Browse Forums General Discussion 1 Jan 16, 2014 11:45 am I have been thinking how I can keep my house cooler in there blazing conditions we have been experiencing down here in vic. I have a house that has a large expanse of flat corr plain zinc roof 200m2 at the rear. When I say flat I mean its at 12 degrees with no valleys or hips. The rear of the house faces north,therefor during the hotter months the sun is approx. 90 *to the roof. The roof runs from the gutter up to the apex of the truss for about 12 m and right across the width of the house. This rear roof is not visible from the street. I have been toying for a while about rebattening the roof,preferably with some 100mm C section or similar and installing some new colorbond-a light color,surfmist or something over the top of the existing roof thus shading it. I realize I will have to talk to an engineer regarding beefing up the top cord of the truss, I would propose keeping it down about 900 from the ridge line,and finishing it short at the bottom to allow water to run off it to the original roof and to the gutter. Since I build this house 14 years ago I skimped and put color bond (red) on the visible front section,and put plain zinc on the rear-thinking that along with the cost saving it would be cooler.Big mistake. I have since built an attic room in the roof space,where my daughter now lives. Altered the trusses, cut out the webs,all engineered,and lined the ceiling (along with insulation) with pine lining. Still hot.I got up on the roof and painted this section above her room with surfmist. What a difference,I carried the paint a little further along the roof beyond her room which I can access through a door into some storage space under the main roof. I can stand on the floor in this roof space area and touch the sarking paper. Where it is painted above,i can hold my hand pressing up to the underside of the iron, though uncomfortably hot,I can withstand it,alternativaly if I do the same on the unpainted section its like touching a hotplate. So apart from answering my own question,I was wondering what the other forum members would do. IE-Strip off the old zinc (which is in good nic)and replace that with a surfmist colour,or go over the top with a twin roof. I figure the cost would be about the same if not cheaper to go over the top. Re: twin skin roof. 2Jan 16, 2014 4:25 pm Funny enough a house I bought had a Corry roof that had aluminium roof tile looking stuff installed over the top. Why I don't know but what I do know is that if you creat a sun shied it will be a lot cooler. Aesthetics from the backyard are another consideration. Sent from my iPhone using Tapatalk Re: twin skin roof. 3Jan 16, 2014 4:46 pm Kill 2 Birds with one stone and get solar panels. The panels will put the tin in the shade and save you stripping the old material off The Harder You Try - the Luckier You Get ! Web site http://www.anewhouse.com.au Informative, Amusing, and Opinionated Blog - Over 600 posts on all aspects of building a new house. Re: twin skin roof. 4Jan 16, 2014 5:08 pm Go get yourself some Dulux Weathershield in Thredbo White as I did, and paint if not all the roof, a significant section of it and feel the difference. We had a big 10 litre spray tank and gun, and did not go to the effort of cleaning it down, other than where the birds left their deposits behind, and 3 + years later it is still there. I missed a section where the solar panels were before they got moved, and you would burn your hand if you left it there for any period of time. The painted section in the same sun, you could sit on it and have a picnic all day. Owner Building at Jimboomba Woods in Logan City Qld. Blog : http://bandlnewhomebuild.blogspot.com H1 thread : viewtopic.php?f=38&t=68283 . Re: twin skin roof. 5Jan 17, 2014 7:09 am Seeing as the section of roof you are talking about faces North and presumably has the most influence on the temp for the rest of the house I'd be tempted to strip off the existing roofing and put extra insulation of some sort on there first - 100mm blanket, poly sheets etc before replacing it with colorbond surfmist. Or seeing as you have obviously got a handle on painting roofing , re-use the same sheets after the above process and paint it instead. Stewie Re: twin skin roof. 6Jan 17, 2014 3:09 pm Thanks to all who have replied. Thanks for your advice Bashworth-That would be the ideal situation but I don't think I would live long enough to recover the money spent.Also does anyone know if the trusses have to be strengthened if someone was to install a whole lot of these?,going on the fact that trusses are comped for the proposed loading. Second thoughts now on going over the top with another layer of iron,I have too many penetrations -skylights-whirlybirds- a chimney and a couple of vents. I think I will paint it white,and because I have a gable at both ends investigate a couple of high volume extraction fans. While Im on this issue,I have been wanting to vent my thoughts on insulation,and would like to hear of other peoples thoughts as well. Ceiling insulation-although great for winter and keeping the heat in rooms I feel is next to worthless in summer. How long in 60-70* heat inside a relatively stable air mass such as a roof space would it take to become completely overwhelmed-I would give it,and I stand to corrected 2 hours,then it is not only uselss,but it itself, after the sun has gone off retains some heat and also helps to stop the plaster cooling off.I know the rooms inside would heat up quicker,but the trade off to my mind is retaining the heat. I know I can't live without it,so This is why I'm going to investigate in some extraction fans. Sorry about the rant,going mad in this heat. Time for a coldie. Rob. Re: twin skin roof. 7Jan 17, 2014 3:41 pm oldchippy Thanks to all who have replied. Thanks for your advice Bashworth-That would be the ideal situation but I don't think I would live long enough to recover the money spent.. Don't know how old you are but if you have money in super the pay back period can be quick. If you have a bit of money the govt reduces your pension by $39/ thousand (pretty much all the interest) I reckon that if you invest around $3000 on solar power you could save around $400+ a year and stop the Govt reducing your pension by $117/year so the payback is around 6 years. The Harder You Try - the Luckier You Get ! Web site http://www.anewhouse.com.au Informative, Amusing, and Opinionated Blog - Over 600 posts on all aspects of building a new house. Re: twin skin roof. 8Jan 18, 2014 12:07 pm Quote: Ceiling insulation-although great for winter and keeping the heat in rooms I feel is next to worthless in summer. It will come down to how well the rest of your house is insulated. No point having a combined roof /ceiling insulation rated at R 5.0 when your walls are only R 2.0 and single glazed window/doors at R 1.5. The heat from outside on a really hot day will find its way into your house through the lowest point of resistance in probably a couple of hours as you already say. Stewie Re: twin skin roof. 9Jan 20, 2014 11:45 am If you have access to the underside of the metal roof you could consider a spray on foam insulation. It will adhere to the metal and lower the heat transfer into the roof space. Cheers, Duke. 2 9448 This certainly doesn't look good. I would be engaging with an independent inspector to have a look at this. 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