U-value optimisation of curtain walls - Part 3

After having dealt with the technical possibilities of thermal optimisation in my last post, this time the focus will be on design aspects: how do changes in facade layout, module size and operable insert units affect the thermal performance of curtain walls?

Reducing operable insert units

The amount of facade profiles (mullions, transoms and frames) affects the Ucw-value in two ways: first, by the U-values of the profiles (which are usually higher than the U-values of the infills/ panels), secondly, by the additional Ψ-values caused by the higher amount of contacting facade components. Therefore, it seems obvious to reduce the amount of operable insert units and replace them with fixed glazing.

The following illustration shows a sequence of our reference curtain wall layout from the previous posts. Below this is the same layout, but this time without operable window units.

As already described in the last post, the U-values of the reference curtain wall layout (i. e. with operable insert units) are as follows (1):

• with standard components:

Ucw = (ΣA×U + ΣΨ×l) / Acw
Ucw = (10.434 W/K + 4.534 W/K) / 12.00 m²
Ucw = 1.2 W/(m²K)  (1.247)

• with thermally optimised components:

Ucw = (ΣA×U + ΣΨ×l) / Acw

Ucw = (5.742W/K + 1.012 W/K) / 12.00 m²

Ucw = 0.6 W/(m²K)  (0.563)

The U-values of the same curtain wall without operable insert units are:

• with standard components:

Ucw = (ΣA×U + ΣΨ×l) / Acw
Ucw = (10.024 W/K + 4.072 W/K) / 12.00 m²
Ucw = 1.2 W/(m²K)  (1.175)

• with thermally optimised components:

Ucw = (ΣA×U + ΣΨ×l) / Acw
Ucw = (5.540 W/K + 0.848 W/K) / 12.00 m²
Ucw = 0.5 W/(m²K)  (0.525)

The use of fixed glazing instead of operable insert units improves the Ucw-value by 6% (standard) and 7% (thermally optimised). By rounding the value to one decimal place in compliance with the standard,  the Ucw-value of the thermally optimised version can be lowered from 0.6 to 0.5 W/(m²K).

It should be noted that - despite these improvements in U-values - natural ventilation by means of operable windows generally has a positive effect on thermal comfort and occupant satisfaction (2).

Wider facade module

Another way of reducing the percentage of facade profiles in the total area of the curtain wall is to use a wider facade module.

Changing the facade module from 1.5 m to 2.0 m - as shown above - yields the following results:

• with standard components:

Ucw = (ΣA×U + ΣΨ×l) / Acw
Ucw = (13.655 W/K + 5.224 W/K) / 16.00 m²
Ucw = 1.2 W/(m²K)  (1.180)

• with thermally optimised components:

Ucw = (ΣA×U + ΣΨ×l) / Acw
Ucw = (7.550 W/K + 1.157 W/K) / 16.00 m²
Ucw = 0.5 W/(m²K)  (0.544)

This means that a facade module increased by 33 % like in this case improves the Ucw-value by 6% (standard) or 3% (thermally optimised).

Additional transoms

The horizontal division of a curtain wall can be modified, too. Often, transoms are added for aesthetic reasons.

For example, the rather large insulated aluminium panel could be replaced by a smaller opaque spandrel panel and an additional glazing unit with a transom at parapet height (see above). In this case, the Ucw-values would be as follows:

• with standard components:

Ucw = (ΣA×U + ΣΨ×l) / Acw
Ucw = (13.322 W/K + 3.994 W/K) / 12.00 m²
Ucw = 1.4 W/(m²K)  (1.443)

• with thermally optimised components:

Ucw = (ΣA×U + ΣΨ×l) / Acw
Ucw = (7.111 W/K + 1.248 W/K) / 12.00 m²
Ucw = 0.7 W/(m²K)  (0.697)

The modified curtain wall layout has a Ucw-value worse by 14 % (standard) and 19 % (optimised) than the reference layout. However, this deterioration in Ucw-value results not only from the additional transoms but also from the higher percentage of glazed areas (opaque insulated panels usually have lower U-values than glazed areas).

Thus, the reference curtain wall layout with less transom and glass areas has a Ucw-value that is much better than the modified layout.

