SteamyTea, you do realise that the perfect way to put your roof in the shade is to fit solar (water or PV) panels



Decor8uk - sounds very good, good post and all that but would you mind just confirming that you have no connection with the product? Or declare your interest so we can grab the salt seller.

I seriously considered all sorts of paint, foil etc, as part of removing all my tiles and replacing them on top of insulation (but I didn't find your product decor8uk); in the end though I went with a ventilated roof and 100mm of insulation on one side and 180mm insulation (unventilated) surronding 100mm insulation with panels on top (a sort of ventilated roof) on the other side.

You wouldn't fancy extending your experiments and do one for me? Instead of foil what would the effect of two layers of newspaper be (no rain etc of course).

If you do do it we would all love to see the comparisons

where ever you put the foil

yes-- I cant see exactly what you are doing but I like it.

Don't want to seem as if I am banging on but what about one unprotected tile with a shade say 75 - 100 mm above? And paint the top of the shade matt black to make the test severe?

Good work.

Perhaps try an enameled baking tray as the shade to simulate a corrugated steel roof or a very basic DIY solar panel.

I can't help but think that a big PV array makes a nice (if expensive) sun shade :)

Four pillars sounds good. In practice it could be a simple corrugated second roof. No weight to speak off and painted light grey shouldn't disturb the neighbours.

My brother-in-law bought a house with a black slate tile roof here in Madrid against my advice and now complains bitterly about his air-conditioning bills. Of course he poo-poos the idea of 300 mm insulation as you can imagine. Thinks it will make the house even hotter. You couldn't make it up.

Great work!!! --- looks like paper works well

Mark

The power is on the secondary axis (to the right) but is really only a comparison/gauge so I can compare later results.
Paper result could be down to colour and emissivity (it is matt) but hopefully today's tests should show a difference between the shiny and matt black finishes. Shall make up a shade today some maybe get it going tomorrow, but I have 3 sets glass to tests which I should hopefully pick up later today.

Tony

Be interesting to see what the paper on the inside performs like, should know tomorrow.


I think the really interesting bit is that the foil (outside) insulates so well as temperature drops. Silver roofs anyone? Interesting that it hit 0 C down here last night as well.

Well was clear when I went to bed and clear when I got up, who knows what happens in between. Just checking it against some local data collected down the road.

Shall have to see what the difference is between foil wrapped around a tile (will have trapped air) and one glued on sometime.

Any change you could make those a bit bigger, it's very difficult to see what's going on!

have you tried copying it and opening it in an image package

If you can wait a few days I shall stick a spreadsheet up with summary results, may be easier to do. Just wish it was sunny today as testing out glazing units, and then onto painted white and shaded.

That's an impressive data set. I need a little help in understanding what's going on though, perhaps a description of the results for say the first experiment to guide me (?) and any chance of sketches to show the construction cross section?

From first glance it does show how effective shading can be. Important to me as I'm relocating next week to sunny climes. Hooray!

Thanks Gotanewlife.

Mark. The shading was simple a tile 300mm square raised up but 40mm above an identical tile, this does allow easy ventilation which would be restricted on a large roof, as well as that is is a very windy place I live in.. The temperatures were taken inside a polystyrene box of internal dimension of 230mm by 230mm by 40mm deep.
All reading were taken at 1 minute intervals apart from the external air temperature (these varied in their sample rate but were about every 6 minutes at best and several hours at worse, they were not from my weather station). Mean values were then calculated and used to construct the anomalies charts. This is the easiest way to see how different materials/finishes affect (or is it effect, I never know) the internal temperature with respect to solar input. By looking at the anomalies numbers you can possibly model (maybe a second stage of this project) expected temperatures rises for any given solar input at a given external air temperature. In all the tests the mean, median and mode results are all very similar and this shows that the temperature distribution is parametric (evenly distributed either side if the mean, the skew and kurtosis figures describe in more detail but are unitless). The range is really the key figure for this dataset/experiment, the small the range the less swing in temperature from the mean, with the Standard Deviation showing percentage of data readings captured with in a temperature range.

So if we look at the first dataset, for the foiled on the outside tile, the temperature swing (range) is 15 C, with a standard deviation of 3.5 (this means that 68% of the temperature readings were within 3.5 C of the mean temperature, 2 SD's would capture 95% of the readings). This chart actually has a largish skew because of the experiment going into the shadow of the house and it was a very bright day (more pronounced contrast, 24 April was very overcast, the min/max/range of Solar mW shows this best), compare the skewness of the two days. But do remember that these are anomalies and not raw numbers like the first charts I posted.

The interesting one is 30 April (the original question) White paint does make a difference, but gloss or matt does not (significantly) It halved the temperature swing for that external air temperature and that solar input. Not as good as tinfoil though, I have got data for that but just not managed to chart it yet. It still tracks the inputs (both solar and ambient) but does damp out the extremes a fair bit. I suspect that tinfoil is still the best though.

I apologise if I have not made things totally clear, it has been a long day, Flora Day in Helston in fact, all that dancing from 7 AM does a middle aged man in.