26 September 2010

Introduction to Architectural Science

Introduction to Architectural Science
Steven V Szokolay is an Australian architect and energy / environmental consultant who has worked in Sydney and London, and teached in Liverpool, London and finally Queensland. In this university he was the founding director of the Architectural Science Unit, as well as Head of the Department of Architecture. He is now retired.

This book is a great introduction to the facts, concepts and numbers of heat, light, sound and energy applied to architecture. The second edition from 2008 is the most recent one. The reader can be a practising designer or an undergraduate student; both will benefit from a clear presentation of facts, examples and data sheets. But the best in my opinion is how difficult issues are treated in a way that sounds as if they were being taught for the first time. Just one example: the description of glare (part 2.2.4, page 148). Szokolay aptly describes the differences between glare due to saturation and glare due to contrast, as well as discomfort vs disability glare. Another clear definition is that of daylight factor (part 2.4.2), also belonging to the lighting chapter. But probably the most useful part of the book is Part 4, Resources. Here we can find the basics of energy, renewable energy, energy use in buildings, water, waste, and sustainibility issues. Short and to the point.

Szokolay has also co-authored with Andris Auliciems a 60 pages booklet on thermal confort. The thesis is very attractive: nowadays lifestyles, clothing, technology in building construction and microclimate controls have tended towards homogenizing indoor environments to which humans are exposed. These developments may be driven by market forces, but the result is that humans are becoming adapted to a very narrow band of conditions. This may be a threat to our survival as species: within a changing environment, survivability is greater among the adaptable than the adapted. Which trend is being favoured by technological development and thermal design?

The booklet is available on the net. Do yourself a favour and have a look at it here: Thermal comfort

25 September 2010

Metal curtain walls

One more example of a great old document, this time from 1955 and related to a then start-up facade system, the metal curtain walls in the United States.

This time it's a book (fully available to us thanks to the 'make no evil' Google guys) with the title 'Metal curtain walls'. It is a compilation of the papers and discussions presented at a conference in Washington in September 1955, organized by the Building Research Institute, then a division of the National Academy of Sciences.

Let's start with the obvious: this conference seems to have been a well organized event, the presenters were among the best available specialists at the time, and the response of the public was overwhelming, judging by the number of companies and experts that attended the conference. It was definitely a good time to talk about the matter. Ten years after the end of the war, and just one year after the Lever House opened at 5th Avenue, there was a lot to say and to learn about curtain walls.

The presenters at the conference came from different grounds. There were architects, some big firms and some from academia. Among the former was Max Abramovitz, partner at Harrison Abramovitz in New York and responsible for the planning process of the United Nations headquarters in Manhattan between 1947 and 1952. There was also a partner from SOM, describing the firm's design method for curtain walls at the Ford Motor headquarter in Detroit. The result of an investigation from the School of Architecture at Princeton University about stainless steel curtain walls (conducted in 1954) was also presented.

There were several specialists from different manufacturing companies and some other experts on thermal and acoustic issues. One presentation discussed the role of curtain wall erectors. It is surprising to see how little things have changed in this regard: the poor chaps who installed facades were experiencing the same problems and showing the same clear logic as their equals do today.
Poorly insulated curtain walls have a two times better U-value than non-insulated brick facades. It all depends on the comparison you select to do...

The general impression among the panelists was that curtain walls were going to be the next big thing in facades design and construction for the years to come. They were damn right. One might expect here a lot of naive comments on the advantages of the new technology. Instead, there was surprisingly very few self-praising; quite the opposite, presenters with different technical backgrounds were rather clear in assessing the many problems still unresolved for lightweight cladding.

It seems that at the time architects and owners had fallen in love with glazed facades, whilst contractors and specialists seemed already worried about the limitations of the technology in terms of thermal & acoustic insulation, air tightness, water leakage, metal corrosion and coating durability. The summary of a survey on metal cladding panels, conducted that same years among owners and contractors, shows it cristal clear. Only 2.5% of building owners were dissatisfied, while 13% of contractors would not recommend using curtain walls again. See the details here below.