More glass

In this example, the percentage of opaque panels was decreased in favour of bigger glazed areas. This leads to the following U-values:

• with standard components:

Ucw = (ΣA×U + ΣΨ×l) / Acw
Ucw = (13.299 W/K + 3.532 W/K) / 12.00 m²
Ucw = 1.4 W/(m²K)  (1.403)

• with thermally optimised components:

Ucw = (ΣA×U + ΣΨ×l) / Acw
Ucw = (7.169 W/K + 1.079 W/K) / 12.00 m²
Ucw = 0.7 W/(m²K)  (0.687)

Although there are no additional transoms like in the previous example, yet the Ucw-values have deteriorated similarly. The main reason for this is the increased frame area (Af) due to the bigger size of the operable window.

Here, too, the reference curtain wall layout has a better thermal performance than the modified layout.

Conclusion

The geometrical optimisation too, has a positive effect on the thermal transmittance of curtain walls. However, the geometrical modifications described here have fewer positive effects on the Ucw-value than the technical optimisation of the individual facade components (as described in the previous post, the Ucw-value could be reduced by half by means of technical optimisation). 

Only two of the four modifications examined here led to an improvement in Ucw value. This suggests that the reference curtain wall layout already has relatively favourable thermal insulation properties due to its simple layout.

In any case, the examined cases allow the conclusion that the following design measures have a positive effect on Ucw-values:

• fewer facade profiles (mullions, transoms, frames)
• larger facade modules
• fewer operable window units
• fewer glazed areas and more opaque insulated panels

The best Ucw-values can be achieved by combining the geometrical optimisation of the facade layout with the technical optimisation of the individual facade components.

It should be mentioned that when dealing with very low U-values, rounding the value to one decimal place can lead to excessive generalisations.  For example, results ranging from 0.550 to 0.649 W/(m²K) yield a Ucw-value of 0.6 W/(m²K), although the difference between the two limit values is 15 %.

References

(1) All calculations of thermal transmittance were performed acc. to ISO 12631 (first edition 2012-10-01), Thermal performance of curtain walling - Calculation of thermal transmittance (Reference number: ISO 12631: 2012(E)) 
(2) Cf. Brager, Gail S.; de Dear, Richard: Climate, Comfort and Natural Ventilation, Berkeley 2001, p. 5 et sqq.

U-value optimisation of curtain walls - Part 2

In my last post I have described some basics of the Ucw-value calculation and defined the layout of a reference curtain wall. This time, the U- and Ψ-values ​​of each facade component will be determined in order to calculate the U-value of the complete curtain wall. Then I will try to answer the question of how far the Ucw-value can be reduced by means of thermal optimisation of each facade component.

Many system manufacturers of aluminium curtain walls offer a standard version of their profile systems with lower thermal insulation and a high-insulation version, often called "Passivhaus-tauglich" (i.e. meeting passive house standards) in German-speaking areas. The same can be said for glazing units: one can distinguish between standard double-glazing units and highly insulating triple-glazing units. I will therefore examine the Ucw-value of our reference curtain wall layout with "standard" components and then a version with thermally optimised facade components.

Ucw-value: "standard" version

Table A.1 in ISO 12631:2012 (1) provides a guideline for calculating the thermal transmittance of curtain walling. It describes how to obtain the necessary U-and Ψ-values of the individual facade components for calculating the overall Ucw-value. In most cases, there are two ways to determine these values: they ​​can be found in the corresponding tables of the standard, or they are determined by using calculation or measurement methods set in the standard (usually this is done by the product manufacturer).

The values given in the tables of the standard are usually on the safe side. The U- or Ψ-value of a particular product which has been calculated or measured by the manufacturer is usually lower and therefore better.

Frames

According to the above table A.1, the values ​​for frames, mullions and transoms Uf, Um and Ut can be determined by a numerical calculation method specified in 10077-2:2012, or they are measured according to EN 12412-2:2003. All major manufacturers of curtain wall systems provide the relevant U-values determined according to these standards.

The U-value for a particular mullion or transom depends on the thickness of the filling element and the internal depth of the profile. With a filling element of eg. 28 mm thickness (double-glazing unit) and an internal profile depth of 150 mm, one can assume Ut-and Um-values of about 2.1 W/(m²K) (2). This applies to standard systems without additional thermal insulation measures. The U-values ​​of a standard frame of an operable insert unit also vary depending on the manufacturer and product, with an average value of about 1.8 W/(m²K). Therefore, for our reference curtain wall, we assume the following values:

-> Ut/ Um: 2.1 W/(m²K)

-> Uf: 1.8 W/(m²K)

The values ​​of linear thermal transmittance Ψm,f and Ψt,f can be taken from table B.6, ISO 12631:2012, or they can be calculated according to ISO 10077-2:2012. Table B.6 provides five different junction types and assigns Ψm,f- and Ψt,f-values ​​to these types ranging from 0.05 to 0.11 W/(mK) to. In our case, we assume an average value of 0.07 W/(m²K).

