreglass, foam, and cellulose use layers of Glass fibre, plastic and wood fibre respectively to reduce convection thereby decreasing the move of heat. These materials also reduce heat move by conduction due to the presence of retained air. ( However, these products, like most building materials, have very high radiant move rates.) Heat flow by radiation has been brought to the public`s attention with high efficiency windows which commonly use the term “low E ” to advertise the higher performance ratings. This value is measured in emitance or “e” values ranging from 0 to 1 (lower “E” value indicates better performance). Most building materials, including fibreglass, foam and cellulose have “E” values in excess of 0.70. Reflective insulation typically have “E” values of 0.03 ( again, the lower the better ). consequently, reflective insulation is superior to other types of insulating materials in reducing heat flow by radiation. The term reflective insulation, in some ways a wrong name because aluminium or polyester either works by reflecting heat (reflectance of 0.97) or not by radiating heat (emitance of 0.03) whether stated as reflectivity or emitance, the performance (heat move) is the same. When reflective insulation is installed in wall cavity, it traps air ( like other insulation materials) and consequently reduces heat flow by convection consequently addressing both modes of heat move. In all situations, the reflective material must be nearby to an air space. 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 unprotected to a u value of 0.16, this can be achieved by using several of our foil materials in co- junction with glass wool or polyisocyanurate (PIR) board.To give you more detail it would be advised to consult your local building control on what specification they require as we have seen many councils differ on specifications. We would recommened the following specification and have had many excellent reports on completed jobs around the UK and France. If this is a to gain more insulation and create a warm roof a DIY job, you would use 70mm of polyisocyanurate board or 100mm glass wool between your rafters, then cover the confront of the rafters with a quilted foil, we would recommend Actis super 10, Super foil 19, Alumaflex or Aluthermo quatro. all these materials we stock for moment despatch. If using the foil on its own you would unprotected to a u- value of somewhere between 0.18 – 0.20, which is quite permissible on a refurbishment project. I f the roof tiles have been removed you would lay the foil insulation on the top side of the rafters and counter pattern would be put in place and a membrane to cover this batons and roof tile. The most important aspect with any foil insulation is to have a 25mm airspace between the foil and any covering material, this will allow for heat transmission to take place, with out this you are eliminating the assistance of reflection from the confront of the foil. Bubble foil is also a low cost great way to insulate your home, very popular in the USA and known as house wrap, low cost and very effective, great for keeping your house cool in sumer months in addition as retaining heat in winter.