PIR vs glass mineral wool

[A_L]

19 minutes ago, Jason L said:

Hi. Can you explain what decrement delay is please? 

 

At the simplest it is the time taken for energy at the outside of a wall to transfer through to the inside.

 

https://www.concretecentre.com/Publications-Software/Design-tools-and-software/Dynamic-Thermal-Properties-Calculator-(1).aspx

 

from the middle of the link :-

 

Quote

This is a property of thermal mass which describes the way in which the density, heat capacity and thermal conductivity of a wall for example, can slow the passage of heat from one side to the other (decrement delay), and also attenuate gains as they pass through (decrement factor). Designing for a long decrement delay of around nine hours or more, and a low decrement factor can help reduce overheating problems in summer.

 

[BartW]

1 hour ago, Buzz said:

So £21m2 to get to .14 in pir , thanks i have somewhere to start ?, going to need somewhere close to 400m2 ?.

Is that your roof size? Blimey, how big is going to be your house ??

[Buzz]

Building a bungalow , about 260 foot print (at the moment ) got to have a high ridge to match the street view , so pricing for 400m2 and hoping for less , every little helps? 

[TonyT]

if you are going for PIR, you need to factor in expanding foam, foil tape etc too.

I wish I had shares in foil tape and expanding foam before starting

[Gone West]

11 hours ago, Jason L said:

Hi. Can you explain what decrement delay is please? 

It's the rate at which heat is lost through a material. It's difficult to model accurately and there are endless constructions to reduce the effects. The effects are more pronounced where there can be a build up of heat on the outer surface such as on the walls of a well sheltered house. Where we are, near the coast in an open area, the effects are non existent because when the weather is hot there is always a sea breeze.

https://www.greenspec.co.uk/building-design/decrement-delay/