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Unread 05-31-2020, 01:31 PM   #1
makethatkerdistick
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tips regarding metal roofing

A new project for my home seems in the offing. As my composite shingle roof is aging, I am considering a metal roof with reflective white coating as a replacement in the next couple of years.
Three reasons come to mind for me: energy efficiency in the summer, longevity and (at least to me) clean good looks.

I've been thinking of a standing seam aluminum roof with the appropriate white coating (Kynar or similar) so I can reduce cooling costs in my climate zone. I had painted my composite shingle roof with hydrated lime as an experiment and have been amazed at the reduction in heat gain in my attic. After years of exposure, the lime is now slowly washing off, diminishing the previous heat gain reduction somewhat.

Additionally, I'll have to take off and reinstall a 4.5 kW solar array (18 panels). I haven't investigated this yet but know that I need a different rail system to attach my panels to a metal roof. While I am not considering a DIY project for the roof proper due to its scope, I plan on reinstalling the solar array myself to save some money. The house itself is approx. 2500 sqf with a hip roof. Not sure what that means cost-wise but I've heard that a metal roof is approximately three times the price of a traditional shingle roof. Not sure if that rule of thumb is true, though.
I am also not sure whether the more expensive aluminum will get me an advantage over zinc-coated steel but I am leaning towards it as it is more corrosion resistant.

If any of the builder-type posters on here or anyone with good knowledge of roofing materials has any tips and considerations, I'd be very fortunate to hear them. I am especially curious about how to successfully vet contractors. I want to ask the right questions to determine if they will provide a top-notch installation. That to me would be much more important than picking the lowest bidder.
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Unread 05-31-2020, 02:32 PM   #2
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I've installed and had installed many metal roofs here in my area of south central Texas, Wolfgang. The ones I've actually installed were of the Tennessee Vee type with no special equipment being required. But the better roofing is the Standing Seam type with no exposed fasteners, which does require some specialized equipment to do effectively.

I have never tried, nor even considered, the aluminum variety. Everything I've used was Galvalume plated steel and that's what I'd use again for my own house. That is available in its natural galvanized look (but a finer textured appearance) or as a coated (painted, colored) product. I've never installed anything but the natural finish, primarily because that's what's been requested by the owners due to the more traditional look of this area. Lots and lots of colored ones hereabouts, too.

Two things I'd caution you about if you start pricing the Galvalume products. First is the thickness of the material. The thinner material is less durable, as you would expect and in your hail-prone area that can make a significant difference. It's less expensive, but it's cheaper. When I started building down here the roofing material was available in 29ga. or 26ga. I'm told now that the good stuff is 25ga. rather than 26, but it's been years since I purchased any.

Second, if you plan to have a colored roof, I don't think I would do white instead of natural for environmental considerations, only if you want it for aesthetic consideration. While the natural will darken a little over the years (nothing like galvanized steel does), I don't think the reflectivity of the white paint is gonna be a substantial environmental improvement.

But if you want it coated, be sure it's not just a coat of vinyl paint (available), but a Poly Vinyl something something something. I think it's PVDF, but you'll need to Google it up. The single coat stuff will fade and even peel in some cases and can surely make you wish you had stayed with the natural finish. The properly coated stuff appears to hold up quite well in my observation over the years. But that's gonna be a sharp difference in the price of a colored roofing.

Even at your tender age, a properly installed standing seam Galvalume roof will allow you to feel quite confident that your new roof will last longer than you. Probably at least as long as all those new soldered copper pipes you installed.

Well, absent one of those bodacious hail storms y'all are prone to having up there. But even in that case you won't get any ice balls inside the house and your roof probably won't even leak before your insurance company buys you a new one.

What's the steepest roof pitch on your house?

For installing the solar panels, or any other reason you need roof access on a standing seam, you'll wanna buy you a half-dozen pair of this style of vice grips. Them metal roofs can be really slippery, 'specially when damp. And they're hot on the outside for more than half the year in your area. In the summer you can't even handle the roofing material without gloves.
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Unread 05-31-2020, 05:49 PM   #3
makethatkerdistick
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Thanks, CX. This is helpful information. I think the pitch on my roof is about 5/12 or thereabouts.

Regarding the bright white, I am determined that I want that coating. For the full thermal reflectivity it has to be bright white with an albedo as close as possible to 1. From my own experiments with the hydrated lime on my composite shingles (don't ask me how I chanced upon this), the effect was astonishing. I measured surface temperature at full sunshine and detected no more than a 10 deg. F rise above ambient air. On the hottest days in the 100s, the roof temperature never rose above 110 deg. F. Likewise inside my attic. On the non-white shingles prior to coating I measured up to 160 deg. F.

After coating my existing shingle roof with the lime, my cooling load dropped a whopping 40%, and that was with all the insulation and air sealing already in place. I can't wait to ultimate have a more durable white roof again. Comfortable and saves money and energy. Plus, as you said, no worries when hailstorms happen. I am a pragmatist and don't care what my neighbors think. I think functionality and durability should be paramount.

