Environmental Criteria Incorporation in a Brazilian ... - · PDF fileEnvironmental Criteria Incorporation in a Brazilian ... standard. A performance ... 4 .11 16 7 1 .9 2 4 .9 3.8

Plea2004 - The 21th Conference on Passive and Low Energy Architecture. Eindhoven, The Netherlands, 19 - 22 September 2004 Page 1 of 6

Environmental Criteria Incorporation in a Brazilian Building Code

Denise Duarte, Rafael Brandão and Alessandra Prata

Universidade de São Paulo / Faculdade de Arquitetura e Urbanismo / Departamento de Tecnologia LABAUT - Laboratório de Conforto Ambiental e Eficiência Energética

Rua do Lago, 876 Cidade Universitária 05508-900 São Paulo – SP, Brasil [email protected]; [email protected]; [email protected]

ABSTRACT: This paper presents an environmental urban study developed to the Mogi das Cruzes Building Code, in the metropolitan area of Sao Paulo, Brazil. It is part of a more comprehensive work, elaborated by a consulting team from NUTAU – Center for Research in Architecture and Urban Design from the University of Sao Paulo. The initial proposal was to give technical support to a performance-based Building Code, not a normative one, as it is usually done in Brazilian cities. The proposals were divided in three levels. The level one’s requirements are related to neighborhood issues, such as frontal and side setbacks, and are mandatory for all buildings. Level two refers to interior recommendations such as room minimum dimension and openings. These criteria are required from all buildings, but single-family housing is dismissed from verification. The responsibility would then be laid upon the owner and the designer. Level three requirements are the ones that are actually performance-based and are optional, aimed towards more complex buildings, which are interested in a higher environmental standard. A performance certificate might be granted to the buildings attending all the criteria, rewarding them by municipal tax reduction, plot ratio enhancement or environmental labeling. This paper discusses the criteria elaboration, the final recommendations and the implementation process. Conference Topic: 4 Energy and urban planning Keywords: energy, urban planning, comfort

INTRODUCTION

Even though Brazilian municipal building codes

usually present environmental concerns, most of them are outdated and non-critical copies of similar European codes, with no adaptation for the specificities of the country’s climate and culture.

This paper describes the support studies developed by NUTAU - Center for Research in Architecture and Urban Design, from the University of Sao Paulo, for the Mogi das Cruzes’ building code. Mogi is a 330.000 inhabitants city (Fig. 1, 2, 3), located at 23º30´S, 46º30´W, in the metropolitan area of Sao Paulo, Brazil, 56 km far from the main city’s downtown.

The climatic diagnosis, based on a five year period data showed thermal stress by warm climate during 60% of the whole year [1], [2].

The results indicated ventilation as the main strategy to compensate the high humidity levels in the region, combined with high temperatures during summer.

From May to September, from 10h to 18h the city presents comfort conditions. Thermal mass is recommended for passive heating during the night and the first hours in the morning during the winter period; this fact indicates the convenience of solar access in buildings.

Air-conditioning is not a priority because the climatic diagnosis indicated this strategy only for a few hours in January, the hottest month.

The sky is partially cloudy, with luminance levels higher than 15.000lux during 80% of daytime hours.

Figure 1: Partial view of Mogi das Cruzes.


Figure 2: Partial view of Mogi das Cruzes.

Figure 3: Urban area of Mogi das Cruzes (http://www.mogidascruzes.sp.gov.br)

2. STRUCTURE OF THE BUILDING CODE

Aiming better results of the building code, the

incorporation of some topics of zoning law and land use law were suggested to the municipal authorities.

The following recommendations were generated based on environmental comfort criteria. The proposal was structured in three levels of requirements: First level is related to neighborhood issues, such as frontal and side setbacks, which are mandatory for all buildings. Since the approval procedures should be simple and fast, these requirements must be verified using only building contour plans.

Second level refers to indoors recommendations such as room minimum dimension and openings. These criteria are required from all buildings, but single-family housing is dismissed from the verification. The responsibility would then be laid upon the owner and the designer.

