Thermal Break & Barrier
Design / Construction Methods
What is the purpose of a Thermal Break or Barrier?
- Thermal barriers improve the U-value characteristics of finished systems.
- Thermal barriers are about energy conservation, U-values and government codes
- Thermal barriers are made from resins that create a “thermal break” between the inner and outer surfaces of aluminum fenestrations.
- Thermal barriers reduce heat loss or heat gain through the aluminum.
- 70% of aluminum fenestration systems produced in North America contain a thermal break
- Used more extensively in colder climates to reduce heat loss
- Increased use of thermal barriers to reduce heat gain, as well as reduce heat loss
- Developers, architects and designers are demanding better performance in terms of power usage to meet both customer requirements and newer, stricter government regulations.
- Stricter government regulations to reduce power usage in buildings to combat environmental concerns, and reduce a facility’s Carbon footprint.
- Aluminum, if it is to retain its market superiority in terms of its structural integrity, will have to achieve better performance in terms of U-values
- The use of thermal barriers will assist manufacturers to achieve improved LEED performance
A thermal break is an element of low conductivity placed between any two materials in an effort to stop or slow down the transfer of heat from one to the other. The principle is based on the second law of thermodynamics formulated by the Irish physicist, William Thomson, Lord Kelvin. All matter will transfer heat, and the transfer naturally moves from the warmer material, or area, to the cooler. Any material that impedes this transfer is a thermal break. It may be an actual material, such as insulation, or it may be trapped dead air; the function remains the same.
The scientific principle, which existed before it was identified, is demonstrated in everyday life. When someone picks up a potholder, they are employing a thermal break. The quilted pad prevents the transfer of heat from a hot pot handle to the cooler hand of the cook and prevents a serious burn. Layering clothing is layering thermal breaks, which is why several thin layers can feel warmer than one thick one. Between each layer of clothing is an air space that acts as a thermal break to prevent the person bundled up under those layers from losing their body heat. When outside air is cold in winter, homes and offices with old windows are cold, and hard to keep warm because the interior heat passes through the glass of the windows. Newer, more energy efficient windows have two panes of glass, or more, separated by a small space filled with air or an inert gas such as Nitrogen or Argon. Air or gas will not transmit heat as quickly as a single pane of glass, so rooms will stay warmer longer with less strain on the heating system. The air pocket between the glass panes is the thermal break.
Uninsulated houses and buildings suffer tremendous heat loss through their walls and roofs during winter months. Modern structures are built with insulation in their walls and between their ceilings and roofs. Spray-on foam is a newer insulation material that provides a thermal break between the inside and outside of a house or office, but other less expensive options are available. In areas where heat is more of a problem than cold, the system works the same way, only in reverse. Placing foam, fiberglass batting or blown-in cellulose between interior and exterior walls and in attic spaces provides thermal breaks and conserves energy. Thermal break Windows, Doors, & Skylights also help keep hot air out and lower utility bills. Examples of these types of Thermal Break and Barriers are shown below:
Currently there are two principal types of thermal barriers used in North America:
Pour & Debridge (P&D) and Polyamide Thermal Barrier Strips as shown above. Details below.
Pour & Debridge
- P&D is the most widely used system for thermal barriers in North America.
- It is a polyurethane-based system.
- An Iso is mixed with a resin at the point of assembly and the mixture is poured into a barrier channel in the aluminum extrusion.
- After pouring and curing, the barrier channel is “debridged”.
- The debridging process creates the separation between the inner and outer surfaces.
- A mechanical locking system on the extrusion is recommended to eliminate possible problems with dry shrinkage.
Polyamide Thermal Barrier Strips
- Pre-extruded profiles made from polyamide with 25% glass-fiber.
- Locked in place in “pockets” extruded into two separate (inner and outer) aluminum extrusions.
- Enables finished assemblies with different finishes and colors on each surface
- Aluminum extrusion pockets need to be “knurled” prior to insertion of the polyamide profiles – and “rolled” to create a structurally-secure finished assembly.
- The polyamide profiles can be supplied with ”sealing-wire” which give a reliable seal and enhanced shear strength when activated by heat e.g. – powder-coating
- The aluminum extrusions can be finished either before or after installation of the polyamide strips.