Sleepout roof - too thin and too hot - new roof on top, or solar, to block the sun?

Forums › Home Workshop DIY › Sleepout roof - too thin and too hot - new roof on top, or solar, to block the sun?

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2236 posts

Uber Geek

#3180198 10-Jan-2024 20:14

Benoire:

Another option is to remove the shingles, seal the roof if not already and then add insulation boards designed for flat roofs and then reapply new shingles. I've got a SheShed 9m2 cabin that has roof insulation on the exterior side of the 20mm roof timber and its fine in summer and winter with a little heat or fan.

thats actually fantastically high performance housing style. i like that a lot. if it was air sealed and all continuous then it would be a "perfect wall" (look up what that means).

external insulation. then strapping screwed through the insulation so you can then fix the roofing (or siding). i would put a metal roof on. its actually cheaper and easier because you would have to put ply down to have something to put the shingles onto. metal roofing just put down the underlay then screw direct to the strapping.

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Benoire

2753 posts

Uber Geek

#3180321 11-Jan-2024 07:40

tweake:

Benoire:

Another option is to remove the shingles, seal the roof if not already and then add insulation boards designed for flat roofs and then reapply new shingles. I've got a SheShed 9m2 cabin that has roof insulation on the exterior side of the 20mm roof timber and its fine in summer and winter with a little heat or fan.

thats actually fantastically high performance housing style. i like that a lot. if it was air sealed and all continuous then it would be a "perfect wall" (look up what that means).

external insulation. then strapping screwed through the insulation so you can then fix the roofing (or siding). i would put a metal roof on. its actually cheaper and easier because you would have to put ply down to have something to put the shingles onto. metal roofing just put down the underlay then screw direct to the strapping.

My shingles are directly fixed through the insulation in to the roof below it as the roof is 20mm tongue and groove so strong enough and thick enough to cope. You could put another substrate below the actual roof but I wonder if its worth it?

timbosan

2134 posts

Uber Geek

#3180339 11-Jan-2024 08:28

Benoire:

My shingles are directly fixed through the insulation in to the roof below it as the roof is 20mm tongue and groove so strong enough and thick enough to cope. You could put another substrate below the actual roof but I wonder if its worth it?

Sounds like a good approach and an alternative to the safari roof, and slightly easier to do. Could you please post a link to the product you used? I cannot find any external products like this, just interal.

Benoire

2753 posts

Uber Geek

#3180343 11-Jan-2024 08:39

https://www.ardex.co.nz/product/ardex-polyiso-roofing-insulation/ appears to be similar to the product that was supplied with the cabin, I bought mine as part of the set from the company. I didn't use a vapour barrier but the timber is painted and sealed with a waterproof exterior sealer and so far during last summer/winter, I've had no moisture issues but then the cabin was a short term fix for working from home until we can move house.

tweake

2236 posts

Uber Geek

#3180628 11-Jan-2024 16:08

Benoire:

My shingles are directly fixed through the insulation in to the roof below it as the roof is 20mm tongue and groove so strong enough and thick enough to cope. You could put another substrate below the actual roof but I wonder if its worth it?

photos please. what sort of insulation is it?

i'm extremely doubtful. the only insulation you could do that with is iso, maybe poly. thats doesn't allow moisture through, so i hope you have a good moisture port setup. also i wonder what the effect of all those hundreds/thousands of holes through the insulation will do. any permeable insulation is far to soft to fasten directly.

timbosan

2134 posts

Uber Geek

#3180637 11-Jan-2024 16:28

tweake:

Benoire:

My shingles are directly fixed through the insulation in to the roof below it as the roof is 20mm tongue and groove so strong enough and thick enough to cope. You could put another substrate below the actual roof but I wonder if its worth it?

photos please. what sort of insulation is it?

i'm extremely doubtful. the only insulation you could do that with is iso, maybe poly. thats doesn't allow moisture through, so i hope you have a good moisture port setup. also i wonder what the effect of all those hundreds/thousands of holes through the insulation will do. any permeable insulation is far to soft to fasten directly.

There is a datasheet - ARDEX Polyiso Datasheet.pdf (ardexaustralia.com)

Has some details, but I am still trying to reconcile that is an external product, but it says "Keep insulation dry at all times. Insulation bundles need to be elevated above the water line to prevent moisture infiltration from the bottom side."

timbosan

2134 posts

Uber Geek

#3180643 11-Jan-2024 16:40

@tweake - I found you a photo :-) Actually, its a screenshot from a Youtube clip - https://youtu.be/xdnLOv-zf_o?t=497

It shows the polyiso but also a top layer, which looks to be waterproof, including what looks like overlaps the edges. Would love to know how that works on a cabin / sleepout!

tweake

2236 posts

Uber Geek

#3180645 11-Jan-2024 16:44

timbosan:

There is a datasheet - ARDEX Polyiso Datasheet.pdf (ardexaustralia.com)

