Full or partial fill cavity insulation preference?

[BadgerBadger]

We're looking at rigid board insulation on a brick/block construction and we're on the edge between moderate-severe exposure for wind-driven rain. 

 

If you had a general preference would you be considering full-fill insulation as opposed to partial-fill?  Are there any advantages for ease of high-quality construction etc. or the other way round?  It perhaps seems a shame to leave the extra insulation space if the wider clear cavity is not strictly necessary.

[joe90]

Well we fill filled a 200mm cavity with rockwall batts in a brick and block structure, the brickie was a bit dubious about it but the insulation had a BBA certificate fir full fill. Our west wall cops Atlantic rain, and the bricks became sodden in winter, however, when I core  drilled fir the ASHP pipes I found the first 10mm of the insulation wet but it had not wicked anymore than that. Because I am OCD the following summer I treated the whole wall with water repellant anyway and water now runs off it like glass (and you can’t see it at all). 

[nod]

Going to have to stop saying this 

Plus one with Joe 

We did exactly that with ours 

Block and Block Full fill Roocwool 

Worked a treat 

Looking at the speck for our next it’s Recticell batts and a 20 mil air gap 

But that may change 

 

Its one of those things that well worth over specking 

 

 

[Buzz]

We have chosen to go with brick and block with a 150mm full filled cavity , using the "32" insulation the SAP report gives the wall section a u-value of 0.17.  

[joe90]

1 hour ago, nod said:

Going to have to stop saying this 

Plus one with Joe 

great minds think alike mate ?

[farm boy]

I ve got full fill 125mm cavity therm by xtratherm. The cavity ends up being about 130mm just due to tolerances in construction. Brick layers took longer  to build, but they had used it once before. Requires patience to cut openings, lap corners, install stepped trays etc. House not finished yet, so time we'll tell.

Edited August 21, 2021 by farm boy
Error

[nod]

33 minutes ago, joe90 said:

great minds think alike mate ?

????

[Moonshine]

2 hours ago, Buzz said:

We have chosen to go with brick and block with a 150mm full filled cavity , using the "32" insulation the SAP report gives the wall section a u-value of 0.17.  

 

I have this arrangement with block external and render.

The architect doesn't like full full cavity but I insisted, and he is a little more relaxed about it that its rendered.

[Buzz]

4 minutes ago, Moonshine said:

The architect doesn't like full full cavity

This statement is one of the things i find difficult to understand with the industry in general, with our build my architect was the exact opposite i mentioned 150 full fill and got" brilliant idea, love it ,fabric first approach " but how can 2 professionals in the same industry have opposite views, either its safe to build this way or its not ! and the only opinion that matters is the clients . 

[joe90]

3 minutes ago, Buzz said:

but how can 2 professionals in the same industry have opposite views,

Perhaps it depends on what insulation, as I said mine had a BBA cert fir full fill (but the brickie had his doubts).

[Buzz]

10 minutes ago, joe90 said:

Perhaps it depends on what insulation,

Fair point , but should the architect not be supporting the idea by saying , but only if you use this type of insulation.

[BenP]

I think architects have been pushed and pulled around by manufacturers - cavity good, cavity bad. Fullfill good, fullfill bad... etc! 

 

If space allows we tend to feel a bit more comfortable down the Rockwool type fullfill arrangement. For people who have seen the quality of a typical partial cavity board install this will make complete sense. Not abutted, at funny angle etc. Awful. 

 

I'll leave you with the attached to further prove my point....and tickle you all...