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Courtyards for climate control

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Started 4 years ago by Catopsilia
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Catopsilia
Member

Does a courtyard improve comfort?

Courtyards have been built next to private houses for thousands of years. According to wikipedia, houses with a central courtyard were built in ancient times in China (siheyuan), Rome (domus), the Middle East and the Andes.
Courtyards are private open spaces shielded from public view and intrusion. They are often decorated, planted and furnished for quiet enjoyment.
Courtyards have various functions, but my interest is in one function only: the control of climate for human comfort, both within the courtyard and within the house. I hope members will want to share ideas, techniques and projects for using a courtyard in this way.
As I mention below, courtyards do not always improve climate control. Perhaps some members may have experienced courtyards that perform poorly, and what can be done to correct that.

Baruch Givoni's work

The authority in this field is Baruch Givoni. In his textbook "Man, Climate & Architecture" (1969, 1981) he explains the principles that apply, but does not analyse the use of courtyards. His later book "Passive and Low Energy Cooling of Buildings" (1994) does analyse courtyard performance. The final chapter "7. Cooling of Attached Outdoor Spaces" (pp.239-257) contains a wealth of advice.
Givoni's work, as shown by his chapter title (and book title), is concerned mainly with making courtyards cooler in hot, dry climates. Readers of this forum who plan to live where summers are hot and dry may consider enclosing courtyards if they can be kept cool without much energy use. In that chapter Givoni does not pursue the idea that a cool courtyard can be the source of cold air to cool the house during summer nights (nocturnal ventilation, or night purge). In other chapters he discusses nocturnal ventilation using cold air from various sources.
Givoni cautions that the use of courtyard houses through millennia in desert regions does not mean that a courtyard always improves comfort there. The passage can be found by searching (One time only!) on "givoni issues specific to adjacent outdoor spaces".

Other authorities

I have not found any detailed advice on designing or using a courtyard for climate control except that of Baruch Givoni. Steve Szokolay, in "Introduction to Architectural Science" (2004), page 68, recommends attaching courtyards to Australian houses in "hot-dry climates". His brief review echoes the advice of Givoni.
It is strange that no courtyard tradition exists in Australia, since several of the climate zones are especially suited to them. The authoritative web-site "www.yourhome.gov.au" is dumb on this topic.
Nick Hollo's book "Warm House Cool House" has a section on "Courtyard Houses". He says: "It is particularly beneficial in arid areas, where the courtyard can nurture a lush garden in contrast with the harsher surroundings, and provide cooled and moitened air to adjacent rooms." Here and elsewhere in the book he cites examples of houses with courtyards. To my mind, hardly any of them would function well enough to change the indoor climate.

My courtyard project

Recently, I had the small courtyard shown here built around the back door on the south side of my house. Every feature of this courtyard was intended to improve the climate indoors.
I have described the courtyard, with photos, and explained its function in my blog:
https://climatebysurly.com/2016/07/21/my-heat-control-courtyard/
There is much more about it on a special page:
https://climatebysurly.com/my-house-page/a-heat-control-courtyard/

I am monitoring its performance with thermometers, and will report the results as they come to hand.

Posted Thursday 21 Jul 2016 @ 1:14:58 pm from IP #
Catopsilia
Member

My climate-control courtyard is on the shady south side of the house. There are good reasons for this, but there is a catch.
Due to the sun angle, the house shades the courtyard longer and more deeply in winter, when I want it warm, than in summer, when I want it cool.
I am taking steps to fight this effect. Perhaps others have suggestions?
There is discussion on reducing summer courtyard heating here:
http://www.ata.org.au/forums/topic/45970
There is discussion on increasing winter courtyard heating here:
http://www.ata.org.au/forums/topic/138

I have considered the idea of deciduous plants that lose their leaves in winter. I don't think they do much good. Only the leaves fall, leaving a lot of shade due to the trunk, branches and twigs. Worse, the leaves don't fall much earlier than the winter solstice: for half the cold season their shade persists.

Trees, not necessarily deciduous, can be placed to shade the courtyard only in summer. In developed suburbs, you are unlikely to be able to do this. Living in a small town, I have been able to plant a eucalypt in a neighbour's yard. Being in the east-south-east, it shades my courtyard and kitchen from summer morning sun. (That tree, planted about 2002, features in the photo in the Opening Post, above.) This year, I planted a kurrajong in my own block to the west-south-west of the courtyard. In a decade, it will shade the courtyard from summer evening sun.