Good to know that I have to look out for standing seam, ideally 25 gauge for aluminum but also shouldn't discount steel. And yes, the PVDF seems to be the durable coating that is desirable. Seems like investing once properly in a good roof could save me a lot of worry down the road.
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Unread 05-31-2020, 06:43 PM   #4
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The flat panel roofing in a light color will tend to reflect a fair amount, but when in direct contact with the roof decking, what does not reflect will conduct the heat into it. My preference is a wood shake like panel. This has only the mounting tabs in contact with the roof deck and the rest is an air gap. Supposed to reflect in the order of 95% of the IR, and with the air gap beneath, most of what gets under it isn't as efficient due to convection to transfer that heat to the decking rather than conduction. These generally are aluminum with a Kynar coating. When I was looking into it, the company showed the engineering results of a country club's main lodge that was installed in 1927. WHen then reviewed it, they said at the rate it was weathering, it had about another 800-years of life.

I don't know how easy it would be to mount your solar panels, but I'm pretty sure that it's been done before. I haven't looked into it recently, but I do know they had at least about 6 different colors available at the time. There are more people out there that are making these now. It's been awhile, but the company was, I think, based in Texas.

If you ever do get snow in your area, you want to install snow hooks, otherwise, the smooth metal roof will dump all of the snow on you with any small vibration or melting as it slide off.
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Unread 05-31-2020, 06:51 PM   #5
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Quote:
Originally Posted by Wolfgang
, as you said, no worries when hailstorms happen.
Not quite what I said, Wolfgang. I said the 26ga. roofing would protect a lot better than the 29ga. I've still seen insurance companies declare 26ga roofs a total loss after really severe hail storms, but they were in a whole lot better shape than the thinner roofs.
Quote:
Originally Posted by Wolfgang
Good to know that I have to look out for standing seam, ideally 25 gauge for aluminum but also shouldn't discount steel.
Confusion there, too. I know nothing at all about the aluminum roofing. And you don't need to "look out for" 25ga. steel roofing, you need to look for the 25ga. Galvalume steel roofing.

In your geographic area I would not recommend aluminum roofing.

My opinion; worth price charged.
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Unread 05-31-2020, 08:02 PM   #6
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Some good thoughts, Jim!

CX, sorry for misinterpreting your comments. It was a hasty read and a hasty reply. I already see I've got lots of reading to do to learn about the different options like material, thickness, underlayment options, gap or not, shape of panel etc. Currently, I am still leaning towards aluminum but that will depend on a lot of factors such as impact ratings etc.

Now, I started to look into copper roofs. They are absolutely astonishingly beautiful. Thankfully, I can't afford one and so don't have to consider this too much.
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Unread 06-03-2020, 12:40 PM   #7
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A local supplier sells high-quality standing seam panels to the general public. As you know, I have a propensity for taking on various projects as DIY.
There is some good advice on Youtube, and I think I'd love cutting the panels with shears and bending the drip edges with those cool little tools. However, doing this by myself with, say, one or two helpers, is a stupid idea, right? A really stupid idea? Say it is so and I shall abstain.

As Jeff has pointed out before, I am a true sucker for punishment. But you all would surely talk me out of this, right?

Good news: Seems that for standing seam there is an approved clip system out there that mounts directly onto the ridges for installing solar PV panels. In fact, this method is apparently preferred as it causes no roof penetrations at all. Thus, standing seam is per se solar PV ready (which I like in case I want to change the panel configuration such as adding a few panels). The reinstallation of my solar PV system is definitely something I will and can do myself.

Also, I learned that the steel roof gauges that are preferred are 24 and 22 (which the latter being highly uncommon for residential). There doesn't seem to be a 25 gauge available. Aluminum thickness, however, is measured metrically and not in gauge.

I am a bit concerned that after a decade or so the steel panels would start rusting at the cut edges, especially where they tend to be in touch with rain water longer (such as intersections of two roof planes), hence I like the idea of the aluminum. CX, from your comments I gather that you don't regard this as a big problem. Is that correct?

Is anyone willing to venture a guess as to average cost of a kynar coated 24 gauge galvalum or equivalent thickness aluminum standing seam roof on a one-story 2500 sqf ranch with a 5/12 hip roof with typical penetrations etc. Am I looking at $20k, $30k or even beyond? I am not ready to get quotes at this point but would like to have an approximate idea so I can work on my savings. I am trying to avoid taking out a loan on this.
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Unread 06-03-2020, 01:28 PM   #8
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Wolfgang, while you may want to DIY a Tennessee Vee roof, you really don't even wanna attempt a standing seam. While it is possible to do using hand tools and buying pre-formed ridges, you will not get a look that you will find satisfactory without an electric seam roller and some experience.

You wanna see a flatbed trailer parked in your driveway with a couple big rolls of flat material and forming jigs on it and a crew of guys with some specialized hand tools and at least one little rolling machine that will climb your roof, bending the sheet edge over the pre-formed standing part. Plus they'll have hip and valley material and.......on and on. Invite them. pay them. Never look back.

