90mm batts wont work if you have created a 20mm cavity . the batts lose their effectiveness when in compression .
bergkamp,
Oct 28, 1:42am
WB
tweake,
Oct 28, 2:02am
don't create a 20mm cavity. i've not seen it as a requirement, tho some gap is wise. the other thing is 90mm batts compressed down to 70mm batts acts as 70mm batts. its more of a cost issue assuming you can get 70mm batts cheaper.
i don't think a 20mm gap helps all that much as weather boards etc are not as air leaky as a rainscreen. be far better off making sure it can drain past the nogs and bottom plate. even a 1-2 mm gap would handle all the water it could ever see.
Not sure if anyone has mentioned, and I'm not sure if it's all areas, but where I am, you need a consent and inspections for wall insulation, but there's no cost from the council.
bergkamp,
Oct 28, 7:52am
it is interesting how you dis the 20mm gap . and 50mm poly with no building paper . yet this is recommended as" best practice " by branz after "increased understanding of drying in walls " presumably by their scientists . i do agree that 20mm gap is dumb and reduces thermal capacity , hence why i started this thread to see what others have done
marte,
Oct 28, 8:10am
I think with weatherboard, but replacing it from the outside. You put your insulation in, building paper over that & use thin wooden slats over the studs to provide the 20mm gap, before putting the weatherboard on over that.
tegretol,
Oct 28, 8:23am
How would a council be liable for the actions of a private homeowner doing their own work? Surely there is a bigger risk to them to put it all under a consent process?
tweake,
Oct 28, 8:24am
got a link on branz recommendation? i'll search when i have more time. the only recommendation i've seen, some time ago, was pocket installing building paper and insulating. no gap mentioned.
the 50mm poly i dis for obvious reasons, same reason its bad when used as direct fixed cladding. its permeability is very low and can stop the wall drying to the inside and stop the inside of the house drying to the outside. its not really suited to our wet climate.
tweake,
Oct 28, 8:29am
because the next owner will blame the council for the mold/rot. kiwis do not live in houses very long. you will always get people cutting corners in the reno. councils are the ones left standing to foot the bill for leaky homes, so i think they have an interest in how the work is been done.
thanks for the link. i see it says the 20mm gap is a recommendation.
i wonder if thats come about from the issue of water running down and hitting the nog and base plate if the weather board happens to be attached to it blocking drainage. ie no drainage and water will go under the paper and into the insulation. give it a 20mm gap to provide a space for it to sit and dry. tho i would rather just cut the nog or weather board so there is a gap for it to drain. by keeping the paper up against the weather board you remove the ledge for water to sit on so the water will run down the face and out the bottom.
i think a bit of drainage mat would would even better. it gives water a path, gives some gap for airflow without creating to much of a ledge for water to sit on the nog/plate.
pauldw,
Oct 28, 10:36pm
I think it's an exercise in theory. In the NZ Standard if it's direct fixed with building paper go ahead and insulate. No building paper either use strapping to hold insulation 20mm off the back of the sheathing or put pockets of building paper in. Then there's the mention that a mix of the 2 methods might be good ie pockets with a gap. Why wasn't that specified as method 2 in the 1st place. I don't think the standards committee could agree.
marte,
Oct 29, 1:14am
I know somebody who retrofitting insulation from inside, a brick house. They are using the tarpaper & making pockets & fitting the insulation into this. This gives a gap between the tarpaper & the brick. Which is what I expect you would have to do with the weatherboard as well, since it's being done from inside. So I expect that no other building paper would be suitable.
While, if it's done from the outside, full depth insulation, then whatever building paper over that, then wooden 20 mm thick slats to provide the gap, then the weatherboard.
tweake,
Oct 29, 1:41am
with brick its not an issue due to them already having a decent gap. that gap is actually for the large amounts of moisture that goes through brick (as its a water storage cladding). that doesn't apply to weather boards hence the direct fix and even today the rainscreen is really for drainage and drying rather than moisture going through the cladding.
not sure what you mean by "So I expect that no other building paper would be suitable." i prefer the most vapour open paper/wrap i could get. you never want anything in the wall that slows down drying. especially on a pocket install where you do not have the overlap that allows air through to do the drying.
the catch with retrofitting a rainscreen is that you also need to pull the windows/doors out to match it. its no small job.
tegretol,
Oct 29, 3:36am
Please explain how the council can be made liable for work done by the homeowner and not advised to them.
bergkamp,
Oct 29, 5:45am
your comments on this thread amuse me , you state that LBS is about people not understanding how buildings can dry yet you seem to have little clue yourself being in total conflict with the latest science , flip flopping your opinions while telling me i am "missing the bus" ! lol
tweake,
Oct 29, 7:51am
resorting to personal attacks, lame.
its two completely different scenarios and branz is a recommendation which looks more like an arse covering exercise than actual science. please try to keep up.
trade4us2,
Oct 31, 9:13am
If you have weatherboards, I decided to take all the weatherboards off and install insulation and building paper etc. The rules have since changed. Anyway, I screwed the weatherboards back on with stainless square drive screws, and I would strongly recommend that. If you need to fix plumbing or wiring, you can just remove a board as needed.
rak1,
Oct 31, 2:14pm
No. Unfortunately had to downgrade the R value of the insulation as the stuff I originally wanted to use would have been to thick to get in. Ended up with a "70" mm insulation in the low R2s but has made a difference.
bergkamp,
Oct 31, 9:16pm
very good idea, but stainless is too soft IMO
tegretol,
Oct 31, 10:50pm
Stainless is too soft? Perhaps you're getting muddled up with lead screws?
tygertung,
Oct 31, 11:02pm
Stainless is much softer than regular steel.
tweake,
Oct 31, 11:38pm
unless your using self tappers and are going through steel, softness doesn't really play much of a role. unless your using worn out driver bits. tensile strength matters a lot more but i think its more than high enough for the job. but it also depends on if you have quality metal or garbage grade. plenty of fake "316" out there.
bergkamp,
Nov 1, 12:35am
I only mean that if you are going to be potentially backing out and redriving the screws then they will tend to slog out over time esp with native timbers.
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