No roofer uses a hammer anymore. They all use nail guns. But I would expect a nail gun to shatter a glass tile...
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Effect of Tesla Roof on Home A/C
- Thread starter SageBrush
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No roofer uses a hammer anymore. They all use nail guns. But I would expect a nail gun to shatter a glass tile...
dhanson865
Well-Known Member
Not everyone agrees with you. I'm sure that a high powered nail gun can split a tile no problem, I'm not sure that everyone or even some are going to use nail guns to install solar tiles.
What hammers do you use on the roof?
THE ROOF FORUM: Hand Nail, Nail Guns, or Staples
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EV-lutioin
Active Member
Here are three different images of existing solar shingle installations. I am not sure how the Tesla Solar Roof will compare, but the "clay" tile version will have a minimal air gap unless they have figured out a way to install them without battens.
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ElectricTundra
P85D AP1
In a properly fully ventilated roof, where the temp in the space between the interior structure insulation and roof (attic) is the same or nearly the same as the outside ambient then I'd not think shingle type of any sort would make any difference. Here the only purpose of the roof (aside from aesthetics) is protection from weather and UV. In a ventilated roof that is not properly ventilated then shingles might make some difference?
In a PERSIST type structure I'd think the amount of heat xfered through could make a significant difference, depending on the insulation layer.
In a PERSIST type structure I'd think the amount of heat xfered through could make a significant difference, depending on the insulation layer.
Bet me to it. If your roof theoretically were 100% covered with solar PV, I expect at least 10% reduction in warming your house is subject to, due to the combination of all effects you mention.
The more efficient the solar cells are the better.
But most heat comes in as IR photons or vibration of molecules, against those, only good old thermal insulation works.
But glass is naturally a good thermal insulator. And having an air cushion below the roof circulated with outside air should help more.
In the future we might have transparent solar cells to place on the sunny side of your house, outside of the roof itself. The more solar radiation gets converted to electricity even outside your roof, the cooler your house gets, as a lot of solar radiation that hits your house become infra red/molecule vibration near your house rather than right at the roof.
If a large very hot metro area were to be mostly covered with solar cells, it would certainly cool down the whole area.
Enough day dreaming... Actually its night here, so I'm just dreaming... But the physics principles are sound.
WannabeOwner
Well-Known Member
I'm curious ...
I live in UK. No aircon here, rarely hot enough to be uncomfortable, although it depends on the build of the house of course.
Mine is built to Passive House standards, which basically means air-tight and lots of insulation, but that's so that we need almost no heating in winter - but of course ti works, in reverse, in the Summer too.
How much heat-effect do hot states get from the roof? rather than windows / walls etc? If lots from the roof isn't the answer just to insulate it and save the energy costs?
We have more than 2x the government requirement for roof insulation ... in my lifetime the government has doubled the requirement about every 10 years, so I'm good for a couple of decades
but that seems to suggest that regulation requirements have been inadequate and better to over-insulate (and spread the benefit over the "lifetime of the building")
We also have high-density block for all internal walls (let alone "stud work"), so a very high thermal mass. When we get a heat wave its at least a week before we start to feel too warm in the house, and opening windows at night to get cold air through pretty much takes care of that - and Summer in the UK is usually defined as "3 fine days and a thunderstorm" so appreciate its less of a problem here, although houses in general are built for "average" conditions so when we get 7 - 14 days "hot" most houses become uncomfortable.
So is "significant insulation" to avoid energy of Heating / Cooling not a thing in hot states such that the possible marginal benefit from Solar Panels, and an air-gap, makes a worthwhile difference?
I live in UK. No aircon here, rarely hot enough to be uncomfortable, although it depends on the build of the house of course.
Mine is built to Passive House standards, which basically means air-tight and lots of insulation, but that's so that we need almost no heating in winter - but of course ti works, in reverse, in the Summer too.
How much heat-effect do hot states get from the roof? rather than windows / walls etc? If lots from the roof isn't the answer just to insulate it and save the energy costs?
