Browse Forums Heating, Cooling & Insulation 1 Jul 08, 2015 1:51 pm Hi all, I am designing a pergola roof and need some advice re insulation / condensation control. The roof will be pitched (21 degree) to a ridge beam with rafters at about 900mm spacing. Then will be batterns and a colorbond roof. On the under side I am proposing a zincalum 'ceiling' (lining) sheet (either custom orb or mini orb profile), screwed to the underside of the batterns i.e. leaving the rafters exposed from underneath. I would like to insulate between the two metal sheets. Would I be better off using an anticon blanket under the roof sheeting, with an air gap the thickness of the battern, or just filling the battern spacings with bulk insulation (batts)? Do I need to be worried about condensation control between these two metal sheets? I need the insulation to perform in both directions i.e. reduce summer heat from above as well as trap winter warmth from below. Interested to know everyone's thoughts. Re: Question for the insulation gurus.... 2Jul 08, 2015 2:11 pm It won't make much difference. With anticon, it will sag down between the battens to mostly fill that gap anyhow. Re: Question for the insulation gurus.... 3Jul 13, 2015 10:08 am Thanks oneJohn. From researching this I can see now that the effectiveness of the insulation is mainly related to thickness, there is little difference between materials' R value for a given thickness. Therefore I will use a thicker battern, say 50mm, to increase the insulation in this space. Do you think condensation in this space is likely to be a problem? I live close to the beach in WA. Re: Question for the insulation gurus.... 4Jul 16, 2015 3:07 pm You'd get condensation anywhere there is a temperature difference between the roof sheeting and the underside. We live 1.2 kms from the ocean and under our neighbours cheap and nasty carport she gets condensation droplets forming year round. Installing the anticon will stop it but the extra insulation will make it as you are after - cooler in summer and warmer in winter. Even sarking would stop the condensation but you won't get the thermal benefit of the extra insulation that the anticon will provide. Stewie Re: Question for the insulation gurus.... 5Jul 22, 2015 12:33 pm Thanks Stewie, As oneJohn indicated anticon would sag to fill the available space, leaving no air gap between it and the lower sheet. Therefore I may as well use a non reflective bulk insulation product here (cheaper). My concern is that inside this space (between the two sheets) condensation will form and be trapped, reducing the effectiveness of the insulation and causing corrosion, or is this not likely to be issue? I realise there may be some condensation under the lower sheet but am not concerned as it is ventilated. 0 6272 I am saying that double brick has similar thermal performance due to thermal mass effect. It will be still very interesting to see the state of your framing after 10-15… 10 29737 |