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?

timbosan

2137 posts

Uber Geek

#311375 10-Jan-2024 16:13

Hey all,

Over the break I build a sleepout, one of these - Log Cabin Garden House Iris 3.6m x 2.7m - Cabins & Studios - Sheds & Carports at Trade Tested

However the roof it just timber and felt, which works well, but it just lets the heat soak through. I can add a heatpump, but that's just covering up the problem. So, I see two options:

1) Build a roof (rafters and purlins) on top of the current roof (and make it into the ceiling), adding in insulation (probably 100mm R3.4) and building paper then steel on top, clean up with ridge boards etc. I can do most of this myself but I have never worked with Coloursteel.

2) Add solar panels. 4 should cover most of the roof. However, would they really be that effective at blocking the heat transfer? I have been thinking of solar as the costs of getting power to the sleepout are not too different (i.e. close-ish).

Anyone done anything similar? Any thoughts on either option?

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110 posts

Master Geek
Inactive user

#3180063 10-Jan-2024 16:33

I have 12kW of solar panels almost completely covering the roof of my Totalspan shed and can confirm it really cuts down the heat on sunny days.

And another bonus, when it rains it just sounds like water trickling across the roof, rather than the deafening roar of millions of raindrops slamming into coloursteel.

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Froglotion

208 posts

Master Geek

#3180066 10-Jan-2024 16:35

Could you do option one, but build it so that any air between new and old roof can move to top of the roof and have the ridge cap spaced off the roof so that heat vents out? Would save insulation and the likes, just use the heat itself to vent itself upwards and out of the ridge cap.

Dynamic

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#3180069 10-Jan-2024 16:41

That looks pretty similar to a cabin I built as a home office over 10 years ago that is still going strong. Mine is showing signs of deterioration in some areas as I was not diligent about re-treating the timber at least every second year. If you really want it to last I would encourage treating it every year if using an oil stain or similar.

A few weeks into my first summer when fans were no longer cutting it, I acquired a freestanding aircon unit which I vented through a hole in the floor. It made a massive difference, though of course these are not exactly quiet. Around 5 years in I insulated it with polyester insulation under plywood sheets. This was a positive move but the cabin still heated up at a slower pace during the day. A year later I had a small split heat pump unit fitted to eliminate the noise of the freestanding heat pump.

I really like your idea of putting a metal roof on. Heat will still soak through the this walls. (Edit - mine had thinner walls than this, but I would expect this thicker timber to warm up almost as quickly in the full sun. If you paint it white that would help deflect the heat, though I would only be guessing how much it would help.)

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tweake

2296 posts

Uber Geek

#3180127 10-Jan-2024 17:25

the simplest would be to insulate inside the cabin and make gib/plywood ceiling. however you still have that god awful disposable shingle roof. otherwise do what you say and build another roof on top. harder, but a metal roof will last so much longer.

timbosan

2137 posts

Uber Geek

#3180153 10-Jan-2024 18:32

Dynamic:

That looks pretty similar to a cabin I built as a home office over 10 years ago that is still going strong. Mine is showing signs of deterioration in some areas as I was not diligent about re-treating the timber at least every second year. If you really want it to last I would encourage treating it every year if using an oil stain or similar.

A few weeks into my first summer when fans were no longer cutting it, I acquired a freestanding aircon unit which I vented through a hole in the floor. It made a massive difference, though of course these are not exactly quiet. Around 5 years in I insulated it with polyester insulation under plywood sheets. This was a positive move but the cabin still heated up at a slower pace during the day. A year later I had a small split heat pump unit fitted to eliminate the noise of the freestanding heat pump.

I really like your idea of putting a metal roof on. Heat will still soak through the thin walls.

I painted mine the moment it went up - 2 coats of undercoat and 2-3 coats of top coat. Plus I have painted the interior of the door, and the door and window frames. I hope that will last some years. I also put polyurethane the floor (4 coats of Resene - How to polyurethane a floor - DIY guide and video | Resene ), and treated the underside of the floorsboards, plus put down a groundsheet and added underfloor insulation.

Funny enough I have been seriously looking at a freestanding heatpump unit, and at the costs to get a wall-mounted one installed (along with the power, its currently just has an extension cable from the house). I know they are noisy compared to split units.

And re the walls, good point! I do think the felt makes the roof far worse though - on days like today (26 in Auckland) you can feel the heat coming off the roof, like a heater. How hot does your cabin get after all the changes?

gzt

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#3180156 10-Jan-2024 18:33

You might get good value simply adding adding venting at each end of the apex. Imo you'll need to do that sooner or later anyway. You'll want to close those vents in winter.

timbosan

2137 posts

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#3180157 10-Jan-2024 18:34

tweake:

the simplest would be to insulate inside the cabin and make gib/plywood ceiling. however you still have that god awful disposable shingle roof. otherwise do what you say and build another roof on top. harder, but a metal roof will last so much longer.