Things were bound to change in the years to come, with owners becoming less and less interested in curtain walls - but this was still 1955. The Seagram Building details were at Mies' desk by then, and Tom Wolfe had not the least idea that 25 years later he would be writing 'From Bauhaus to our house'.

The architect's view
Max Abramovitz's text is very interesting. We are literally attending to an architect's explanation of modern architecture provided to an audience of builders and manufacturers. He could be outspoken and not too academical. He started saying that the idea of curtain wall was not new, but a development of wooden skeletons and non-bearing stone veneers or other lightweight walls. He then described the factors that made curtain walls so appealing to architects. The list deserves a quotation:
  1. The dry wall, allowing facade construction to proceed even in wet and cold weather.
  2. Lightweight, saving in construction manpower and load to support.
  3. Larger units, thus reducing the number of joints in the facade. For him joints were an architect's headache: the less of them the better.
  4. Non-corrosive and fire resistant materials, that is, metals. A curtain wall wasn't more fire safe then than today, but architects have always found it difficult to distinguish between fire reaction and fire resistance.
  5. Prefabrication, very neatly expressed: 'We will get more construction for our money'.
The facade contractor's view
My favourite presentation, though, is the one given by the erectors representative, a such Mr. Collier, president of a facade contracting company. Among many interesting things in his text, there is a lateral comment that struck my attention. Remember, we are in 1955. Weather proofing concepts such as rain screen or pressure equalization had not been identified yet, and do not appear along the conference proceedings. On the other hand, selants based on silicone had not been developed at the time. Facade joints were caulked with Thiokol at best. Mr Collier, though, was not happy with the then predominant solution of open joints in lightweight facade panels to allow for movement, with an internal air and water sealed barrier. He prefered, based on his personal experience, an externally sealed wall to prevent water to come into the building in the first place. Well, of all the predictions made in this interesting book, the preference of Mr. Collier for externally sealed facades was going to become the mainstream solution in the US, as soon as silicone became available, and lasting until today. Dow Corning was going to be more convincing to American builders and architects than the rain screen principle. 

We Europeans laugh at the Americans love for sealed joints in stone or aluminium veneer facades. But apparently Americans prefered the reasoning of Mr. Collier, an entrepreneur, to that of G.K. Garden in 1963, a researcher from a Canadian building institution and the father of the open joint design in modern facades. And they still do...

20 September 2010

The facades of the future

This is a post under construction. In fact, it may be under construction for years, since its theme will always remain open. What are the key indicators of the facades of the future? What will matter - and what won't - in relation to how we design building envelopes today?

The following is a list (yes, I love lists) of the issues that will define facades design in the near and longer future. Let's put a time lag to this: by 2020? That's rather soon. 2030 is better: twenty years from now.

1. Image:
a) Media facades - they tell us a changing message. See below and here for a video of Ned Kahn's facade moved by the wind:
        Ned Kahn, Technorama facade - Swiss Science Centre, Winthertur

        N Building, Tokyo. Terada Design and Qosmo - The facade is covered in QR codes. Clic a pic of this building and you will get info of all its inhabitants in your mobile.

        b) Interactive facades - we can ask them for something, and they will answer. See above and here for more information.

        c) Dynamic facades - they will move, in order to perform better, but also in a way we will consider aesthetically pleasant - as it should be: utilitas & venustas. See below and here for the video.
        Kiefer Technic Showroom, Giselbrecht + Partners - The louvers move constanty depending on the day and light conditions, and on the inner use of the rooms.
        2. Performance:
        Future facades will be extremely performant. We have almost reached the limit of tectonics nowadays (what can be done to make any element structurally resistant and stable) but we have just started to grasp the surface of the non-tectonic issues (what can be done to improve the capacity of building elements to reduce thermal transmission, reduce emissivity, limit noise transmission, avoid air and water penetrations, maximize visible light transmittance whilst blocking UV and infrared rays, etc etc).