-> Ψm,f; Ψt,f: 0.07 W/(mK)

Glazing

The values for Ug can be taken from ISO 10077-1:2006 or determined by calculation and measurement methods specified in EN 673:2011, EN 674:2011 and EN 675:2011. State of the art for double-glazing units is a Ug-value of about 1.1 W/(m²K).
-> Ug: 1.1 W/(m²K)

The values of linear thermal transmittance Ψf,g, Ψm,g and Ψt,g can be taken from tables B.1, B.2, B.3 and B.4 or calculated according to 10077-2:2012. The standard distinguishes between "normal" and "thermally improved" types of glazing spacer bars. Moreover, the table values ​​depend on the type of neighbouring profiles and of the glazing type. For normal spacer bars with low emissivity glass and aluminium mullions and transoms, Ψm,g- and Ψt,g-values are 0.11 W/(mK). For a metal frame with thermal break, the Ψf,g-value is also 0.11 W/(mK).

-> Ψm, g; Ψt, g; Ψf, g: 0.11 W/(mK)

Panels

The thermal transmittance of panels Up can be determined by calculation methods specified in ISO 6946:2007. Since the thickness of the insulating layer in the panel is crucial for the Up-value, we can for now neglect the inner and outer metal cladding as well as other components of the panel. With an insulation thickness of 140 mm and a thermal conductivity λ: 0.035 W/(mK) we reach a U-value of 0.24 W/(m²K).

-> Up: 0.24 W/(m²K)

The Ψp-values can be taken from table B.5 or established by calculations specified in 10077-2:2012. According to table B.5, Ψp-values depend on the thermal conductivity of the spacer, the panel type (Type 1: with air-filled space; Type 2: without air-filled space), as well as on the materials of the inner and outer panel cladding. Thus, panel type 2 with aluminium cladding on both sides and spacers with λ: 0.2 W/(mK) has a Ψp-value of 0.2 W/(mK).

-> Ψp: 0.2 W/(mK)

Determination of Ucw-value

All the necessary data are thus set for the calculation of the reference facade. The following two tables show the subtotals for ΣA×U and for ΣΨ×l.

The Ucw-value for the facade with standard components is thus:

Ucw = (ΣA×U + ΣΨ×l) / Acw

Ucw = (10.434 W/K + 4.534 W/K) / 12.00 m²

Ucw = 1.2 W/(m²K) (1,247)

Ucw-value: thermally optimised version

Frames

High-insulation curtain wall systems usually have an additional insulating body between the profile on the room side and the pressure plate on the external side. With a filling element of eg. 44 mm thickness (triple-glazing unit), Ut- and Um-values can get as low as about 0,8 W/(m²K) (due to the on-going development of all facade components, these and many other values mentioned here might be outdated soon again).

-> Ut; Um: 0.8 W/(m²K)

Additional insulation inserts and glass rebate insulation in frames of an operable insert unit can significantly reduce the Uf-value. Most manufacturers have high-insulation frames with a U-value of 1.0 to 1.2 W/(m²K).

-> Uf: 1.1 W/(m²K)

As described above, Ψm,f and Ψt,f can be taken from table B.6, ISO 12631:2012, or they can be calculated according to ISO 10077-2:2012. Values of about 0.025 W/(mK) are currently possible.

-> Ψm,f; Ψt,f: 0.025 W/(mK)

Glazing

Ug-values for a triple-glazing unit currently range between 0.7 and 0.5 W/(m²K), depending on the glass coatings and the gas used for the space between the glass panes.

Ψf,g, Ψm,g, Ψt,g can also be determined by calculations according to EN ISO 10077-2:2012. In Germany, the working group "Warme Kante" (warm edge) has published data sheets for thermally improved glass edges (spacers) of various manufacturers. With some products, values for a triple-glazing unit used in an operable insert unit can be reduced to 0.030 W/(mK). For our case we use slightly higher values:

-> Ψm,g; Ψt,g; Ψf,g: 0.04 W/(mK)

Panels

The thickness of opaque insulated facade panels is usually limited by the depth of the facade structure. If, for example, the mullion and transom profiles are 150 mm deep, the insulation thickness in the panel usually cannot exceed 150 mm. Another optimisation method would be the use of insulating materials with a lower thermal conductivity. But even here optimisation options are limited.

