better temperature control in shed house

[ajm]

our house is a steel portal shed that has been done up. the roof and walls are insulated with yellow batts and earth wool (in the newer section). the place still heats up like satan's undies. inside is standard gyprock sheeting which follows the line of the roof. aren't we posh with our cathedral ceilings! they suck. at best the outside (trimdeck) to the inside gyprock sheets can't be more than 20cm, if that.

I really do not want to lift the roof and redo the insulation at this stage. Does anybody have an idea on what else we could do to keep the heat out? i thought that a new horizontal ceiling might do the trick. but because of the flat pitch of the existing roof, the new roof would have to be quite low which would make for a very boxy space. it would also be very expensive to do.

Any suggestions?


Blue lines below represent the existing insulation in the ceiling/roof.
Red line depicts the "false ceiling" that would be insulated.

A

[r3nov8or]

Blue lines below represent the existing insulation in the ceiling/roof.
Red line depicts the "false ceiling" that would be insulated.

Sorry, can't see any attachments

[ajm]

Sorry, can't see any attachments

Bugger. Basically, drew a flattish triangle to represent the roof. Drew a blue line under each side to indicate where the insulation was already. No Rembrandt but conveyed the idea, I think.


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[droog]

Not too many options apart from replace existing or add another layer underneath.
Only one that springs to mind is adding another roof above the existing with an air gap, lots of caravans that have been located permanent onside have done exactly this to reduce heat.

https://www.ausbuildannexes.com.au/f...stropical-roof

[r3nov8or]

^^ +1. Very effective

[ajm]

Other option we considered was reroofing with 75mm insulated panels.
Job for the winter this year perhaps.

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[ForeverYoung]

not sure changing the existing insulation will have a big effect.
I have a cathedral ceiling similar construction to yours so I know the feeling
Even tho previous owner put new insulated in 10 years ago.

Can you keep the sun off the roof from outside with some method?
shade trees - slow solution.
Sun sails?
even if just for the afternoon sun which is usually hotter.

Can you vent more? let the heat escape.

Ceiling fans -I find they help

Other than that, lower the ceiling as you say - the air space above will be a good insulator as well as insulation in the new ceiling.

[mic-d]

What you need in addition is either shade on the roof or a radiant barrier. You can buy very effective radiant barrier which is in a roll like sarking but is much more reflective and usually double sided. You might get some cheap on marketplace like I did years ago and try a section of the roof and see if it makes the ceiling cooler. You can either lift the tin and lay it over the battens keep it off the insulation underneath and refit the tin. You can also staple it to the gyprock ceiling, install battens and another layer of gyprock inside. You will need to check the weight bearing of the roof if you do this. A fan will do sweet fa. The void volume will be so occluded you will not get effective volume exchange. The heat will be coming by conduction and radiation. If you have a radiant barrier above the insulation but with an air gap you will stop a lot of tge radiant energy from the tin reaching the insulation. If you put it underneath the ceiling with an air gap to the new sheet it will achieve the same thing. If it’s single sided, place the shiny side down in either situation. The foil may still feel very hot but because of the low emmisivity of reflective surfaces it is unable to radiate the heat… but you need the air gap or heat will conduct across

[ajm]

why cant these problems have a simple and cheap solution? I have just replaced some of the tin sheets on the roof and its a bugger of a job as you only get a few done each day before the sun makes it too uncomfortable to work. I raise my broad brimmed hat to all the roofers out there!

I wonder if covering the roof with solar panels would do the same thing as a tropical roof? current panels are only an inch or so off the roof. is there a reason they don't mount them higher than that?

[ForeverYoung]

...
I wonder if covering the roof with solar panels would do the same thing as a tropical roof? current panels are only an inch or so off the roof. is there a reason they don't mount them higher than that?

I have a bunch of panels on my north side, so not sure it is making a difference.
but like you, mine are only an inch or so off the roof.
I want them higher, not a small job on a 44deg roof pitch, not because the air under will provide better insulation but at the moment they are a leaf litter trap and bushfire hazard.

Have seen them mounted higher so no big deal - if done at original install.