We have more than 2x the government requirement for roof insulation ... in my lifetime the government has doubled the requirement about every 10 years, so I'm good for a couple of decades
but that seems to suggest that regulation requirements have been inadequate and better to over-insulate (and spread the benefit over the "lifetime of the building")We also have high-density block for all internal walls (let alone "stud work"), so a very high thermal mass. When we get a heat wave its at least a week before we start to feel too warm in the house, and opening windows at night to get cold air through pretty much takes care of that - and Summer in the UK is usually defined as "3 fine days and a thunderstorm"
so appreciate its less of a problem here, although houses in general are built for "average" conditions so when we get 7 - 14 days "hot" most houses become uncomfortable.So is "significant insulation" to avoid energy of Heating / Cooling not a thing in hot states such that the possible marginal benefit from Solar Panels, and an air-gap, makes a worthwhile difference?
ElectricTundra
P85D AP1
The U.S. is far behind most EU countries for energy construction. This in both cold northern states and hot southern states. I think a lot of this has to do with how cheap energy is here which makes payback a bit longer and that Americans are generally a bit more focused on self than on common externalities like Environment, Pollution, Road Deaths, etc.
EV-lutioin
Active Member
I'm curious ...
I live in UK. No aircon here, rarely hot enough to be uncomfortable, although it depends on the build of the house of course.
Mine is built to Passive House standards, which basically means air-tight and lots of insulation, but that's so that we need almost no heating in winter - but of course ti works, in reverse, in the Summer too.
How much heat-effect do hot states get from the roof? rather than windows / walls etc? If lots from the roof isn't the answer just to insulate it and save the energy costs?
We have more than 2x the government requirement for roof insulation ... in my lifetime the government has doubled the requirement about every 10 years, so I'm good for a couple of decades
We also have high-density block for all internal walls (let alone "stud work"), so a very high thermal mass. When we get a heat wave its at least a week before we start to feel too warm in the house, and opening windows at night to get cold air through pretty much takes care of that - and Summer in the UK is usually defined as "3 fine days and a thunderstorm"
So is "significant insulation" to avoid energy of Heating / Cooling not a thing in hot states such that the possible marginal benefit from Solar Panels, and an air-gap, makes a worthwhile difference?
Ha, no amount of insulation is enough when it's 105' F (41' C) here in the Central Valley (CA)! I think we officially qualify as a "hot state".
See: Newtons law of heat.
If 20C is the target, then areas that are -30C (not uncommon) in the winter have a 50C gradient. You would have to enjoy a 70C (158F) summer roof for equivalent cooling requirements.
We built a home once that had a roof specifically made to incorporate an air gap. It was a standing seam metal roof that was elevated from the roof deck by diagonal members. At the top of the gables, the cap was also elevated from the roof sheathing, which covered the top edges of the metal roof for water penetration but allowed hot air to escape.
I'm not sure how one would do this with individual tiles, but it's the kind of installation air gap I'd expect for solar tiles due to thermal efficiency.
I'm not sure how one would do this with individual tiles, but it's the kind of installation air gap I'd expect for solar tiles due to thermal efficiency.
WannabeOwner
Well-Known Member
Sure, but it reduces the rate at which you lose "cold" from the building, therefore reducing your A/C energy cost and slowing the rate that it heats up - e.g. if A/C is off / broken / power is out.
Our Passive house, during winter, has the benefit of waste heat - from lights, cooking, and just "people!"
none of which applies to cooling in Summer of course.I wonder if PV panels, powering A/C equipment, are cheaper than insulating the building more?!!
It is a balance. Usually the low hanging fruit is energy efficiency. To optimize efficiency and solar panels you need lots of data and a program to do the energy envelope calcs for hot and cold.
Before efficiency ..
Operate the windows -- free
Operate the blinds -- free
Plant some deciduous trees in appropriate spots -- really, really cheap.
Wear appropriate clothes for the season -- really, really cheap
"Why should I turn up the heat because you don't want to wear a sweater?"
"There is no wind in the house. If you are cold even with a sweater, it is your body's way of telling you to get some exercise."
EV-lutioin
Active Member
Considering all the above, the optimum would seem to be a white roof with R-60 insulation, and solar panels installed with an air gap between them and the roof. It should also be cheaper than the Tesla roof, a more proven (and more easily installed) technology, and with financing the Tesla roof does not have as of 7/11/17. Additionally, more panels and/or improved panels could be added as needed; can’t do that with roof tiles.
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