Attic and wall insulation

The easiest way to save is not to spend

Energy efficiency measures for buildings may include the insulation of floors, walls and attics as well as energy efficient windows (double or triple glazing – see the specific fact sheet on this).

Because many of Europe’s rural homes and buildings predate stricter insulation requirements that were introduced since the 1990’s – and are therefore poorly insulated, they are a significant source of heat losses during winter, increasing heating needs, and can lead to overheating in summer, thereby creating additional need for cooling. Rural homes and buildings also often need more energy for heating and cooling than their urban counterparts and have a harder time keeping air from leaking outside; they tend to be larger and are often free-standing.

The amount of energy and money that can be saved by applying floor, wall and roof insulation depends on several factors including the type of insulation used, climate, size of the building, current insulation levels, the type of heating and cooling equipment installed and related cost of fuel.

Payback periods vary widely depending on these conditions, although insulation is usually very attractive and affordable, particularly when the original level of insulation is low. In those cases, simple measures already improve the energy performance of a building significantly, thereby reducing energy expenditures. This will benefit cash-strapped farmers, rural businesses and households that face challenges associated with being located in low population density areas. Insulation also increases the comfort of a building for its inhabitants. Measures have a long lifetime and are effective for several decades.

General Info

What is it?

Heat flows naturally from a warmer to a cooler space. In winter, the heat moves directly from all heated building spaces to the outdoors and to adjacent unheated attics, garages, and basements - wherever there is a difference in temperature. During the summer, heat moves from outdoors to the house interior.

By improving a building’s insulation, less heating is needed in the winter and less cooling is needed in the summer. The more heat flow resistance insulation provides, the lower the heating and cooling costs are of a building. Properly insulating also improves comfort.

There are different applications of building insulation. Generally a distinction is made between floor, wall and roof insulation. These are discussed in this fact sheet. Also windows are an important source of heating and cooling losses and are discussed in a separate fact sheet. Recently adopted European building regulations have set stringent rules for new and existing buildings in Member States. Chiefly, the Energy Performance of Buildings Directive

(EPBD1) that sets minimum energy performance requirements for buildings or building units. For example, as of 31 December 2020 new buildings in the EU will have to consume 'nearly zero' energy and the energy will be 'to a very large extent' from renewable sources. Also, minimum energy efficiency requirements for components such as insulation and windows are introduced for all replacements and renovations.

What are the benefits?

Main benefits of improving the insulation of walls, roofs, lofts and floors of a building are:

  • Saving energy and money;
  • Increasing the comfort of a building for its inhabitants.

The amount of energy and money that is saved depends on several factors: the local climate; the size, shape, and construction of the building; the living or dwelling habits; the type and efficiency of the heating and cooling systems; and the fuel that is used for heating and cooling.

How does it work?

The natural flow of heat from warm to colder spaces involves three mechanisms: conduction, radiation and convection. Conduction is the mechanism through which heat travels through materials (for example, a spoon placed in a hot cup of coffee conducts heat through its handle to your hand). Radiant heat moves in a straight line and heats anything solid in its path that absorbs its energy. Convection is the way heat circulates through liquids and gases, and is why lighter, warmer air rises, and cooler, denser air sinks.

Insulation serves to reduce the flow from warm to colder spaces by forming a thermal blanket around a building.

Most common insulation materials work by slowing conductive heat flow and -- to a lesser extent -- convective heat flow. Radiant barriers and reflective insulation systems work by reducing radiant heat gain.

Suitability/applicability

From the 1990s onwards most buildings are built following stricter insulation requirements. Older buildings are very likely to have hardly any insulation at all. Because most of Europe’s rural homes and buildings predate 1990 and are poorly insulated, they are a major source of heat losses during winter2, increasing heating needs, and can lead to overheating in summer, thereby creating additional need for cooling. In these buildings, efficiency can be greatly improved by applying insulation.

The appropriate insulation for a building depends on the climatic conditions of a region as well as the level of insulation that is desired (the so-called U or R-value). It also depends on whether insulation is added to existing buildings or new builds. Other considerations may include indoor air quality impacts, life cycle costs, recycled content, embodied energy, and ease of installation. Some insulation measures require professional installation, while many forms of insulation can be handled by homeowners themselves.

