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In this business model the key player is supported by digital tools supporting home-owners as well as designers in the initial planning of the renovation work. The tool usually act as a guide to optimize the application of the overall retrofitting process by for example collecting all the information related to the initial state of the building to be renovated and the preferences, the needs and desiderata of the building owner. The ICT tool processes the information gathered and suggests an optimised approach to the renovation project. The main advantage is the possibility to effectively manage the whole process in a comprehensive way. The possible disadvantages of the model are the resources needed to produce all process descriptions and checklists needed. It may also be difficult to make sure that all adopt the new working models. The commitment of the whole organisation is needed.
As the idea is very much based on creation and availability process descriptions, checklists and tools, the maintenance and keeping the material up-to-date has to be carefully checked. Thus it is highly important to be able to create reliable initial information about the building and rely on the initial model. In order to make reliable assessment about the saving potentials in terms of energy and costs, the actors involved must be able to use appropriate tools for energy performance assessment, and be able to make justified conclusions about the savings. Here the quality of the initial information is highly important. In addition, a solid understanding of the users’ behaviour and willingness to commit to energy savings is essential.
The renovation of Torrelago district was implemented in the framework of the FP7 funded CITyFiED project (http://www.cityfied.eu/) .
Torrelago district involves 31 private multi-property residential buildings (1488 dwellings) that were constructed in the 1970s–1980s, more than 140,000 m2 and 4000residents involved. Former conditions of the district were very low in terms of efficiency, comfort and costs, which fostered the intervention. Main energy measures implemented at the building scale are buildings external insulation (Composite System-ETICS, ventilated façade), connection to district heating (twelve new heat exchange substations at building level), individual metering to raise users’ awareness.
This package consists in the very first step of the thermal insulation of a building and includes the following components:
- Roof insulation, using either an insulation panel/roll or a spray foam under the roof. External roof insulation is also possible (i.e. built-up roof insulation under waterproofing)
- Energy efficient windows (double or triple glazing)
Without proper insulation, as much as 25 to 30% of the heat in an uninsulated house is lost through the roof, and 10 to 15% through the window. Those two points are usually addressed first (i.e. before the walls – 25 to 35% of losses, and the floor – 10 to 15% of losses) as they are the most easy to deal with and the most profitable in the short term. Loft insulation and new windows act as a barrier, slowing the movement of heat out of the building during the winter and into it during the summer.
On its own,this package will not increase the performance of a building sufficiently for this building to become energy-efficient, but it can be complemented at a later stage with additional technologies so as to generate more substantial energy savings.
Roof / loft insulation
Different types of materials can be used for internal and external insulation, either in a roll, panel or spray foam form, each having its own benefits and limitations: wool (glass, rock, sheep or hemp), polyurethane, expanded polystyrene (EPS) or extruded polystyrene (XPS). The recommended uses are the following:
There are two main ways to insulate a loft or a roof: at the joists or at the rafters.
Cold loft insulation at the joists
The insulating material is laid (or sprayed) on the floor of the cold loft.
Warm loft insulation at rafter or externally
For the insulation of warm and occupied lofts under a pitched roof, two techniques are available:
The internal insulation can be done with semi-rigid panels or rolls, whose layout will depend on the structure of the building frame and the available space.
A loose-fill insulation can also be injected in an air-tight cavity under the roof cover.
Insulating from the outside avoid loosing living space but requires to remove the existing covering. Load-bearing panels can be used, or insulation can be added between the rafters and the roof covering, with a roof sarking (i.e. a protective and waterproof second skin under the roof). This last solution requires raising the roof line.
Flat roofs insulation
For flat roof, external insulation (“hot roof”) is recommended. Insulating from the inside can cause damage as it will inevitably lead to the formation of condensation. In this case, a rigid insulation is fitted outside, above the existing weatherproofing. This is then covered with a further weatherproofing layer.
The performance of the windows depends on the glazing and the frame. The level of performance is expressed by the thermal transmittance coefficient Uw. Performant solutions exist with timber, PVC or aluminium (with thermal breaks) frames.
Double glazing is made of two glass layers separated by an air gap. It is more performant than simple glazing and reduces the condensation and heat losses through the windows. The new generation of double glazing includes argon instead of air, as well as a fine transparent layer with low emissivity, usually silver-based: its insulating capacity is 2 to 3 times that of standard double glazing.
Triple-glazing is made of three layers of glass separated by two layers of argon or krypton and two low-emissivity metallic layers. The Uw value is excellent, however the ligh transmittance can be lower than for a good double-glazing.
Windows can be changed with two main techniques:
- By keeping the existing frame: this a simplest option, however the performance and the glazed area are slightly reduced
- By removing the existing frame: this is the most performant option, however it requires more work and some finishing
As double or triple-glazed windows will be more airtight than the original single-glazed frames, condensation can build up in the building due to the reduced ventilation. If there is not a sufficient level of background ventilation in the room, replacement windows should therefore have trickle vents incorporated into the frame, that let in a small amount of controlled ventilation.
The project STUNNING aims at building up a stakeholder community around a Renovation Hub designed as a knowledge sharing platform, providing information on innovative solutions for building renovation and novel business models (illustrated through case studies) for their adoption and large scale replication. The provided solutions involve affordable and adaptable refurbishment packages, taking into consideration the whole renovation value chain.
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