Full-Fill PIR

[limerockconstruction]

Hi Chaps, any of you been asked to use full fill PIR boards in a 100mm cavity before. Apparently Xtratherm do a product called CavityTherm - my brother has used it and said it was ridiculously hard to use.

I wondered if any of you other chaps had had a go at it?

 

[noseall]

No never, can't see the point when there are (much) easier alternatives.

Why make our job any harder than it already is!

 

[freddiemercurystwin]

New Part L nosey!

 

[limerockconstruction]

New Part L nosey!

Is that why? The upgrade in regs? Could it just be used in a 115/120 cavity or does it need to be full fill?

 

[freddiemercurystwin]

New Part L nosey!

Is that why? The upgrade in regs? Could it just be used in a 115/120 cavity or does it need to be full fill?

Well I have no idea why your brother used it, the new regs have only just come in so anything built up to now would have used the old regs so 40 or 50mm of PIR would have sufficed.

That said it does appear to be a means of achieving a really good U Value without compromising wall width.

That said increased insulation to meet the new regs is more prevalent for new builds than domestic extensions.

 

[tony1851]

New Part L nosey!

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

 

[limerockconstruction]

Just spoke with Xtratherm - they said that CavityTherm is better than Edison discovering the phonograph!

My main concern is about the details around trays, corners and jambs etc. Rockwool is so much easier to get right!

 

[freddiemercurystwin]

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.

 

[freddiemercurystwin]

Just spoke with Xtratherm - they said that CavityTherm is better than Edison discovering the phonograph!

My main concern is about the details around trays, corners and jambs etc. Rockwool is so much easier to get right!

Yes but 100mm rockwool in the cavity won't achieve the same U Value. I'm not defending it but that seems to be their aim. Its installation method seem to be very labour intensive/open to poor workmanship.

 

[limerockconstruction]

I can't see blokes on big sites taking their time to instal it that well. As a more domestic firm we've got a bit more time on our hands to get it right, but i'd imagine that even with the best will in the world it's still gonna be tricky.

 

[noseall]

Very tricky indeed, especially a product that will not compress.

Sounds like a nightmare!

 

[mikric]

See this used more and more on new build sites, and yes its a bricklayers worst nightmare.

 

[jeds]

Cavitytherm comes into its own for stone faced cavity walling. In standard brick/block I'd stick with Dritherm.

 

[ban-all-sheds]

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?

 

[Emeraude119]

Cavity therm consists of various thickness of PIR insulation board with a 5mm finned sheathing board that goes in front of it. Consequently when 100mm Xtratherm cavity therm is specified it is made up with 95mm PIR board and the 5mm sheathing.
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.
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.
Where wider walls are required, this also means wider foundations, wider threshholds cills and window boards, wider cavity closers, wider lintels, etc all of which increase the costs. With land prices as they are many developers see all this as unacceptable.
Many want to build houses which comply with Approved Document L1/A without having to resort to the use of Eco Bling, e.g Solar thermal panels, solar Pv panels, ground / air source heat pumps, all of which are expensive and require on going maintenence, (Cleaning, new pumps, new inverters etc_and which will need expensive replacement at some point.
Cavity therm, Like Recoh Verte WWHRS waste water heat recovery systems are a fit and forget option for a develpoer / builder to achieve compliance with Part L1/A which is why some will go for it.