Posted Monday 8 Aug 2016 @ 2:45:34 am from IP #
Greg C
Member

My Dad's house, designed and built very well from a passive solar house perspective was extended around a rear deck which of course became a courtyard. The problem of course is we now had east and west facing windows which the house did not have before. That is the first thing to check, as the courtyard could possibly have windows on any side is or will there be any unwanted sun entry and take steps to mitigate that. As originally built it was shaded by a pergola over the top, and filled with pot plants. It was a nice source of cool air most times and helped in the cross ventilation of the extension.

I think a shaded area on the southern side of a passive solar house would be a very good addition, as a cooler place to live in hot summer afternoons and maybe provide a cooler source of cross ventilation as well. It doesn't really fit my definition of a courtyard, unless you enclose with external walls. I wonder of the benefits of this from a climate perspective, as if the outside conditions are very hostile the house should be closed up. Based on Dad's house it made a noticeable difference when outside conditions were suitable ( breeze, not too hot). This is quite common at the end of a hot summer day in Sydney so it worked.

I don't see any possibility of generating heat and transferring it to the house. There are other ways to do this that aren't courtyards and would be more efficient. Their traditional use is to provide comfortable outdoor living in hot weather, if they can also help cool the house that could also be a bonus.

Posted Monday 8 Aug 2016 @ 8:50:25 am from IP #
Catopsilia
Member

Hi Greg C
Thanks for joining in.
I am guessing a bit about the details of the courtyard that was formed by the extension of your father's house. My first guess is that the front of this solar-passive house faced north, putting the original deck and its pergola on the south side. Did the east and west facing windows open on to the former deck? Wouldn't that mean that the two wings of the extension would each provide some shade to the windows of the other? (The west-facing windows of the east wing being shaded by the west wing and vice-versa.) If the pergola was retained, didn't that shade the windows too?

You then discuss the benefits of shaded areas on the southern side of a solar-passive house. In my town, while solar-passive houses are rare, shaded (and insect-screened) areas on the south side of houses are very common indeed. Like you, I would not call them courtyards, because they are not enclosed by walls. They are a kind of verandah.

I think there may be ways of generating heat in a courtyard and transferring it to the house. I am experimenting with that. As you say, there may be better ways to do it without a courtyard. Every house site, with or without a house already on it, has its own limitations and possibilities. A courtyard could work.

Posted Sunday 14 Aug 2016 @ 9:18:56 am from IP #
Greg C
Member

The deck on Dad's house was on the north side. It wasn't very big so yes the wings did provide some shade, but the pergola over the top was needed. The kitchen moved into the extension into the eastern wing and sun getting in there in the early afternoon on a summers day was not pleasant, hence the pergola. There was access from the kitchen and family room in the west wing to the deck, the latter with floor to ceiling glass.

The pergola used angle cut boards that still allowed sun into the old part of the house. It wasn't really a passive solar house, just my mother grew up in the old house on the next door block and there a was sitting room with large windows facing west. She said it made the room unusable so when they talked to the architect, he took that in and what was built was a long skinny house in the east/west direction with no windows on the west or east walls. Eves on the northern face with several big windows but it also had floor to ceiling glass on the southern side because that was where the view was. We moved in in 1955. I owe it to my mother for my interest in passive solar houses.

Forgive my but I am a bit of a fundamentalist when it comes to passive solar. I wince whenever I see west or east facing windows, do we really need them etc. However in the extension we did on our house we had to put a small window on the west wall for the bathroom. I got away with it because it is very close to a vertical rise with plenty of shrubs and trees on top. On really hot days the white internal venetian blind provides additional defence. Killed the purity of the house though, however the local microclimate allowed it to work and as you say, that is unique to every house.

Posted Monday 15 Aug 2016 @ 6:28:05 am from IP #
Catopsilia
Member

Courtyards need walls

A private open space can hardly be called a courtyard if it is not surrounded by walls. People built courtyard walls to protect themselves from the world outside: from wild animals, and from people who were hostile, criminal, uncouth, dirty, or simply different: outsiders, not insiders. Courtyard walls keep outsiders out (as in a castle) and insiders in (as in a prison).
Once built, courtyard walls were then found to protect those inside from harmful aspects of climate: from strong winds, from sand and dust, and from extreme heat and cold. Within a courtyard there is a "microclimate" that is different from the climate outside.

That is what I would like to discuss.

