Buildings 5
III) ECORENO'V: housing energy refurbishment platform: Grand Lyon, France Lyon Metropole's eco-refurbishment platform was launched in 2015 after a 2-year experimentation
5.3 Measures for energy efficient buildings
All the processes that are involved in the energy efficiency of buildings, from the design and the construction, to the renovation and operation, recognize the provision of healthy and comfortable environments to its occupants as the main purpose of any buildings. The 'sustainable comfort' can be defined as achieving good comfort conditions with no or limited use of resource energy and through the use of environmentally non-harmful materials.
In this framework, a ten-step approach is provided to improve the energy efficiency of buildings, which implies also adopting measures on both thermal and electric energy (e.g. through reducing the wall transmittance in the former and using efficient appliances in the latter). The approach leaves ample freedom to designers while supporting them in adopting solutions that also take into consideration local specificities of climate, culture, locally available materials:
1. Define explicitly the building objectives, with particular focus on the thermal comfort.
2. Assess the microclimatic factors and intervene on the site layout and features which can affect the comfort indoor.
3. Control the heat gains at the external surface of the building envelope.
4. Control and modulate heat transfer through the building envelope.
5. Control the internal gains from appliances and lighting.
6. Allow for local and individual adaptation.
7. Use passive means and strategies (28) to deliver and remove thermal energy to/from the building.
8. Use active heating and cooling systems assisted by natural (and renewable) energy sources.
(27) Moschella, A., Salemi, A., Lo Faro, A., Sanfilippo, G. Detommaso, M., Privitera, A. (2015). Historic Buildings in Mediterranean area and solar thermal technologies: architectural integration vs preservation criteria. Energy Proceedia 42:416-425
(28) This does not exclude the use of a fan or a pump when their application might enhance the performance.
9. Use high efficiency active conventional heating and cooling plants, if still necessary.
10. Train building managers and occupants on how to use, monitor the performance of and adequately operate and maintain the building.
The first two points refer to the comfort requirements and the multiple interactions between indoor and outdoor environments. Steps 3 and 4 include all technologies and strategies associated to the building envelope from which the net thermal energy needs for heating and cooling (29) depend. Steps 5 and 6 have to do with the way a building is used and occupied. Points 7, 8 and 9 provide a sustainable approach to reach low levels of delivered (or final) energy consumption (30) implementing appropriate system solutions. The last step includes all strategies needed to verify and adapt the building performance during the real-life operation.
Mostly, the suitability of energy-efficient solutions mainly depends on the micro-climate conditions and their cost-effectiveness. The economic issue is related to the maturity of the local market (of materials, technologies and jobs) and to the construction type (i.e.
new building or building retrofit). The tables below provide an overview of the prevailing technologies and strategies, which could be considered for cold and intermediate/warm climates (Table 10) in accordance to the methodological step (introduced above) and the building type.
(29) Energy needed for heating and cooling means heat to be delivered to or extracted from a conditioned space to maintain intended temperature conditions during a given period of time.
(30) Energy, expressed per energy carrier, supplied to the technical building systems through the system boundary, to satisfy the uses taken into account (heating, cooling, ventilation, domestic hot water, lighting, appliances, etc.).
Table 10. Building technologies and strategies for cold, warm and intermediate climates, according to methodological step and construction type Cold Climate
(Heating degree days > 3 350)
Warm and intermediate Climate (Heating degree days < 3 350)
New building Renovation New building Renovation
- Summer Adaptive comfort - Optimised distribution of internal spaces
- Summer Adaptive comfort - Optimised distribution of internal spaces
- Main building axis oriented east- west and optimised distribution of internal spaces
- Main building axis oriented east- west
- Cool materials and finishing for urban surfaces
- Inclusion of greening strategies in the design (vegetation and surface water)
- Cool materials and finishing for urban surfaces
- Inclusion of greening strategies in the design
- Triple or double-glazed low-e windows
- Double-glazed low-e windows - Exterior storm windows with low-e coating
- Internal insulated shades
- Architectural shading - Reflective (cool) roof - Ventilated roof, double-skin façades
- Double-glazed low-e or windows with low g-value
- Exterior window shading/blinds and dynamic shading
- Finishing material
- Low heat conductivity building materials
- Reflective (cool) roof
- Double-glazed windows with low g- value
- Exterior window shading/blinds and dynamic shading
- Window film reducing g-value - Finishing material
- Low heat conductivity building materials
- Highly insulated roof, external walls and basement
- Reduction of thermal bridge - Windows and doors with high airtightness levels
- Medium-highly insulated roof, external walls and basement - Main envelope joints thermal bridge free
- Windows and doors with good airtightness levels
- Medium-highly insulated roof and external walls
- Optimised thermal mass inertia
- Medium insulated roof and external walls
- phase-change materials
- Daylighting solutions
- Efficient lighting sources & syst - Efficient appliances & equip.
