Hip Roof Pitch

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Hip Roof Pitch

Postby oldmankit » Mon Mar 28, 2016 6:30 pm

I've got an architect who has drawn up a set of plans for our two-storey house. We've been planning on a hip roof with a 30 degree pitch, which seems pretty common here for residential projects.

When he drew up the elevations he said he preferred a shallower pitch: 20 degrees. He said it could save a bit of money, but mainly he felt it would look better. Here's a view of it in 3D that I did using Sketchup:

20 degree pitch.jpg


And the elevation:

20 degree pitch - South Elevation.jpg


If you compare this with a 30 degree pitch, I tend to agree with the architect that the shallower one looks better:

30 degree pitch - South Elevation.jpg


However I've put a huge amount of effort into making this house as cool as possible with as little need for air conditioning as is possible in the outskirts of Bangkok.

I just wondered how much of a difference this would make to the overall temperature inside the house. We plan to insulate the roof/attic well, and will install soffit vents. Neither my wife nor the architect are keen on putting a whirly-bird vent on top, and I just get the feeling that we could be looking at an unecessarily hot second floor.
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Re: Hip Roof Pitch

Postby Sometimewoodworker » Tue Mar 29, 2016 6:57 am

oldmankit wrote:I've got an architect who has drawn up a set of plans for our two-storey house. We've been planning on a hip roof with a 30 degree pitch, which seems pretty common here for residential projects.

When he drew up the elevations he said he preferred a shallower pitch: 20 degrees. He said it could save a bit of money, but mainly he felt it would look better. Here's a view of it in 3D that I did using Sketchup:

20 degree pitch.jpg


And the elevation:

20 degree pitch - South Elevation.jpg


If you compare this with a 30 degree pitch, I tend to agree with the architect that the shallower one looks better:

30 degree pitch - South Elevation.jpg


However I've put a huge amount of effort into making this house as cool as possible with as little need for air conditioning as is possible in the outskirts of Bangkok.

I just wondered how much of a difference this would make to the overall temperature inside the house. We plan to insulate the roof/attic well, and will install soffit vents. Neither my wife nor the architect are keen on putting a whirly-bird vent on top, and I just get the feeling that we could be looking at an unecessarily hot second floor.


A point that he may have overlooked. You look to be using tile (heavy, absorbs, stores and then radiates heat very well all through the night) and some tiles require more than 20 degrees to remain waterproof. So be sure that the tiles you want to use will permit the roof slope.

I have just built a roof with a 14 degree slope and chose a light weight roof that is waterproof down to about 1 degree.

You say you are making the house as cool as possible. If so then you would use white for the roof. This is available in tile if you want.

I have personal proof that the roof colour, by itself, makes more than 15 degrees C difference under the roof.

Insulation will help. I don't know if it can completely eliminate the difference of the heat produced by the colour.
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Re: Hip Roof Pitch

Postby oldmankit » Wed Mar 30, 2016 12:52 pm

Thanks very much, Jerome.

The tiles we have in mind are CPAC monier, and the minimum pitch is 17 degrees for those. (Spec sheet.)

I've seen more and more roofs around Thailand that have white tiles. I just had a look at CPAC's site, and they have some silver and grey ones. I guess these would be almost as good as white.

Could you give some more details about the light-weight roof you just built. What material is that?

I'm still not sure if the pitch directly affects the amount of heat radiated to the house.
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Re: Hip Roof Pitch

Postby schuimpge » Wed Mar 30, 2016 1:03 pm

Pitch might directly affect the heat-buildup, but you can totally neglect the 'pitch-factor'... It is the space below the tiles. More space is better, but venting that area, isolating it both under the tiles and on top of your ceilings (foil or PU-Foam or anything else) that is where you will achieve the biggest gains (or losses) in battling the heat.
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Re: Hip Roof Pitch

Postby oldmankit » Wed Mar 30, 2016 1:05 pm

schuimpge wrote:Pitch might directly affect the heat-buildup, but you can totally neglect the 'pitch-factor'... It is the space below the tiles. More space is better, but venting that area, isolating it both under the tiles and on top of your ceilings (foil or PU-Foam or anything else) that is where you will achieve the biggest gains (or losses) in battling the heat.


Thank you so much. That's abundantly clear.
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Re: Hip Roof Pitch

Postby Sometimewoodworker » Wed Mar 30, 2016 6:10 pm

oldmankit wrote:Thanks very much, Jerome.

The tiles we have in mind are CPAC monier, and the minimum pitch is 17 degrees for those. (Spec sheet.)

