Vacuum Packed Insulation Panels or VIP's are thermal insulators that combine high thermal performance properties with limited thickness. VIP's consist of a nano-structured open-celled core material with a composite material wrapped around it which functions as a gas barrier; all of the air is then evacuated. This structure is then tightly sealed into a low permeation barrier envelope which normally consists of either multilayered metalized polymer film or a multilayered aluminium foil.
Initial Use
Due to the high insulation properties of VIP's they were first designed for refrigeration purposes however as building designers became more aware of their high insulation properties they began to specify their use in construction projects that required highly thermal efficient elements, that minimised heat transmission through the building envelope whilst still being of limited thickness.
Advantages of VIP's
- VIP's can provide an extremely thermal efficient barrier of minimum thickness.
- VIP's provide up to 10 times higher insulation performance compared to conventional insulations.
- High quality and long product life time.
- Impermeable to moisture.
Disadvantages of VIP’s
- If the VIP gets punctured on-site then its thermal performance rating is compromised.
- More expensive than other types of insulation.
- Thermal bridging is a constant construction issue.
VIP Risks
However the use of VIP's does not come without risks and careful consideration must be taken with regards to the thermal performance of the panel, the hygric performance, the hygrothermal performance and the structural behaviour and performance of the VIP. In order for VIP's to be successfully integrated into wide scale construction projects they must first be able to demonstrate that they meet the requirements of the 1988 European Construction Products Directive. This directive specifies that construction products must be meet the following requirements:
- Structural requirements.
- Thermal requirements.
- Functional service life requirements.
- Fire protection requirements.
- Hygiene, health and environmental requirements.
- Safety in use requirements.
- Acoustic requirements.
Thermal Performance vs. Structural Performance
Thermal performance is a critical element of all VIP's and an important point to note is that; when using VIP's in order to provide maximum thermal performance thermal bridging must be kept to a minimum. This requirement can however impact on the structural performance of the VIP as the designer seeks to minimise connection points and edge spacers which act as thermal bridges and thus reduce the thermal performance of the completed VIP structure. One way to minimise thermal bridging when using VIP's is to replace one thick panel with several thinner ones and position them in such a way that the joints of the panels are staggered. Another method of reducing thermal bridging in VIP construction is to use spacers made from low thermal conductivity materials and of limited thickness.
Functional service life vs. Thermal Performance
When designing a building it is important to choose materials with a long service life so as to increase the durability of the building in question. The functional service life of a VIP depends mainly on the rate of thermal conductivity aging inside the VIP. Some factors that are known to influence the aging of VIP panels are;
- The initial vacuum and water content.
- Water vapour.
- Temperature.
- Atmospheric pressure.
- VIP Panel dimensions.
In general, thick and large panels with a ratio of panel perimeter length to surface area as high as possible have a longer expected service life than thin and small panels so for construction details this author advises only specifying VIP's for use in large scale applications. The functional service life of a VIP can also be extended through the use of thick metal based foils to seal the panel however these foils also result in energy losses due to their high thermal conductivity, so here a catch 22 situation is presented to the designer.
Conclusions
- VIP's provide an extremely efficient thermal barrier with minimal thickness of materials.
- When designing VIP's careful consideration must be given to thermal performance, structural integrity and the functional service live of the element.
- VIP's have the potential for widespread use throughout the construction industry.
Hello Dave, Can you tell me what the nano-structured open-celled core material consists of? Also is there a tested thermal conductivity for the panels? Sean
ReplyDeleteDavid,
ReplyDeleteJust in relation to the structural performance, can these VIP pannels be used for thermal resistance barriers in floor and wall constructions, and from a positional sence you mentioned that "One way to minimise thermal bridging when using VIP's is to replace one thick panel with several thinner ones and position them in such a way that the joints of the panels are staggered" would this add extra cost and what material is used to bond the edges of the panells or can they be interlinked.
Regards,
Martin.
Hi David,
ReplyDeleteAre the VIP pannels passive certified. Can they be instaled both externally and internally? What percentage diffrence is there bettween traditional insulation and tgis newly marketable product? From reading I would think this product would have to prove itself with i the construction sector as a whole before being adobted into passive house specification,
Regards
Luke
Well Sean; the the nano-structured open-celled core material can consist of many different types of materials and each of these materials have there own specific thermal conductivity value:
ReplyDeleteGlass Fiber: 37 [mW/(m.k)]
XPS - Foam: 31 [mW/(m.k)]
Precipitated Silica: 26 [mW/(m.k)]
Fumed Silica: 20 [mW/(m.k)]
Aerogel: 12 [mW/(m.k)]
@ 1000 gas pressure [mbar]with an external pressure = 1 bar
Well Martin; Yes these panels are used as part of thermal barriers in wall constructions however they are not common in floor constructions. Also the use of several thinner VIP panels instead of one large thick panel will add to extra costs but savings will be realised due to the lower operational costs of heating the building thanks to the better thermal performance of several thinner, staggered panels. Finally when joining these panels they can simply be pushed together and when the flanges of each panel is overlaped the thickness of the metallization is tripled so as a consequence it increases the thermal bridge effect.
ReplyDeleteWell Luke; Currently as far as i am aware these panels are not passive certified. These panels are mainly installed within the wall structure, whether these panels can be installed externally depends of there specific construction and the weather resistance of the outer foil used to form the panel. With regard to its performance versus traditional insulation, VIP's perform significantly better due to their minimal rate of heat transfer and also due to the modern materials that are used.
ReplyDeleteThanks for taking the time to discuss this, I feel strongly about it and love learning more on this topic. If possible, as you gain expertise, would you mind updating your blog with extra information? It is extremely helpful for me. attic insulation removal and replacement
ReplyDelete