Skillion Roof Insulation

Hi All,

Looking for some ideas on insulating a Skillion roof on a shed for maximum R value, the roof is constructed with 200mm C purlins, 40mm top hat and 22mm ceiling battens.
I know that the recommended procedure is to put on Anticon above the top hats and let it sag down from the Colourbond sheet but WHY not stretch it over the C Purlins and fix it under the top hat?? am I missing something here?, it would look a lot better, whats the catch?.
My thought would be from top, Roof sheet, Anticon, 25mm gap, Batts, and then gyproc, any body got any other suggestions?

TIA

Colin

Hi Dims
It's metal sheet cladding-> Anticon-> Metal Roof battens-> Metal CPurlins -> Metal Ceiling battens->Roof Insulation-> Gyprock Ceilings.
Why
1. Safety
2 Cost
3.Ease of Placement
4. Minimise condensation
5. Break Thermal bridging to minimise gyprock/ceiling cracking
BTW I would add in another layer of insulation ie batts
Also give some consideration to fixing plasterboard that allows thermal movement Of metal & Non metal materials hth

Thanks StructuralBIMGuy,

Regarding the Anticon, I realise that the fitment wouldn’t be as easy but had noticed in a lot of roofs that in the early morning you can see the condensation sitting between the battens and thought surely this is not the best option.
Am I right that a 25mm gap is necessary between Anticon and batts? Therefore maximum batts thickness would be 175mm in my case?

Cheers

Colin

IMO There shouldn't be an air gap between the underside of the sheeting and top of the anticon
Not sure about an air gap between The anticon and Batts as I think it has minimal effect
You might find this resource useful
Lysaght Installation Roof Manual

insulation in australia is a flawed and poorly executed science.

3 keys to insulation

airgap , airflow , thermal barrier

Thanks Dr Buildwell, would you care to elaborate? I have looked at “Solarspan” which have a 200mm panel which has a R rating of 5.22 but due to cost would like to try and get a traditional style roof with similar properties, do you think this would be possible?

TIA

Colin

you're welcome .

it really is hard to elaborate as every building is unique. but having a greater r value does not gurantee your job will be insulated better.

on compact roofs i believe the best way to insulate is to have insulation as thick as possible above the plaster ceiling then at least a 50mm airgap and also a way for the air to be moved in that gap (most important). i.e whirly bird and vented eaves

Why would you go into so much trouble insulating a shed? What am I missing?

Hi building-expert, I have a small welding/ fabrication business and if you can imagine sitting welding all day and it’s 40deg outside and over that in the shed then you would also be looking for some insulation The shed is part of a new project of mine where I’ll be building the shed with Pro9 global
125mm sips panels and the house with 210mm sips panels. Both have skillion roofs so the shed was the experiment before moving onto the house a few months later. I would appreciate any further ideas as this is a dream OB project of mine and would hope to get it right. It was designed with Solarspan but due to difficulty running services, thought I would look for other ideas especially for the shed as there aren’t any false ceilings.

Thoughts?

Cheers

Colin

You might think this is a bit extravagant but the shed and house will be double glazed as well!
Why? Because I want to and I can😜

A product you may consider is foil board, it comes in various thicknesses and there is nothing to stop you from using2 layers with services sandwiched in between. Its light and easy to handle and is rigid and comes in 2.4x 1.2 sheets

I agree with building expert , foil board is a great product I have also used it on my workshopwith great results. If you call foil board or email them your specs they will create an optimum insulation plan for you.

Thanks for your input Building -expert and Dr Buildwell, I will contact Foilboard and discuss.

Cheers

Colin