Yeah I have seen that done online, and I did look seriously at a 'proper' sleepout with stud walls etc, but the cost is a lot more, especially if properly insulation. One of the reasons I chose this particular model was for the wood look, particularly the ceiling!

And yes, I have heard the felt doesn't last too long. I guess steel or solar will help with that.

gzt

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#3180158 10-Jan-2024 18:35

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

timbosan

2137 posts

Uber Geek

#3180160 10-Jan-2024 18:38

CrazyM:

I have 12kW of solar panels almost completely covering the roof of my Totalspan shed and can confirm it really cuts down the heat on sunny days.

And another bonus, when it rains it just sounds like water trickling across the roof, rather than the deafening roar of millions of raindrops slamming into coloursteel.

Interesting, and very good point - it does make me think of the front rooms of the house which are skillion roofs with just the steel, paper and insulation, and they are NOTICABLE louder when raining than other parts of the house (with 'proper' roofs).

Do you have it grid tied? Just to the shed with an inverter? Battery? I am thinking of a very basic setup, few panels, inverter and a battery to last the night.

Ge0rge

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#3180164 10-Jan-2024 18:56

Froglotion:
Could you do option one, but build it so that any air between new and old roof can move to top of the roof and have the ridge cap spaced off the roof so that heat vents out? Would save insulation and the likes, just use the heat itself to vent itself upwards and out of the ridge cap.

This works incredibly well, having done it to multiple shipping containers in the Islands I can definitely vouch for it.

Land Rover used to do it on their African variants - they called it a "Safari Top" and it made a huge difference to the temperature in the vehicle.

CrazyM

110 posts

Master Geek
Inactive user

#3180170 10-Jan-2024 19:16

timbosan:
CrazyM:

I have 12kW of solar panels almost completely covering the roof of my Totalspan shed and can confirm it really cuts down the heat on sunny days.

And another bonus, when it rains it just sounds like water trickling across the roof, rather than the deafening roar of millions of raindrops slamming into coloursteel.

Interesting, and very good point - it does make me think of the front rooms of the house which are skillion roofs with just the steel, paper and insulation, and they are NOTICABLE louder when raining than other parts of the house (with 'proper' roofs).

Do you have it grid tied? Just to the shed with an inverter? Battery? I am thinking of a very basic setup, few panels, inverter and a battery to last the night.

Mine is grid tried with an inverter and no battery.

It sounds like something like an Ecoflow Delta Max and a couple of 400w solar panels would suit you well, but not cheap at ~$5000. Depends how much storage and how much power output you are wanting I guess

timbosan

2137 posts

Uber Geek

#3180171 10-Jan-2024 19:18

Ge0rge:
Froglotion:

Could you do option one, but build it so that any air between new and old roof can move to top of the roof and have the ridge cap spaced off the roof so that heat vents out? Would save insulation and the likes, just use the heat itself to vent itself upwards and out of the ridge cap.

This works incredibly well, having done it to multiple shipping containers in the Islands I can definitely vouch for it.

Land Rover used to do it on their African variants - they called it a "Safari Top" and it made a huge difference to the temperature in the vehicle.

You have got my interest! So does that mean its not a waterproof system? And that the current roof would be what protects from water ingress? And the steel just acts as a combination of extra weather protection, and a mechanism for heat extraction? Also sounds like something I can do myself, as I don't need to worry so much about insulation, building paper, and hence the space to fit insulation.

Anyone got any links or examples of how best to do this?

Ge0rge

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#3180182 10-Jan-2024 19:43

This is probably a good example:

You wouldn't need the horizontal framing though, as you already have the angle sorted.

Do both sides, with a gap at the ridge to let the heat out. It won't work as well if you attach a ridge capping to the top of the iron, but if you have it slightly raised above the ridge on some timber, it will allow the heat to escape via convectuon and stop water getting in.

tweake

2296 posts

Uber Geek

#3180183 10-Jan-2024 19:52

timbosan:

tweake:

the simplest would be to insulate inside the cabin and make gib/plywood ceiling. however you still have that god awful disposable shingle roof. otherwise do what you say and build another roof on top. harder, but a metal roof will last so much longer.

Yeah I have seen that done online, and I did look seriously at a 'proper' sleepout with stud walls etc, but the cost is a lot more, especially if properly insulation. One of the reasons I chose this particular model was for the wood look, particularly the ceiling!

And yes, I have heard the felt doesn't last too long. I guess steel or solar will help with that.

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

solar won't help. apart from the holes through it, shingles are basically disposable. solar complicates things when it comes time to fix it. sorry but shingles is cheap nasty roofing thats become fashionable here (why do kiwis love crap housing), nz has traditionally done pretty good roofing.

Benoire

2760 posts

Uber Geek

#3180187 10-Jan-2024 19:57

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.

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