Building Regulations in Reunion

Presented byEmma Özsen

Sustainability ConsultantM.Sc. Environmental Design and Engineering

Overview of the RTAA-DOMand transposition to Mauritius

Introduction• RTAA DOM = Réglementation

Thermique, Acoustique et Aération -Départements d’Outre Mer.

• The requirements of the RTAA DOM amend the “Code de la construction et de l’habitation” in Reunion.

• Sets out a number of requirements for new residential buildings only.

• Officially published in April 2009.• RTAA DOM came in force on 1st May

2010 .

• Proximity of Reunion and Mauritius• Similar socio-cultural characteristics • Fairly similar climatic conditions,

especially in lower areas of Reunion (altitudes < 400m)

Relevance to Mauritius

• Prone to adverse climatic conditions such as cyclones

• RTAA DOM came in force only recently (early stages of development)

Regulation Method• Three main articles inserted in the Building

Regulations, regarding the thermal and energy performance characteristics, and ventilation of dwellings specific to the DOM are: Article R. 162-1.-I: in the DOM, new dwellings or extensions

to existing dwellings shall be constructed such that solar protection and natural ventilation limits the use of air conditioning.

Article R. 162-4.-I: in the DOM, new dwellings or extensions to existing dwellings shall be designed and constructed such that natural ventilation is favoured.

Article R. 162-2.-I: in the DOM, new dwellings shall be equipped with a solar hot water system, which can meet at least 50% of the dwelling’s hot water demand.

Overview of regulations

Requirements for the performance of the building envelope to reduce the solar gains:

S = solar factor (proportion of solar energy which is transmitted through the structure. S is strongly influenced by the extent and efficacy of solar shading structures).

Transparent structures

Adjacent to an air-conditioned space: S ≤ 25%

Adjacent to an un-conditioned space: S ≤ 65%

Technical RequirementsBuilding Envelope

Opaque vertical structures : S ≤ 9%

Opaque horizontal structures : S ≤ 3%

Horizontal structures notto contain windows or transparent material

Technical Requirements Building Envelope (continued)

Exceptions for buildings at high altitudes (> 800m)

• In the higher zones of Reunion (altitude > 800m), a minimum insulation is required:Horizontal opaque structure: U-value ≤ 0.5 W/m².KVertical opaque structure: U-value ≤ 2 W/m².K

• Horizontal structures should notcontain any windows or transparent/translucent material, except for buildings which are located at an altitude greater than 800m.

Technical Requirements Natural Ventilation

• Objective of natural ventilation: to ensure minimum thermal comfort for occupants while contributing to the quality of indoor air.

• Requirements for natural ventilation:

Openings in at least two facades with different orientations, allowing an un-interrupted flow of air.

Minimum opening-to-wall ratio of the facades.

Openings in exterior facade: ≥ 20% (altitudes < 400m)

≥ 15% (between 400 and 800m)No requirement for alt. > 800m

Area of interior openings > area of

smallest facade opening

Air flow through perpendicular walls

Lmin = L .2

Uninterrupted air flow through building

Technical Requirements Natural Ventilation

Other requirementsCeiling fans and Ventilation

In living areas, provision has to be made for the later installation of

ceiling fans (provision for 2 fans in areas > 30m2)

Ceiling fans mandatory in rooms with one facade

with openings to the outside *

In air-conditioned rooms, controlled mechanical ventilation is required

* Does not apply to buildings in altitudes > 800m

Other requirementsMechanical Ventilation

Where mechanical ventilation is required due to high external noise levels, minimum air extraction rates are specified.

For utility spaces (kitchen, toilets, and bathrooms):House with 1

bedroomHouse with 2

bedrooms3 or more bedrooms

Kitchen Air change rate ≥ 20 m3/h

Air change rate ≥ 30 m3/h

Air change rate ≥ 45 m3/h

Bathroom

Air change rate ≥ 15 m3/h Air change rate ≥ 30 m3/h

Toilet Air change rate ≥ 15 m3/hFor living spaces, minimum outdoor air exchange rates:Bedrooms: ≥ 20 m3/hLiving room/dining room/lounge: ≥ 40 m3/h

Other requirementsSolar water heaters

All new dwellings must be fitted with a solar hot water system.