As for rust on the edges of Galvalume, I worried a lot about that when I first started using the stuff 30-some years ago, but it just doesn't happen with good quality material. Why not? I got no eye-dee, but it doesn't.

I've not priced such roofing for years, but I'm sure you're looking at waaay over $100 a square for the colored standing seam roof you want. But I've just been out of that game too long to know.

My opinion; worth price charged.
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Unread 06-03-2020, 02:21 PM   #9
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Thanks for talking me out of this hare-brained idea. Points well taken!

$100+++ per roofing square? That's for material only, right?
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Unread 06-03-2020, 09:32 PM   #10
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That's what I recall for the material when I installed 26ga Tennessee Vee roofing, Wolfgang. And that was a long time ago. For an installed heavy gauge (whatever that is these days) colored Galvalume standing seam roof today I wouldn't be surprised if you pay eight or ten times that price per square, depending upon how complicated your roof is, what preparation is needed, etc.

While they may not be expensive for their lifespan, they're costly as hell up front. One of the reasons many of my earlier new home customers opted for the Tennessee Vee roofing. Much the same look for a quarter of the price.
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Unread 06-03-2020, 09:39 PM   #11
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FWIW, when we were looking to reroof our condo buildings, the aluminum shake roof was maybe 30% more than a premium asphalt roof. Personally, I was annoyed they didn't go with the aluminum one. One of my coworkers had that system installed on his home, and when he got home that evening, he said he immediately noticed that the whole house felt more comfortable...I think, as a result of the great radiant barrier effect. You don't get the full effect without an air gap, which, on most flat panels, because there's none, you get heat transfer to the decking. Reflecting the heat is one thing, but none of the panels is perfect. If I build a home, I'll go that way if I don't end up with an earth sheltered one if I can find the ideal site for it.
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Unread 06-05-2020, 11:42 AM   #12
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Sigh! I interviewed my first roofing contractor. The person was nice and patiently addressed my questions. He seemed knowledgeable at first but then started making up stuff. I hate when people do confabulation-style story-telling when they don't know the answers instead of just admitting that they don't know something.

Ballpark is $25-30k, pending a more specific quote. That's for a coated 24 gauge Galvalum standing seam roof. Given that some people's bathroom remodels can be more than that, I think this is GREAT value for a nice roof.

Here are some of the weird stories the guy told me that I believe to be wrong:
No difference between regular galvanized and galvalum
Natural galvalum color cooler than bright white
aluminum is generally not available for standing seam roofs
their polyester finish is better than the industry standard PVDF (aka Kynar).

I had already set my eyes on the PVDF finish which has a record of durability. I've read somewhere that polyester finishes are considered mid-range and not top quality but that source could be wrong. But just the fact that the salesperson seemed to bash the PVDF as something that prematurely chalks and flakes off (as opposed to their Valspar Weather XL polyester) made me suspicious. I think he made that one up on the fly, actually. Same thing about the reflectance of bare galvalum vs. bright white. I looked it up and it seems nothing comes close to bright white in measured reflectance and emissivity . Thus, the claim that silver is cooler than white is untrue.

I'll have to keep interviewing.
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Unread 06-05-2020, 07:04 PM   #13
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1. Nonsense!

2. I would not be surprised that a new Galvalume finish could be more reflective than a white finish, Wolfgang. It's pretty brtight stuff when fresh. But the galvalume will tarnish a bit and at that point I just don't know what the comparison will be with a white roof of similar age and wear.

3. I don't know about aluminum standing seam roofing being available. Again, I would not recommend such for your house.

4. I doubt it, but have neither education nor experience to back that up.
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Unread 06-06-2020, 06:24 AM   #14
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Almost everyone in my area except I has a metal roof. I don't think I have ever seen an aluminum one. Most are natural galvanized color. Occasionally I'll see a painted (powder coat) one. All are standing seam.

As to reflective value, I think plain galvanized will work as well as any. Spraying the underside of the roof sheathing might do something also.
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Unread 06-06-2020, 10:50 AM   #15
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Thanks all for your feedback. I enjoy listening to you while I learn and dig in.

I found this manufacturer's data sheet that clearly shows that nothing comes close to bright white. The SRI value (which includes both emissivity and reflectance) for "natural white" is quite a bit higher than for the Galvalume (see premium color section):
https://www.berridge.com/resources/chart-of-sri-values/


I also found a VERY HELPFUL Youtube channel: "Metal Roofing Channel" provides very specific technical knowledge. I love that. And it just so happened that I chanced on a video in which the VP of Sales for Valspar himself directly admits that PVDF coatings are ultimately more durable for non-vertical applications than SMP (such as the Weather XL product). That clearly confirms what I had loosely researched.
https://www.youtube.com/watch?v=Jaz81F303DI

From what you all are saying, aluminum is a rather uncommon material in various areas of Texas where you (John, CX) and I are based. It seems that I want to look for the 24 gauge Galvalume standing seam with a bright white PVDF coating to match my needs for a cool roof with a long life. I honestly also aesthetically prefer the white color over any other finish, as strange as that may perhaps sound.

I'll be talking to another roofer on Monday. Hopefully, that guy will be more technically informed.
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