# Forum Home Renovation Heating & Cooling  Retrofit cavity wall insulation in Perth

## dustyfeet

Hi,
Recently moved into a double story house, double brick walls in Perth. Want to improve insulation and thinking about putting insulation in the brick cavity walls.  
Having trouble finding anyone in Perth who does foam or styrofoam bead injection.  
Have ceiling insulation and single glazed windows. Thinking of also installing evap cooling. 
Any suggestions? 
Thanks,

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## GraemeCook

Good Morning Dustyfeet 
Retrofitting insulation to a cavity brick wall is relatively uncommon in Aus, but virtually the norm in UK.   Have a look on British renovation forums for the debate.  English weather is much less benign than Perth! 
The width of the cavity determines how much insulation you can add.  The width varied greatly depending on the era, local building customs, and the whim of the bricky.   Three inches was common in Tas, some older houses (Federation era were 4.5 inches (half a brick) whilst some modern cavities are only about 35mm. 
You may find it difficult to find a supplier of styrofoam or polystyrene bead insulation anywhere in Australia.  Granulated rockwool is the flavour of the month in UK and is readily available here.  Its effectiveness will depend on the width of your wall cavity. 
Its also worth looking at double glazing, ensuring roof cavity is properly sarked and the sarking is as air-tight as possible,  insulating the floor, and adding additional insulation around the outside of your hotwater cylinder. 
Fair Winds 
Graeme

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## Moondog55

The better alternative ( but probably much less pretty and more expensive) would be to batten out the wall on the outside, insulate with rigid board and reclad, thus keeping all that thermal mass inside the insulation envelope

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## Bloss

> The better alternative ( but probably much less pretty and more expensive) would be to batten out the wall on the outside, insulate with rigid board and reclad, thus keeping all that thermal mass inside the insulation envelope

   :What he said:  Have look at the Insulation Handbook in the Forum Library too. Rockwool works quite well and there are quite a few who can install it. . You say you have ceiling insulation - in Perth you should have foil under the roof cladding as well as batts on the celling - batts should be R5 - your existing insulation might well be R2.5 or R3 - perhaps lower. 
Look at shading on outside walls and windows too - the type varies based on the orientation of the house and each wall should be treated separately. This might be physical additions to the building such as fixed or variable shades, solid or slatted (at the same angle as the latitude on North walls) or might be trees or shrubs - deciduous or not depending on what sort of protection is needed. 
You could look at one or more solar chimney vents and so on. 
Then you could look at double glazing & e-glass etc (or just do that as part of future renovations) and the very last things should be A/C of any type as it simply costs you more and more money, but can be a smaller size and run less if you have taken the other measures first. 
All these measures will make for better comfort levels all times of day and across all seasons and save money - which is why they should be looked at first. 
In Perth evaporative A/C is a good choice - occasional humid days can make it less effectively, but mostly it is OK. Of course if we get long drought runs then water use and cost might become an issue.

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## dustyfeet

Thanks for the info. 
Looks like I have a few options,
- Install wall insulation, from the comments it looks like this will be very difficult in Perth due to the lack of suppliers. I think my cavity is only around 100mm.
- Improve my roof insulation. I have the basic glass fibre insulation around 100mm. Horrid stuff to work with. Have thought about adding a layer of Polyester over the top.
- Install sarking under the tile roof. I have looked into this. Couple of things put me off, I read that it should be installed during construction between joists and battons. Retrofitting under the joists will be difficult to get the seal. Secondly I saw the cost of it in Bunnings, nearly fainted. 
- Installing double glazing. I have lots of windows in the house including a large feature window (3 sliding doors, and about 16 others). Bit worried about the cost.
- Have considered installing external blinds on the North facing windows for summer. Wife is worried this might make the house look daggy. 
What order of priority should I do the upgrade?

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## Moondog55

Keep the sun OFF the windows, (Awnings/Trees/vine covered pergolas) make a note that most specialist awning companies get it wrong
Keep the sun off the walls ( Shade sails/extended eaves/vine covered trellises) Designed in accordance with latitude specific angles
Sark the roof with reflective insulation. We think this gave us the most immediate and direct benefit in summer and well worth the  $3.3k it cost us
Double the insulation in the ceiling
Then do the insulation on the outside of the double brick.
If power costs will quadruple over the next decade payback time will be incredibly shortened, and with most of these meausres implemented supplementary cooling needs should be decreased anyway 
She wants pretty or comfortable? What's daggy got to do with efficiency? CC and I think external shading looks climate specific great, white sails in the sunset and all.

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## GraemeCook

> Thanks for the info. 
> Looks like I have a few options,
> - Install wall insulation, from the comments it looks like this will be very difficult in Perth due to the lack of suppliers. I think my cavity is only around 100mm.
> - Improve my roof insulation. I have the basic glass fibre insulation around 100mm. Horrid stuff to work with. Have thought about adding a layer of Polyester over the top.
> - Install sarking under the tile roof. I have looked into this. Couple of things put me off, I read that it should be installed during construction between joists and battons. Retrofitting under the joists will be difficult to get the seal. Secondly I saw the cost of it in Bunnings, nearly fainted. 
> - Installing double glazing. I have lots of windows in the house including a large feature window (3 sliding doors, and about 16 others). Bit worried about the cost.
> - Have considered installing external blinds on the North facing windows for summer. Wife is worried this might make the house look daggy. 
> What order of priority should I do the upgrade?

  
Good Morning Dusty 
If your wall cavity really is 100mm then you should be able to fit in granulated rockwool to give an insulation value of about R=
[ 0.5 + 0.7*100/25  =  3.3 ]  The existing cavity brick wall  is about R=0.5 and rockwool is about R=0.7 per 25mm. 
Sisalation sarking can be fairly easily, if awkwardly, stapled to the underside of roof rafters.  Use ducting tape to ensure all joints are airtight.  Sarking operates by stopping air movement (read heat and cold) between the tiles, and by stopping radiation of heat from the hot tiles.  It is particularly effective in hot weather. 
More insulation is always better, and is a balance between the capital cost and the heating/cooling saving.  In Europe passivhaus and superinsulation standards are R values of 10, 7 and 5 for the ceiling, walls and floor - way above Aus customs. 
Lots of glass area means lots of heat flow in and out - always the reverse of what you want.  Window glass has an insulation value of R = 0.2 only.   For 3mm float glass my glazier's rule of thum is $50 per m2.  Double glazing IGU's are $120 per m2 - 2 sheets 3mm glass plus an "assembly fee" of $20.   Low-e glass costs more, and is very worthwhile.   Exotic gases are a wank - they will leak out fairly quickly.   The effect of double glazing is much more than the R value indicates;  it eliminates convection drafts in a room. 
Shading is great when its hot, counter effective when its cold. 
You could break the project down into many small components, cost each, and then start prioritising. 
- shade on north windows
- sarking
- wall insulation
- double glaze living area
whatever. 
Fair Winds 
Graeme

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