The applicability and suitability of different materials and techniques also depends strongly on the building (in case of retrofitting). This is especially true for wall insulation. For example, while most buildings built after the 1920’s have cavity walls3, older buildings often only have a solid wall without a cavity4:

  • In case of cavity walls (that already insulate better than single walls), it is most suitable to fill the gap between the two walls with insulation. Materials often used are mineral wool, beads or granules as well as foamed insulants. The latter can be installed in building cavities through holes drilled (usually) on the exterior of the house. After the installation, the holes are plugged and finish materials replaced.
  • In case of single walls, one has the choice between internal or outside wall insulation. Internal insulation is done by fitting rigid insulation boards to the wall, or by building a stud wall filled in with mineral wool fibre. External wall insulation involves fixing a layer of insulation material to the wall, then covering it with a special type of render (e.g. plasterwork) or cladding. Internal and external insulation both have their specific advantages and disadvantages.

Suitability of roof and attic insulation materials also depends on aspects such as the accessibility of the space that needs insulation, the (ir)regularity of the joists, the roof type (e.g. flat or pointy).

Depending on the type and form of insulation, insulating buildings may be disruptive or inconvenient to the inhabitants of buildings. This is particularly so for internal wall insulation, in case of single walls.

Adding insulation to existing buildings could result in an increase of damp or condensation issues in spaces such as lofts and attics that become cooler as a result of insulation. Damp and condensation issues need to be resolved before installing any insulation (this also applies to walls).

Detailed Info

Costs, Savings, Earnings

The cost of insulation consists of raw materials and installation charges. In proportionate terms, insulation has probably the highest return among low-carbon investments and many measures are very affordable.

Costs, savings and earnings of insulation measures depend on a number of factors:

  • The climate, country or region where they are installed;
  • The wall (and roof) surface of the building;
  • The current insulation levels and energy performance of the building;
  • The type of heating and cooling equipment installed (and related cost of fuel);
  • The level of insulation desired (and used materials).

Payback periods vary widely depending on these conditions, although they are usually very attractive and affordable, particularly when the original level of insulation is low. In that case, simple measures already improve the energy performance of a building significantly and take only several years to pay for itself. Insulation has a long lifetime, is effective for several decades and will pay itself back several times in that period.

In the context of recently introduced European energy performance standards of buildings regulation, it is expected that more European countries will introduce obligatory energy performance certificates or labels for buildings that are being sold or rented-out. Proper insulation is a major contributor towards having a good energy label, which will increase the value of a property.

In a number of countries, insulation retrofits are financially supported by government grants or low-interest loans and other incentives.

Environmental Impacts

Well-insulated buildings reduce energy consumption of a building, thereby reducing the negative environmental impact (CO2, local air pollutants) that is a result of heating and cooling. There are no significant negative environmental impacts associated with insulation.

Efficiency

Not applicable.

Commercial Maturity

Insulation materials and techniques are commercially mature and widely available.

Level of Maintenance

VERY LOW: Insulation usually does not require any maintenance, except for replacement at the end of its lifetime (several decades).

Technical Details

There are many different insulation types5, materials and techniques, for different applications. Insulation materials6 differ in their applicability, thermal resistance (the R or U - values – see below), costs, and environmental impacts.

An insulating material’s resistance to (conductive) heat flow is measured or rated in terms of its resistance to the flow of heat, the so-called R-value. For insulation materials this means that the higher the R-value, the better its insulating effectiveness. The R-value depends on the type of insulation, its thickness, and its density. So-called U-values are the direct opposite of R-values, representing the amount of heat that escapes through a material. The lower the U-value, the slower the rate of heat flow and the better the insulating quality. A standardized insulation rating system ensures consistency, with insulating materials rated in R- and/or U- values.

Each region has its own recommended R – or U-values for insulation, depending on climatic conditions of that region. The table that can be found in the link below shows the recommended U-values for insulation material for walls, roofs and floors for 31 countries in Europe: http://www.eurima.org/resource-centre/facts-figures/u-values-in-europe

Regional variations

The most suitable insulation material and techniques, as well as the most optimal (economic) levels of insulation vary between regions. For example, optimal insulation in Sweden is different from insulation in Spain. It is therefore recommended to survey the U or R-values that are appropriate for a specific region (see above in the section technical details).

Trade associations

PU Europe

www.pu-europe.eu

European Insulation Manufacturers Association

www.eurima.org