• Enrate
  • Blackberry Lane
  • Delgany
  • Co. Wicklow
  • 085-1359151

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registered with SEAI

Useful Information

Types of Insulation

Wall Insulation; Internal Insulation (Dry Lining)

During the 1970's, 80's and 90's "dry lining" involved covering over damp mildewy walls with sheets of plasterboard which were nailed onto wooden battens. Nowadays "thermal liners" or "warmboards" are used; these are factory insulated sheets of plasterboard having a layer of high performance foam insulation bonded to the plasterboard. Usually the walls being upgraded now are not damp at all, but simply require better thermal insulation, though the term "dry lining" is still used. When fitted to cold or damp walls thermal liners will dramatically improve heat retention. The thermal mass (see below) of the dwelling will at the same time be lowered.

Internal wall insulation is cheaper than external insulation, but there are some disadvantages to this method:

  • Rooms will be made slightly smaller, (by the thickness of the thermal liners). The value of this lost floor area should calculated when comparing to the cost of external insulation on the same house. For example, a 3-bed semi detached house of 100 m² might have an exposed perimeter (3 sides) of 20 metres. Insulated warmboards having a thickness of 3-4 inches (90mm) are fitted to these exposed walls. As a result, the floor area is reduced by 1.8 m² downstairs, and by the same amount upstairs. At average property values of €2500 per square metre, that lost 3.6 m² was €9000 worth of space.
  • It may not be possible to insulate the reveals around windows, or if some insulation is added, the windows may look a bit odd from the inside because less window frame is visible.
  • If the internal walls between rooms are constructed of solid masonry, then heat will be transferred to the external walls at the junctions where a room dividing wall meets an external wall. This is an example of cold bridging. These junctions, will be susceptible to condensation and mildew growth, unless the room dividing walls are also dry lined for some distance.
  • Special fixings may be required when hanging pictures or shelves on a dry lined wall in order to get adequate support.
  • There will be considerable disruption and redecoration to the inside of the house during the work. Any kitchen units attached to an exposed wall will have to be removed temporarily.
  • The blockwork or masonry of the original wall is now on the cold side of the insulation. Being colder, it dries out more slowly after rain. In situations where the wall is exposed to driving rain, a water resisting sealer should be painted onto the original external rendered surface.

Wall Insulation; External Insulation

External insulation involves wrapping the entire outside wall of the building with insulation. Normally expanded polystyrene (EPS) boards are used. The insulation then has to be protected from the weather so a thin layer of cement render or some external finish is applied. This technique is relatively new to Ireland although it has been used very successfully for "Passive" and other houses in continental Europe. It has the potential to upgrade a property from having the worst insulated walls to the best insulated walls in one step. However, external insulation may change the whole appearance of your house. If it was a brick house, then it will no longer appear to be brick (although there is an option to face the insulation with thin brick slips or an imitation brick finish). On the other hand, if a low maintenance finish is applied, you may never need to get the house painted again. It is best to check with your local authority to find out whether planning permission is required before changing the appearance of your house. The thermal mass of the dwelling will increase (see below). Always seek the services of a specialist contractor who has received some training from the manufacturer of the particular brand of insulation system being used.


  • It is more expensive than internal insulation.
  • The outside walls of the house will be extended outwards by the thickness of the insulation, around 150mm. In the case of a semi-detached house this step might look strange if the other house was unchanged. But if the neighbours can be persuaded to join in and get the pair of houses insulated, then the insulation will be better and the price cheaper.
  • The window frames may be partially obscured when viewed from the outside, or they may have to be moved outward on new metal covers fitted to the window cills. If the windows are substandard or are single glazed, consideration should be given to replacing them and possibly enlarging the openings as part of the process.
  • The external rendered finish coat is thin. It could possibly be dented by a bad driver parking a car or it could start to peel off after a few years if not properly applied. Ensure that the installing contractors have undergone the appropriate training courses which are normally provided by the manufacturer of whichever external insulation system is being used.
  • Satellite dishes, gutters and ESB or telephone wires may have to be moved and refixed afterwards.
  • External insulation is the most effective way to upgrade an old building. As the Building Regulation standards become ever more demanding, external insulation is likely to become the only method whereby the owners of older properties can upgrade to the same standard as new homes being built.
  • As the work is all done on the outside of the house, there is little or no disruption to the occupants inside.
  • There is no reduction to the floor area inside the house.

