INSULATION - OVERVIEW
The great thing about insulation is that, long after it has been fitted and has paid for itself, it continues to fulfil its purpose and never wears out. Well, hardly ever.
But without high quality insulation, you are wasting your time and money, even if you have the most sophisticated heating system on the market.
Conversely, it is important to consider the overall energy efficiency of the home, as opposed to insulating just one or two particular areas only. For example, a homeowner may carry out an insulation upgrade to walls which could be either internal, external or cavity insulation. However, there would be little point in spending money doing this, if the heat loss from existing windows which are old, or ill fitting were ignored.
The types of insulation that a homeowner may consider will depend on the house type and its age. Ideally, an assessment of the energy requirements of the house should be carried out, by an approved BER assessor.
Insulation is one of the most solid investments a homeowner can make in terms of return in investment. In order of priority - attic insulation is very important and one of the easier methods of increasing energy efficiency (potential heat loss can be up to 25%). This can be followed by externally or internally insulating walls and finally increasing floor insulation.
While natural insulation may cost more, there are additional benefits in terms of ease of use, thermal performance in terms of offsetting over-heating in summer and effective insulation in winter, not to mention acoustic and environmental characteristics.
Surprisingly, however, more and more insulation is not necessarily always better. There are cases where too much of it is actually a bad thing – and other cases where the economic return on extra insulation is negligible and not worth installing.
There are two important aspects to insulation:
1. Choosing the correct material.
2. Having it installed correctly.
1. The most common insulation materials we use in Ireland are mineral wool, polystyrene, polyurethane, polyisocyanurate, sheep’s wool and hemp. They all have their different uses. Some of them are rigid and are better used under floor slabs, not in an attic where it would be impractical to cut them precisely enough to avoid thermal bridging. On the other hand, some of the pliable materials are perfect for an attic because they completely fill the space between the joists.
The performance potential of the different materials has been measured scientifically and each has a figure known as its Thermal Conductivity. The lower the figure the better the material. Polyisocyanurate or polyurethane have a figure of 0.023; polystyrene and sheep’s wool 0.035; cellulose, hemp and rockwool 0.04; wood 0.15.
There are of course other forms of insulation that should also be taken into account: double-glazing in windows and doors, heavy lined curtains for windows, underlay and carpet for floors. Good insulation can reduce by 75% the heat lost through the roof, walls, windows and doors.
Sheep’s wool is, perhaps, an insulating material that many people may not be familiar with. Sustainable Energy Ireland (SEI), the independent government agency, describes it as “a highly efficient natural sheep’s wool based thermal and acoustic insulation product.” It is naturally treated with ecological and environmentally friendly borax in order to ensure protection against vermin and fire. It can be used in walls, floors, attics and roofline situations.
2. Good workmanship and attention to detail are “most important” when insulating a building, according to SEI. This is to avoid thermal bridging and other related problems which can undermine even the most efficient of insulation material.
Insulation is not the sort of thing that one can be against. But there are caveats. SEI, for instance, warns that the effectiveness of an insulated wall or ceiling depends on how and where the insulation is installed. “For example, insulation which is compressed will have reduced effectiveness,” it says.
It is also very important to ensure that when we introduce insulation, we do not introduce more problems than we solve e.g. as a result of condensation where once this did not exist.
Cost (initial)
It is possible to achieve significant savings in the long-term. And insulation is probably the cheapest form of ‘energy’ you can get. Insulating the attic of a typical house can cost about €250 and yield great dividends from the very start.
Cost (running)
No running costs.
Cost (maintenance)
No maintenance costs, bar the replacement of the odd piece of insulation which deteriorates through human neglect or carelessness.
Efficiency
Exceptionally high.
Payback
Some payback periods are short: as little as 2-3 months in the case of a lagging jacket on a hot water cylinder, about three years for insulating a typical attic of a house (SEI figures).
Glossary
Thermal bridging
The process of losing heat through uninsulated joints such as where walls meet walls, floors meet walls, ceilings meet walls, and where insulation is not snug enough to fill such joints. Thermal bridging occurs through studs and fixings – even through the fixings used to install the insulation material itself. Windows and doors are also notorious for thermal bridging.
U-Value
The measure of the rate at which heat is lost through a material. The lower the figure the better.