I've seen more and more roofs around Thailand that have white tiles. I just had a look at CPAC's site, and they have some silver and grey ones. I guess these would be almost as good as white.

Could you give some more details about the light-weight roof you just built. What material is that?

I'm still not sure if the pitch directly affects the amount of heat radiated to the house.

The closer you can get to white the better the heat performance.

The build thread is here http://bit.ly/NJnewHouse I think the roof starts on about page 13. There are several builds using the same material

I mentioned the roof pitch in relation to waterproofness not in relation to heat. However the more mass you have in your roof the greater the heat storage capacity.

Concrete is used as the main heat store for storage heaters in the UK. They heat up overnight and release the heat during the day. Massive roofs in Thailand have the same function in reverse, heating up during the day and keeping you toasty all through the night :lol: :roll: :roll: :twisted: Of course you can use enough insulation together with radiant barriers so the heat just keeps the next house and birds hot.
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Re: Hip Roof Pitch

Postby iantip » Sat Apr 16, 2016 6:59 pm

oldmankit wrote:I've got an architect who has drawn up a set of plans for our two-storey house. We've been planning on a hip roof with a 30 degree pitch, which seems pretty common here for residential projects.

When he drew up the elevations he said he preferred a shallower pitch: 20 degrees. He said it could save a bit of money, but mainly he felt it would look better. Here's a view of it in 3D that I did using Sketchup:

20 degree pitch.jpg


And the elevation:

20 degree pitch - South Elevation.jpg


If you compare this with a 30 degree pitch, I tend to agree with the architect that the shallower one looks better:

30 degree pitch - South Elevation.jpg


However I've put a huge amount of effort into making this house as cool as possible with as little need for air conditioning as is possible in the outskirts of Bangkok.

I just wondered how much of a difference this would make to the overall temperature inside the house. We plan to insulate the roof/attic well, and will install soffit vents. Neither my wife nor the architect are keen on putting a whirly-bird vent on top, and I just get the feeling that we could be looking at an unecessarily hot second floor.


Hi oldmankit. I would like to add up other option for heat protection and recommend using a light-weight CMU such as QCON or Superblock which you might want to go double-layer for the west wall. Another problem I had was the water tank placed outside without a roof which caused too hot water to shower. Hope this helps.
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Re: Hip Roof Pitch

Postby oldmankit » Mon May 09, 2016 3:15 pm

I'm really grateful for the replies. In the end we've gone for a 30 degree pitch, which I'm happier about, using a silvery-coloured CPAC tile.

Thanks @iantip for the tip about covering the water tank. That's a very good idea. Oh, and We've spec'ed for cavity walls using 7.5cm aerated low-density concrete blocks, so that should insulate pretty well, as well as getting rid of visible columns inside the rooms of the house.

The plans are with the engineer now, so the next stage will be getting planning permission.
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Re: Hip Roof Pitch

Postby pipoz » Mon May 09, 2016 7:24 pm

oldmankit wrote:I'm really grateful for the replies. In the end we've gone for a 30 degree pitch, which I'm happier about, using a silvery-coloured CPAC tile.

Thanks @iantip for the tip about covering the water tank. That's a very good idea. Oh, and We've spec'ed for cavity walls using 7.5cm aerated low-density concrete blocks, so that should insulate pretty well, as well as getting rid of visible columns inside the rooms of the house.

The plans are with the engineer now, so the next stage will be getting planning permission.


I used 30 Degree Pitch for my house "Udon Thani Happy House", although mine is only a single level. Naturally, it takes on a different dimensional look as you get closer to it.

Attached are some views of the 30 Degree pitch roof, from as far away as 50 meters and then up closer around 10 meter. Looks quite steep/high, when viewed 50 - 45 meters away for a single level house and much less prominent when you get up closer, say 10-15 meters. Yours wont look as steep/high because yours is two levels

30 Degree Pitch looks good on a two level House, I wouldn't go less. Suggest that you also have a look at Jomoblues thread, as he also used 30 Degrees and his is a two level House

Hope this given you some idea :o

pipoz
Attachments
View from approx 10 meters (M).JPG
View from approx 10 meters (M)
View from approx 15 meters (L).JPG
View from approx 15 meters (L)
View from approx 45 meters.JPG
View from approx 45 meters
View from approx 50 meter (M)(M).JPG
View from approx 50 meter (M)(M)
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Re: Hip Roof Pitch

Postby oldmankit » Tue May 10, 2016 2:34 pm

Thanks for posting those pictures, Pipoz. I see what you mean about perspective changing as you get closer.

By the way, I really like the design and style of your house exterior, and drive-way.
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