Third level is actually performance-based and is optional, aimed towards more complex buildings, which are interested in a higher environmental standard. A performance certificate might be granted to the buildings attending all the criteria, rewarding them by municipal tax reduction, plot ratio enhancement or environmental labeling.

2.1 Level 1: Setbacks Level 1 requirement refers to neighbourhood

impacts, not to internal performance. However, each building’s resources availability will be guaranteed by compliance to the code of all adjacent constructions. Verification procedures require only building contour plans.

One of the impacts of new buildings on their surroundings is the obstruction of sky portions, and thus, of solar and lighting access, determined by obstruction angles. The code regulates obstruction angles by establishing variable setbacks according to building height. The criteria were adapted from the Belo Horizonte (another Brazilian city) plan guidelines [3]: one hour solar incidence on the façade in the winter solstice (June 22nd) whenever possible.

internal daylight levels efficiency during 60% of daytime hours for large size, high-contrast visual tasks.

Different angles are proposed for each orientation. Solar setback angles were determined from infinite obstructions for the opposite façade, plotted on the solar chart for the city’s latitude (Fig.4). Since façade azimuths ranging from 135° to 225° will never be exposed to direct sunlight in winter in this latitude, long permanence rooms should not have that orientation. Therefore, northern setbacks for solar access are unimportant.

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Figure 4: Setback angles marked on a solar chart for south, southwest, northwest and west.

Daylight factors were determined from the Fhrüling formula [4] which relates the average DF to window-floor area ratio. Sky view for different obstruction angles are calculated for CIE overcast sky. By using external iluminance probability given in [5] it is possible to determine the efficiency of the daylight system. The relationship among these variables is shown in Table I.


The final choice was up to the municipality, but an obstruction angle of 70° would be compatible with solar access recommendation and would provide reasonable sizing for openings, maintaining daylight quality. At this point only average levels were important, but distribution will be referred to in item 2.2.

Table I: Floor-window area ratio necessary to attain daylight efficiency with given obstruction angles

Obstruction angleIluminance (lux) Efficiency 55° 60° 70° 80°

60% 14 13 11 8 70% 10 10 8 6

300

80% 7 7 5 4 60% 7 7 5 4 70% 6 5 4 3

500

80% 4 4 3 2 60% 6 5 4 3 70% 4 4 3 3

750

80% 3 3 3 2 Setbacks are measured from the bottom point of

the neighbour’s window, which was assumed to be 1,20m high and 2,00m far from the site boundary (Fig.5). In the frontal boundary, street width is subtracted from the necessary setback. Final results are shown in Table II.

Obstruction angle

Exisiting building

New Building

Site boundary

Figure 5: Setback reference point.

Table II: Set-backs for each orientation as a function of building height (H)

Orientation Angle Set-back (m)

S (± 15°) 45º H - 3.20

NE - NW - L - W (± 20°) 65° 0.45 H - 2.50

N - SE - SW 70° 0.35 H - 2.50

2.2 Level 2: Sizing of openings and rooms

Level 2 requirements intend to ensure a minimal indoors environmental quality. It was not possible to propose an entire performance-based code at this level, so this item presents recommendations for

minimum opening areas, courtyard sizing and maximum room depth. Since it refers exclusively to indoor quality, compliance is required from all buildings, but single-family houses are dismissed from verification. Calculations for ventilation openings were made so that they would supply sanitary ventilation. Necessary flow was obtained as in [6] and the minimum area was calculated using modelling proposed in [7]. As a result all long permanence rooms must have effective opening area of 3% of the floor area.

Minimum daylight opening size depended on obstruction. Brazilian building codes usually present a 1/6 window-floor area ratio, in any climate or sky condition. With a 70° obstruction angle, this would provide 300 lux for more than 70% of daytime hours. Since it is very common in Brazil that only half of windows’ area is actually glazing, the 1/6 criteria would mean an effective 1/12, providing 300lux for only 60% of daytime hours. The municipality considered this number acceptable.