- Smart shutdown logics
- Efficient lighting sources and systems
- Efficient appliances and equipment - Smart shutdown logics
- Daylighting solutions
- Very efficient lighting sources and systems
- Very efficient appliances and equipment
- Smart shutdown logics
- Very efficient lighting sources and systems
- Very efficient appliances and equipment
- Smart shutdown logics
Cold Climate (Heating degree days > 3 350)
Warm and intermediate Climate (Heating degree days < 3 350)
New building Renovation New building Renovation
- Openable windows
- Flexible dressing code - Openable windows - Flexible dressing code
- Openable windows - Ceiling fan
- Low thermal insulation furniture
- Flexible dressing code
- Openable windows - Ceiling fan
- Low thermal insulation furniture - Flexible dressing code
- Architectural features - Dynamic glass/shades
- Comfort daytime and night ventilation - Ground heat exchanger
- Dynamic glass/shades
- Comfort daytime and night ventilation
- Architectural features - Dynamic glass/shades - Comfort daytime and night ventilation
- Ground heat exchanger - Direct or indirect evaporative cooling - Radiative cooling - Open groundwater or surface water systems
- Dynamic glass/shades
- Comfort daytime and night ventilation
- Ground source heat pump - Ground source heat pump - Ground source heat
pump
- Solar cooling systems
- Ground source heat pump
- Solar cooling systems - Very efficient HVAC systems
- Condensing boiler
- Highly insulated distribution plant - Straight distribution ducts layout and efficient fans/pumps
- Very efficient HVAC systems - Condensing boiler
- Highly insulated distribution plant
- Straight distribution ducts layout and efficient fans/pumps
- Very efficient HVAC systems
- Condensing boiler - Insulated distribution plant
- Straight distribution ducts layout and efficient fans/pumps
- Very efficient HVAC systems
- Condensing boiler - Insulated distribution plant
- Straight distribution ducts layout and efficient fans/pumps - Exhaustive building manuals
- Monitoring plan - Maintenance plan
- Clear and exhaustive building manuals - Monitoring plan
- Maintenance plan
- Clear and exhaustive building manuals - Monitoring plan - Maintenance plan
- Clear and exhaustive building manuals - Monitoring plan - Maintenance plan
5.3.1 Improvement of the envelope and other aspects
One of the most common strategies for energy retrofit of buildings usually consists in reducing both thermal losses through the envelope and cooling loads, and in controlling the solar heat gains.
The losses of energy through the envelope may be reduced through the implementation of several measures that affects glazing and frames and the walls and roofs characteristics.
Gains and losses of energy through windows are four to five times higher than the rest of the surfaces. Both daylight provision and gaining or protecting from solar radiation penetration must be taken into account in the choice of appropriate glazing. New technologies with decreased values of transmittance for glazing are available: double-glazed with low emissivity coating, low-Emissivity Argon filled double glazing and triple glazing (respectively up to 1.1 W/(m2·K) and 0.7 W/(m2·K)). Moreover, since the characteristics of frames affect the global window performance, it is necessary to consider also the replacements of these elements in the energy retrofitting of the building. In this regard, thermal break aluminium, plastic and wooden frames show good performances.
Either internal or external thermal insulation of walls reduces their transmittance values according to specific needs and location of the buildings. Commonly-used types of insulation in building construction include: Fibreglass, Polyurethane foam, Polystyrene foam, Cellulose insulation and Rock wool. These materials also contribute to reduce the effect of thermal bridge and to improve sound insulation and thermal inertia.
The abatement of cooling loads is achieved by reducing solar radiation penetration through the use of shading devices. These comprise: movable devices which can be controlled either manually or automatically; internal and external blinds which help control lighting level and uniformity, and allow stopping solar radiation before penetrating into the room when arranged externally.
An increased energy performance of buildings is achievable by operating on the heating system. The overall efficiency of the space heating system includes the efficiency of the generator and the losses of distribution, emission and inaccurate control systems.
Box 11.