Vacuum insulation panels (VIPs) could be a promising alternative. The use of these panels has not yet become widely accepted. However, one can assume that this insulation method will soon become more popular especially for curtain wall systems. Particular advantages are insulated panels which have the same thickness like glazing units as well as a high degree of prefabrication due to  standardised curtain wall modules.

Vacuum insulation panels which have the same thickness like a triple-glazing unit currently have Up-values of 0,15 to 0,2 W/(m²K) and Ψp-values of about 0,02 W/(mK). Here, too, one can expect further improvements in the near future due to the continuous development of this relatively new panel type.

-> Up: 0.18  W/(m²K)
-> Ψp: 0.02 W/(mK)

Determination of the Ucw-value

Thus, we have all the necessary data to calculate the thermal transmittance of the optimised curtain wall. The following two tables show again the subtotals for ΣA×U and for ΣΨ×l.

The Ucw-value for the facade with standard components is thus:

Ucw = (ΣA×U + ΣΨ×l) / Acw
Ucw = (5.742W/K + 1.012 W/K) / 12.00 m²
Ucw = 0.6 W/(m²K)  (0.563)

Conclusion

Compared to the standard version of our reference curtain wall, the Ucw-value could be reduced by half (from 1.2 to 0.6 W/(m²K)) with the use of thermally optimised components. One can even assume that a Ucw-value of 0.5 W/(m²K) is quite possible by using optimum values for every single facade component.

It is striking that the overall U value of the curtain wall is similar to the U value of the glazing in both cases (standard and optimised). The Ug-value can therefore be taken as an indication for the Ucw-value for typical curtain wall layouts which are similar to the one illustrated here.

In addition, Ψ-values seem to leave more room for improvement than U-values. Comparing the U-values of the standard and the optimised version, values could be cut by half. The Ψ-values, however, could even be reduced to a quarter of the original value.

The individual values with the greatest potential for optimisation are on the one hand the Ut- and Uf-values (improvement from 2.1 to 0.8 W/(m²K)) and on the other hand the Ψp-value (tenfold improvement from 0.2 auf 0.02 W/(mK)).

As indicated above, the thermal optimisation of curtain wall components is only one side of Ucw-value optimisation. In my next post I will therefore be focusing on the other side, the geometrical optimisation of curtain walls.

References

(1) ISO 12631 (first edition 2012-10-01), Thermal performance of curtain walling - Calculation of thermal transmittance (Reference number: ISO 12631: 2012(E))
(2) current aluminium profile systems (February 2015) of brands Schüco, Wicona, Raico and Hueck were used to determine the U- and Ψ-values. Values ​​vary partly depending on manufacturer and product line. In this case, mean values ​​were taken as a basis for calculations.

U-value optimisation of curtain walls - Part 1

Thermally insulated facades are an integral part of energy efficient building concepts. A thermal optimisation of all facade components is needed to meet the ever increasing requirements for facades. In this and the following posts I would like to point out some possibilities of thermal facade optimisation.

 

The specific reason to take on the topic is my current project, which is located in Central Europe. The specifications stipulate a U-value of less than 0.65 W/(m²K) for the curtain walls. Meeting this demand has proved to be quite difficult. In the following posts, I would therefore like to discuss in more detail the possibilities to influence the thermal performance of curtain walling. But first a few basics ...

Ucw-value: Two calculation methods

The decisive physical value of (winter) thermal insulation of facades is the thermal transmittance or U-value. ISO 12631: 2012-10 (1) specifies the procedure for calculating the thermal transmittance of curtain wall structures. The standard provides two calculation methods: the single assessment method and the component assessment method.

The single assessment method is based on detailed computer calculations of the heat transfer through the facade construction and is usually more complex than the component assessment method. In practise, the single assessment method is particularly useful in advanced design stages. It is well suited for special cases such as non-standard facade areas, local penetrations and individual facade component designs. The component assessment method, on the other hand, is very helpful during earlier design stages, because larger geometry or component changes can be incorporated in the calculations with relatively little effort. 