Wall Insulation; Cavity Wall Insulation (retro fit)

Granular beads of expanded polystyrene or fibreglass are pumped or injected into cavity walls.
Unfortunately most Irish dwellings are constructed of either;
(a) Hollow block.(b) Cavity walls already containing insulation.

The technique has limited value in both of these situations. It is very beneficial and highly cost effective where there is a clear cavity but no insulation, such as with brick-faced concrete block properties built prior to about 1977. Cavity wall insulation typically consists or expanded polystyrene beads, similar to those found inside a "bean bag" type cushion. Holes of about 25mm diameter are drilled at internvals along the wall, and the beads are pumped into the cavity under pressure. The beads spread around, filling any air spaces. A liquid resin glue mixed with the beads will solidify soon afterwards, bonding them into a solid mass; hence the name "bonded bead" insulation. 
Pre-2013 cavity walls are generally 300mm wide. That is 100mm for each block or brick leaf (inner leaf and outer leaf), and 100mm of cavity in the middle.
If the 100mm cavity was partially filled with rigid board insulation at the time of construction, then the remaining space is air. The earlier walls tended to have less insulation. For example;
Pre- 1977 (approx) 300mm wall. No insulation board. The 100mm residual airspace can be filled.
1977-1993 (approx) 300mm wall. 40mm insulation board. The 60mm residual airspace can be filled.
1994-1999 (approx) 300mm wall. 50mm insulation board. The 50mm residual airspace can be filled.
2000-2008 (approx) 300mm wall. 60mm insulation board. The 40mm residual airspace can be filled.
2009-2011 (approx) 300mm wall. 100mm insulation board. There may not be any residual airspace that can be filled.
2005-2011 (approx) 350mm wall. 120-150mm insulation board. There may not be any residual airspace that can be filled.

The photo above shows a cavity wall built circa 1980 with inner and outer leaves of brick. The original 40mm white expanded polystyrene (EPS) board is visible pressed up against the inner leaf. The grey EPS bonded bead was pumped in circa 2010. As the original cavity in this case was closer to 110mm, there was 70mm space available for the bonded bead. In this situation, it was well worth pumping the cavity.
Some of the bead has travelled up into the soffit area towards the roof, but that is no harm. This would not usually happen because most walls are built with a "cavity closer" at the top course. The "cavity closer" is a standard solid concrete block laid "on the flat" which bridges across from the iner leaf to the outer leaf. It adds some structural strength to the cavity wall, but unfortunately it also forms an uninsulated "thermal bridge" between the warm inner leaf and the cold outer one. In some houses a faint line of black mould stain is visible along the top of the wall, just below the ceiling level. This marks the level of the cavity closer block, which being colder than the insulated part of the cavity wall, attracts any condensation in the room.

The residual airspace in an unfilled or partially filled cavity wall has some insulation value, but mainly it was there to prevent dampness from driving rain wicking across to the inner leaf. This effect is lessened anyway when houses are close together in an urban setting, and when there is 300mm or more overlap of the roof (ie the width of the soffit board) Nevertheless only non-wicking insulation materials should be used when filling a cavity. EPS bead is the usual material, but a special "closed cell" polyurethane foam has also been developed. EPS is always a "closed cell" non-wicking material.
Most polyurethane boards are made from an "open cell" foam. A broken piece of standard polyurethane board dipped in a bucket of water will soak up the water like a sponge, whereas a broken piece of aeroboard dipped in water can be shaken afterwards and found to be completely dry.
Mineral wools such as glass fibre and rockwool are wicking materials.

"Hollow Block" is a single leaf construction, and was commonly used in Dublin from the 1960's onwards. It is quick and cheap to build.
Rural houses tended to be built using a cavity wall technique, because in more exposed situations driving rain can soak all the way through a hollow block. Also because many rural houses are one-off houses that were built by their owners.
A hollow block itself is 215mm wide, and when plastered inside and rendered outside the wall will be about 250mm wide. This is a common wall type in 1960's Dublin suburbia. The insulation and water resistance of the wall would be considered very poor by modern standards. 
If dry lining or internal wall insulation has been applied to the inside face, the hollow block wall can be more than 300mm wide. A construction method commonly used in 1980's Dublin involved battening out the inside face of the block with 2" by 1" (50 x 25mm) timber battens and then lying 40mm -50mm of glass fibre insulation between the battens. This was finished with a 12.5mm dry liner sheet (plasterboard) and then skimmed ith a thin plaster coat to cover the joints between the dry liners. In later years the insulation/timber batten layer was increased to 60mm and then 100mm.

