http://arizonaoddities.com/2009/07/roof-rocks-help-cool-hot-house/ Thu, 17 May 2012 23:21:52 +0000 hourly 1 http://wordpress.org/?v=3.3.2 http://arizonaoddities.com/2009/07/roof-rocks-help-cool-hot-house/comment-page-1/#comment-963 Stuff I Googled « Why Do People Have Rocks on Their Roof Sat, 15 Oct 2011 14:11:29 +0000 http://arizonaoddities.com/?p=254#comment-963 [...] also found some weird Arizona thing about large rocks being placed on the roof to supposedly control the heat but I don’t know if [...] [...] also found some weird Arizona thing about large rocks being placed on the roof to supposedly control the heat but I don’t know if [...]

]]> http://arizonaoddities.com/2009/07/roof-rocks-help-cool-hot-house/comment-page-1/#comment-93 John Violette Sun, 19 Jul 2009 19:30:21 +0000 http://arizonaoddities.com/?p=254#comment-93 Hope you won't mind if I disagree on your assessment of how the roof rocks work. You said that roof rocks give off heat and this causes a kind of updraft that helps cool off the house. Gotta say that the kind of updraft this creates would only cool off the rocks, unless there are large holes in the roof to allow the air inside the house to rise. That would unfortunately allow the rain to come in though! I live in a house that has 12 inch thick solid concrete walls on the first floor and the second floor is made of standard frame construction. On a hot day, the upstairs is boiling hot and the downstairs is so much cooler you have to see it to believe it. In fact, I can get by with very little air conditioning. The reason is the thickness of the walls is excellent insulation and also there is the principle of thermal mass. During the night the walls cool down and when the day comes and it gets hot, the walls absorb the heat slowly, which is totally different from wood walls, which heat up very rapidly. Plus, the R value of the wall's insulation is very high. So, putting rocks on the roof does the same thing, high insulation from the outside heat; then the rocks absorb a lot of heat into themselves and give it back off to the air after the sun goes down, rising heat as does moves it away from the house... Another way to look at it, would be to imagine a house completely incased in rocks, think how great the insulation would be! Hope you won’t mind if I disagree on your assessment of how the roof rocks work. You said that roof rocks give off heat and this causes a kind of updraft that helps cool off the house. Gotta say that the kind of updraft this creates would only cool off the rocks, unless there are large holes in the roof to allow the air inside the house to rise. That would unfortunately allow the rain to come in though! I live in a house that has 12 inch thick solid concrete walls on the first floor and the second floor is made of standard frame construction. On a hot day, the upstairs is boiling hot and the downstairs is so much cooler you have to see it to believe it. In fact, I can get by with very little air conditioning. The reason is the thickness of the walls is excellent insulation and also there is the principle of thermal mass. During the night the walls cool down and when the day comes and it gets hot, the walls absorb the heat slowly, which is totally different from wood walls, which heat up very rapidly. Plus, the R value of the wall’s insulation is very high. So, putting rocks on the roof does the same thing, high insulation from the outside heat; then the rocks absorb a lot of heat into themselves and give it back off to the air after the sun goes down, rising heat as does moves it away from the house… Another way to look at it, would be to imagine a house completely incased in rocks, think how great the insulation would be!

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