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rebar
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# Posted: 28 Sep 2018 12:44pm - Edited by: rebar
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I think the Texas Smart Cool Roof is a great idea and have read a few testimonials about the energy savings. But I wonder if it could be done cheaper.
I want to use AG metal that has a rib every 12" instead of every 9" and place the panels on top of new sleepers installed every 12" over the existing roof. This would mean the panel ribs drop down over the sleepers, and nothing supports the low flat metal until the next sleeper inside the next rib.
I understand the metal would sag a little in the 12" wide valley's, especially with a snow load. It would also be much louder since the metal is suspended between the sleepers like a drum.. But the three big advantages about my plan is all the screws will be on top of the rib peak's where water doesn't run.. Second, the screws have a solid place to draw down to compress the washer correctly unlike screwing through ribs over horizontal battens.. And third, you will have a Texas Smart Cool Roof for cheap, and will see a reduction in utility costs
Does this sound like a reasonable plan? I'm not very worried about sagging because it's a beater mobile home. But I am more concerned with how loud the roof would be when raining? Bad idea?
Thanks!
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rockies
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# Posted: 28 Sep 2018 06:24pm - Edited by: rockies
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Are you suggesting that metal roofing panels be applied over sleepers with no sheathing between them? If so you'll dent the panels whenever you walk on them.
I have read lots of research on this topic on the Green Building Advisor website.
They suggest that the best method of installing a "cool roof" system is to build your "main" roof using 1/2" or 5/8" sheathing and then cover the sheathing with 30 lb felt paper. This will allow any moisture that gets into the roof framing structure to escape to the exterior (should it need to).
On top of the felt paper attach 2x4's to the roof (running vertically) every 16" on center. Add a second layer of 5/8 sheathing on top of that. Leave a vent gap at the ridge and overhang the new "cool roof" about 3" beyond the main roof at the eave in order to install eave vents.
If you are in a fire danger zone (and most cabins are) add a fire barrier like Versashield to the top surface of the cool roof and then your metal roofing. Many people don't realize that the heat from a wildfire can radiate through the metal roofing and set the sheathing on fire.
https://www.gaf.com/en-us/roofing-products/residential-roofing-products/roof-deck-pro tection/fire-resistant/versashield
The image shows a cold roof built over a SIP roof, but it would work on a traditional stick framed or truss built roof too.
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creeky
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# Posted: 28 Sep 2018 07:55pm
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A diagram would help for sure.
Lots of cool roofs done with metal roofing. I think the original design was done with two layers of metal.
Great idea.
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rebar
Member
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# Posted: 29 Sep 2018 01:06am - Edited by: rebar
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Quoting: rockies Are you suggesting that metal roofing panels be applied over sleepers with no sheathing between them? If so you'll dent the panels whenever you walk on them.
Yes. I figured I'd walk on the ribs every 12" and use 24g.. Stupid idea, Im realizing.
Its just a shame you have to build two roof decks for a cold roof and I don't trust AG metal screwed in the flats over my home. So adding the additional new plywood and switching to standing seam just blew the budget over the top.
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ILFE
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# Posted: 29 Sep 2018 06:09am - Edited by: ILFE
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Here in Cambodia, I have zero intentions of walking on any roof, anywhere. But, I did want to have a fairly strong roof on our container. Khmers, though, being so much smaller than we (typical westerners) are, not to mention being able to climb like monkeys, are another story.
The attached images show how we had our roof installed. It may look like a good wind could take it off, due to the incline. And, to be honest, I didn't have to have such a high pitch. But, I made sure it was a rigid installation. And, it sheds rainwater pretty fast. The gutter can handle everything the roof throws at it, and directs every drop to the storage vessel.
This roof has been in place since since May 2017, and has endured some pretty severe winds, especially those that can come with the monsoon rains we have here. (I apologize for the photos not being the best possible views. But, they were the only two I could find right away, without looking through tons of other images.)
Anyway, to the main reason for this post.
I hear very little noise from the rains hitting the tin roof. I also had the ceiling in the container well insulated. So, even if I did not run the air-con 24/7, the container would remain fairly cool inside, even during the day. The roof reflects the suns rays fairly well, being a very light color (snow white).
