Housing - New Build: Passive solar on the equator.

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- CommentAuthorSimonH
- CommentTimeSep 7th 2011
Hi All,

Apologies for the long post, but its a bit out of the ordinary and needs some background...

I am upping sticks to move to Kenya later this year. Will be living at 1850m altitude. Sunny and warm by day, cool at night. Think British summer all year round, but the nice days. Probably no more than 1 or 2 km either side of the equator. So all the advice for passive solar I've read says put your windows on the south if you are northern hemisphere, a or vice versa. But what if you are on the equator?

The background... the sun angle will move throughout the year - getting used to unusual Solar azimuths charts have hurt my head - but sun comes at 90 degrees over head in March and September, and then 65ish degrees N in June 65ish deg S in Decemeber. Sun rise is 6am every day and sets 6pm every night (so it will be dark when I eat dinner unless I can change my routine and get up to catch the rising sun :-) (Sunrise and sunsets are why I fell in love with the country - well the people too).

There doesn't seem to be a strong weather pattern - above 20degC all year in the day, and above 12C at night. Coolest highs are July and August (20 degrees) and least sunny is May with just 6 hours a day, LOL. All the other months average 8 or 9 hours. Hottest is Feb and March with 26/27 averages. So no real variations thru the year.

They do have something called the small rains (Oct) and big rains (Apr/May).

There's a nice views of mount kenya to the east from most parts of the town (Nanyuki). So likely to want to make use of that. Or a range of hills to the north west.

So with that knowledge, things I've considered... get the glass on the east so it gets a heat top up in the morning (and views of the mountains) . And shade the west so it's not too hot later in the day on the hotter months.

Or... get glass east and west and stick a breakfast kitchen in the east and stick a living room in the west so you get heat in the rooms you are most likely to be using as the time of day when its warm.

One other factor - my other half likes to be very warm. She's kenyan, and when she was in the UK - she would leave the electric fire on in the lounge till it was 27 degrees and I was sitting in my pants :-(. I think I have to deal with the psycholoigical effects of heat... reducing air movement and increasing radiant heat. I'm most likely to build using rammed earth or more likely compressed earth blocks with a straw cavity - as otherwise the house will need top up heating (wood is used almost exlusively for this - but they have had terrible deforestation). I'd like to try and avoide the need for heating given the climate. The soil colour over there is a beautiful orangey brown so will make great feature rammed earth trombe walls. Labour is cheap, embarrasingly so... I've "upset" people by giving them a Ã‚Â£2 tip which is like a days wages. A labourer can be had for Ã‚Â£50 a month. ???!!! (It seems so low I feel compelled to pay more but I've been advised against it, so instead will provide a suprise bonus at the end!) Anyway - it makes eco building the cheapest, fastest and most sustainable, and hopefully I might be able to get the locals to avoid using concrete blocks that seem to be the vernacular! Shipped in from the cement works 150km away! Hmmmn. If it all works as planned, I'll be building a whole eco village from what I learn.

Any ideas / suggestions. Further reading etc? Specifically Looking for how to deal with passive solar on the equator.

Cheers.

Simon.
- CommentAuthorSimonH
- CommentTimeSep 7th 2011
Sorry forgot the other option - orient the house diagonally so the passive solar gain is recieved on the north east. This would pick up sun more in the "summer" months, when it's cooler there. But keep the sun off the "heat collectors" in the afternoon, and still give decent views.
- CommentAuthortony
- CommentTimeSep 7th 2011
I dont think you want passive solar gain! insulate the roof well and even think about a kind of double roof with a ventilated fly sheet to help keep roof solar heat up to a minimum.

solar thermal for hot water, oversize it and could be used as a heat source for those cooler evenings?
- CommentAuthorSimonH
- CommentTimeSep 7th 2011
Good point - active solar heating would be a much better and controllable option! Back to the drawing board. :-( At least it gives me more flexibilty on room layouts though.

Trouble is - they tend to have about 5 powercuts a week, between 6 and 9pm (when it's dark and everyone is switching on their electric immersion heaters).

Oh well, I just need to get a plot nowhere near an electric line to justify offgrid PV to myself to run the pumps.