To my mind, the courtyards of houses described in Nick Hollo's excellent book "Warm House Cool House" are unlikely to have much effect on house climate because they do not have walls that function to isolate the climate within them.
Courtyard walls need doors or gates in them to let people and animals through. When closed, these doors must form just as much of a climate barrier as the walls do. On the other hand, opening the doors can open the courtyard to the outside climate when it is better to do so.

Posted Friday 26 Aug 2016 @ 9:34:24 am from IP #
Catopsilia
Member

Katabatic flows in courtyards and other living areas

Some of the climate effects of courtyards are due to katabatic flow.
Katabatic flow, or cold air drainage, occurs when air cooled by contact with a cold surface flows down the slope.
Katabatic flows are well understood. The most striking example is the blizzard of air that pours off the frozen Antarctic continent (see google images). In Australia, katabatic winds flow down from ranges of hills in the pre-dawn hours whenever winds are light. The animated maps of EarthWindMap show this clearly:
https://earth.nullschool.net/
For houses that could have courtyards, we are concerned with katabatic flow off roofs or higher ground in areas of hectares or less. At this scale, things are simpler. Cooled air flowing down a slope will warm up ("adiabatically") as it gets lower. However, it warms at the rate ("DALR") of just one degree per hundred metres of height loss. In air that descends only a few metres, this warming is too small to detect.
Small-area katabatic flow, as cold air drainage, affects horticulture, particularly in giving rise to "frost hollows" or to "flow frosts".
http://www.weatheronline.co.uk/reports/wxfacts/Frost-hollow.htm
Courtyard walls, as well as steel-sheet boundary fences and the walls of houses, will affect cold air drainage. They can be arranged to improve the microclimate for comfort.

Posted Thursday 15 Sep 2016 @ 12:07:13 am from IP #
Catopsilia
Member

A book about courtyard houses

I have found a comprehensive book about courtyard houses, published ten years ago:
Edwards, B. et al. (Eds.) (2006) "Courtyard Housing Past, Present and Future". Abingdon, Oxon: Taylor and Francis.
http://www.academia.edu/12290858/Edwards_2006_Courtyard_Housing_Past_Present_Future
https://www.amazon.com/Courtyard-Housing-Past-Present-Future/dp/0415262720
The book is an edited selection of papers from an international conference held in Homs, Syria, in 2004. (That was before Syria's crippling drought, collapse of its oil production, and civil war.) The conference speakers came from Britain and eight other countries, mainly in the Middle East and North Africa (MENA).

The book title reflects the three-fold aim of the conference. It was:
(1) to review the history of courtyard housing and its benefits,
(2) to point out how courtyard houses have fallen from use, except by the destitute, and
(3) to propose that new courtyard houses should be built to allow living in some degree of comfort in hot dry climates without wasting scarce energy.

History and benefits

Speakers from the Middle East told how courtyard houses developed for much the same reasons in their different countries. A walled enclosure gave protection from heat, wind and sand. Equally or more important were the social benefits. By inclination, and in accord with Islam, the courtyard gave privacy to the family, especially to the women, and encouraged social activity within the family. Others were very welcome, but only as guests, and some rooms were not open to them.
I wonder whether the absence of a tradition of courtyard housing in Australia may be due to a lack of interest in privacy and in social life within the family?

Courtyard houses not now built

Oil has made middle eastern countries suddenly enormously wealthy, and has brought them great trouble. Those citizens now able to afford modern housing can also afford continuous indoor climate control by Air Conditioning. As a result, utterly unsustainable types of housing dominate.

Courtyard houses for the future

Several speakers proposed that intensive architectural effort should be applied to adapt the courtyard concept for improved low-energy, socially supportive houses in the future. They pointed out that some modern houses that include courtyards "for show" have not been well thought out, and function poorly.

Posted Friday 14 Oct 2016 @ 9:00:33 am from IP #
architect_yourself
Member

Hi there,
I have just stumbled upon this thread - some great info in here.

I too am a big believer in courtyard houses both from a climate control point of view but also a privacy and safety aspect. For me they are a perfect solution for battle-axe blocks and tight urban sites that might be overlooked from various aspects. As we continue to densify our cities, courtyard houses need to be considered even more.

For me a courtyard house allows every room to have direct access to private open space and, more importantly fresh air. Adding a courtyard to the centre of a house usually allows for fairly shallow rooms around it which allows for great solar access (when required) and natural ventilation.

Id love to chat about this more!