The U-value of curtain walling systems (short: Ucw) according to the component assessment method is calculated using the following complicated-looking but ultimately simple formula:

Ucw = (ΣAg×Ug + ΣAp×Up + ΣAf×Uf + ΣAm×Um + ΣAt×Ut + Σlf,g×Ψf,g + Σlm,g×Ψm,g + Σlt,g×Ψt,g + Σlp×Ψp + Σlm,f×Ψm,f + Σlt,f×Ψt,f) / Acw

where

• A is the area [m²]
• U is the thermal transmittance [W/(m²K)]
• l is the length [m]
• Ψ is the linear thermal transmittance due to the combined thermal effects [W/(mK)]

the subscripts mean:

• cw : curtain wall
• g : glazing
• p : panel
• f : frame
• m : mullion
• t : transom

The following figure illustrates the meaning of the different U- and Ψ-values:

U- and Ψ-values: schematic section through a curtain wall

According to the above formula, the U-values ​​of the individual components are multiplied by the respective facade surfaces and the Ψ-values ​​are multiplied by the corresponding lengths. Both products are then divided by the total facade area. The above formula can therefore be summarised as follows:

Ucw = (ΣA×U + ΣΨ×l) / Acw

Ultimately, the thermal transmittance values of the components are weighted according to their area percentage, with the Ψ-value additionally taking into account the thermal interaction between contacting components.

Essentially, there are therefore two groups of factors in the U-value calculation: physical factors and geometrical factors. In other words, there are technical aspects on the one hand and design aspects on the other hand (here, the interface between design and technology shows up once more, reflecting the title of this blog).

What is a "typical" curtain wall?

If the aim is to come to general conclusions about the possibilities to influence the thermal performance of curtain walls, it makes sense to choose a facade layout which is as general as possible. But what does such a facade layout look like?

Office buildings are a classical field of application for curtain walling. According to Eugene Kohn and Paul Katz, a typical planning module in the US is 1,5m (5 ft.), while in Europe and Asia it is 1,2 m (3' 11'') and 1,5 m (5' 0''). The typical floor to floor height of high rise office buildings in the US is between 13' 0'' and 13' 6'' (4.0 and 4.2 m), in Europe (Germany and France) it is 3.75 m (12' 4'') (2).

A general curtain wall layout - so to speak, the lowest common denominator of a global facade layout - could therefore look like this:

The horizontal division is also kept as simple as possible: there is an opaque area (here: 1.6 m for installation space + floor slab + parapet) and a glazed area (here: 2.4 m high). A transom and mullion width of 50 mm is assumed. Added to this is an operable insert unit with a frame width of 80 mm.

As seen above, the U-value of the curtain wall is determined in large parts by the surface area A of each facade component and the length l for contacting components. Therefore, it seems appropriate to have a closer look at these values ​​and their percentage of the total facade area. The following figure shows the areas of the each component of our reference facade in different colours.

The surface areas A and the percentage of the total facade are:

As expected, the glazing and panel areas Ag and Ap account with almost 90 % for the majority of the facade area. However, the facade profiles (Af, Am, At), despite the relatively slim profile widths, reach ​​almost 1.3 m² per facade field.

The following figure shows once more the reference facade. This time, the lengths l for contacting facade components are highlighted.

The lengths l and their percentage are:

It is remarkable that the lengths l total approximately 34 m despite the relatively simple division of the reference facade module with only few profiles. The area around the insert unit accounts for a large percentage of these lengths, since there are not only the contact areas between the frame and glass (lf, g) but also between mullion or transom and frame (lm, f and lt, f).

After the geometry of our reference facade has been defined, we need the U- and Ψ-values ​​of the individual facade components in order to calculate the Ucw-Value. More on this in the next post ...

References

(1) ISO 12631: 2012-10, Thermal performance of curtain walling - Calculation of thermal transmittance (ISO 12631: 2012)
(2) Cf. Kohn, A. Eugene; Katz, Paul: Building Type Basics for Office Buildings, New York 2002, p. 35 et sqq.

Skyline Comparison

This post is going to be a bit image-heavy. I have found many interesting photos of skylines from around the world which I would like to share with you. But the post is not only about some nice pictures. It is also about facades and the status of climate adaption in modern architecture.

Toronto: humid continental climate Dfa/ Dfb (1)

Chicago: humid continental climate Dfa (2)

Similar or unique?

