SDN - Design a house

[Korto]

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.

[madd0ct0r]

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

[FireNexus]

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.

[madd0ct0r]

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.


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)

[Korto]

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... 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.

[madd0ct0r]

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.'

[madd0ct0r]

Hey Korto, did you get anywhere with this?

[Korto]

Still working it out, bit by bit.
Our current mortgage will be paid off around the end of next year, at which point we'll be able to start saving up a deposit again.
I've done some looking into it. A carpenter who lives a few doors up from me gave a rough guess that it would cost about $200K to build a basic two-story. I'm looking into the idea of Owner-Building, as you can save around 20 to 30% doing that. Or it can crash and burn horribly. Banks don't like Owner-Builders (something to do with that "crash and burn horribly"), so we'd need a bigger deposit, which will at least save us money on interest.

A demolition guy gave a quote of $23k to clear the yard ready for building, including getting rid of the old garage and all the asbestos. The quote won't be any good by the time we build, of course, but it gives me an idea.
I'm considering aerated concrete panel flooring covered with those big 300mm tiles the shopping centres and supermarkets use, both of which we should be able to install ourselves; and metal-foam sandwich panels for the exterior walls. Then dress it up by sticking some stone facade on the outside. The roof will likely be concrete tiles done to look like slate

The owner-building thing's amusing. To do that here, you've got to have a license, which you get by doing a course. Among the options for the course for the license was TAFE (trades school), who had a year-long course for hundreds of dollars; or some private company who had a few-hour course for maybe it was $30? I think I'll take the TAFE course, thanks, I'm a little suspicious of the second one.

Got a basic house-sketch, and an architect I like the sound of (I have no idea who's good and who isn't, but she's got the same name as my daughter and a nice smile in her picture. Good enough reasons to talk to her). It's going to take some years to get the finances together, maybe six or so, but there is stuff I can work out or even prepare while waiting.

[madd0c0t0r2]

Hey Korto, did you get anywhere with this?

[His Divine Shadow]

Based on my experiences now I'd recommend moving to Scandinavia and live in a log house.

Semi-seriously though, a log house is a good old fashioned design. Most non scnadinavians will probably think of a small log cabin when they hear log house, but log houses can be quite large. From small 50m2 cottages to 200m2 houses with several floors. The massive walls are both insulating and accumulate heat. Additional insulation can be added (preferrably on the outside) and will stand many centuries. Possibly not a good candidate for australia tho, so move!