        We are so behind in non-techtonic related issues that there isn't even a name for those (let me suggest one: herkonics, from 'herkos', building fence and interface in Greek)

        3. Sustainability:
        If a building envelope performs well in terms of energy, it should already be sustainable, right? Well, in the future that won't be enough. As long as we will achieve zero-energy buildings (by both passive and active means) other issues will become more important than what they are now. That's the case with materials carbon footprint, re-usability of elements as per the cradle to cradle mantra, water retaining and reusing, etc.

        4. Buildability:
        Facades will always have to be fabricated, transported and installed on site. That must be made in a more efficent way - to reduce their carbon footprint, to reduce time, to reduce costs, to reduce uncertainty and risk of malfunction. This is really difficult and will consume the 20 years period I have given for this list to become reality. Can you imagine a robotic factory? You surely can. Now try to imagine a complete robotic jobsite!

        Joints and interfaces between facade elements will become even more critical in the future. Again , this is science fiction, regardless the fact that we have been dicussing it since the 50's.

        5. Post-occupancy:
        This involves first of all facades design that allows user comfort, adaptability and dynamic response to different needs.

        Second, it means that our envelopes should be easy to maintain, but really so; reducing the costs, the effort and the spill of water and consumables we need now. And easy to replace: when something breaks or underperforms, the system detects it and the substitution is done together with the cleaning... Sounds futuristic, doesn't it?

        And, last but not least, durable facades. This is the Holy Grial of the whole story. Sustainable in Darwinian terms means lasting. Our facades today are creationists, not evolucionists. We act like gods, but gods without the power - and our 'creatures' disappear swallowed by the harshness of the real world. Some day our building envelopes will again, as in the past, be durable. It will definitely take time: I don't care if it's more than 20 years, as long as the trend goes in that direction.

        15 September 2010

        Facade - structure tolerances: the buffer zone

        A visit to the Arup central library in London is always a great experience. The other day I found this book, out of catalog and unavailable in Amazon: 'Interfaces - Curtain wall connections to steel frames'.
        One of the interesting sections is devoted to discussing the tolerances that a designer should always consider between the plane of the building facade and the alignment of the structural steelwork. For the purpose of this post, the main structure can be steel or concrete, and the lightweight facade can be a curtain wall or any other system.

        The idea of writing about this issue comes from an architect with whom we are working these days. The project name and location aren't relevant. Our architect wanted to stick the curtain wall plane to the front plane of a steel column, with no space in between. This would surely make a nice detail as shown on a Scheme Design drawing: all flush and neat. We have had to go some length to explain something quite clear to us facade engineers, but obviously not so to architects in general. The point in discussion was the need to consider a separation between the main structure and the inner plane of a curtain wall. Why is it necessary, and how big should that space be?

        Let's go with the why first 
        The structure of a building is not built by Swiss watchmakers. For example, the edge of the steel decking is is often set out from the centre line of the steel beam. In a concrete structure, the formwork is positioned in relation to the axis of the adjacent columns. Both are not proper methods - the setting out line should be the main axis lines at each floor. The result is that dimensional variations in the positioning of beams or columns are transferred to the alignment of the edge of slab. Add movements of the formwowk (in case of concrete) and you have a wobbly line instead of a perfect vertical plan.

        Bosch CST Berger laser
        The same, at a much smaller scale, happens with the curtain wall or lightweight facade installation. Facade contractors use accurate positioning tools as laser beams for the setting out of their lines and brackets. The image to the left is a high quality laser level, capable of self-leveling in horizontal, vertical and plan. The reader unit can find the laser beam as far as 800m away. But its accuracy is not perfect: +/-3mm vertical misalignment every 30m. Add small mistakes when marking lines with chalk on the concrete slab, bracket positioning and profiles drilling, and there you go with a certain degree of variation.