You may have noticed that I have arranged the photos according to the climate zone the depicted cities belong to, from rather cold (Toronto) to hot climates (Singapore). The climate descriptions and the associated letter symbols in the captions are based on the Koeppen Climate Classification, one of the most widely used climate classification systems.

I have tried to make the photos look as similar as possible: I have only used pictures taken at daytime and at nice weather conditions, showing only skylines with a waterfront. I retouched and cropped the pictures to give the them a similar scale.

Critical viewers may find some of the depicted city centres replaceable. However, the photos still don't look exactly the same. You can probably identify at least some of the cities just by looking at the photos. Each of these cities have their landmark buildings, some of which have become iconic images inseparably connected to their cities.

In addition, shape, size, colour and materials of the buildings indicate the time of their creation or give hints about the predominant design preferences of the place. Often, the shape of the building or the layout of the facades reveal its function and use (real estate, office, look-out or television tower, etc.).

New York: humid subtropical climate Cfa (3)

Shanghai: humid subtropical climate Cfa (4)

Climate Adaption

But what about climate adaption? Can you also identify the climate zone the city belongs to just by looking at the buildings? Does the amount and size of the windows provide an indication of the climate? Or the ratio of opaque and transparent building skins? Are different facade materials used in the different climate zones? Or can you distinguish more sun-shading devices on the buildings in hot climates? Can you, for that matter, identify any visible measures of climate adaption in these photos?

I'm afraid that the answer to most of these questions is 'no'. Climate adaption seems to be a widely neglected subject in modern architecture (9).

Hong Kong: humid subtropical climate Cwa (5)

Dubai: hot desert climate BWh (6)

 Respiration exacte

Le Corbusier's words of the "respiration exacte" aptly describe these circumstances. In a lecture held in Buenos Aires in 1929 he proposed "...one house for all countries, the house of exact breathing" instead of houses built "...in response to climate" (10).

Le Corbusier's words were guided by a strong belief in technological progress, but they have since then proved to be very true. The achievements of modern technology - in this case of modern HVAC systems - seem to have eliminated the need for a facade design that takes the climate into account.

All around the world, modern buildings are constructed by using almost identical "construction sets". Once the building is completed and in use, energy-intensive building services must compensate the shortcomings of the design. Only recently, as negative impacts of rising energy consumption have become more and more obvious, such concepts are put into question.

Abu Dhabi: hot desert climate BWh (7)

Singapore: tropical rainforest climate Af (8)

It is interesting that Le Corbusier has run a completely different path in his later works. The facades of his buildings in India designed in the 1960s have many features responsive to the local climatic conditions. Many of these strategies can also be found in the traditional architecture of these climate zones (see also this post).

All in all, it seems that traditional buildings often provide more sophisticated climate-responsive design strategies than modern buildings. I plan to deal with these traditional strategies in more detail in one of my next posts.

References

(1) "From Hanlan's Point" by BriYYZ , CC-BY-SA-2.0 (altered: retouched, cropped)
(2) "Loop skyline from the lakefront, Chicago, IL, USA" by J. Crocker , license details
(3) "NYC Mini Cruise 2014" by Liz Novak , CC-BY-2.0 (altered: retouched, cropped)
(4) "Shanghai on the Bund The Pudong skyline" by Matt_Weibo, CC-BY-SA-2.0 (altered: retouched, cropped)
(5) "Hong Kong Skyline" by Daniele Cardone, CC-BY-2.0 (altered: retouched, cropped)
(6) "dubai-600870" von dbenthien, CC0-1.0 (altered: retouched, cropped)
(7) "Near Heritage Village @ Abu Dhabi" by Guilhem Vellut, CC-BY-2.0 (altered: retouched, cropped)
(8) "Singapore skyline" by Bryan Allison, CC-BY-SA-2.0 (altered: retouched, cropped)
(9) cf. Harmann, Ralph E. Urban Space, Building Orientation and Design, p. 202 et sqq., in: Hindrichs, Dirk U., Daniels, Klaus (ed.), Plusminus 20/ 40 Latitude. Sustainable Building Design in Tropical and Subtropical Regions,  Stuttgart et al. 2007
(10) Le Corbusier. Precisions sur un état présent de l'architectureet de l'urbanisme, Paris 1960, p. 64, quoted from: William W. Braham, Daniel Willis. Architecture and Energy: Performance and Style, London 2013, p. 136

I'm looking for modern examples of climate-responsive building skin design. If you know one, please write me!