This photo shows a hollow block (above) and for comparison a standard solid block (below, which is lying "on the flat" as opposed to upright on its edge)
It can be seen that there are two cavities in each hollow block, but there is also a very large amount of concrete bridging across from the inside face to the outside face. It is impossible then for the inside face of the block to be warm and dry, at the same time as the outside face is cold and wet. So the presence of these cavities is really to make the block cheaper and lighter to handle. A hollow block wall is not a cavity wall.
For this reason SEAI specifically exclude hollow block walls from the grant aid available for pump filling a wall. Some hollow block walls have been pumped to some degree, but no reputable firm would do it.

A hollow block wall can be upgraded. The trick is to think of it as only a single leaf in the wall. If a thick External Wall Insulation is applied, the hollow block becomes the warm inner leaf of a full fill cavity wall. In this situation the EWI forms a water resistant, low maintenance outer skin.

If thick internal wall insulation is applied, the hollow block becomes the cold outer leaf. In this situation it may be advisable to paint on a water resistant masonry sealant afterwards, because the block will become colder, and therefore less able to evaporate off any rainwater soaking into it.

Roof Insulation

Cold Attic

This is the usual set-up, where the insulation is at the level of your feet when standing in the attic. Layers of fibreglass wool or a granular material are laid between the joists. Nowadays another layer is required on top of the joists and first layer. Insulating an attic which had little or no insulation is relatively inexpensive but has huge benefits. The attic space remains cold afterwards. Precautions may be needed to prevent the pipes around the water tank from freezing in winter.

Pitched Roof Insulation (attic conversion)

Insulation is placed between the rafters (at head height). Another layer of foam insulation which is bonded to plasterboard is fixed onto the rafters. The area requiring insulation is larger than for a cold attic, and it will be much more expensive, but potentially a useable warm room is created.


Thermal Mass

Thermal mass is the ability of the dwelling to absorb heat and then slowly it release it over a period of time, about two or three days. The internal walls of a house with a high thermal mass will typically feel very solid, whereas those in a low thermal mass house will appear to be light or hollow. Concrete built houses without dry lining have high thermal mass. Timber frame houses usually have low thermal mass. Both types can have either good or bad insulation.

Advantages of High Thermal Mass

In the spring and autumn chilly nights can follow warm sunny days. You may be able to take advantage of the warmth stored up during the day by not turning on the heating system at all in the evening. This is especially effective where there are south facing windows.
It is usually easier to fix pictures and shelves to the solid walls.
The internal temperature of the dwelling tends to remain stable. High thermal mass often suits a situation where there are people at home during the day.

Advantages of Low Thermal Mass

When you come home from work in the evening, the house will heat up very quickly, within about ½ hour, so the heating will not need to be on for long. If the house is unoccupied during the day and therefore unheated, overall fuel bills will be lower. The walls of a modern house with low thermal mass, such as a timber frame house, may feel "hollow" or "paper thin" but they are actually a complex arrangement of many different layers.

Condensing Boiler

A condensing boiler incorporates a heat exchanger in the flue pipe which extracts heat from the exhaust gases. This gives it an efficiency of more than 90%, as opposed to about 65% for an older 1980's standard model. The Building Regulations require that only condensing boilers be fitted nowadays.

Further energy savings can be achieved by situating the boiler inside the dwelling and not outside in a boiler house. The boiler can often be situated in a kitchen or utility room. A balanced flue is used in this situation which ensures that no exhaust gases of any kind can get into the dwelling.

By combining the above upgrade with more efficient heating controls it is sometimes possible to cut the fuel bill in half.

Wood Gasification Boiler

This burns fuel (usually logs) at a higher temperature than the normal wood stove with a back boiler, allowing for a more complete combustion of gases. It is therefore more efficient and less smoky. A normal wood stove should be seen as a replacement for an open fire in the living room, whereas a wood gasification boiler is a replacement for an oil fired boiler in a utility area.

