Browse Forums Heating, Cooling & Insulation Re: Is sarking necessary with Colorbond roof? 21Sep 19, 2008 2:30 pm Well... all I can say is that my parents have a dark colorbond roof without sarking - and their roof space (and therefore garage) is hot as hell on any semi warm day November-April. It gets so hot that the house warms up significantly as well, just from the heat coming down through the ceiling (even with ceiling batts). The architect who did their pre-purchase inspection commented that the colorbond roof should not have been installed without sarking and additional vents.
We were working in our house on a few really hot summer days pre-plaster (no ceiling) ... I reckon the sarking under the tiles probably made it at least 5 degrees cooler. My vote is that it is well worth the money. Re: Is sarking necessary with Colorbond roof? 22Sep 19, 2008 4:07 pm Yep, tend to agree with Lyn. Our builder would not allow us to go colorbond roof without the anticon/sarking - he insisted we would regret it in the Canberra climate and he didn't want to be held responsible (and this is with R2/R4 insulation)!
As for being ineffective if not installed correctly I think that would be a case of being forewarned is forearmed. BTW we went tiles in the end but only due to cost. 'We make a living by what we get, but we make a life by what we give.' - Winston Churchill Re: Is sarking necessary with Colorbond roof? 23Sep 19, 2008 7:02 pm To those who have gone without it - too bad your mistake IMO.
Trying to feel better about if by saying it can be incorrectly installed is a cop-out - its almost impossible to install corrct unless your a complete idiot. Re: Is sarking necessary with Colorbond roof? 24Sep 19, 2008 7:44 pm Well I've fired off an email to our builders asking about adding it to the contract if it's possible. Asking what he thinks of the need for it. And what it would cost to add to the contract assuming it's possible to add it. Re: Is sarking necessary with Colorbond roof? 25Sep 19, 2008 7:53 pm Interesting that so many people have so many varying opinions!
Will be interesting to see what your builder says kexkez. Lyn - the hotness in the roof cavity can be countered with whirly birds I have heard from someone that lives in the same city as me, and has lived in two houses with Colorbond roof and no sarking, both over 8 years old, has been in the roof on different occasions - cold day, hot day, heating on, heating off, and never seen any condensation. Also that the curvy nature of the corrugated iron lets enough ventilation out (ie the top part of the curve that is not attached to the roof trusses - forms a gap). Luke - yes it was a copout, but I don't think there is anything wrong with trying to see the positives in something - especially as in my case it is - unfortunately - too late to get sarking. Thanks so much for your advice though Re: Is sarking necessary with Colorbond roof? 26Sep 22, 2008 9:06 pm OK I received a reply.
My email 1. I'm wondering if we've made a mistake with our colorbond roofing. I've been doing a bit of reading recently and keep coming up with information that suggests that sarking /anticon should be installed/is recommended below colorbond roofing. Is this the case? Email 2. I was worried about the need for sarking as I kept reading it was a recommended thing to do and then I remembered a builder friend had also suggested we do it if we were having colorbond and we'd not asked him why or taken his advice. The general comments seem to run along the lines of it stopping the extremes of temp's especially with a dark roof (like our chosen ironstone) and because it reduces the amount of damage condensation can do to roofing timbers by protecting them from direct contact with water. Replies: As far as insulation goes we have already included R3 Batts which are fantastic. I can speak from personal experience here as I had anticon put on my home and it was still a warm house (in summer) we then put R3 Bradford batts in the roof and the difference was noticeable from the morning when I went to work and when I came home that afternoon after they were installed. We had a dark roof as well Unless you simply must have it , I would stick with the R3 batts. Re: Is sarking necessary with Colorbond roof? 27Sep 22, 2008 9:22 pm kexkez I can speak from personal experience here as I had anticon put on my home and it was still a warm house (in summer) we then put R3 Bradford batts in the roof and the difference was noticeable from the morning when I went to work and when I came home that afternoon after they were installed. We had a dark roof as well Unless you simply must have it , I would stick with the R3 batts. Batts and anticon are different products that serve different purposes. You do not install anti-con to 'keep the house cool in summer and warm in winter' - thats the job of the batts. People seem to be pigeon-holing them as 2 products used for the same application. Re: Is sarking necessary with Colorbond roof? 28Sep 22, 2008 11:22 pm As luke said.
