Browse Forums Heating, Cooling & Insulation 1 Feb 14, 2013 9:37 pm Is the ceiling cavity temperature irrelevant in determining how hot a house is provided that you have decent insulation? I have heard people suggest this but equally find it hard to believe (i.e. to my way of thinking insulation can only delay heat transfer - if you hold onto a hot pot with oven mitts for long enough, eventually the mitts will heat up and you will get burnt). Re: Ceiling cavity temperature irrelevant 2Feb 15, 2013 4:56 am I agree with you..........but i can 'sort of' see their argument although I don't agree with it. In summer although the roof space can get very hot in summer it can cool quickly at night .......But I would prefer to be keeping the heat out of the house altogether. In winter the roof space can be hotter than the inside of your house on hot days.... but not on rainy or cloudy days days 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: Ceiling cavity temperature irrelevant 3Feb 15, 2013 7:08 am It is a factor, but small I think. If the roof space does cool at night and gives the roof insulation a chance to cool down all well and good, but if it stays hot a long enough the insulation eventually no longer resists heat transfer. bringing down the temperature is as easy as a whirly bird though, the space still gets hot but not as hot! 2 Re: Ceiling cavity temperature irrelevant 4Feb 22, 2013 6:02 am BHP have a new Colorbond product that keeps a house cooler by use of roofing material. Must be a point here in respect to the cavity? Re: Ceiling cavity temperature irrelevant 5Mar 08, 2013 8:11 pm Say you have R4 insulation. That means the U value is 0.25 which means 0.25W per degC per sqm of heat will flow through the insulation. Say you have a room 4 x 4m (16sqm). So 16 x 0.25 = 4W per degC temp diff'ce will flow through the ceiling. If its 25 in the room and 45 in the ceiling, 80W of heat will penetrate. If its 65 in the ceiling (temp diff'ce = 40) then 160W will penetrate. You will probably have much more heat penetrating through walls and windows than through the ceiling/insulation, even at 65C. And insulation doesn't "delay" heat penetration - it prevents/reduces it. Only thermal mass will delay heat penetration by absorbing the heat as it flows through. Thank you @ashington Homes for your reply! They just got back to me and offered credit for me to just take it as is. It was a less than quotes I got from ceiling… 6 2915 Firstly, if your house is still under builder's warranty (10 years in Victoria) you should have no need to crawl into roof space but let the builder handle it, unless you… 3 5867 How do you remove one of these ceiling air con vents? And is it possible to disconnect the duct joined to the vent from inside the house, without going into the roof cavity? 0 6573 |