I wonder... a large basement store of water - with some kinds of bimetallic strip thermostat valve - to allow convection to flow the water into above basement floor heating. No pumps = Less PV, less batteries.

As a side note, I've been reading horror stories of trying to import anything zero rated for VAT. Their customs seem to think that unless they get some money, then something is wrong. You end up having to get a letter from the ministry of finance and bullying the customs guys in to releasing your shipment. And plan for 4-5 weeks of delays and runing around between different departments and flying back and forth between mombasa and nairobi. Hmmmn. Not good if its meant to be a low carbon build!
- CommentAuthorSimonH
- CommentTimeSep 7th 2011
Aha - this is sounding good - coz I need to dig a big hole to get the earth for the walls. May as well be a basement!
- CommentAuthorSteamyTea
- CommentTimeSep 8th 2011
What are the local houses like? Do they use a lot of thermal mass? or are they low mass timber.
Did you see the BBC Documentary 'Altitude, Alcohol And Adultery', that was about Kenya.
- CommentAuthorJoiner
- CommentTimeSep 8th 2011
ST - Was it a DIY programme on those topics?
- CommentAuthordjh
- CommentTimeSep 8th 2011 edited
I'm not an expert on tropical building though I am familiar with the tropics. There are a few sources of information I can think of:

* The Australians have a manual that covers different climate regions http://www.yourhome.gov.au/technical/index.html

* There's lots of US publications that will be relevant since they have a variety of hot climates. For example: http://www1.eere.energy.gov/buildings/building_america/index.html

* There are Mediterranean designs for passive houses, so searching for that might be useful. For example http://www.passivhaustagung.de/Passive_House_E/PH_MedClim.html

One topic you didn't mention was humidity. There's a huge difference between a hot, humid climate and a hot, dry one. (e.g you can use Frank Lloyd Wright's 'water fire' in a hot dry climate).

I agree with Tony's suggestion of a double 'fly' roof. Generally, large overhanging roofs and high ceilings are useful. The overhangs also work well with clay walls.

There's a lot of historical precedent for passively-cooled buildings in Persia and India etc that may give you some useful ideas.

You may find compressed stabilised earth blocks to be useful. This is earth, mixed with a little cement, compressed in a small press and dried in the sun. It can be a local craft industry and you can also make tiles this way. There are small firms and development agencies that produce the tools. Try googling "stabilised earth blocks" (without the quotes) for lots of interesting links. "stabilised earth tiles" is also good - timbrel vaulting would make a good roof!

edit: I forgot, there are different types of glass for the different aspects. Varying transmission and U-values. The Australian docs are good on that subject, IIRC
- CommentAuthortony
- CommentTimeSep 8th 2011 edited
I love thatched roofs too in this environment, cool in summer warmer in the night, use local materials and labour.

Use a steeper and it will last longer, 55+ degrees will last almost for ever
- CommentAuthorSimonH
- CommentTimeSep 8th 2011 edited
Posted By: SteamyTeaWhat are the local houses like? Do they use a lot of thermal mass? or are they low mass timber.
Did you see the BBC Documentary 'Altitude, Alcohol And Adultery', that was about Kenya.

Sadly 60% of people still live in what we would refer to as a garden shed. Either made from rough cut timber, or corrugated steel, or occasionally - sticks with plastic bags and mud hand plastered over. The "temporary" sort of stuff you've been seeing on the news in northern Kenya but most towns have areas like it. Execept temporory seems to mean - till it needs fixing. I'm hoping to do something about that once I've built my own place and a few more like it to get the capital I need. I'm reminded of projects I've seen in the UK where people get help to build their own homes and learn new skills in the process. Where people most people see poverty and desperation, I see an opportunity to make things better, and earn a living too. Today's people living in poverty are next years working class. My biggest problem is getting cash to flow into Kenya from outside. But I think if I can demonstrate annual returns of 20% or more then friends and family etc will pour in some extra money.