Sarking/sisalation as primarily used as a moisture barrier in OZ and it has a minor thermal property of r0.5 at best. Batts and insulation product are there to provide the thermal barrrier which is r3.5 or better for up or down heat Re: Is sarking necessary with Colorbond roof? 29Sep 23, 2008 8:10 am that was why i fired off the second email mentioning the condensation but all i got back was that he'd had a dark roof too. Re: Is sarking necessary with Colorbond roof? 31Sep 23, 2008 8:32 am double posting sorry Blog http://wherethehearthis.blogspot.com/ Build https://forum.homeone.com.au/viewtopic.php?t=6634: Yard https://forum.homeone.com.au/viewtopic.php?f=19&t=27687&p=378401#p378401 Re: Is sarking necessary with Colorbond roof? 32Sep 23, 2008 8:34 am Donuts not sure yet. DH was at work when I got the email reply and I was asleep when he got home. I've told the builders rep no but I'll talk to DH and see what he thinks when I get home from work. I'm almost tempted to ring our builder friend in Perth again and ask why he had suggested it. Or speak to him next week when I am in Perth. I'm assuming since we don't even have a slab yet let along roofing timbers we had time to think about it. Yes, put sarking in! 33Sep 24, 2008 1:16 pm Hi,
Yes, you need sarking under a metal roof. Apart from needing it with Colorbond, Reflecive foil is teh best type of insulation to keep the heat out in summer I'll show you how to keep your new home betwen 15 and 26 degrees celcius all year round - in your buget - GUARANTEED! www.sunrisehomes.net.au Re: Yes, put sarking in! 34Sep 24, 2008 8:14 pm libechacos Hi, Yes, you need sarking under a metal roof. Apart from needing it with Colorbond, Reflecive foil is teh best type of insulation to keep the heat out in summer I agree 100% with the first statement but disagree as most here will with the second comment. Why some houses with insulation just dont cut it 35Sep 25, 2008 8:11 am Have you ever been in a reasonably new home with insulation in the walls and ceilings but it still isnt comfy? Chances are the insulation has been instlled poorly, or it has the wrong type of insulation.
The heat transfer in and out of buildings occurs through a combination of radiation, conduction and convection. Research has shown that when heat flows down such as heat gain through the ceiling in summer, and losing heat through the floor in winter: Up to 93% is transferred by radiation Up to 7% is transferred by conduction 0% is transferred by convection When heat flows up, such as heat loss through the ceiling 45 - 50% is transferred by radiation 5 - 7% is transferred by conduction 45% is transferred by convection When heat flows sideways such as through the walls of a house: 65 - 80% is transferred by radiation 5 - 7% is transferred by conduction 15 - 28% is transferred by convection Getting your insulation right will go along way to not needing air conditioners or heaters. Most people do 80% of the work (ie put insulation in), but its the last 20% that gives you your bang for buck: do it right and do the right type I'll show you how to keep your new home betwen 15 and 26 degrees celcius all year round - in your buget - GUARANTEED! www.sunrisehomes.net.au Re: Why some houses with insulation just dont cut it 36Sep 25, 2008 8:52 am libechacos Getting your insulation right will go along way to not needing air conditioners or heaters. Most people do 80% of the work (ie put insulation in), but its the last 20% that gives you your bang for buck: do it right and do the right type so are you saying putting in sarking is "doing it right"? or if you have the rest then it doesn't matter. I got the impression sarking is recommended more for stopping condensation on roofing timbers rather than insulation. Surely if you put in other roofing vents (eco vent) or whirly birds it would stop condensation anyway and stop the heat build up. Those non electric type vents that open and close depending on the temp sound like the way to go. ( someoone else posted a link about them before) getting insulation right 37Sep 25, 2008 10:34 am CSIRO studies have shown if you have as little as 10% of the area of your insulation as gaps because the insulation is installed poorly (including downlights) then you can decrease the level of insulation by as much as 40%. Thats what I mean by doing it right
Yes putting sarking under your colorbond is doing it right in my opinion too, and also for a tiled roof. Bulk batts lose their effectiveness when the humidity rises, and dont work as well as reflective foil against summer heat. I'm not 100% sure, but I think condensation will still form under the sarking. Same as with single glazed windows - it just needs the right conditions and a cool surface. Thats why they have anticon blankets There was a recent sudy in QLD that showed many types of 'whirlybirds' dont actually vent the roof space. So have fun and do your research. I'll show you how to keep your new home betwen 15 and 26 degrees celcius all year round - in your buget - GUARANTEED! www.sunrisehomes.net.au Re: Is sarking necessary with Colorbond roof? 38Sep 25, 2008 7:37 pm Roof sarking and anti-con are the same thing. Are you talking about wall-wrap when you refer to sarking? the difference between anticon and sarking 39Sep 26, 2008 8:49 am Sarking is just the paper - silver one side and blue the other
Anticon (which is a brand name) is the same stuff, but with insulation adhered to it. The insulation goes on the top side to keep the sarking paper from getting cold, thus avoiding a cold surface for condensaton to form on I'll show you how to keep your new home betwen 15 and 26 degrees celcius all year round - in your buget - GUARANTEED! www.sunrisehomes.net.au Re: Is sarking necessary with Colorbond roof? 40Sep 26, 2008 3:18 pm Exactly right.
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