Heating, Cooling & Insulation
Apr 15, 2021 12:29 pm
Note: as I get more info, I'll add it as edits at the bottom in case it's useful to others at some point.
I'm in a weatherboard exterior, fibrous plaster interior in Melbourne northern suburbs, which we bought late last year. Currently, none of the walls have any insulation - there's plaster, 90mm gap, then weatherboards.
We are about to get a permanent bookshelf added on an external (west-facing; 10ft ceilings, 3750mm wide) wall. The bookshelf will cover the wall, so I though it might be an opportunity to add insulation from the inside, given that any imperfect plaster patching will be covered up.
I'm trying to get quotes from insulation installers, but I don't think I'm necessarily asking the right questions to get a good quote or good result (the only one I have had back is $950 to put R2.5 batts in the wall by cutting out sections of plaster). I was hoping people here would be able to answer some questions, or even help me be asking the right questions when I call insulation installers. (It's made more complicated because there's also a gas heater on the wall, and a window in the middle of it).
- I'd rather not pull off _all_ the internal plaster and/or all the external weatherboards at this stage if I can avoid it. The weatherboards were just painted before we bought, so I'd rather hold out until they need attention before ripping them all off. None are obviously rotten etc at this stage.
Questions I'd be eager to get input on:
- A lot of the information I've read has talked about the importance of having a 25mm air gap between batts and weatherboards to avoid condensation being captured and leading to rot. Is it plausible that batts could be fed in through sections cut in the interior plaster and actually have the necessary gap? (i.e. cutting out a section of the plaster the full width of the wall and 10-20cm high aove and below the noggings, and feeding batts in through it). Is this something an insulator is likely to have tricks to deal with, or should I be assuming they'll just be ignoring that guideline when putting the insulation in?
- I've also been looking at blow-in insulation, but 'the talk' is that it is fairly costly, less effective than batts, and I haven't found clarity on whether it needs the space from the weatherboard as well in which case it would be a no-go I imagine. Does anyone here have direct experience of this?
- Does it even make sense to try to go through the plaster, or would it be more sensible to just go in from the weatherboard side - even if it is just pulling off one weatherboard up high and one down low to avoid the noggings, equivalent to cutting holes in the plaster?
- Are there products (like anticon) which have some kind of a moisture shield already on one side that could potentially be put in that would avoid the need for the air gap?
A (not great) photo of the wall is attached - the black thing on top of the heater is just a speaker so can ignore that.
Only other thing of note is a new roof (colorbond with 55mm space blanket below) was just installed.
Thanks for any ideas, warnings, etc!
Enviroflex Melbourne had a minimum of $800/20sqm, so chances are if we go that way we may well just do the whole house. The salesperson seemed confident they could spray something in first to provide a moisture barrier, and then the filler.
I've read now in a couple of places that RockWool is better than just straight glass wool in terms of acoustic protection, but the same in terms of thermal protection (based on call with JustRite, who these days only operate in Canberra). In this case because there is a window smack bang in the middle, using RockWool over glass wool seems pretty pointless but given the whole house I'll be looking at the price difference vs value.
The end result was that we didn't put insulation in the wall yet. We got a quote from Enviroflex Melbourne for $3800-ish for the walls of the whole uninsulated part of the house (house is 124-ish sqm with 10ft ceilings, and probably 1/4 of the house is a batt-insulated extension). That involves booring in through the weatherboards and filling (but not painting the fills in any way).
One concern I had was that if I needed to cut out and repair a weatherboard etc at some point, the insulation would fall out but the rep was confident that if I were just removing one board or small sections then the insulation would hold itself together. I imagine that means that if I was going to replace the boards wholesale and try to retain the insulation in place I'd be pulling boards one at a time and stapling a length of building wrap on or something to hold it in as I went. Hard to know.
Thanks for the suggestion of InsulGuard. I don't _think_ that's so suitable for weatherboard/plaster but I'll check!
Re: Add insulation to exterior wall without complete strippi2
Apr 16, 2021 8:51 pm
Anticon is for under roof only. My thoughts are it’d be a right pain to do hundreds of cuts or holes. It will never look original again. And wouldn’t get you properly fitted batts.
If money is no option it’s best to pull the weatherboards off. Then you can properly fit insulation batts. The tack a vapour barrier to cover everything with no holes. Screw battens to the studs then refit the weatherboard.
Re: Add insulation to exterior wall without complete strippi3
Apr 16, 2021 9:00 pm
Stupid homeone iPad theme has no edit button....
You need a vapour permeable water barrier house wrap. You could do away with battens as weatherboards are not really airtight. Pretty much no difference between batts of the same R value. Not a fan of polyester though.
Try dyi’ing as short inconspicuous wall.
Re: Add insulation to exterior wall without complete strippi4
Apr 17, 2021 3:05 pm
Not sure if these guys have a branch in Melbourne but this may be something worth looking at
InsulGuard Insulation - Home Comfort, Security & Sustainability Lives Here
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