The middle classes - well I'd say most of the earlier pre 1960's buildings are stone (think crazy paving) or timber. And post 1960's are a mix of brick or concrete blocks. Often left unrendered for a nice dull grey effect. :-(. Ocassionally timber is used, but I think they see it more as a fuel source than a construction material. Plus if there's a public disturbance it's harder to set a stone house on fire. (I expect it to kick off again late 2012 after the next elections down on the coast - wanted to move there, but it's like a touch paper). So yes most have decent thermal mass. Even down to tiled floors. I've noticed the posher houses have large overhangs fo rthe shade. But also everyone has a woodpile and smokey chimneys. Isn't it weird how much you notice when you are interested in building!

One thing I'm really worried about and will be hoping to educate the local tradesmen on is site safety! I Was looking at some of the buildings going up last time I was there. Scaffolding was loose cut trunks - no problem with that, but there was no safety guards, access controls to site, or protection for the public. (All kids like to play on building sites when the workers go home right!?).

Regarding the documentary - I'll have to check it out (I have access to the full BBC catalog at the moment). But there are problems. The town has a british army base and a kenyan airforce base. And lots of young girls ( like from 12 years and up !!!) who need money. So you can guess what happens in the bars on Friday and Saturday nights! Not a quick problem to fix - but my other half has ideas there. (But secret LOL!).

I expect to have problems: getting supplies, beauracracy (bribery even), workers who understand, etc. But why let that put you off! All my life I've been solving problems - just in a different way.
- CommentAuthordjh
- CommentTimeSep 8th 2011
Posted By: SimonHAll kids like to play on building sites when the workers go home right!?

Right, I certainly did it as a kid. But how's climbing scaffolding any more dangerous than climbing a tree? You obviously want to lock up tools and equipment, but I can't think of anything else on a building site that is more dangerous than you find in the country. Holes, cliffs, trees, deep water, rocks to throw or knock over, sticks to beat things or people, dirt to eat.

As a work site, there are risks, but as a playground?
- CommentAuthorSimonH
- CommentTimeSep 8th 2011 edited
Posted By: djhYou may find compressed stabilised earth blocks to be useful. This is earth, mixed with a little cement, compressed in a small press and dried in the sun. It can be a local craft industry and you can also make tiles this way. There are small firms and development agencies that produce the tools. Try googling "stabilised earth blocks" (without the quotes) for lots of interesting links. "stabilised earth tiles" is also good - timbrel vaulting would make a good roof!

That's exactly what I was thinking. Rather than just making some blocks for me. Get someone else to start making them and help them get a business running.

Posted By: djhOne topic you didn't mention was humidity. There's a huge difference between a hot, humid climate and a hot, dry one. (e.g you can use Frank Lloyd Wright's 'water fire' in a hot dry climate).

Hmmn, it's not sweltering neither is is desert. Again a bit like the UK - in that it changes depending on the direction of the wind and cloud cover. Would say it's slightly more on the moist side - when the wind comes from the west - mount kenya squeezes all the rain out. Last time I flew in I had a beatiful sight... cloud cover was heavy, but poking it's head up above the clouds was mount Kenya with a clear gap of about 10 km all round. When I got up there the next day it was similar conditions, and it was raining on and off. Just like back home. LOL What's this "water fire". Been trying to google it but not getting the right mix of words to find anything.

Starting to read your links, I'm realising one thing... I need to start learning from scratch, forget summer and winter, and deisgn for the location. Which means getting more accurate daily data and looking at degress days etc. It makes me think I should get a uni over there involved as a project for a final year architecture student as they hopefully will have been looking at how to design for their local environments.
- CommentAuthorSimonH
- CommentTimeSep 8th 2011 edited
Posted By: tonyI love thatched roofs too in this environment, cool in summer warmer in the night, use local materials and labour.

Use a steeper and it will last longer, 55+ degrees will last almost for ever

I would - except for the tendancy for people to still throw burning torches on them over there! This is one area, where I'm going to compromise ideal and aesthetic for - security. I don't even think they have a fire station in town!

I've done my research on the political situation since the post 2002 and 2007 election violence and things still haven't been sorted. There's a lot of resentment on the coast and in Naivasha about common ancestral land being put in to trust by the british govenment, which was then sold off to private friends and business acquatances by the first post independence government. So now you have foreign - and other other tribal groups owning "Your" land and making moeny, whilst you live in poverty. Always a recipe to allow politicians to exploit the voters making promises and then claiming the election was a fix. That's why I decided to steer clar of any tourist business - at least until 2013! A court case is going through the hague now of those who were accused of orchestrating the violence, but I think it will fall apart.
- CommentAuthordjh
- CommentTimeSep 8th 2011
Posted By: SimonHWhat's this "water fire".