I realize the costs will be significantly different in the US or Canada. But, here is the breakdown for adding the steel trusses and tin roof to a 20' sea container:
7 each - sheets roofing steel, snow white color. 3.5 meters long x 1.10 meters wide. $12.95 each, $90.65 total
6 each - 40 x 40 x 1.50 x 6 m long, $7.695 each, $46.17 total (for purlins)
5 each - 40 x 80 x 1.50 x 6 m long, $12.433 each, $62.17 total (for roof trusses)
1 bag - mounting screws with rubber washers, $3.50 total
Transportation from the city to the farm, $15.00 total
Total Cost: $217.49
Welding was another $70.00 USD, to manufacture the trusses and weld them, along with the purlins, to the container.
EDIT: I found two other images to add, A and B.
Roof Install 1
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Roof Install 2
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Roof Install A
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Roof Install B
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rockies
Member
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# Posted: 29 Sep 2018 05:52pm
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Well, if you'd just like to apply a metal roof right onto the main roof sheathing (no cold roof) then why not go to corrugated metal panels?
https://vicwest.com/products/commercial/steel-cladding/exposed-fasteners/78-corrugate d/
This style has continuous ribs all across the panel and allows air to flow under it nicely. A thicker gauge metal will allow you to step anywhere on the panel without denting.
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Steve_S
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# Posted: 30 Sep 2018 09:29am
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geez, what a burn, wrote a nice reply with images and POOFDAH...
This type of roof works really well... I did it and now recommend it to everyone and some around here are now doing it and loving the results.
My build thread has info on it... Basically I built my roof as a "Hot Roof" for Cathedral Ceilings... that means no internal venting between insulation & sheathing... Now I used 2x8's with 7-1/2 of PolyISO between the rafters (obtained from a commercial roofer). We laid Typar Surround SR on the roof, NOT tar paper and the reasons are obvious. REF: https://www.typar.com/products/surround-vr-underlayment/ Then we put a Batten X Batten layup on there with 2x4's running over the rafters @ 24oc and the 1x6 cross battens @ 16oc, providing low turbulence airflow up. At the Eaves we cut in a 2-1/2" air channel & condensation drain into the eaves to allow air in and installed a standard vented ridge cap. Should have used a Tall Vented Ridge Cap - see image below, which would have improved out flow.
Tin used was "Ameri-Cana Rib" by Ideal Metals in Forest Green (I am in an Evergreen Forest & with live edge cedar siding it's just right, so... ) BUT I did not go for the CondenStop coating which would have cut the rain noise as well as the expansion / contraction popping tin roofs make.
REFS:
CondenStop: (many companies offer similar) http://www.idealroofing.ca/english_canada/pdf/products/americana/CondenStop.pdf
Ameri-Cana Rib: http://www.idealroofing.ca/english_canada/html/prod_americana.php?type=lw&ct=DFGSDFHS FG30
Batten X Batten design layout
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Batten X Batten Airflow
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Tall Ridge Vent Cap
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Borrego
Member
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# Posted: 30 Sep 2018 12:05pm
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Rebar - question: Is the main purpose for this type of roofing system the heat problem? Are you set on metal roofing?
Reason I ask is because out at our cabin community (in the SW desert), no one uses metal roofs or shingles for that matter.....everyone installs flat rolled roofing, regardless of roof pitch.....
Then it gets painted regularly with the elastomeric roof paint. This reflects the sun's heat and turns the roof into a hard, almost plastic - like surface, they last forever. And the desert sun is nothing to mess with.....
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creeky
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# Posted: 30 Sep 2018 11:49pm
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Quoting: Borrego elastomeric roof paint
So regular painting results in a long life surface. What kind of schedule are you on? 5 years, 10 years?
Do you have any favorite brands? I have a rolled roof I would like to paint.
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rebar
Member
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# Posted: 7 Oct 2018 02:45pm - Edited by: rebar
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Quoting: Borrego Rebar - question: Is the main purpose for this type of roofing system the heat problem? Are you set on metal roofing? Reason I ask is because out at our cabin community (in the SW desert), no one uses metal roofs or shingles for that matter.....everyone installs flat rolled roofing, regardless of roof pitch..... Then it gets painted regularly with the elastomeric roof paint. This reflects the sun's heat and turns the roof into a hard, almost plastic - like surface, they last forever. And the desert sun is nothing to mess with.....
Thanks everyone..
Borrego, I'm trying to reduce the utility costs is all.. But winter is expensive to. Plus, I really wanted a over hang so we could leave windows open, and vented soffit.
Any idea what rolled roofing costs installed per square and how much the paint costs? Because Im looking at $5500 if my roofer installs malarkey legacy's. My roof is 13 square. I could have my roofer install the rolled roofing and paint it myself.
 
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