Full-Fill PIR

[Emeraude119]

New Part L nosey!

Have the U-values changed in the latest revision? I thought not?

I don't think they have for extensions to dwellings.

the U-values for the walls to extensions is unchanged at 0.28 W/m2K under the latest 2013 edition of Part L1/B.
The only time lower wall U-values are required for extensions, is if the extension has a higher than the permitted amount of openings, in which case a calculation must be carried out to offset the extra heat lost via the openings, by reducing the U-value of the other elements (floors, walls, roof)
The requirement for openings to extensions is to add the area of any existing openings which as a result of the extension are no longer exposed, to a figure representing 25% of the total floor area of the extension. provided the elemental U-values are then achieved in the floor walls and roof, the extension will comply with AD-L1/B.

 

[limerockconstruction]

OOI - what am I missing?

For sure I didn't look at their site in detail, but at first glance it's a rigid insulation board - is it simply that any board like that will be a PITA to install compared with rockwool batts, or is there something special about that particular board?

Its because bricklaying is never as much of a science as people think, you often need to pinch a few mm here and there to make things work, and this is where a compressible full fill comes into its own.

 

[Emeraude119]

Also builders might allow a small airspace between a cavity fill insulation and the outer leaf to stop the insulation pushing the outer leaf off bed when it is being brought up.

 

[ban-all-sheds]

Reports from sites seem to indicate it can be a problem to fit, but, this could be looked at in the context of people on site wanting an easy life, or avoiding a build method that slows them down.

Well - the latter makes perfect sense - if it slows them down it pushes their costs up.

It is usually used where very low U-values are required to bring a dwelling into compliance with Part L1/A without the wall coming up too wide.

Interesting.

I did ask out of general interest, but that resonates with me - depending on things as yet to be resolved, I might be very interested in being able to make the walls of an extension thinner.

 

[ban-all-sheds]

Its because bricklaying is never as much of a science as people think, you often need to pinch a few mm here and there to make things work, and this is where a compressible full fill comes into its own.

OK. But presumably using blocks for both leafs would lessen the possibility of that happening?

 

[limerockconstruction]

You are right in theory, but there isn't really much roof left for working tolerances....so although once you've laid the block worked it to the line and chopped your excess muck off and you have a lovely clear Cav, really you need that little bit of room to work with.

I've never used it before, its just what i've heard from good experienced and conscientious brickies.