It's a device to increase humidity indoors whilst providing ventilation. It consists of an open fireplace/pool with a fountain in the middle, all under a chimney. The water spray cools and humidifies the air which flows out into the room and more air is sucked in down the chimney. I don't remember where he used it.

Posted By: SimonHIt makes me think I should get a uni over there involved as a project for a final year architecture student as they hopefully will have been looking at how to design for their local environments.

I expect you could also involve development agencies and/or European universities looking for international collaborations to qualify for grant money. It might also bring a lot of red tape for variable benefits though!

BTW, a hint: when you post quotes, choose Format comments as Html. If you post URLs choose Format comments as Text. Sadly, you can't do both.
- CommentAuthorRobinB
- CommentTimeSep 8th 2011
Adobe? - Wikipedia has a good global view of the subject and some good links.
- CommentAuthorwookey
- CommentTimeSep 9th 2011
Starting to read your links, I'm realising one thing... I need to start learning from scratch, forget summer and winter, and deisgn for the location

Exactly. Reading your initial mails I thought 'this man is still thinking like an englishman about heating and solar gain'. You need to forget all those background assumptions we have here about heating as well as the ones about orientation and humidity being on the inside - check your asssumptions carefully :-) As djh said - look at info for the relevant climate.

It does sound like you won't need much heating at all, with cooling more of an issue, and clearly it should be relatively easy to design a passivehouse for such a benign and stable climate. And with labour 1/30th of the price of here and fancy tech hard to get that does lean you heavily in the direction of local materials and low-tech massive designs.
- CommentAuthordjh
- CommentTimeSep 9th 2011
Here's another link I remembered, to a pretty impressive organization:
http://www.earthbuilding.info/index_gb.html

And they have a bunch of links to more :)
http://www.earthbuilding.info/gb/07_links/07-2_links_resources.htm
- CommentAuthorSimonH
- CommentTimeNov 3rd 2011
Well, I've just got back from another trip. Have finally bought land which has views of mount Kenya and the Aberdares (just). I've given up on trying to design a house... There's no real concept of summer or winter, but nights get cold as it's 6000ft above sea level. Some days are pretty cool too when theres cloud cover.

However - it's got some of the higest average solar raidation in the world - 7kwH/m2/day. I think actually it needs active solar. Becuase with passive - there will be days when it overheats - however you decide to design the overhangs for shading. That might be active louvering, or using solar thermal with a 5-7 day heat bank to cater for worst scenario. I'd love to design it myself but, really want to get the thing built and then try a different design with a follow on and see which works best. So...

I've decided to see if I can get a local uni involved and let them run a competition. Most people out there are still building with concrete and including open fires. So using earth walls with solar heating will be a nice change. I'd like to try and use bamboo for the timber - as a few people have taken up the governements initiave and started growing it as an alternative to chopping down their native forests.

Whilst I was there did some tests on the soil - and it compresses well, doesn't crack when dropped, but has too much silt content and not enough sand. Luckily ,theres part of the land that has a lot of sand on it, so it will just require some mixing. I'm also going to have to truck in a small amount of red earth, as the part I'm only is mostly black volcanic soil - which won't be very pretty. First test will be for a small "caretakers" cottage.

It's only 1km from electricity so it's tempting to get grid connected - only Ã‚Â£230. However in 2 weeks there were about 25 powercuts, so I will need battery storage and inverters anyway, epsecially if the missus wants to watch a whole episode of X-Factor USA :-( They don't have fits for domestic, only people with more than 50KW upto 50MW. But with that much radiation - fairly evenly spread through the year, I'm sure I won't need many panels.
- CommentAuthordjh
- CommentTimeNov 8th 2011
Posted By: SimonHHave finally bought land which has views of mount Kenya and the Aberdares (just)

Congratulations! And good luck with your building project.
- CommentAuthorEd Davies
- CommentTimeNov 12th 2011
This project in Botswana might be of some interest: http://www.rammed-earth.org/botswanaproject.htm

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