Roof Insulation. Worth It? Experiences?

[wilko]

Sheesh... see what you've started wilko?

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Who? li'l ol' moi?

[Aikido]

A mate of mine whos been in the building trade for 30 odd yrs has put the foil lagging in his house and a freinds who also lives on te same estate, and they both rekon they are saving at least 30% on electricity bills. I did ask him why he didnt opt for the sray and he tells me that they dont apply enough of it to be affective, in so much that you need at least 3 inches + to actually keep the heat out, mind you rekon itll keep the insects and the rain out so its good for something but its bloody expensive dont you think when you can buy the foil insulation for about a 1/4 of the price.

[ozzydom]

Are you sure? In blighty its the south facing wall that gets the sun and the north one that does not.

As Thailand is the other side of the equator surely Ozzydom is correct

Um... not wishing to cast nasturtiums on your intelligence richardb, but have you checked an atlas recently to see which side of the equator both Thailand and England are on?

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I just looked at an atlas

I shall no longer be applying to travel agent school

Richard

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If directly on the equator, depending on the time of year the sun goes round either to the North or the South....does anyone know if Thailand ever experiences this????

<{POST_SNAPBACK}>

OK folks, here is the definitive answer to the question about the sun azimuth and elevation at the location of Pattaya:

Facts:

The latitude of Pattaya is 12.68 degrees North

The Vernal Equinox takes place on or about March 21

The Summer Solstice occurs on or about June 21

The Autumnal Equinox takes place on or about September 21

The Winter Solstice occurs on or about December 21

The Earth's rotational axis is inclined to its orbital plane by 23.5 degrees

Any location with a latitude between 23.5 degrees North (Tropic of Cancer) and 23.5 degrees South (Tropic of Capricorn) is 'in the tropics'.

At the Summer Solstice the elevation of the sun for locations on the Tropic of Cancer, at local noon, is 90 degrees, i.e. directly overhead. This occurs on only one day per year for these locations.

At the Winter Solstice the elevation of the sun for locations on the Tropic of Capricorn, at local noon, is 90 degrees. Again, this occurs on only one day per year for these locations.

For locations on the Equator the sun is directly overhead, at local noon, at the Vernal and Autumnal Equinoxes so these locations experience this phenomenon twice per year.

Locations 'within the tropics' also experience the sun directly overhead, at noon, on two days each year.

Approximate calculations for Pattaya (based on circular geometry - should be elliptical geometry but it's too hard so figures will not be accurate) indicate that the sun should be overhead, at noon, approx. one month after the Vernal Equinox (i.e on about April 21) and approx one month before the Autumnal Equinox (i.e. on about August 21). This partly explains why the hottest time of year in Pattaya is in April / May. It would also be very hot in July / August except that there is usually much more cloud at that time of year (but not this year, it seems).

For dates before April 21 and after August 21 the azimuthal angle of the sun will be 180 degrees at noon, i.e. the direction of the sun will be South.

For dates between April 21 and August 21 the azimuthal angle will be 0 degrees at noon, i.e. the direction of the sun will be North.

Therefore we can see that for about four months of the year the noonday sun will in fact be in a northerly direction although for a week or so around 'changeover time' the elevation will be so nearly 90 degrees it would be hard to tell.

As an additional, totally irrelevant, snippet of information did you know that days on the equator (sunrise to sunset) are always 12 hours long, regardless of the time of year? You do get short twighlights of course so it's light for a bit longer than this.

If you build a house with wide verandhas, most of the time the house walls will not see any direct sunlight, unlike the roof tiles. This is because, in tropical locations, the elevation of the sun is high. The walls may see the sun early and late in the day but, at these times, its heating power is much less than in the middle part of the day. It is much more important to insulate the roof - the walls are a secondary consideration and, unless you are going to run air-con during the day, may not be worth the expense.

How you orientate the house seems pretty much irrelevant - getting a good view from your terrace is probably more important than worrying about which wall should face North. Of course, if you can stand the mozzies and like sitting outside in the early evening it might be a good idea to have the terrace facing East. That way you won't be looking into the sun. On the other hand, if you're into sunsets face it the other way. Up2U.

Confused? This is all part of tropical living.

DM

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The last time I looked,the sun moved through 180 degrees horizon to horizon,suggest you sit outside one day and take note of when the suns rays left the East side and when they started shining on the West side.

[wilko]

DM

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The last time I looked,the sun moved through 180 degrees horizon to horizon,suggest you sit outside one day and take note of when the suns rays left the East side and when they started shining on the West side.

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- EH?!?

Edited August 26, 2005 by wilko

[doctormann]

DM

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The last time I looked,the sun moved through 180 degrees horizon to horizon,suggest you sit outside one day and take note of when the suns rays left the East side and when they started shining on the West side.

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- EH?!?

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Pardon? What are you trying to say?