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Comment by tjoff | Hacker News Reader

I feel the failure mode should be pretty good though, degrade to a normal solar setup - probably with less airflow and higher temps but not worse than that.

Heat degrades panel longevity too so I'd actually assume a water-cooled system to outlive a normal one, in the long run I would be surprised if it wouldn't end up being cheaper.

I do agree with the simplicity of a solid state setup though. Whether it makes sense probably depends on where you live. Thinking about it, temporarily running "warm" water might help with keeping snow away, though I am aware that many setups won't generate much in the winter anyway.

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Longevity doesn't really matter as most roofs are only good for 25-30 years. As such you are removing the panels anyway to repair the roof, there is not much additional cost to just replace them. Odds are newer solar technology will exist by then and so you will want to upgrade.

My tile roof is 120 years old, on a house that is 220 years old.

Yo my knowledge it has had basically no maintenance in that time.

Yeah our (concrete tile) roof is about 80 years old. The only maintenance has been replacing broken tiles after a particularly bad hail storm.

Wait really? Why are we using regular (asphalt?) shingles?

As an Australian who has moved to the USA, I don't know why it's done. I don't know a single person in Australia who has ever replaced their roof. My dad lives in the same house I was born in 40 years ago, same roof. I've been in Colorado for 4 years. We had a new roof put on 2 years ago, then another 6 weeks ago due to a bad hail storm.

A quick search suggests that it's because historically clay tile roofs didn't do well in environments that regularly drop below freezing (like Colorado). It sounds like newer materials can handle freezing weather fine, so our usage of asphalt probably is just a cultural habit at this point.

Slate handles cold weather and lasts for hundreds of years. It also looks fucking awesome.

We don't use it anymore because it's expensive.

Also because no one knows how to handle it anymore and ignorant roofers will break your really expensive slate roof.

Installing tiles requires more skill than asphalt.

In California, because of clumsy rules around workers compensation insurance, low-skilled high-risk labor is much cheaper than high-skilled labor. As a homebuilder explained it to me: if you hire actual roofers you have to pay very high insurance rates (roofing is quite dangerous). But if you hire day laborers and tell them to install the roof, you don't. So they prefer roof designs that day laborers can install.

There are also earthquakes, during which I'd rather have shingles than concrete tiles above me.

But there's wildfires, in which case you want tiles not extremely flammable petroleum products above you.

Asphalt shingles are usually quite resistant to fire. IIRC, wildfires most often enter a structure through a window.

What about the rest of the country. What state predominantly installs tiled roofs?

Florida has a lot of houses with tile roofs. I think Arizona, New Mexico, and Texas also have lots of places with tile roofs due to the Southwest aesthetic.

California also has wildfires and at least in SoCal the homes primarily use a fire resistant tile or slate.

Haha, no. Some high end housing uses clay or tile, but the vast vast majority of roofs in California are Asphalt shingle.

[https://kelly-roofing.com/what-roof-styles-are-popular-in-ca...]

Installing concrete tiles requires pretty much no skill. Anyone could do it after watching a 20 min youtube video. They literally just interlock and hold each other in place. You only need to nail down edge ones. A whole roof can be done in a day by 2 people - and most of the time is spend hauling the tiles to the roof - they're heavy!!

The weight of roofing construction above the truss/rafter may be estimated with the calculator below[1]:

Clay tile (10.8 lbm/ft2, 52.7 kg/m2)

Concrete tile (9.3 lbm/ft2, 45.4 kg/m2)

Slate - 3/8" thick (12.8 lbm/ft2, 62.5 kg/m2)

Slate - 1/2" thick (18.8 lbm/ft2, 91.8 kg/m2)

Slate - 3/4" thick (26.0 lbm/ft2, 127 kg/m2)

Asphalt roll roofing (1.1 lbm/ft2, 5.4 kg/m2)

Asphalt shingle or asphalt-fiberglass composite shingle (2.7 lbm/ft2, 13.2 kg/m2)

Metal roofing - aluminum or steel - panel, sheet or shingle (1.2 lbm/ft2, 5.9 kg/m2)

[1] https://www.engineeringtoolbox.com/roofing-materials-weight-...

I did find it super weird the first time I heard of Americans using asphalt shingles. Everything over here is either corrugated steel (often powdercoated) or tiles, apart from some fancy upmarket properties with zinc roofs.

As child poster notes, the weight is a factor, and US houses uses wood frames for construction, where warmer parts may use brick construction. Can carry heavier roofs.

My house is wood frame, brick veneer. It was relatively cheaply built government housing back in the 40s/50s. It seems to have held up just fine with the weight of concrete tiles.

Most tiles roofs have underlayment (around 30 years) or some other waterproofing that needs to be serviced. You move the tiles over, replace, then move them back. The tiles, alone, don't make a waterproof roof.

What's under your tiles?

All the tiled houses I lived in (in Melbourne, Australia) had nothing under the terracotta tiles. Standing in the loft, you saw the underside of the tiles.

Late in the day when the sun was low, you would see chinks of sunlight through the gaps between tiles.

Romantic, but sadly thermally unsuitable in many places.

Nearly all houses have the thermal insulation flat across the ceiling of the room below, rather than diagonally across a slanted roof.

Having it flat means you need far less insulation for equivalent results.

Downside is the loft space is effectively unheated/uncooled.

This wouldn't work where I am, where it's windy when it rains. The tiles themselves don't make a roof waterproof.

If the roof is covered with solar panels, the roof itself will last a lot longer since it's not directly exposed to the sun.

Except solar panels don't cover the whole roof, and that last 10% means the whole roof must come off

Winter freezing conditions seem like that could suck out any potential ROI. In freezing temperatures, you would need to drain the system and/or add a heating element to ensure the water does not freeze and burst the outdoor pipes. Warming water in freezing conditions is going to be energy intensive. Maybe you could get away with some anti-freeze additive to lower the threshold point.

Just drain them in the fall. It’s not like you need to wait till the last minute.

With irrigation it can be kinda tricky to judge when to blow them out. But with this? Just when you’re averaging temperatures of 10-15, blow the pipes out.

Why wouldn't you get a way with anti-freeze?

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