Introduction & Terminology
Insulation is the most effective way to improve the energy efficiency of a home or a building. Insulation of the building envelope helps keep heat in during the winter and out in summer to improve comfort and save energy. Insulation could add additional benefits such as acoustics and waterproofing. Effective draught proofing, moisture control and ventilation are important at design stage.
The appropriate level of insulation intervention will depend on climate, building construction type, and whether auxiliary heating and/or cooling is used.
Insulation – Overview
Insulation reduces heat flow and is essential to keep a building warm in winter and cool in summer. A well-insulated and well-designed building will provide year-round comfort, decreasing energy costs. This, in turn, will reduce greenhouse gas emissions.
Climatic conditions will influence the appropriate level and type of insulation. Establish the climatic zone from the Map of Climatic Zones of South Africa.
Passive design techniques must be used in conjunction with insulation. For example, if insulation is installed but the building is not correctly shaded, built up heat can be trapped in by the insulation creating an ‘oven’ effect. Air tightness of a building is important, as draughts can account for up to 25 percent of heat loss in winter.
Ensure proper ventilation in buildings where fossil fuels are burned as an energy source.
Certain types of insulation can assist with weatherproofing and control moisture problems such as condensation. Some types of insulation also have soundproofing qualities. Some products are environmentally friendly and contain recycled material.
The most economical time to install insulation is during construction.
How does insulation work?
An un-insulated home is subject to considerable winter heat losses and summer heat gains.
The term ‘insulation’ refers to materials or a combination thereof which provide resistance to heat flow.
When these materials are installed in the roofs, ceilings, walls, and floors of a building, heat flow into and out of the building is reduced, and the need for heating and cooling is minimized. Although ceilings and walls may be insulated, heat loss will still occur in winter if there are large areas of unprotected glass or through fixed wall vents, gaps electric light entry points and cracks around external doors and windows.
Appropriate internal window coverings (e.g. lined drapes with pelmets) and draught proofing are vital to complement insulation. Insulation should always be coupled with appropriate shading of windows and adequate ventilation in summer. Without shading, radiant heat entering the home through the windows will be trapped inside by the insulation and cause discomfort.
Principles of Insulation
Resistance to heat flow is achieved by the use of either bulk insulation, reflective insulation or a combination of both, which work in different ways.
What you need to know
There are various factors to consider before making an insulation decision:
Thermal Performance – Installed R-value
When insulating a home or building, it is important to ascertain the R-value specified by the National Building Regulations.
It’s also important that the product provide long-lasting thermal performance. It is the overall R-value installed that is important.
Life Time Performance
In order to ensure the expected energy savings, it is important that the insulation does not deteriorate, or settle, over time.
In accordance with the application of the National Building Regulations SANS 10400-T Fire Protection, all insulation products should be independently tested in accordance with SANS 428 Fire performance classification of thermal insulated building envelope systems, prior to being sold.
SANS 428 incorporates all factors required for fire-hazard or fire-risk assessment of the materials, products, or assemblies under actual fire conditions.
SANS 428 provides a standard testing procedure to measure:
- combustibility;SANS 10177-5:2007, Fire testing of materials components and elements used in buildings Part 5: Non-combustibility at 750 ºC of building materials.
- surface fire properties;SANS 10177-10:2007, Fire testing of materials, components and elements used in buildings Part 10: Surface burning characteristics of building materials using the inverted channel tunnel test
- designated use and application.SANS 10177-11:2007, Fire testing of materials, components and elements used in buildings Part 11: Large-scale fire performance evaluation of building envelope thermal insulation systems (with or without sprinklers)
Insulation will lose its insulating efficiency or R-value when exposed to moisture. Some insulation products are not absorbent and, if exposed to moisture, will not wick up or hold water. If allowed to dry out insulation may retain its original R-value. In wall applications certain insulation material may be applied as vapour retarders, or moisture barriers.
Air infiltration generally occurs in the areas of a home that are not correctly sealed or insulated, such as around windows, doors, fireplaces, HVAC ductwork and perimeter joints. It can, and should, be controlled with proper caulking, and sealing of band joists, sill plates, header plates, and around doors, windows, electrical outlets and other openings.
In assessing the environmental characteristics of insulation materials, consideration must be given to a broad range of issues relating to the resources going into their production, manufacturing processes, pollutants given off during their lifecycle, durability, recyclability, and impact on indoor air quality. Recycled content is the most recognized environmental feature of building products.
Materials with recycled content have four advantages:
- they require less natural resource;
- they divert materials from the solid waste stream;
- creating additional job opportunities for the unemployed by collecting waste;
- they use less energy during manufacturing.
The insulation industry is full of good examples of recycled material use:
- Cellulose Fiber uses recycled newspaper by weight; the rest is comprised of fire retardant chemicals and—in some products—acrylic binders.
- Fiberglass uses recycled glass
- Mineral wool actually refers to two different materials: slag wool and rock wool. Slag wool is produced primarily from iron ore blast furnace slag, an industrial waste product and Rock wool is produced from natural rocks.
- Polyester Fiber uses recycled PET bottles and some use Kenaf (similar to hemp)
- Polystyrene uses recycled plastic resin in some extruded and expanded polystyrene.
A life-cycle analysis is an appraisal of the environmental impacts connected with a product through an examination of the product’s environmental traits during many stages including pre-manufacturing; manufacturing; distribution/ packaging; use, reuse, maintenance; and waste management. In reviewing each of these stages, a life-cycle evaluation clearly shows its environmentally beneficial attributes.
This is just the first step…”
How insulation performance is measured.
The thermal performance of all components and systems except windows and doors is expressed in terms of R-value; for windows and doors, performance is expressed in terms of U-value.
What is an R-value?
Insulation materials are rated for their performance in restricting heat transfer. This is expressed as the R-value, also known as thermal resistance. The R-value is a guide to its performance as an insulator—the higher the R-value, the better the insulation (i.e., resistance to heat flow) it provides.
R-values are expressed using the metric unit’s m².K/W, where:
• m² refers to one metre squared of the material of a specified thickness;
• K refers to a one degree temperature difference (Kelvin or Celsius) across the material;
• W refers to the amount of heat flow across the material in watts.
Use the nominal R-values as listed by the manufacturer on the packaging of the insulation to determine the performance.
Products which have the same R-value will provide exactly the same insulating effect as each other, provided they are correctly installed. The higher the R-value the more effective the insulation. Products must be installed in accordance with the manufacturer’s specifications.
The information available on the product data sheet and/or label must include the R-value and whether it must be installed professionally or DIY. Ensure that it suits your particular application. Ask if performance guarantees and/or test certificates are available.
SANS 10400-XA Energy usage in buildings and SANS 204 Energy efficiency in buildings are currently under review, all publications will be republished.