Thread: Oh to finally have a roof over my poor head - new pictures from 06/03

t is a good job our HSE department is not on your site but a great project. What will you do when its finished?

If the Al foil reflects the heat, then how to you account for the baked potatoes in Al foil, in an oven? Better check your physics, Markit...

Originally Posted by tintin

If the Al foil reflects the heat, then how to you account for the baked potatoes in Al foil, in an oven? Better check your physics, Markit...

Typical, you question my roof rather than your potatoes

Originally Posted by Butch

Great pics Markit. Good to have a roof over head so you can get started on the inside.

I was wondering what the go is with the lightning rods. I understand it's good to get the strike to ground if it does happen but what's the chance of getting hit. You've got heaps of coconut trees around you. Wouldn't they be a natural target/ground for lightning? Is there that much lightning in your area that calls for these measures? Not having a go just doesn't seem to be a priority when building here.

Lightening is a funny old thing - it will usually hit the highest object - the operative word here is "usually" - sometimes it just decides to go just a little to the left or right - are you willing to bet the house on that? Lightening rods also fulfil a preventative function in that they siphon the energy out of a potential thunderstorm before it gets "mad".

Originally Posted by Jimbo

t is a good job our HSE department is not on your site but a great project. What will you do when its finished?

Good question Jimbo... wanna buy it?

Originally Posted by Jesse

Wow. The development of the house is getting better. I wonder when will your building be completed.

Never, ever, ever... it seems endless

Originally Posted by ronb

Well I'm no physicist, but non-microwave ovens get the heat to the food by a mixture of radiation and convection. The alfoil around the potato will surely reflect a proportion of the radiant heat arriving, but this heat will just bounce around inside the oven and help the convection process. So no matter how reflective the alfoil is, in the end the alfoil gets hot, the potato gets hot and cooks.

In my experience the foil only seems to keep them from drying out. Back in LOF-HOB (land of the free, home of the brave - USA) they used to originally only do foil on the tates when we put em in the barby with the shinny side out to slow em down a little...

In the case of the baking of a potato, the only reason why a tinfoil is used is to retain the moister inside the potato and keep its skin moist. As one puts the wrapped potato inside the oven, the temperature of the Al foil almost perfectly tracks that of the surrounding air. Very little heat transfer to the Al is due to radiations, but practically all of it is due to heat conduction, between the air and the Al foil, which in turns heats up the potato. But for all practical purposes, it's as if the Al foil was not there.


The same is true with your roof. The tiles, which are heated up by the sun radiation and the surrounding air through conduction and to a small extend, convection, heat up the Al foil by conduction (just as the air does in the oven), which in turn heats the room below.

The advantage of an alang-alang over tiles is that the former is not a good heat conductor, therefore becoming an insulator for the room underneath.

Actually, although you are not from Texas, I think you've read too many William Faulkner's novels...

Actually red tiles are almost as good a reflector of heat as white - but I agree the aluminium foil is pointless. It was easier to agree then to fight about it and it is very cheap too. "When in Rome, do as the Romans".

Markit, just for fun.

Definition, albedo: the fraction of incident electromagnetic radiation reflected by a surface.

You will be surprised to know that the albedo for,

- Red tiles = 0.3

- White plaster = 0.93

- Bright Aluminum foil = 0.85

I knew that the albedos of white surfaces were superior to colored ones (in this case, 3 times better), but it is surprising to find out that a white plaster surface should be a little more efficient at reflecting radiations than bright Al foil (I sure hope this latest finding does not prevent me from sleeping to night)

PS. Really enjoy your pictures documenting the progress of the building of your house. Keep them coming.