Openings should all face either the exterior or internal courtyards. Courtyards must be sized so that obstruction angles do not exceed the ones required for external façades, which guarantees solar access and daylight availability to internal openings.

It is also important that rooms do not exceed a certain depth, in order to prevent high contrast situations. Maximum depth was determined so that minimum iluminance levels were not inferior to 1/10 of average levels as in the equation below, adapted from [7].

For 0.1 h ≤ w < h => Dmax = 3.5 x h For w ≥ h => Dmax = 4.8 x h Where w is the window width and h its height. The length of the wall that contains the window

must not be more than 3 times the window width. If a room has windows in two adjacent walls, room depth can be doubled. For rooms with windows in opposite walls, in three or more walls or with roof openings, there is no depth limit. 2.3 Level 3: Thermal and luminous performance evaluation

Level 3 requirements are the ones that are actually performance based. They refer to thermal and daylight performance of one or more critical rooms, by means of simplified calculations. The consulting team suggested its mandatory application and verification for larger or more complex buildings, interested in a higher environmental standard.

A performance certificate might be granted to the buildings attending all the criteria, rewarding them by municipal tax reduction, plot ratio enhancement or environmental labeling.

The calculation is done for the critical long permanence room under summer and winter conditions, based on energy consumption for heating or cooling as in [8] and the procedure was improved in this work by considering thermal inertia.


The first step is a routine to determine the critical room for summer and winter period, which must be verified. Checking the following table (Tab.III) the designer should sum all points for each long permanence room of the building and take the one with the highest score.

For this room average gains and losses are computed in a 24h basis. Calculations are simplified and, even possible, the necessary information were tabulated (materials absorption and resistance, solar factor, wind and radiation data, internal loads, etc.).

The sum of the total loads divided by the sum of the total losses shows the room mean temperature. This temperature is subtracted from the neutral temperature to find the base temperature, which is used to calculate cooling loads. The outdoor temperature, which determines the degree-hour number, is a function of the building thermal inertia, representing the damping of the temperature curve, because of building mass.

Table III: Score to choose the critical room.

Criteria options summer winter SE – S – SW 3 3

O 2 1 L 1 1

Orientation

NE – N – NW 0 0 ≤ 40% 0 2

between 40 e 70%

1 1 WWR

/70% 2 0 External 0 - Internal 1 - Solar shading in

openings none 2 -

≤ 30 m3 0 - between 30 e 90

m3 1 - Room’s volume

/90 m3 2 - Building with all windows in only

one façade

2 -

room with all windows in one

façade

1 - Ventilation

room with windows in two

façades

0 -

light 1 0 heavy 0 1 Enclosure

medium 2 2 ground floor 0 0 Intermediate 1 1 Floor

last floor 3 2

Summarizing the procedure, separated calculation tables are presented for summer and winter (Tab.IV).

In this proposal, for naturally ventilated rooms the summer calculation does not indicate cooling loads. This is because ventilation losses would increase that load, what does not correspond to the reality. This way the criteria are based on the number of degree-hours (Gh) in spite of the cooling load (EC). For summer calculations in air-conditioned buildings and for winter, the designer should consider one renovation of the air volume per hour, assuming

sanitary ventilation and infiltration losses. Final classification is presented in Table V.

Table IV: Summer table calculations.

Table V: Classification of the rooms as a function of energy and thermal performance.

room Gh summer (naturally ventilated)

Gh/day

EC summer (air- cond)

KWh/month

EC winter

KWh/month

excellent inferior to 30º inferior to 700 zero

sufficient between 30 and 40º

between 700 and 1200

between zero and 500

not sufficient higher than 40º higher than

1200 inferior to

500

A qualitative weight matrix in which the window-

floor area ratio, the existence of external shading devices, the maximum room’s depth and the windows distribution are considered does daylight evaluation. The scores run from zero to 6, being the higher, the better the rooms. The final result is a product of the


partial scores, what means that no room should have zero in any criterion. Table VI shows the ranking:

Table VI: Building’s classification as a function of daylighting performance.

