# Forum Home Renovation Heating & Cooling  Cavity wall insulation

## kwoolard

What would be the best way to go about doing cavity wall insulation on a brick veneer rendered home dating from approx the 60's with the minimum of disruption and cost. 
I hear you can pump foam in via external or internal walls and possibly via the roof space? 
The other more costly method would be to rip of the existing plaster and install batts and then fix new plaster boards but I guess this would be the expensive way.

----------


## intertd6

The first method would bridge the cavity between the timber frame & the brick work & allow moisture to travel to the inner wall = BIG problems
method 2 is really the way to go
Regards inter

----------


## Bloss

> The first method would bridge the cavity between the timber frame & the brick work & allow moisture to travel to the inner wall = BIG problems
> method 2 is really the way to go
> Regards inter

  Nah - Both methods are an accepted way to post-insulate double brick and brick veneer houses and even in tropical climates is no problem when done according to the manufacturers instructions (and Aust Standards). In Melbourne definitely a good option. Not a DIY job of course. 
Likewise with blown in insulation - it fills the gap completely between the bricks and the inner wall, but the right material is used and it is installed correctly no problem at all. That too is blown in via the roof space with access to under window areas via holes through brickwork. 
Even in humid climates moisture transfer from brickwork to an inner walls by any means is rare and any damage is usually from a local and acute (or chronic leaking) plumbing failure or breach of the covering (like broken tiles or rusted gutters) - not from normal climatic environmental conditions. 
If you want to DIY though then plaster board removal and insertion of batts can work - but very labour intensive (OK if you have time on your hands and o not mind the disruption it causes (and dust!). The other two are done by professionals and cause no disruption to the home occupants at all. 
Have a read of this: http://www.yourhome.gov.au/technical/fs47.html

----------


## kwoolard

Like the idea of blown in insulation from roof space but would that only fill as far as the Noggins and not fill the complete cavity. This is a brick veneer construction.
So to do the the fill below the noggin then you would have to do this from the subfloor ? and if so how to stop insulating material coming out onto the subfloor. 
Also do you know any companies in Melbourne area that specialise in brick veneer wall insulation

----------


## Vernonv

> ... but would that only fill as far as the Noggins and not fill the complete cavity. This is a brick veneer construction.

  No there is normally a gap between the internal stud wall (including noggins) and the external brick wall.

----------


## Bloss

:What he said:  The blown in rockwool (usually) fill fills the whole gap from the back of the internal wall lining (plasterboard) to the inside face of the brickwork and from the bottom plate to the top plate. Depending on the gap between the timber frame and the brickwork this will be from 130-170mm of insulation giving and R-value of around R2.5-R3 - high for walls. 
The usual process is that the gap between bottom plate/ bearers and brick work is filled with strips of fibreglass batts cut to suit then the loose fill tube is sent to the bottom, the blower turned on then as the fill goes in the nozzle is lifted - so it fills from the bottom up. They can be sealed with tape, but in fact aside for a little dropping through on the first blast of fill it holds itself together very well and except in wide gapped veneer spaces doesn't need the blocking. 
See attached PDF

----------


## intertd6

All very good in theory, I have had to chase moisture bridges across veneer cavities on a couple of jobs from a single mortar dag on a tie, good luck
Inter

----------


## Bloss

> All very good in theory, I have had to chase moisture bridges across veneer cavities on a couple of jobs from a single mortar dag on a tie, good luck
> Inter

  Not theory - more than 50 years of solid practice. A mortar dag is not insulation - and it is a sign of poor building practice. In any case even in tropical climates external brick walls are rarely saturated or even damp all the way through unless there is a failure in plumbing or drainage. In most of Australia the humidity and rainfall are low and brickwork even on south walls is generally extremely dry - again unless there is some failure in dampcourse or other water prevention structure (eg gutters & drains). 
But believe what you want - I prefer evidence from practical experience of many, not the single or few experiences of one.  :2thumbsup:

----------


## intertd6

Every cavity brick job I do, I will set up a hose & spray the walls for at least 1/2 an hour to check for leaks in flashings & mortar dags before internal finishes are started, because some tradesmen have poor building practice & economics doesnt allow constant supervision of them & sometimes things just happen even after cavities have been washed out properly. This practice is only copying what happens in driving rain weather conditions, brickwork does get saturated & water does run down the internal face in the cavity, if you have had to fix leaks in cavity work you would know this. The only time you can fill a cavity with insulation is if it has been designed & detailed to be filled which a standard cavity is not, you might get away with it in melbourne, or canberra, but not coastal NSW or QLD 
regards inter

----------


## Bloss

What you a say is not very common - much of my experience has been on Nth Coast NSW and some FNQ, not just Canberra (as was much of my my Dad's experience too which I often draw upon). Properly constructed brick veneer simply does not generally have the problems you describe - and in my experience most are properly constructed. 
I have years of experience looking at moisture problems and repairing them - few have ever been from what you describe even in high rainfall areas as I have said. 
I stand by the advice I have given which is supported by manufacturers and independent technical and scientific advice here and internationally. You might think there is a great conspiracy to provide poor building advice - I don't. 
In this particular case the residence is in Melbourne - none of the issues you raise, rare in wet climates IMO, are relevant in that climate. 
We'll just have to agree to disagree - I don't plan on continuing the posts as kwoolard has answers and can go ahead with whatever they choose to do.