        Now the dimensions
        How big should the tolerance space be? What I liked about the book above is the way the authors divide the requested space - the total tolerance - in three areas:
        1. Tolerances which define the zone within which the main structure should be built. Their value depend on the national building codes, the material, the quality of workmanship and the building size and shape.
        2. Tolerances to absorb the misalignments of the facade elements in relation to their theoretical plane. These are smaller than the first ones, a rule of thumb is three times smaller.
        3. A 'buffer zone' between the two tolerances above. This is an additional contingency against excessive dimensional errors. In practice, all structural frames exceed their specified tolerances at least in some points of the structure. 
        The buffer is the way to avoid breaking arms and legs in order to fix a facade in every building. But remember, they are not intended to be a relaxation of the structural specification (or of the facade installation), rather they are a recognition that sometimes work does not go as planned - even in Switzerland.
        The drawings below show, nº 1 for steel structure + curtain wall and nº 2 for concrete structure and precast, my personal rule of thumb for a general structure - facade tolerance. The three areas are shown in each case.

        Steel structure plus curtain wall tolerances
        Concrete structure plus precast concrete cladding tolerances

        The buffer must not be excessively large, since fixing details which have to trasfer the cladding loads across the zone will themselves become significant and costly structural elements. As the cladding contractor effectively carries the cost of the buffer, the designers should consult him to assess a realistic dimension, at least in special cases.

        You've got the point now. Let's assume this is too detailed to remember; what should be the real rule of thumb for architects? Easy: the theoretical distance between outer structure and inner wall should be 60mm for curtain walls, 70mm for precast. This is easier to keep in mind.

        11 September 2010

        Matteoli: Water and air tightness of external windows

        This post inaugurates the recovery of old documents from which we must still learn a lot: oldies but goldies. The first one is almost 40 years old, it is written in Italian and was published in 1971. Its title is 'Tenuta all'aria e all'acqua dei serramenti esterni'. The author is Lorenzo Matteoli.

        Why was it important?
        Italy in the 70's - as all Southern Europe - had very low quality windows. The typical window frame was made in aluminium, although there were still many hot formed steel sections. Their water and air tightness design was based in the steel sections of European 1930's suppliers: the best ones had two gaskets, one on the outside and one on the inside of the frame.
        Lorenzo Matteoli was leading the testing laboratory of the Istituto di Elementi Costruttivi, a branch of the Architectural School at the Politecnico di Torino. By 1971 his team had conducted six years of window testing, and he had extracted some design principles to improve the window performance. I assume he was aware of the work by O. Birkeland and G.K. Garden about rain-screen and pressure equalization, appeared in 1963-64. But in my opinion the bulk inovations of his paper came from analysing the window tests conducted at the laboratory.

        After its publication in 1971 this paper became inmediately influencial for facade contractors and window suppliers, but it was especially followed among aluminium extruders who had window profiles to sell. The aluminium extrusion companies were big conglomerates with very basic products, which they had to improve if they wanted to win in the market for new housing, then booming. This paper explained the new idea of pressure equalization and how it could be applied to windows, and it did so starting from scratch. The text is so basic that there are no drawings or references to central gaskets at all. But the concept of a gasket located in the center of the frame and not on the outside was already being applied in Germany, and with Matteoli's help it became obvious what a central gasket could do, and why it was better to have an external open joint between the frame and the sash.

        But what did it say?
        1. The water running along the outer surface of a window...

        Matteoli's paper has an additional advantage: it can be understood almost without reading it, because it comes with a number of hand sketched drawings and captions that are the real summary of the paper. I assume not everyone reads Italian, but please have a look at the first four sketches with translated captions here below, and judge by yourselves.

        2. ... through vertical and horizontal joints...
        3. ... gets in contact with the outer gasket. Since Pe is higher than Po, water tends to come in, helped by capillarity processes...
        4. ... by pressure differencial and by air movement inside the intermediate chamber, until it reaches the inner gasket where, helped again by capillarity and pressure differencial (Po is higher than Pi), it finds a way to the inside.