Classification Weight score

Excellent Higher than 24

sufficient between 3 and 24

not sufficient Inferior to 3

3. BUIDING CODE IMPACT ON URBAN DENSITY

Given the complexity of set-back regulations, the

municipality grew concerned about resulting urban densities, which could not be more restrictive than those proposed by urban zoning plan. A density study was made by constructing solar volumes using the proposed setback angles and analysing occupation alternatives [9]. The typical plot for local real-state market is about 40 x 50 m and orientation ranges widely.

Density studies were made for 120 x 100 m blocks (6 site units), oriented N-S, E-W and NE-SW (which mirrors SE-NW orientation). Site occupation (Fig.6) could be maximized (using the whole volume) or conventional (rectangular or square plans with four 100 m² dwelling units).

Figure 6: Occupation study for a E-W oriented block, maximized and conventional

Table VII presents the results of density studies.

Area for conventional occupation is given in number of stories and for maximized occupation in square meters. The later was obtained by dividing solar volume by floor-to-ceiling height (3 m). Plot ratio here is defined as building-site area ratio.

Corner sites presented higher densities, since street width was subtracted from setbacks. The worst results were attained on the N-S block, especially on intermediate sites. The best ones are on NW-SE and SW-NE blocks. Buildings can be eight to twelve stories high, even with conventional architecture, which is reasonable for medium sized cities. Plot ratios can be tripled with more creative solutions, ranging from 6.5 to 10.0. Since the zoning plan proposes a maximum plot ratio of 5.0, setbacks will not cause further restriction to urban densities.

Table VII: Density studies for different block orientation

Block orientation

E-W N-S SW - NE

Site Area Plot Ratio Area Plot

Ratio Area Plot Ratio

A 10 2.0 8 1.6 12 2.4 B 8 1.6 8 1.6 9 1.8 C 9 1.8 8 1.6 12 2.4 D 10 2.0 8 1.6 12 2.4 E 8 1.6 8 1.6 9 1.8 C

onve

ntio

nal

F 9 1.8 8 1.6 12 1.8 A 14600 7.0 14300 7.0 20300 10.0 B 12950 6.0 11600 5.5 17400 8.5 C 14600 7.0 13300 6.5 20700 10.0 D 15400 7.5 14300 7.0 20100 10.0 E 13700 6.5 11600 5.5 17200 8.5 M

axim

ized

F 15400 7.5 13300 6.5 20450 10.0

4. IMPLEMENTATION PROCESS

During the elaboration process, some barriers

were observed concerning the performance based code implementation. The first obstacle was the simplification policy of the municipal administration aiming to make the approval process faster and simple using the building contour plan. This means that single-family houses should not be verified besides the contour plan of the building. The municipal administration considers that the environmental quality of the single-family house is a responsibility of the designer and the owner. More complex buildings should have to attend more strict verification, but the demand was still for a normative code, which should establish building parameters and minimum dimensions directly applicable to the design project. This led to the three level proposal.

The second barrier was that the municipal administration was concerned about implementing a complex code, for this would mean the need of training for local designers and even for the staff in the approval sector. They believe that it would be impossible to enforce some parameters proposed by the consulting team. Complex procedures were systematically questioned and refused, and even the final simplification process was not satisfactory. The procedure was presented, in spite of these obstacles, summarized in tables using very simple calculation and tabulated data at maximum. Building density was questioned too, due to the political influence of builders. However, the municipal administration judged the restriction reasonable, considering the density studies.


