The best place to start is identifying what you need your pipe insulation to do; this may seem to be an obvious question to ask yourself, but if you overlook it then you can end up costing yourself time and money in the long run.
Common applications such as heating & plumbing or frost protection are usually best served by standard polyethylene foam - it is cheap, easy to work with and has thermal values as good as any other flexible foam. It is often regarded as low quality, but this is not the case; it is more than adequate for the majority of domestic applications if used at the correct thickness for your application. Thinner wall material is OK for use in areas such as airing cupboards or heated rooms within the main building, but you would need to use thicker material for frost protection where the smaller the pipe is the thicker you need the insulation to be.
The one area where polyethylene falls short is it does not have a fire rating to BS 476; all good quality flexible elastomeric foams, mineral fibres and phenolic foam products will have this and it is a requirement to have a minimum of a Class 0 fire rating when you need to comply with Part L of the building regulations.
More complicated applications such as personnel protection or condensation control require a little more thought as you must consider the surface of the insulation as well. For personnel protection or condensation control you would ideally want a High Emissivity Surface; typically a black finish such as you would get with a flexible elastomeric foam (also commonly known as nitrile rubber). The reason for this is that a high emissivity surface allows for a more efficient exchange of heat with the surrounding area, meaning the surface of the insulation is generally closer to ambient temperature. This will by extension mean personnel are less likely to injure themselves by touching the surface of the material, or that condensation is less likely to form depending on your point of view. Of course you must still use the correct thickness of insulation, but this must be calculated according to you conditions - if you aren't able to do this yourself give us a call and we will be happy to calculate the correct thickness for your application.
Conversely, if you are working to achieve maximum energy loss prevention, then you would be better served using a Low Emissivity finish; typically meaning a silver foil surface. This will give you a lower heat loss; a very general rule of thumb might be that assuming to materials have the same thermal conductivity but differ in the surface's finish then a product with a Low Emissivity surface would have around 8% lower heat loss than a product with a High Emissivity surface in the same situation.
You must also consider the temperature constraints of your application, as most materials have upper service temperature limits. For applications below 100°C you will usually be safe in your choice of materials, but for higher temperatures you need to use the appropriate material. Mineral Fibre can be safely used up to around 250°C to 300°C before the binding agent begins to evaporate and the material softens.
If you have situations where you start to combine factors such as personnel protection and high temperatures you will need to look at jacketing products as well. If you have a high temperature pipe, say carrying steam, and you need to prevent people burning their hands on it then you would want to combine a high temperature material such as Rockwool with a High Emissivity finish which could be achieve by applying a product such as PIB, though of course you must take care that the insulation is thick enough to protect the outer coating.
The basic efficiency of the material must be considered as well; ideally you want a product with as low of a thermal conductivity as possible. A lower thermal conductivity means a lower rate of heat transfer through the insulation, so less energy wasted. Combined with a Low Emissivity finish you can therefore achieve very low heat loss; a product such as phenolic foam gives you both of these attributes. With a thermal conductivity as low as 0.021W/m.K at 10°C (thermal conductivity is relative to temperature) and a Low Emissivity BCO Foil finish you can achieve a very low heat loss. The upper temperature limit is around 120°C, so you cannot use it for every application, but in applications such as commercial heating it would be ideal.
And of course, it goes without saying price will always be a factor in these decisions. To look over the costs for any of the materials mentioned on this page, you can visit our e-commerce site: .
Generally speaking, polyethylene foam is the cheapest available insulation, and Flexible elastomeric foams tend to be more expensive as they have a Class 0 fire rating. Foil faced mineral fibres tend to be a little bit more efficient and more expensive too. Phenolic foam is the most efficient product on a thickness for thickness basis, and the most expensive, but you can achieve the same results with say 15mm of phenolic that you would need 20mm of mineral fibre to achieve.