Has some details, but I am still trying to reconcile that is an external product, but it says "Keep insulation dry at all times. Insulation bundles need to be elevated above the water line to prevent moisture infiltration from the bottom side."

if you dip the ends in water you could get water wicking up between it and the structure. not sure if it would soak it up itself, maybe between the iso foam and the outer fiberglass layer.

getting it a bit wet from rain or leaks is no big deal so ok to act as a house wrap, but you still want a roof or siding over it to keep rain off it. its not made for direct exposure. personally not a big fan of it as all your house drying is now internal. much prefer something like mineral/rock wool. vapor open, sheds water.

remember every fastener through the insulation is a potential leak path. shingles are a disposable roofing product.

tweake

2236 posts

Uber Geek

#3180647 11-Jan-2024 16:46

timbosan:

@tweake - I found you a photo :-) Actually, its a screenshot from a Youtube clip - https://youtu.be/xdnLOv-zf_o?t=497

It shows the polyiso but also a top layer, which looks to be waterproof, including what looks like overlaps the edges. Would love to know how that works on a cabin / sleepout!

notice how it has a board over the top of it, then the roofing membrane is fitted over that. thats a whole lot different than stapling shingles through it.

Handle9

11119 posts

Uber Geek

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Lifetime subscriber

#3180753 12-Jan-2024 07:48

tweake:

its not actually felt. felt is what they used to put under the shingles. they are bitumen shingles.

The base kit comes with felt only. Shingles are an optional extra

• Roofing felt included (Shingles an optional extra - 6 packs required)

timbosan

2134 posts

Uber Geek

#3180759 12-Jan-2024 08:53

Based on all the replies so far, it looks like two options are available:

* A 'safari' roof - steel on a frame over the existing roof with a vent out the top to allow natural flow of heat. Looks like the simplest and cheapest option, and one I can do myself.
* Solar - I could do a grid-free kit, like from gridfree.store, but this would need better planning, sizing, and cost a lot more. Initial estimated come out about $6000 for a kit

I will research the safari roof more - the diagram from @Ge0rge is a good start, I just need to modify for peak roof of my sleepout.

Happy to have input on this from geekzone of course ;-)

travellingkiwi

1 post

Wannabe Geek

#3181574 14-Jan-2024 09:00

gzt: Great product. It's amazing we're importing these from Estonia when NZ has mountains of timber. Underinvestment in timber processing strikes again.

Pretty much the wrong timber. The Estonian stuff is Northern European pine. Apart from maybe colour, the timber itself is almost nothing like the radiata pine we get here. NZ Pine has been selected to grow fast, and fast means pulpy soft wood. The cold climate timer from Europe is way denser and harder.

And you know kiwis. it'd be one more excuse to clear fell a thousand ha just because it's easier and cause disasters like the esk valley.

timbosan

2134 posts

Uber Geek

#3181617 14-Jan-2024 11:23

So I found another couple of ideas, pretty much the same concept:

1) Vent out the top of the eves, like a bathroom / kitchen fan
2) Add a ceiling vent like this TDX Solar Roof Exhaust Fan | Trade Me Marketplace

Option 2 obviously adds compromise as it means cutting out part of the roof and I am worried about waterproofing it. Option 2 seems far easier but probably less efficient (top at the very top of the roof) but way less problematic than holes in the roof.

I am still leaning towards the safari roof idea as that treats the root cause - heating up of the current ceiling.

dustysmurf

19 posts

Geek

#3181623 14-Jan-2024 11:45

You could also look at this as option rather than the Ardex product, directly from manufacturer here in NZ https://conquerornz.co.nz/pir-product-range/pir-insulated-roofing-solutions/ it has zinc aluminium coated steel bonded to the PIR insulation.
I was previously looking at adding the ceiling panel version these under my existing title roof , between the rafters, but ended up going with a ducted heat pump.

When I got a quote from them (Sep 2022), the 90mm R4.38 was $165+gst for the 1200x2400 (plus shipping)

tweake

2236 posts

Uber Geek

#3181680 14-Jan-2024 12:17

dustysmurf:

You could also look at this as option rather than the Ardex product, directly from manufacturer here in NZ https://conquerornz.co.nz/pir-product-range/pir-insulated-roofing-solutions/ it has zinc aluminium coated steel bonded to the PIR insulation.
I was previously looking at adding the ceiling panel version these under my existing title roof , between the rafters, but ended up going with a ducted heat pump.

When I got a quote from them (Sep 2022), the 90mm R4.38 was $165+gst for the 1200x2400 (plus shipping)

this is not a bad idea. have them fitted a bit short at the top so moisture can vent up through the roof cap. even better if its spaced up a bit so there is airflow underneath. otherwise moisture will accumulate at the ridge as it can't go through the insulation.

however as a ceiling panel in a normal roof, its not a great idea. you have to be very very careful on using non-permeable products.

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