Determinación Problemas jurídicos en base a como resolvió la Corte Constitucional

Insulation acts as a barrier to heat flow and is essential to keep buildings warm in winter and cool in summer. There is a wide variety of insulation materials. The first parameter used to distinguish them is their thermal performance, represented here by their U-value. There are many other factors that can influence the choice of a material over another. These factors include embodied energy, suitability in the building, ease of installation, environment impact, fire resistance, durability and, of course, cost (Burton 2011). In this study we will focus on the thermal performance of the materials, leaving aside the other parameters. Table 2.2 shows the U-value of common generic insulation materials used in houses. In this list Aerogel is the “best” material because its thermal conductivity (U-value) is the lowest.

In the case of uninsulated dwellings, insulation can be added to them with varying effectiveness depending on the construction type and where the insulation is placed. If a building has cavity walls, the first choice is to fill the cavity with insulation (cf. Figure 2.6). The insulation, which is injected into the cavity via holes drilled through the outer leaf, can be selected from many kind of materials. The most common cavity-fill insulations are polystyrene beads and mineral fibres. This method allows to greatly reduce the U-value of a standard cavity wall without affecting the existing exterior or interior surface, and with minimal disruption. Depending on the dimension of the cavity and on the type of insulation, cavity wall insulation may not be enough. If this occurs there are other insulating solutions that can also be applied to solid walls.

The first measure is external insulation. It has the advantages of less disruption inside the house, retaining thermal mass inside, eliminating cold bridges and providing a weather-proof barrier. It has some disadvantages such as the need to extend the roof and openings sills and the necessity to move drainage pipes. Moreover it changes the external appearance of the building, a fact that can be positive if the existing finish of

Figure 2.6: Cavity wall insulation (Source: www.greenspec.co.uk/building-design).

the building is poor, or negative if the building has good architectural features. This last factor can be crucial in the decision whether or not to opt for external insulation. In fact, if the external walls are uninteresting. As they are affected by dampness and present cracks or other problems, the externally applied insulation may be the ideal solution. In one operation, it improves thermal performances, appearance and protection from the external weather. There are two ways to insulate the building from the outside:

• Wet render system: It consists of insulant, adhesive mortar and/or mechanical fixings, profiles and edgings used on corners and on windows reveals, a base coat render incorporating a glass fibre or plastic or metal mesh and a top coat render with or without a finish. It is the cheapest method among external insulation (cf. Figure 2.7).

• Dry cladding system: it differs from the previous system because the insulation is fixed to the external wall in particular points instead of all the surface. It consists of: insulant, a supporting framework or cladding fixing system connected to the wall, a ventilated cavity, cladding materials and fixings (timber panels, stone or clay tiles, brick lips)(cf. Figure 2.8).

The second type of measure that can be applied both to cavity and solid walls is the internal insulation. It has the advantages of not changing external appearance and of being less expensive compared to the external insulation. Moreover it is not affected by external weather and its application does not require scaffolding if the ceilings are not too high. However there are also some disadvantages. The first one is the reduction of the internal space, the second is the need to move power points, skirting boards, radiators and wall fittings, and another one is the difficulty of fixing heavy items to the wall afterwards. Other drawbacks are the interstitial condensations that can occur and the impossibility to eliminate structural cold bridging. There are three common systems of internal insulation:

Figure 2.7: External wall insulation: typical wet render system applied to an existing

solid masonry wall (Source: www.greenspec.co.uk/building-design).

Figure 2.8: External wall insulation: typical dry cladding system applied to an existing

Figure 2.9: Internal wall insulation: insulated plasterboard (Source: www.greenspec.

co.uk/building-design).

• Insulated plasterboard: thermal boards are glued directly on to the internal walls. Some of these boards have a built-in vapour control layer to stop moist internal air condensing on the cold wall behind the insulation. The internal wall must have an even surface. Airtightness must be preserved with continuous ridges of plaster adhesive round the edges of the wall and around all windows and doors. Between the board and the insulation there must be no gaps and between the insulation and the internal wall air movement must be avoided (cf. Figure 2.9). • Insulation and battens: a rigid insulation must be fixed to the wall trough battens.

It consists of vertical timber battens or metal furrings fixed to the wall, rigid or semi-rigid insulation boards between the battens and plasterboard. Also in this case a vapour check barrier is necessary between the insulation and the plasterboard (cf. Figure 2.10).

• Stud insulation: it should be employed on a wall that has previously suffered from damp. In this way it is possible to create a cavity gap between the internal wall surface and the insulation. This system is also good where the wall is bowed or uneven. It consists of: timber, extruded polystyrene or metal frame braced between the floor and ceiling, insulation stapled to the frame leaving a 30 mm air gap between insulation and wall, a damp-proof membrane between the studs and the wall and plasterboard. The number of studworks depends on the use of the dwelling. In some situation, in fact, for example in rented accommodation, a more robust structure is needed. Anyway, it must be kept in mind that more studwork will reduce thermal performances due to thermal bridges (cf. Figure 2.11).

Figure 2.10: Internal wall insulation: battens with insulation (Source: www.greenspec.

co.uk/building-design).

Figure 2.11: Internal wall insulation: stud insulation with air gap (Source: www.greenspec. co.uk/building-design).

Figure 2.12: Timber ground floor insulation (Source: www.greenspec.co.uk/building-

design).

In some cases, a combination of different refurbishment technologies may be justified. However, in most cases, the use of a single system is usually a better solution. Some possible combinations of the three solutions are cavity insulation combined with internal or external insulation and internal insulation combined with external insulation (Energy Saving trust 2006a, Highfield 2009; Burton 2011; Thorpe 2010).