----------


## intertd6

The way to get around the pumped insulation bridging the veneer cavity problem here would be to paint the rendered walls with the appropriate product & seal all gaps around openings, this way you would effectively make the outer leaf of masonry waterproof & preventing moisture from ever having a chance to reach the insulation & the inner face of the wall.
Regards inter

----------


## GraemeCook

Nice to see you examining this issue in depth, Inter, but in this case I think Bloss is correct. 
Wall grade rockwool - its different from the ceiling grade - is water repellant.   Put a drop of water on it and it will bead.  It will not wick along the fibres.   Lots of cavity walls have been filled with rockwool and moisture has not been a problem. 
Cheers 
Graeme

----------


## intertd6

Well there is a thing called capillary action & it doesn't matter if the rockwool is water repellant, once the wall ties are in close contact with the material moisture can travel along the tie. When you look at some of the suppliers of this type insulation they say that "it is extremely difficult and costly to insulate walls after the home is constructed"
Being a builder myself there is no way I could be sure that this type of system would be watertight & when you have 10% of the project cost tied up in home owners warranty & that 10% is part of your home, you could imagine how carefull you have to be these days.
Regards inter

----------


## GraemeCook

> Well there is a thing called capillary action & it doesn't matter if the rockwool is water repellant, once the wall ties are in close contact with the material moisture can travel along the tie. When you look at some of the suppliers of this type insulation they say that "it is extremely difficult and costly to insulate walls after the home is constructed"

  
Sorry, Inter, the science is not there.   You simply cannot get capillary action along a water repellent surface. 
And there are  many rockwool insulated walls; they simply do not have these problems. 
Agreed, it is more difficult to insulate an existing wall, but not impossible, and rockwool is frequently the best option. 
Cheers 
Graeme

----------


## intertd6

"Sorry, Inter, the science is not there. You simply cannot get capillary action along a water repellent surface."
I will have to remember that the next time I have to fix a leaking vertical apron flashing joint that has been silicone sealed.
Regards inter

----------


## Gravy258

What would be the best way to go about doing cavity wall insulation on a brick veneer rendered home dating from approx the 60's with the minimum of disruption and cost. 
I hear you can pump foam in via external or internal walls and possibly via the roof space? 
The other more costly method would be to rip of the existing plaster and install batts and then fix new plaster boards but I guess this would be the expensive way.[/quote] 
This way is by far the cheapest option  :2thumbsup:  
Remove the first two rows of tiles on your roof. You should then see the frame and plaster of the interior walls. Your then able to poke Batts down to the first noggin. You can almost get a whole Batt down, say about 40 cm to cut off. You might need a length of broom stick or similar to push em down, but it works.  
On a hot day, if you feel the interior walls, especially on the west side, the top will be very warm. this will stop this. As heat rises it will also make a difference in winter.
I pushed Poly 1.5's down about a year ago. I then put a skirt of concertina foil between the end of the brick veneer and the top of the wall frame. 
This also cut out a lot of street noise. 
If your going this far make sure you block all wall vents off, just fill em full of clear silicon, and make sure all ceiling vents are blocked and any exhaust fans have covers on with one way flaps. 
regards 
Gravy

----------


## Bloss

If you are any good at plastering or know a good plasterer who will do the work for the right price this can be a good option. Can be done in stages - room at a time and so on and if your labour is 'free' works well. Dusty work and I have seen the repair work look damn awful, but it costs only the batts and a bit of plaster board for patching (often free from building mates or skips) etc. 
Walls you want R-2 minimum though and with regular batts installed that way it can be hard to be sure you do not end up with moisture problems from the batts breaching the cavity. Again in most parts of Oz that is a rare issue.

----------


## kwoolard

Defintely going to get the insulation done but now have 2 choices.
 Either going with the rockwool ( just-rite home) - getting quoted at $1800 for 60m2 or go with foam (Wall Insulation | Roof Insulation | Rebate | Wall Insulation | Ceiling Insulation | Gov. Insulation Rebate.) - getting quoted at $2500 + GST 
Anyone have any background on either of these methods or the comapnies involved ? feedback would be appreciated. 
I more inclined to go with the foam

----------


## Bloss

Either will be fine.

----------


## GraemeCook

> Either will be fine.

  
True, but I would have a preference for the rockwool as it is both cheaper and an inert substance.   There is always some doubt about the solvents used in foams. 
Insulation values are similar. 
Cheers 
Graeme

----------


## kwoolard

Rockwool it is then - thanks for all the advice

----------


## Bloss

Rockwool's what I have and it's a fine choice . . . but many the supposed issues with foam are exaggerated IMO. I reckon the fiddling later if you need to add or move powerpoints etc is more of an issue.

----------


## charli

Hi ken,
wondering if you booked in the rockwool? If so have you been given a date or whenever more jobs get booked in melb?

----------