Posted Thursday 17 Nov 2016 @ 3:53:24 am from IP #
Catopsilia
Member

Hi, architect_yourself
It strikes me that a typical McMansion now occupies so much of its urban housing block that the surrounding space is no bigger than a Middle Eastern courtyard. Many fences, too, are not much different from courtyard walls, when they are panels of 1.8 metre pre-painted steel or even polystyrene sandwich.
However, a garden with a high opaque fence is not the same as an interior courtyard. I am not familiar with building regulations. Don't they usually prevent a property boundary wall from being a house wall? Aren't roof eaves prohibited from overhanging the boundary?
Now that new houses occupy so much of their housing blocks, surely it would make sense to encourage taking the house walls right out to the boundary and having all the outdoor space as one or more courtyards within the house. That is how it was millennia ago.

Posted Saturday 19 Nov 2016 @ 6:17:27 am from IP #
Catopsilia
Member

Sun-trap courtyards

Because so many courtyard houses are found in desert climates, much that is written about them relates to providing coolness. Keeping cool in hot weather is required in Australian summers. However, in Australian winters the courtyard should be a warm place.
When I showed my newly-built courtyard and its mirrors to an architect friend he said "It's a sun-trap!"

My three sun-traps

The term "sun-trap" is in dictionaries, and there are various kinds. "Solar gain" is a similar idea, but "solar gain" usually refers to indoor spaces and "sun-trap" to outdoor spaces.
I have said that my west-facing upstairs veranda (or "talar") forms a sun-trap in winter, so long as its south-facing awning is fastened down.
https://climatebysurly.com/2016/08/13/porch-is-a-breezeway-or-a-sun-trap/
I call my small enclosed entry porch with its full-height north window a "sunporch". Because it is not part of the living space of the house, but a source of air that has been heated by the sun, it could perhaps better be called a "sun-trap". The intentional over-heating of the entry porch is documented here:
http://www.ata.org.au/forums/topic/2285#post-20059
Finally, my courtyard is a part of the garden that has been enclosed to form a "sun-trap" in winter time. A full description of the way the courtyard operates is here:
https://climatebysurly.com/my-house-page/a-heat-control-courtyard/
The use of mirrors to direct the trapped sunlight is here:
https://climatebysurly.com/2017/03/16/mirrors-to-reflect-the-sun/
Like most sun-traps, my courtyard not only catches and traps sunlight, but also gives shelter from cold winds.

Posted Thursday 18 May 2017 @ 2:54:10 am from IP #
jdaley
Member

Interseting topic

Posted Friday 23 Jun 2017 @ 10:10:39 am from IP #
Catopsilia
Member

My courtyard now has solid gates AND wicket gates

Courtyard gates, to be effective in climate control, should be tall and wind-proof. At some times it may be better to let the wind flow through, yet one may still need to keep dogs or small children either out or in.
To achieve that flexibility, I have had wicket gates installed as well.
https://climatebysurly.com/2017/08/07/courtyard-wicket-gates/

Posted Monday 7 Aug 2017 @ 10:06:59 am from IP #
Catopsilia
Member

A serious attempt by researchers at the University of Seville, Spain to model the airflow patterns that heat, cool and ventilate courtyards and the buildings around them:
http://www.mdpi.com/1996-1073/5/7/2381/htm

Posted Friday 2 Mar 2018 @ 2:07:07 am from IP #
Catopsilia
Member

Courtyard gates affect temperature

In late autumn, my heat-control courtyard should prevent the south side of the house from getting as cold at night as the other sides of the house do.
The courtyard has solid gates that completely enclose it to a height of 1.8 metres. I am trying to find the effect of these gates on the courtyard temperature. I keep the gates open or closed for a month at a time. For each calendar month I alternate between open and closed in successive years.

I have some preliminary figures for the month of May.In May months, the normal indoor overnight minimum in my (unheated) house is 21° and the normal outdoor ("Environmental") overnight minimum is 6°.

The figures here are daily minima from two Gill screens, one in the Courtyard and one ("Environment") ten metres north of the house. They were recorded in 2016 (Gates Opened), 2017 (Gates Closed) and 2018 (Gates Opened).
I plotted the nightly difference between the courtyard minimimum and the environmental minimum versus the environmental minimum. From the linear regression I found the difference in each case when the environmental temperature was 6°:
May 2016 (Gates Opened) +0.95°
May 2017 (Gates Closed) +1.14°
May 2018 (Gates Opened) +0.85°
Mean,when gates were opened +0.90°
Increase when gates closed +0.24°

Keeping the gates closed raised the minimum temperature in the courtyard by a quarter of a degree. That may not seem much, but it carries a lot of calories!

Posted Sunday 27 May 2018 @ 4:33:36 am from IP #

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