SDN - Design a house

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Korto
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Re: SDN - Design a house

Postby Korto » 2017-02-02 07:26am

madd0ct0r wrote:As it happens I'm in my father in laws house. This is based in central Vietnam. It's the middle of winter here, and therefore roughly the same temperatures and humidity as Korto described.
If it has days over 40 in winter, I don't want to hear about it.
The bedrooms need aircon in the summer, but that's 40 degrees at 90% humidity, there's not much you can do at that extreme.
Not going to Vietnam. I'm sure it's a beautiful place, with wonderful people, but I don't care, I'm not going.

One idea I would have liked would have been to have a view of the sky from the stairs, so you could just look up and see the stars. Unfortunately, I can't think of any practical way to do it. I think I'd need a pretty big skylight window for a decent view, and to avoid heat coming in it'd have to be special glass, it would take up a lot of roof space (which would be otherwise used by solar panels), and would probably leak sooner or later. I'd be paying a fortune for a whole lot of problems. Clerestory windows probably don't have the same amount of problems--the overhang of the top roof should shield them from summer sun, and from rain, but they also wouldn't give the same view of the sky.
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Re: SDN - Design a house

Postby madd0ct0r » 2017-02-03 04:57am

There are some truly excellent guides to tropical houses.
http://design490.org/tropical-climate-b ... derations/

I can't find the best one I remember, may have been a un or shelter doc, but it had a great graph for air temp vs humidity vs contours of the air speed (fan) needed for comfort
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Re: SDN - Design a house

Postby FireNexus » 2017-02-03 11:12am

You might, if you can afford it, consider a ground source heat pump. With the flooding you describe, you likely have a fairly high water table, too. So a standing column well or dual purpose well (if you use well water) might be possible. Even if not, you're going to need to excavate somewhat regardless to get your stilts going, you may as well dig an additional hole and bury a closed loop while you do.

The system will be fairly costly to start with, but they're extremely high efficiency cooling systems that can save you a ton of energy down the line. And unlike airspurce heat pumps, they don't lose efficiency as the temperature outside increases. Since you're going to have solar electricity as a supplement, you'll be more likely to be able to essentially run your AC for free during peak demand times, since you won't have an inverse correlation between your generation capacity and your cooling efficiency.
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Re: SDN - Design a house

Postby madd0ct0r » 2017-02-05 08:07am

OK!
We have better than a chart of comfort zones for different indoor wind speeds and humidities - we have an interactive tool!
http://comfort.cbe.berkeley.edu/EN

What we can do with this is build up a few scenarios. Possibilities:
summer nightime, what fan speed is needed for comfort for sleeping people, is that a sensible speed?
winter early morning: is it chilly, or do we still need the fan?
Summer hot rain: extreme air temps and extreme humidity combine. what air speed do we need?
Summer rain: with lower summer temps, but higher humidity, what air speeds are we looking at?
Summer cooking: with the extra humidity and heat and activness in the kitchen, what additional comfort is needed?

Vica versa, for the above cases and humidities and sensible fan speeds (or local off shore breeze), what temp do we need to keep the living space below for it to remain comfortable?

Basically, we use these to flesh out the design envelope, and get a feel, in numbers, for how different the different cases all are.


Now this image is pretty useless for design purposes, but it's a good checklist of ideas to work down.
http://terra-pacific.com/wp/wp-content/ ... 1-B-01.pdf

The aussie goverment has developed a really nice set of guides, actually.
Image

http://www.yourhome.gov.au/passive-desi ... ve-cooling
Temperate climates (Zones 5 and 6)

With good design, temperate climates require minimal heating or cooling. Good orientation, passive shading, insulation and design for cross-ventilation generally provide adequate cooling. Additional solutions from the range explained here can be used where site conditions create higher cooling loads.

Design for compact form in cooler zones, extending the east−west axis in warmer zones (see Orientation).
Prefer plans with moderate building depth — two rooms is ideal.
Design for the impacts of climate change and consider highly efficient heat pump systems to cope with increases in extreme weather events.
Use thermal mass levels appropriate to the amount of passive cooling available (cool breezes, consistent diurnal variations) and use thermal mass to delay peak cooling needs until after the peak demand period.
Choose window opening styles and position windows to ensure good cross-ventilation.
Orientate for passive solar heating and divert breezes.
Employ larger northern and southern façades.
Design for moderate openings with the majority to the north.
Use minimal west-facing glazing (unless well shaded).
Use moderate east-facing glazing and moderate south-facing glazing except where cross-ventilation paths are improved by larger openings.
Use bulk and reflective foil insulation.
Use low to medium U-value and SHGC glazing in milder areas and double glazing where ambient temperatures are higher.


Why am I focussing on this?
Becuase 1) you'll have hot summers every year, floods are far less common, so should be the secondary consideration
2) Becuase most of this defines the outline of the house - the rough shape. That, and the anti flood design, will inform the construction methods used. (i've been thinking it over and I'm really unsure strawbale is the way forward for you in this climate and with the risk of a flood entering the bales. The wall is going to rot, even based on air moisture alone. You won't get your design life achieved)
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Korto
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Re: SDN - Design a house

Postby Korto » 2017-02-10 07:24pm

I'm not concerned about a flood entering the bales, because I'm not having the bales at ground level, they'd be up at the "living" level, 2.5m up. Otherwise the bales would definitely be ruined after the first heavy rain (something we've had every few years).
That won't help against humidity, however, so I will need to find out if that will be a problem.

The ground floor I'm thinking of Styrofoam panels between the posts, taking the role of insulation and physical barrier, with a "water wall" of water-filled plastic bottles behind as a thermal mass.

I'm having trouble using that interactive comfort-zone. I'm using the Adaptive model, and it's asking for the mean outdoor temperature. Do you know if that means during the day only, or the entire 24 hours? Because it only goes up to 30C, and if the temperature didn't go over 30C during the day, there wouldn't be a problem. And Mean Radiant Temperature... :wtf: I don't know. Who the hell knows that?

Whether I could fit a two-room deep house in the right orientation is questionable, although I could have a look when it cools back down. It's a bit warm here at present.
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Re: SDN - Design a house

Postby madd0ct0r » 2017-02-11 06:19am

Mean radiant temperature is the weighted average of the temperature of the surfaces around you.

basically. The temperature of the walls ceiling and floor,weighted by area.
Cold floor helps balance out hot roof. Shaded walls helps balance out sun box walls ect. I had issues with one house in Vietnam where the walls stayed cool, but if you opened the curtains the floor got really warmed up and stayed warm.

Mean outdoor temperature - yeah take as 24 hours and maybe take a second set of results at thirty.'
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