Iea ebc energy in Buildings and Community Proposal for a new iea ecbcs‐Annex

Definition of Super-Insulating Materials (SIM)

First of all, one must keep in mind that the main component of an insulating material is gas although it is generally named by the “packaging” material: glass wool, rock wool, expanded or extruded polystyrene, polyurethane, polyisocyanurate and phenolic foam. Indeed, the thermal conductivity of still-air is around 25 mW/m.K compared to 1 for glass, 0.2 for polymer. This is a lower limit for most forms of traditional insulation materials with a high the porosity above 90% and filled with air. Nevertheless, the “packaging” material plays a role for radiation extinction and to avoid any convection flow.

Therefore, three main principles can be applied to reduce thermal conductivity:

- removing the gas, this technique is used for Vacuum Insulation Panel (VIP)

- changing the gas, this principle is used for Gas Filled Panel (GFP). This technique is similar to the one use for Double-Glazing filled with Argon or Krypton.

- trapping the gas in tiny pores with a size lower than the mean free path (MFP) of the entrapped gas in order to limit energy transfer between molecules. This technique is used for Aerogel or other nano-porous materials.

In the present Annex, SIM are considered to have a thermal conductivity.

- below 25 mW/(m·K) if air filled such as aerogel.

- below 20 mW/(m·K) if gas filled such as gas filled panel (GFP).

- below 15 mW/(m·K) if evacuated such as VIP.

Vacuum Insulation Panel : VIP	Aerogel Based Product : ABP	Gas Filled Panel : GFP

Figure 5: Three types of Super Insulating Materials : SIM

The Scope

At the end of the Workshop organised by BBRI and EMPA in Brussels (April 27 – 2012), most participants expressed interest in continuing IEA activities on the Super Insulation topic. A special focus should be on long term issues related to aerogel materials and applications, but also VIP applications should be further investigated. There was especially a common understanding that the confidence of end-users regarding super-insulating materials needs to be improved to foster a wider public acceptance in the future. The present new annex aims to fulfil these needs by characterizing and evaluating the long-term performance of advanced insulating materials such Vacuum Insulation Panel (VIP), Gas Filled Panel (GFP) & Aerogel Based Products (ABP), used in Building Components (roofs, walls, floors) & Systems (DHW, Pipes, Refrigerators, Freezers & Oven), in order to meet the future energy requirements.

The Objectives

This Annex follows and enlarges the HIPTI Annex 39 (2001-2004) which explored only the applications of VIP in building construction. The objectives of are as twofold:

- on the one hand, to improve knowledge and confidence of end-users regarding super-insulating materials (SIM), such as VIP, GFP & ABP

- on the other hand, to foster a wider public acceptance of SIM in the future.

The Means

The Annex will be organized in several Tasks and Subtasks with one leader for each of them. There are already some volunteers as task leaders.

1 - Description of commercially available VIP, GFP & ABP – State of the Art

Task leaders: ASPEN AEROGEL & VA-Q-TEC

The main objective of this task is to provide an up-to-date catalogue of commercially available materials. This catalogue will provide technical description of each product with technical data and information about the application domains and the implementation rules, either in plant for composite panels or on site.

1.1 – VIP

By applying vacuum to an open-cell structure, the contribution of the gas conductivity goes to zero. Hence, the main challenge of VIP manufacturer is to keep vacuum inside using gas-tight films and /or getters. The sealing of the film is also challenging. Since the end of the HIPTI Annex 39, new manufacturers appeared on the market and the initial unclad VIP panels moved to more designed products easier to handle and implement in building components & systems. In Europe, some VIP products have obtained Technical Agreements for building applications.

1.2 - ABP

Aerogel is a nano-porous material with a high specific area (a few hundred of m²/g) and very narrow pores (10 to 100 nm). These specific characteristics make aerogel very sensitive to moisture if there no hydrophobic treatment. At this moment, there are a few aerogel manufacturers which offer commercial products with technical assessment for building applications. At this time, one ABP has obtained a Technical agreement in Europe.

1.3 - GFP

Gas filled panels (GFPs) are similar in many respects to vacuum insulated panels but they are filled with a gas such as argon or krypton rather than vacuum. In particular, their performance and their durability strongly depend on the quality of the film. Moreover, the honeycomb structure creates thermal bridges which degrade the thermal conductivities.

Theoretically, the conductivity of GFP’s containing argon or krypton could reach a value below 20 mW/mK but by experiment these values are not achieved. There are very few papers being published on this subject at this moment, more information are needed and it will be the objective of this task.

2: Description of Building Components & Systems – Best Practice Catalogue

Subtask leaders: ARCELIK & ROCKWOOL

2.1: Building Components – Best Practice Catalogue

During the last decade, basic research and first demonstration projects have shown that SIM such as VIP and ABP can be applied in buildings. However, a large use of these components is still hindered by skepticism on the reliability in practice. In order to improve the confidence in these new components, this task will make a detailed analysis of these components offered by manufacturers. In particular, real performances will be carefully investigated including thermal bridges and airtightness. An overview on all the application areas such as external & internal wall insulation, roofs, floors, ceilings …will be given. The deliverable of the German project VIP-PROVE⁷ could be a starting point of this Task. Special attention will be paid to the implementation requirements of SIM.

2.2: Systems – Best Practice Catalogue

Three main types of systems will be investigated in this subtask:

• 
  Water tanks for Domestic Hot Water (DHW)
  
• 
  Large Household appliances used to store foods & drinks, such as Refrigerator and Freezers (R&F)
  
• 
  New applications such as pipes used for District Heating Systems (DHS)
  

The common objective is to use SIM to lower the thermal losses from above systems (DHW, R&F, DHS) without an increase in size. For example, using SIM technology, its’ possible to reduce energy consumption without changing the appliance geometry, which is a real advantage for refrigerators and freezers.

According to a recent publication, using Vacuum Insulation Panels (VIPs), it would possible to reduce losses of water tanks, by a factor of 6 to 10, compared to conventional insulation materials.

In this task, an analysis of SIM will be done with a special focus on the durability at low and high temperature.