Building geometry and sun-shading

When it comes to reducing solar energy input into buildings, external sun shading systems are one of the most efficient measures. In most cases, fixed or operable shading devices are placed in front of the glazed areas. A clever alternative is the use of the building geometry itself for sun-shading. Here are some examples.

Niterói Contemporary Art Museum, Brazil

Brazilian archiect Oscar Niemeyer (1907 - 2012) can be regarded as a true virtuoso of building envelope design. During his career which lasted for more than 70 years he explored all varieties of facades and sun shading systems especially for hot climates. The Niterói Contemporary Art Museum is one of his more recent projects. It was completed in 1996.

The Niterói Contemporary Art Museum sits like a landed UFO on a cliffside at Guanabara Bay, Brazil (2)

The sloping glazed facades reduce the solar radiation input drastically. The solar transmission is further reduced by the use of dark-tinted absorption glass. In addition, the sloping facades face towards the sea and offer a nice panoramic view of the sea shore below the museum.

The roof is exposed to most of the solar radiation. Its white colour reduces the heating of the roof surface by increasing the transmission and at the same time reducing the absorption of the solar radiation. The mechanical area below the roof serves as a buffer zone between the outside and the main floor of the museum.

Hanoi Museum, Vietnam

The Hanoi Museum combines several sun-shading strategies (3)

This building is located in the Hanoi, the capital of Vietnam. It was designed by German architects GMP and completed in 2010. The cantilevering floors serve as shading devices for the floors below. The top floor has protruding horizontal aluminium louvres. In addition, all glazed areas are covered with perforated elements who resemble the traditional Arabian Mashrabiyas (see also this post).

 

Two examples from the seventies

The Tempe Municipal Building has the shape of an inverted pyramid (4)

The City Hall of Tempe, Arizona dates back from 1971 and was designed by architects Michael Goodwin and Kemper Goodwin. The basic design of an inverted pyramid is quite obvious in this case.

Like all examples shown in this post, the roof is exposed to the bigger part of the solar radiation. The sloping facades are protected from the midday sun by the protruding building top. In addition, the inclination of the facade reduces the sunlight transmission through the glazing.

The Dallas City Hall was designed by I. M. Pei and completed in 1978. The concepts of stepped and non-stepped inverted pyramids are combined in this building.

Dallas City Hall by I. M. Pei (5)

Buildings shaped like an inverted pyramid seem to have been quite popular in the seventies because of their strong formal expression. In these two cases - both located in the south of the U.S. - their shape has without doubt a positive impact on the energy consumption of the air conditioning, too.

Update (2015-04-08)

My colleague from the old days (thanks, Mihail!) has pointed me to two other examples that match well with those shown here.

Slovak radio building in Bratislava (6)

The Slovak Radio Building was designed by architects Štefan Svetko, Štefan Ďurkovič and Barnabáš Kissling and completed in 1983 (the project started already in 1967). The British "Telegraph" has included the building in its list of the 30 ugliest buildings in the world (7). Together with buildings by Frank Gehry and MVRDV, which also appear in this list, the Slovak Radio is not even in bad company...

St. Petersburg Pier, Florida/ USA (8)

Another example of an inverted pyramid is the St. Petersburg Pier in Florida, USA. Although you can't really tell by looking at the building, it was completed more than 40 yeaers ago, in 1973 (architect: William B. Harvard, Sr.). Unfortunately, there seem to be plans to demolish the "Pier" and replace it with a new building (9).

References

(1) "Niterói Contemporary Art Museum" by Rosino, CC-BY-SA-2.0 (altered: reference number added)
(2) "Niterói Contemporary Art Museum" by Rosino, CC-BY-SA-2.0
(3) "Hanoi Museum, Hanoi, Vietnam" by Daaé, public domain
(4) "The Tempe Municipal Building in Tempe, Arizona" by Visitor7, CC BY-SA 3.0
(5) "Side view of City Hall" by Daniel Lobo, CC BY 2.0
(6) "Slovak Radio" by Dushan Hanuska, CC BY 2.0 (altered: cropped)
(7) cf. http://www.telegraph.co.uk/finance/property/pictures/9126031/The-worlds-30-ugliest-buildings.html?frame=2875010
(8) "st-petersburg-pier-1024x768-2653" by Texx Smith, CC BY 2.0
(9) cf. https://en.wikipedia.org/wiki/St._Petersburg_Pier


Do you know other examples of building geometry and sun-shading combined? Leave a comment!