All installations of hot water should be powered by solar energy, such that the latter meets at least 50% of the hot water needs.

General comments from professionals regarding RTAA DOM (architects, engineers, trainers...)

• Requirements set by regulations are less stringent than existing PERENEreferential tool and technical guidelines (non-mandatory).

• 20% façade openings for natural ventilation can be onerous and expensive to achieve in residential buildings.

• Location of openings does not take into account prevailing wind direction.

• Only cross-ventilation is considered as method of natural ventilation.

• Lack of financial incentives (incentives are more suited to metropolitan countries, i.e. geared towards insulation).

• RTAA DOM does not take into account the building’s surrounding environment (whether shaded by another building or trees; ground cover, etc.).

• Different Solar Factor requirements for air-conditioned and non air-conditioned spaces. © F. Garde (Reunion), Presentation at workshop 01/10/2010

Transposition to MauritiusASPECT MAIN POINTS TRANSPOSITION TO MAURITIUS

Overallregulatory method

Applies only to new residential buildings and extensions to existing residential buildings.Focuses mainly on natural ventilation and sun protectionand solar hot water potential.First regulations in Reunion regarding energy efficiency. Overall , RTAA DOM is a concise as compared to other international codes.

Mauritian code will cover different building types.Due to climate, focus should be solar protection and natural ventilation, but other aspects need also be covered (esp. for large non-residential buildings), e.g. efficiency of mechanical systems and lighting, provision of controls for systems..Easy-to-follow guidance for early code development in Mauritius = more likely to be adapted.

Compliancemethod

Prescriptive requirementsonly (maximum Solar Factor or U-values for walls and roofs, % openings in walls..).

Prescriptive requirements = less design flexibility but also less demanding calculations.It is proposed to have alternative compliance methods for Mauritius, which includes whole-building performance.

Transposition to Mauritius (cont.)

ASPECT MAIN POINTS TRANSPOSITION TO MAURITIUS

General Requirementsfor Building Envelope

Solar Factor or insulation required, independent of orientation.Does not take into account surrounding environment.

Flexibility should be allowed (e.g. Walls/windows facing south: less stringent requirements, choice of insulation v/s shading...).Surrounding trees or buildings causing shading, ground cover (albedo effect) should be accounted for.

Natural Ventilation

Only cross ventilation considered.Facade openings requirements onerous (15% or 20% of facade area) and does not consider orientation.Ceiling fans or provision for future installation required for all living spaces.

Consider other means of natural ventilation (night ventilation, stack effect).Openings requirement (location, area) should be carefully assessed , also not to increase solar heat gains. Possibility to base opening area on floor area of room(?)Ceiling fans can increase thermal comfort and air flow, but requirement could be restricted to some rooms only (e.g. where opportunity for natural ventilation is limited).

Transposition to Mauritius (cont.)

ASPECT MAIN POINTS TRANSPOSITION TO MAURITIUS

Solar Hot Water

Solar Hot Water system to be installed in all dwellings and to provide for at least 50% of dwelling’s hot water needs.

Mandatory requirement for SHW for building types other than dwellings, where hot water demand is high (hospitals, hotels, care homes..) to be considered.

Building Services Systems&Lightingefficiency

Not covered in RTAA DOM

Building services and lighting account for a large amount of energy consumption in the building life cycle, therefore should be considered in Mauritian codes, especially w.r.t. large commercial buildings.E.g. Requirements for specific fan power, min. efficacy of lighting systems, provision of controls..

SUMMARY Key points of RTAA DOM

Conclusions and way forward:Re-adapt the successful and positive aspects covered in RTAA-DOM to Mauritius.

Consider any weaknesses of RTAA-DOM during the development of the Mauritian codes.

Targets: Reduce energy use, minimise use of fossil fuels, increase thermal comfort.

How: Natural ventilation for thermal comfort,solar protection, use of solar energy.

THANK YOU!