The last issue was the administration policy for the minimum interference on private property. Restrictions suggested for indoors were systematically refused and responsibility laid upon designers and owners. Because of that, maximum attention was paid to exceptions, avoiding, for example, to restrict set backs wherever it was not necessary. FINAL CONSIDERATIONS

The initial proposal to work fully in a performance base was not possible; it happened only for level 3. Important steps for building environmental quality, as solar access, were discussed and proposed. This study showed the viability to implement set backs regulation as a function of solar orientation, guarantying a minimum solar access for buildings. The same method can be adopted for similar issues. A remaining question is that different setbacks could generate an irregular distribution of maximum plot ratios, with some plots with a higher plot ratio that other, if the solar envelope is the only parameter. There is a great possibility for the valorization of the plots situated in a NW-SE and SE-NW axes, as well as plots located in the middle of the blocks. Level 2 goes further, in a normative basis yet, to attend the administration needs. The advantage is that the criteria were based on openings sizing for sanitary ventilation and daylighting, and maximum room depth to maintain minimum iluminance levels.

Level 3, despite its restricted mandatory application, starts a performance-based proposal, by means of a maximum tabulation of usual data, and by the filling a very simple calculation sheet.

One expect that this proposal and structure can be useful for future experiences aiming more advanced building codes and urban legislations. ACKNOWLEDGEMENTS To the Mogi das Cruzes Municipal Administration, especially to the Urban Planning Secretary João Francisco Chavedar and to the Arch.Erineuda Clementino Ventura. To the IAG/USP especially to Prof. Dr. Pedro Leite da Silva Dias, Prof. Dr. Ricardo de Camargo and Demerval S. Moreira, for climatic data and support. To the Arch.Mônica Marcondes, for the drawings. To the consulting team of NUTAU - Center for Research in Architecture and Urban Design from the University of Sao Paulo. REFERENCES [1] ALUCCI, Márcia Peinado, AUDI, Gabriela. Climaticus, versão 4.1. São Paulo. Disponível em: <http://www.usp.br/fau/deptecnologia/docs/conforto.html>. Acesso em: 7 mai.2003

[2] GIVONI, Baruch. Climate Considerations in Urban and Building Design. New York: John Wiley & Sons, 1998.

[3] ASSIS, Eleonora Sad de; VALLADARES, Victor Mourthé; , SOUZA, Roberta V. G. de. Bases para a determinação dos recuos e volumetria dos edifícios considerando a insolação e a iluminação natural, na revisão da Lei de Uso e Ocupação do Solo de Belo Horizonte, MG. In: ENCONTRO NACIONAL DE CONFORTO NO AMBIENTE CONSTRUÍDO, 3, Gramado, 1995. Anais... Porto Alegre: ANTAC, 1995. 511-516.

[4] HOPKINSON, R.G.; PETHERBRIDGE, P.; LONGMORE, J. Iluminação Natural. Lisboa: Fundação Calouste Gulbenkian, 1975. 776 p.

[5] BRANDÃO, R., Disponibilidade de Luz Natural: avaliação de método para cálculo das iluminâncias externas. ENCAC & COTEDI 2003 – VII Encontro Nacional sobre Conforto no Ambiente Construído e III Conferência Latino-Americana sobre Conforto e Desempenho Energético de Edificações, Curitiba, Brasil, 2003.

[6] FROTA, Anésia, SCHIFFER, Sueli. Manual de Conforto Térmico. 4ed. São Paulo: Nobel, 2000.

[7] ALUCCI, Márcia Peinado. Conforto térmico, conforto luminoso e conservação de energia elétrica. Procedimentos para desenvolvimento e avaliação de projetos de edificações. 1992. 225p. Tese (Doutorado em Arquitetura) – Faculdade de Arquitetura e Urbanismo, Universidade de São Paulo, São Paulo.

[8] RORIZ, Maurício. Consumo de Energia no Condicionamento Térmico de Edificações: um método de avaliação. In: ENCONTRO NACIONAL DE CONFORTO NO AMBIENTE CONSTRUÍDO, 6, São Pedro, 2001. Anais... São Pedro: ANTAC, 2001.

[9] KNOWLES, R., BERRW, R. Solar Envelope Concepts, Los Angeles: University of Southern California, 1980.

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Environmental Criteria Incorporation in a Brazilian ... - · PDF fileEnvironmental Criteria Incorporation in a Brazilian ... standard. A performance ... 4 .11 16 7 1 .9 2 4 .9 3.8