Garage roof insulation?

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mattwnz

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#3177381 3-Jan-2024 18:33

Is the roof rusted through on the trough of one of the trays? If you are getting water coming though there then that tray may need to be replaced before you do anything, otherwise your insulation is going to get wet. IMO the garage is performing what it was designed and built to do, and the fact that it isn't insulated or lined probably helps vent any of the moisture and condensation. Basically it is a large shed so not designed for insulation or linings. So anything that is retrofitted will be a compromise and has to be carefully considered.

tweake

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#3177390 3-Jan-2024 19:09

mattwnz:

IMO the garage is performing what it was designed and built to do, and the fact that it isn't insulated or lined probably helps vent any of the moisture and condensation. Basically it is a large shed so not designed for insulation or linings. So anything that is retrofitted will be a compromise and has to be carefully considered.

nah they are designed to be cheap. lack of house wrap tends to keep moisture in rather than out (as they dry back into the shed).

tho quite right you do have to consider things carefully.

Lias

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#3180136 10-Jan-2024 17:54

Okay so my dad who is far more handier seems to think taking the roof off the garage isn't actually that much of a mission, but if we do it I wanna do it properly so I'm back to confirm this is what we should be doing.

Lift roof iron
Put down new barrier over top of the purlins (is there any advantage for my scenario to moving to Tyvek etc or is tarpaper still fine?)
Staple polyester insulation under the purlins
Winning?

Also for the walls, taking the exterior iron off looks to be much more of an issue than the roof. Would lining what we could from the inside be viable? Not worried about building code or anything like that, just in practical terms?

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tweake

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#3180176 10-Jan-2024 19:35

Lias:

Okay so my dad who is far more handier seems to think taking the roof off the garage isn't actually that much of a mission, but if we do it I wanna do it properly so I'm back to confirm this is what we should be doing.

Lift roof iron
Put down new barrier over top of the purlins (is there any advantage for my scenario to moving to Tyvek etc or is tarpaper still fine?)
Staple polyester insulation under the purlins
Winning?
Also for the walls, taking the exterior iron off looks to be much more of an issue than the roof. Would lining what we could from the inside be viable? Not worried about building code or anything like that, just in practical terms?

i'm a fan of modern synthetic roofing underlay as it allows more moisture to move through it than tar paper, especially the high perm ones. however check uv rating if you have a lot of windows or tend to have doors open for a long time.

walls you can pocket install the house wrap. i don't like that much, but it is a garage and its regularly done (and allowed) on houses. you simply fold the house wrap so it covers all 5 sides and is stapled in on the sides.

SomeoneSomewhere

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#3180188 10-Jan-2024 19:59

You will want a good impact driver (or two) and a bucket of roofing screws. You don't really want to be mailing, and the existing screws/nails will be had it.

tweake

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#3180201 10-Jan-2024 20:16

SomeoneSomewhere: You will want a good impact driver (or two) and a bucket of roofing screws. You don't really want to be mailing, and the existing screws/nails will be had it.

good point. also get the washers (i think they are for clear roofing) as they cover the mark left by the roofing nail.

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Lias

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#3180260 10-Jan-2024 21:07

I've got my admittedly DIY grade Ozito impact driver and dad has AEG kit so I think we're sorted on that.

The half of the garage roof I can easily view is already screws not nails so that's a bonus.

Re: Tyvek there's 10 windows (5* 2 pane ones) and currently the doors stay open a lot because of the heat so will bear that in mind.

Lias

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#3180281 10-Jan-2024 23:07

Another question.. in the very short term, would it be safe to start stapling polyester insulation to the underside of the purlins in the areas of the roof that DO currently have tar paper? I figure some insulation gotta be better than none?

tweake

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#3180625 11-Jan-2024 15:59

Lias:

Another question.. in the very short term, would it be safe to start stapling polyester insulation to the underside of the purlins in the areas of the roof that DO currently have tar paper? I figure some insulation gotta be better than none?

yes thats fine. just remember insulation needs to be continuous to work well.

Lias

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#3180640 11-Jan-2024 16:33

"Silverzone foil insulation is ideal for use as an insulation product fitted to the underside of the roof of commercial sheds / buildings". I'm thinking this could be an alternative to the polyester?

tweake

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#3180654 11-Jan-2024 16:52

Lias:

"Silverzone foil insulation is ideal for use as an insulation product fitted to the underside of the roof of commercial sheds / buildings". I'm thinking this could be an alternative to the polyester?

no. that stuff is really expensive and poor performing. also not legal for residential use.

commercial insulation standards are a lot lower and cost of working at heights means easy to install products are a major cost saving even if its a more expensive product.

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#3180668 11-Jan-2024 17:22

tweake:

no. that stuff is really expensive and poor performing. also not legal for residential use.

commercial insulation standards are a lot lower and cost of working at heights means easy to install products are a major cost saving even if its a more expensive product.

Price wise it's cheaper than most of the other insulations ($13.19/sqm) but okay I'll ignore it.

SomeoneSomewhere

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#3180670 11-Jan-2024 17:33

Several people have been killed either installing or working in the vicinity of conductive foil insulation. Driving staples into cables results on the whole product becoming live. Sometimes it gets the installer, sometimes the next person to work in the space.

As such it's banned from domestic use. It's less of an issue in commercial where it's probably being fixed to earthed steelwork, and being applied from a scissor lift rather than a confined attic/underfloor floor space.

I'm also not sure whether it's as effective at preventing heat loss as it is heat gain.

tweake

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#3180671 11-Jan-2024 17:34

Lias:

tweake:

no. that stuff is really expensive and poor performing. also not legal for residential use.

commercial insulation standards are a lot lower and cost of working at heights means easy to install products are a major cost saving even if its a more expensive product.

Price wise it's cheaper than most of the other insulations ($13.19/sqm) but okay I'll ignore it.

its been a long time since i looked. but quick look shows more expensive for r value, but many don't list r value. the other issue is if it gets installed correctly. it needs an air gap to work. so many times you see it hard up against cladding which stops its from working or the single sided foil thats facing the wrong way.

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