        Now a personal comment 
        I first found this document while I was studying architecture in Madrid, at the school Library, together with other oldies as the curtain wall series published by Folcrá in the seventies. It didn´t make an impression to me then, but some years later I was going to be working for one of those big aluminium extruders: Hydro Aluminium, owner of the window brand Domal. At Hydro's technical department near Milan, led by Massimo Dampierre, this document appeared again. They told me the story of the evolution from the two gaskets to the central gasket, the move from punched hinges to a channel where all accessories could be fitted and removed (the 'European channel'), the birth of thermal break profiles. The Italians had coined a hip name for the new family of windows that became popular in Southern Europe: these new windows were 'systems', just because their elements were interchangeable. You can use the same glazing bead profiles, gaskets or acessories for different window types and it works, saving time and reducing stock at the window manufacturer. Now it's pretty obvious and has become standard, but it all started at a hidden testing place in Turin...

        A real pleasure to read. The whole document is just seven pages long: go to the link and check your Italian!

        10 September 2010

        From Wigwarm to Ikea (houses)

        'I find it incredible that there will not be a sweeping revolution in the methods of building during the next century. The erection of a house wall, come to think of it, is an astonishingly tedious and complex business: the final result is exceedingly unsatisfactory'

        Wells, H.G. 'Anticipations of the reaction of mechanical and scientific progress upon human life and thought', Chapman, London 1901. 
        Taken from Alan Brookes, 'The turning point of building'

        Who said H.G. Wells was not a man of vision? Some might argue, though, that Mr Wells failed by not predicting the arrival of mass housing prefabrication systems in the 20th century. Well, if that was the question, I'm afraid the answer is even tougher: he didn't have to predic anything, because house prefabrication was well known by the turn of the century. And again, if he new it, he didn't fail in his predictions at all: prefab houses today are as much 'the next thing to come to building' as they were in 1900. Only that we are still waiting for this to happen...

        One of the first succesful examples of prefab housing in the USA is the E.F. Hodgson Company, active in Dover, Massachusetts between 1894 and 1944. Their houses came under the brand Wigwarm. The word is a mixture of wigwam, an Indian tent similar to a teepee, and warm. Its meaning: quick to assemble but comfy.

        A Hodgson cottage in Dover, MA, as appeared in the 1935 E.F. Hodgson Catalog

        One of the remaining Hodgson houses, built in 1940, in pristine condition inside and outside
        The Wigwarm construction was a framed house, lighter than a standard timber frame construction, based on several timber sections fastened together with key bolts of special design. With just a blow of a hammer the wedge key tightened up the bolt, saving time during erection or dismantling. Frames were covered with a very heavy waterproof fibre or lining and then with a rabetted siding. The basic modulus for the houses was 6 x 12ft (1.80 x 3.60m). Mr Hodgson didn't just prefabricate houses, he also sold brooders, tool houses, dog houses, car garages - there is one in the top image to the right - or, during war periods, barracks for the military. In the '20s and '30s you could see Hogson houses in places as Europe (Belgium and Italy), Israel, Africa and South America.

        Was it a commercial success? It really was, and it was simply based on selling by mail. A response to an ad in a newspaper would get the potential client a full catalog with photographs, floor plans and comments by satisfied customers. The company did not survive its founder: Mr Hodgson, without a son to continue the business, sold it in 1944, four years before he died.

        The story is surprisingly similar to today's prefab, portable houses through catalog: the brand new Ikea/BoKlok house. Even the look is familiar. BoKlok, the webpage tells, builds homes for ordinary people who want to have money left over. But the idea for this house was born in very different circumstances, as a dialogue between IKEA and Skanska chairmen in 1996. A retailer and a construction company sharing forces to create affordable apartments. Up to now they have sold more than 4,000 houses in five countries, and the idea is booming, from Scandinavia to Germany to the UK. 

        Who knows, maybe now it's the time for the sweeping revolution in the methods of building that H.G. Wells was asking for: his period of 100 years is finally over...