thermal resistance of laminate underlay

[mebumu]

I am in debate with a colleague about the relative merits of using Envoy Ultra underlay versus Timbermate Excel; the debate is centred on which one has the better heat insulation properties, i.e. higher thermal resistance.

Visual inspection alone would tend to favour Timbermate Excel; it looks and feels thick and cosy and, with the addition of the foil vapour barrier, it would be logical to think this would win the contest by a country mile.

However my limited research is as follows:

Unit of thermal resistance = R(SI) is measured in m2K/W

Timbermate Excel: Quoted tog value = 0.55 = R(SI) value of 0.055 m2K/W
Envoy Ultra : Quoted R(SI) value of 0.088 m2K/w

making Envoy Ultra the better heat insulator!

Another argument put up is that the foil barrier would surely act to reflect the heat back in the case of Timbermate Excel. Does the foil barrier act purely as a vapour barrier in this case and have no thermal insulation qualities?

I am also totally confused with manufacturers claims that laminate underlays can have both good insulation properties and yet also be recommended for use in underfloor heating.

any experts here who can clarify these points please?

 

[freddiemercurystwin]

The higher the R Value the better so Envoy Ultra is better although frankly they are both so thin neither will have any significant effect on reducing heat loss.

Its just spiel, manufacturers can make any claims they like. Compared to a single sheet of newspaper they are very effective.

Frankly though its a bit like two fleas arguing about who's got the longest knob!

 

[mointainwalker]

A very good reply by Freddy

It's pointless talking about insulation properties when you you are dealing with the equivalent of a few sheets of newspaper, there are not yet any magical thin materials.

Having said that, the figures you quoted are amazingly good, really too good to be true, so need looking at.

Your confusion about the good insulation/suitable for UFH is well-based,Since there is no defined criterion, any company could say that a steel plate is good insulation or equally that a feather duvet makes a good conductor for UFH ( sorry, rather silly but nothing more apt came to mind )

 

[mebumu]

mointainwalker and freddymercurystwin:

Thanks for the excellent replies; very useful points indeed and this confirms my suspicions that manufacturers data should be treated with the proverbial pinch of salt!

 

[mointainwalker]

manufacturers data should be treated with the proverbial pinch of salt!

Yep. There are an awful lot of companies that publish data that, viewed objectively, shows poor performance , but which they will say is "excellent".

This trick works because many people see "complicated" numbers like the m2/K W and then just believe the "excellent" comment, even though it is completely unjustified, but legal.

In fact a lot of companies go out of their way to over-complicate the data so it is not widely understood and potential customers have to fall back onto the manufacturer'r interpretation of the results.