Browse Forums Heating, Cooling & Insulation 1 Aug 09, 2010 10:08 pm Hi all - my first post this. I'm owner-building a home up in the tropical top-end. As you probably know, it's hot and humid here for most of the year, with buckets of rain during the wet season. My house design is extremely simple (read stupidly low budget). It's made almost entirely of steel, with a simple, open steel roof over the top. The style is a "tropical roof"; more like a steel shade-sail than a roof, as such. It's simple pent-roof design, with no gabled ends. My builder friend has strongly recommended getting air-cell between the corrugated roof iron and the purlins, saying that condensation would be the main reason. But I can't see the logic in this. If the roof is completely open, why would there be condensation? I can certainly see why I would want a "radiative barrier" on the underside (and later I plan to paint the top surface white). But I can't see a reason for any bulk insulation or anti-condensation material. One advantage I can see, is that putting something between the roof iron and the roof beams might reduce the popping noises from the thermal expansion. But it's an expensive way of achieving that! I have noticed some sheds here that are enclosed, which have insulation where the shiny side is facing downwards. Can anyone explain the logic of this? Is it just double-sided? Is it for light? Any and all wisdom and preferably actual experience in this tropical region, would be hugely appreciated. cheers Biz Re: Open metal roof in the tropics - insulation needed? 2Aug 11, 2010 6:44 pm The roof sheeting will condensate, that is a given. It will get cooler than the surrounding moist air over night and you will get moisture settling on it. I found this out the hard way when I was putting the antenna up in the evening and ended up slipping and a roof screw very nearly ripped me a new one. (Tore a hole in my pants, jocks and me!) You will want to get some sort of insulation immediately, don't wait. Unless you have lived here for at least one summer, you won't appreciate how hot it will be under a tin roof with no insulation. Re: Open metal roof in the tropics - insulation needed? 3Aug 11, 2010 8:33 pm The foil down recommendation used to confuse me as well. Being of high reflectivity, the foil is also of low emissivity. That means if you heat it up, very little radiant energy is actually emitted from the shiny surface. Think of a stainless steel pot full of boiling water. Place you hand an inch away (but not touching) the pot. You would not realise how hot it is because very little radiant heat is escaping. Of course if you touch the pot, heat is CONDUCTED away and it will transfer heat energy. That is why the shiny side must face an inch air gap and not contact anything Foil down also prevents dust settling on it. It the shiny surface gets dusty it no longer posseses low emissivity and the thermal effect is lost. Fine with me... just let 'em step in with some affordable (but good) gear... 12 6002 1 1238 Any structural alteration to your home requires building permit. Before you get it you will have to supply plans with structural assessment, you will also be removing… 2 5529 |