Posted By Lbear on 02 Nov 2012 08:46 PM

Posted By Dana1 on 02 Nov 2012 12:36 PM

TN has not adopted IRC 2012 (or even IRC 2006), but for zone 3 the  IRC 2012 specifies R38 min, up from R30 (which meets current code in TN.)  R49 is now called out for zone 4, but not zone 3.

Wow, TN is really holding out if they don't even recognize the 2006 IRC. Out here they will implement the 2012 IRC sometime in 2013. They will amend the fire codes but will hold to the energy codes.

Would it be fair to say that Zones 1 - 3 make up about 20% of the entire USA while Zones 4-7 make up the remaining 80%?

The statewide template is currently based on IRC 2006, but Memphis & Shelby County building code is based on IRC 2003, with amendments.

I'm not sure if you're counting population, numbers of single-family homes, or land area when talking percentages of the US taken up by different climate zones (or what relevance that really has?). 

Climate zones 1-3 cover some very high population-  high growth rate areas (with lots of new construction), and probably houses WAY more than 20% of the US population, and an even larger fraction of the single-family dwellings.  Just the zone-3 parts of CA and zone-2/3 TX together account for about 20% of the US population, FL adds another ~6%, then you have to start counting up the piddly-populations of the rest of the zone 2 & zone 3 fractions of states from Las Vegas NV to Oklahoma to Charlotte & Wilmington NC and add it to the other gulf-coast states.  I wouldn't surprise me if that all adds up to nearly half the US population, but possibly more than half of the single-family dwellings.

Zones 4-7 claim substantial populations, but also  on average have older housing stock, lower (in some instances negative) growth, and probably a larger fraction of multi-family dwellings.  For example, greater NYC is huge in population, small in area, with proportionally lower percentage of people living in single family homes, and very low building rates for single-family homes compared to the recent booms in places like Las Vegas and southern CA, and AZ.  (The population of all of NY state is at parity with that of FL.)  L.A. county CA is similarly huge in population, but has far greater fraction of single-family homes, a good fraction which are post-1980, whereas greater NYC was mostly built-out before 1970, (with less insulation than would meet IRC 2003 for zone 3.)

But Memphis is in only one zone- the cool edge of zone 3.

My experience with cool roof.

I coated my roof with hydrated lime. 2 bags at a cost of $23.
It dropped my roof temps from 150+ degrees to about 105 degrees. Less than 10 degrees over ambient. It worked really well. My kwh usage dropped by about 20+%

I liked it so well that I also coated my exterior walls. Now my electric use is about 60% of what it used to be.

In September of this year in Dallas Texas I used 700kwh for the month in a house built in 87 and a family of four . 1800 SQ ft house.

Oh, the walls used to get to 140 degrees now they get to about 100 degrees

I see all these so called green buildings with dark walls and roofs and no shade and I can't help but wonder how much more green they could have been with a simple white wash.

I also see net zero houses with no overhang and I wonder how much more efficient they could be in the summer with good overhang design. A white wall in shade does not exceed ambient temp. A dark wall in sun can get to +50 degrees f over ambient.

Posted By 1201 on 18 Oct 2018 05:55 AM
I see all these so called green buildings with dark walls and roofs and no shade and I can't help but wonder how much more green they could have been with a simple white wash.

I also see net zero houses with no overhang and I wonder how much more efficient they could be in the summer with good overhang design. A white wall in shade does not exceed ambient temp. A dark wall in sun can get to +50 degrees f over ambient.

I wonder if there is a gain in the wintertime with having darker colored exterior walls? Enough of a gain to offset the loss in the summer when heat is your enemy?

Jumping in here - hopefully keeping somewhat on topic. Several years ago we replaced our asphalt shingle roof. Instead of the top vents we went with ridge vents. Unfortunately, I did not monitor the attic temperature before we replaced the roof, so I don't know how things changed. However, after the roof replacement and conversion to ridge vents and adding 4 about 1 sq ft vent panels low on the corners of the side wall, in the summer the indoor / outdoor thermometer read 150 degrees.

I don't know much about attics, but seems pretty high. We have pretty good insulation between the attic space and the living space, but still, must contribute to summer heat in the house. In Denver, it always cools off at night and we have trees to the west, so the attic temperature drops to the outside air temperature within a few hours after shade hits.

I tried hooking up a box fan to blow air into one of the lower 1 sq ft vents as a test. Maybe helped a little with the upper temp and maybe cooled off a little faster, but less than spectacular results. I thought about adding barn doors on the side walls, but didn't do it.

I like the look of our gray roof, however, next time I think I'll go as light as possible.

Posted By Lbear on 12 Dec 2018 07:09 PM

Posted By 1201 on 18 Oct 2018 05:55 AM
I see all these so called green buildings with dark walls and roofs and no shade and I can't help but wonder how much more green they could have been with a simple white wash.

I also see net zero houses with no overhang and I wonder how much more efficient they could be in the summer with good overhang design. A white wall in shade does not exceed ambient temp. A dark wall in sun can get to +50 degrees f over ambient.

I wonder if there is a gain in the wintertime with having darker colored exterior walls? Enough of a gain to offset the loss in the summer when heat is your enemy?

I think I read somewhere that cool roofs/cool walls save money in all zones but zone 6?

Posted By Denver Dave on 12 Dec 2018 08:03 PM
Jumping in here - hopefully keeping somewhat on topic. Several years ago we replaced our asphalt shingle roof. Instead of the top vents we went with ridge vents. Unfortunately, I did not monitor the attic temperature before we replaced the roof, so I don't know how things changed. However, after the roof replacement and conversion to ridge vents and adding 4 about 1 sq ft vent panels low on the corners of the side wall, in the summer the indoor / outdoor thermometer read 150 degrees.

I don't know much about attics, but seems pretty high. We have pretty good insulation between the attic space and the living space, but still, must contribute to summer heat in the house. In Denver, it always cools off at night and we have trees to the west, so the attic temperature drops to the outside air temperature within a few hours after shade hits.

I tried hooking up a box fan to blow air into one of the lower 1 sq ft vents as a test. Maybe helped a little with the upper temp and maybe cooled off a little faster, but less than spectacular results. I thought about adding barn doors on the side walls, but didn't do it.

I like the look of our gray roof, however, next time I think I'll go as light as possible.

this is my uneducated opinion. when you consider how many btus a dark roof can absorb from the sun, it doesnt surprise me that the attic is still 150 degrees. they can get to 180 degrees. switching to white roofs/white walls cut my cooling bill approximately in half.