Why use Insulation?
The first statement of the 2nd law of thermodynamics – heat flows spontaneously from a hot to a cold body
In winter, the colder it is outside, the faster heat from your home will escape into the surrounding air. It is therefore vital that as much as possible is done to prevent this. Insulation makes it much more difficult for heat to pass through your house exterior by filling up the exterior walls, roof and ground floor with a material with lots of air pockets in it. These pockets greatly reduce what is known as your walls’ U value. The lower the U value, the slower heat is lost – and the less energy you need to keep your home warm. It is therefore imperative that considerable time is devoted to ensuring the new build is insulated to the highest possible standard.
Insulation is generally categorised into two types, bulk insulation and reflective insulation.
Types of Bulk Insulation
Bulk insulation traps millions of tiny pockets of still air or other gases within its structure. These air pockets provide the resistance to heat flow. Bulk insulation reduces radiant, convective and conducted heat flow.
Blanket Insulation is generally the most common and widely available type of insulation available and comes in the form of batts or rolls. It consists of flexible fibres, most commonly fibreglass. It is made from mineral wool, plastic fibres, and natural fibres, such as cotton and sheep’s wool.
Foam Board Insulation
Foam boards or rigid panels of insulation can be used to insulate almost any part of your home, from the roof down to the foundation. They provide good thermal resistance and often add structural strength to your home. Foam board insulation sheathing reduces heat conduction through structural elements, like wood and steel studs. The most common types of materials used in making foam board include polystyrene polyisocyanurate or polyiso, and polyurethane.
Loose-fill insulation consists of small particles of fiber, foam, or other materials. These small particles form an insulation material that can conform to any space without disturbing any structures or finishes. The most common types of materials used for loose-fill insulation include cellulose, fibreglass, and mineral wool. All of these materials are produced using recycled waste materials. Most fibre glass contains 20%–30% recycled glass. Mineral wool is usually produced from 75% post-industrial recycled content.
Liquid foam insulation materials can be sprayed, foamed-in-place, injected, or poured. Their ability to fill even the smallest cavities gives them a considerably better U-value than traditional batt insulation. Most foam insulation consists of materials similar to those found in pillows and mattresses and can now be used with foaming agents that don’t use chlorofluorocarbons (CFCs) or hydrochlorofluoro carbons (HCFCs), which are harmful to the earth’s ozone layer. Some types of available liquid foam insulation materials include these cementitious, phenolic, polyisocyanurate and polyurethane. Spraying expanding insulation foam.
Types of Reflective Insulation
Reflective insulation systems are fabricated from aluminium foils with a variety of backings, such as kraft paper, plastic film, polyethylene bubbles, or cardboard. The resistance to heat flow depends on the heat flow direction. Reflective insulation is most effective at reducing downward heat flow.
Foil Foam Foil
Foil Foam Foil consists of two layers of polyethylene backed foil with a centre layer of polyethylene foam. Foil Foam Foil has a greater insulation value than 100mm of common mass insulation. It has become very popular in Ireland as a method of achieving the recommended Uvalues without increasing the cavity depth.
Foil Bubble Foil
Foil Bubble Foil consists of two layers of polyethylene backed foil with a polyethylene bubble layer in between. Both Foil Foam Foil and Foil Bubble Foil reflect radiant heat, act as a barrier to convective and conductive heat transfer, are vapour-proof, and are unaffected by humidity. They are used in roofs, attics, ceilings, walls, floors and metal buildings.
Foil Foil consists of two layers of aluminium foil backed by woven polyolefin. It is used to reflect radiant energy as a house wrap, under the roof, in the attic, and with under floor heating.
There are a number of sustainable solutions to insulation available on the market, although generally more expensive they tend to perform as good as or even better than their counterparts.
Sheep’s wool is a superb insulator, having a slightly better U value than standard fibreglass. Wool’s unique advantage is its breathability. One of wool’s greatest benefits is that it insulates when wet. Wool is naturally flame resistant, too. Although wool can be damaged by moths, it contains lanolin, a naturally occurring oil that protects it from insects. From an environmental standpoint, sheep’s wool is a sustainable product.
Cellulose is composed of recycled newspaper and small quantities of shredded cardboard. This is a loose material that is installed with professional air blowers through injection holes – usually into walls or attic from the building exterior. It carries less health risk than fibre glass, but can condense as it settles and take on moisture, which will significantly degrade its resistance value and potentially grow mould if it stays wet.
Straw bales or loose straw can be installed in ceilings and walls to provide very effective resistance to convective heat transfer. Straw bales are inexpensive and readily available. Loose straw is lighter than bales and reduces the need to fortify roof framing. To reduce fire potential, straw is treated with natural flame retardants such as boric acid or clay slip.
Grants for home insulation, subject to Terms and Conditions, are available from SEAI http://www.seai.ie