Table of Contents

1		Introduction
2		Is it for me?
3		How much does it cost?
4		What are the benefits?
5		Step by step guide
6		Case studies
7		Where can I find out more?

Step by step guide

1 Good building management is the first step to improving comfort: Keep doors closed and open windows only to ventilate the room. In winter, open blinds during the day to get free sunlight and heat. Close them during the evening to reduce heat losses. Repair any damaged doors or windows through which air may come in.

2 Design and selection of doors: Install a double door or a rotating door in the entrance to the building to avoid cold air coming in from outside. Exterior doors should close by themselves. Internal doors in large buildings improve the insulation level.

3 Make sure the building is well insulated: Good insulation can reduce heat transfer through walls, ceilings, windows etc by three quarters (see Figure 2). For optimal results, you should always consider three factors: selection of appropriate materials, insulation thickness and appropriate installation.

Figure 2: Insulation reduces thermal losses of your building!

• Select appropriate construction materials. Careful selection of construction materials is the key to achieving high comfort levels at low cost. A hollow ceramic brick has thermal conductivities between 0.49 and 0.76 W/m°K. Other materials like thermic clay have k values of less than 0.14 W/m°K. At present, this is the better construction option in cold countries. Table 2 shows U values of different construction materials. Figure 3 shows an example of a good construction material. This brick has an internal structure of air chambers, helping to achieve good thermal and acoustic insulation.

Table 2: Variation of U-values, depending on thermal insulation level

Key

Figure 3: example of a hollow brick with excellent insulating properties

• Good insulation materials have low thermal conductivity (0.03 - 0.05 W/m°K), low water absorbing capacity (wet insulating material has greater thermal conductivity), are non-flammable and resistant to chemical agents and rodents.

Insulating materials can be classified according to type:

• Vegetable: cork, wood fibre, flax, straw etc
• Mineral: fibreglass, mineral-wool, expanded clay, metal carbides, foamed glass etc
• Synthetic materials: expanded polystyrene, polyurethane and phenolic foams, PVC etc

In the UK, for example, the most common solutions are concrete blocks containing a core of expanded polystyrene or a double skin wall with foam insulation between. For buildings built with double skin walls to prevent damp, filling the cavity with foam is a good option.

Faulty design and installation can result in a serious reduction in the overall effectiveness the insulation. Continuity of the insulating layer and careful installation to prevent gaps and draughts ensures good performance and takes full advantage of the thermal properties of the material.

4 Make sure all building cavities are sealed: Small draughts are very common in buildings that have not been sealed correctly. Draughts often make people feel colder than they actually are since they can degrade R-values by as much as 40%. Draughts often come from electrical outlets, around ceiling fixtures and at openings to the attic. Holes where pipes and cables pass through also need to be sealed. Use foam insulation or a caulking compound to plug holes rather than fibreglass which allows air to pass.

5 Avoid thermal bridging: Thermal bridging occurs when a conductive material, such as a metal, crosses an insulating layer. Pipes, bolts, beams, doors, windows and areas of damp often provide thermal bridges between the inner and outer surfaces. Up to 20% of the energy loss in a building is due to thermal bridging. As well as leading to increased energy demand, the higher heat flow through thermal bridges lowers internal surface temperatures and is commonly associated with condensation and mould growth.

Thermal bridging can be avoided by:

• Exterior insulation
• Removing unnecessary structural elements
• Compact windows

6 Avoid condensation risk: condensation of moisture from the air appears when warm damp air from a kitchen or bathroom comes into contact with a cold external surface. Condensation can cause damage to building insulation and structural materials and can be a factor in triggering asthma and other health problems. Therefore it is advisable to minimise access of water vapour to the cool regions by placing a barrier with low water permeability on the inner surface of external walls, ceilings and floors. Low cost plastic sheeting is commonly used for this purpose.

7 Pay attention to glazed surfaces: one of the most effective ways to improve building insulation, is to improve the efficiency of windows and glazed surfaces. These are the weakest parts of the building envelope since they have U-values of 4 to 5 times greater than other surfaces.

• Maximise the glazed surface on the south face of the building. If windows are inefficient, there will be greater heat loss during the night and in winter. (This depends on the location - in the North we would minimise North facing windows since the main energy use is heating, not cooling!)
• Improve the efficiency of your windows by draught proofing with a caulking compound and weatherstripping.
• In warm countries use coloured glass to avoid excessive solar radiation. However, this prevents sunlight from entering and creates a gloomy and oppressive atmosphere entailing high artificial lightning demands. Superwindows allow light to enter while rejecting infrared heat radiation.
• Consider upgrading to double glazed windows. Double glazed windows have up to 55% greater R-values than single glazed units (0.4 vs 0.18 m²°K/W). The most efficient double glazed windows allow about 80% of the sunlight received to enter and have R-values of approximately 0.5. Windows with R-values of 0.7 or greater are sometimes called "superwindows". Many of the commercially available superwindows are filled with a highly insulating gas and have invisible coatings that only transmit radiation with specific wavelengths. Figure 3 shows typical U-values of different types of windows. Remember that the heat transfer coefficient U is the inverse value of R.
• Glazing should allow the maximum amount of sunlight to enter, always giving priority to natural lighting. This will also reduce utility costs.
• Avoid cheap windows with low U values and poor draught proofing such as aluminium or steel frame ones.

Figure 4: U-values of different types of windows