Heating Controls

The best heating controls have separate time and temperature control for hot water and space heating. Time control means they are each on a timeswitch. Temperature control means that there are thermostats, so that the burner in the boiler shuts down immediately when both the air temperature of the dwelling and the domestic hot water (DHW) temperatures are sufficient.

In any event the hot water should be on a separate zone, so that the boiler can be utilised for DHW during warm weather without heating the radiators.

When all these arrangements are in place, it is called boiler interlock. The interlock is not an actual device. This can be achieved in various ways; by having an advanced digital programmer and thermostatic radiator valves (TRV's) with a bypass valve or by the right combination of simple time switches and thermostats controlling the heating zones.

Householders need not fully understand the interactions of various heating controls, but they should ensure that they know the whereabouts of both the time and the temperature controllers and how to operate both. Then they should reduce the space heating control (room thermostat and/or TRV's) to a level which still provides sufficient comfort. At this point the optimum energy efficiency is achieved.

If your boiler has a tendency to "cycle" (i.e. it fires up for a short period of time, perhaps only a minute or two, and then shuts down again, and keeps on repeating this every twenty minutes or so) then that is an indication that you could benefit from better controls. It is the equivalent of having your car start up by itself every half hour and idling for 2 minutes without going anywhere.

Heating Zones

Most central heating installations are subdivided into separate zones. The heat supply to each zone can be turned on or off independently. In a typical 2-zone installation the radiators are on a different zone to the DHW .This is a basic arrangement. In a 3- zone installation the upstairs or bedroom radiators are on a separate zone. This allows them to be left unheated during the day which can cut fuel bills. Larger houses can have more zones dividing various areas.

Motorised valves, thermostats, timeswitches and pumps control the flow of heat to the different zones. T.R.V.'s or thermostatic radiator valves gradually restrict the heat supply to the radiator when the local air temperature reaches a set level. This set level can easily be adjusted by twisting the TRV. The effect of the TRV is to turn off the radiator automatically when the room gets warm.

In theory each room behaves like a separate zone with individual temperature control. In practice it will often be found more economical to supply quick bursts of heat at full flow to the radiators at set time periods throughout the day. This avoids having the boiler continue to pump heat wastefully around the pipework when most of the TRV's have closed or are almost closed.

If you are installing a few TRV's (maybe three to avail of the grant) put them on the radiators where you do not need heat so much. For example put them in bedrooms if they are not already on a separate zone, or in a spare room.

Cold Bridging

Cold bridging is where heat finds a path around the insulation to the outside. An example would be where a piece of insulation is missing. Other examples would be where a concrete window cill forms a continuous bridge from the inside to the outside of a cavity wall. Or the metal handles inside and outside of an insulated or double glazed door. The affected area is a cold spot and likely to attract condensation. The amount of cold bridging in a building is mainly determined by materials, techniques and good practice during construction, but it can be alleviated afterwards to some extent. For example you could check that attic insulation covers the entire ceiling area, and no pieces have been peeled back or removed.

Calculating Energy Costs

How can I easily calculate the running costs of an electrical appliance?

To calculate the cost in € cent per hour of running any electrical device, simply multiply its wattage by 0.018. You may find that the resultant cost is actually quite low. The fact is that most electrical gadgets are very good value when their convenience is measured against running costs. It's only when you leave them switched on for too long that the cost mounts up. Electric heaters are the usual reason for very high electricity bills.

An example;

  • (a) A 300 watt outdoor halogen security floodlight incorporating a PIR passive infra red detector. Average "on" time is ½ hr per night. 300 x 0.018 = 5.4 So running cost is 5.4 cent/hour of "on" time. This adds up to 19 cent per week or €10 per year.
  • (b) The same security light malfunctions or is incorrectly set up and stays on all night. (12 hours) It is again costing 5.4 cent/hour but is on for 84 hrs per week instead of 3½ hrs. This adds up to €4.54 per week or €236 per year.



Sustainable Energy Ireland
Information on BER , grants, lists of approved contractors and general advice all from an independent government agency.
Passive House Plus
Online magazine showcasing sustainable building techniques and projects in Ireland.
Department of The Environment website with current Building Regulations and standards, planning policy and related recent government announcements.


About Us

Enrate was founded in 2009 by Clive Dalby to provide an energy rating service for residential dwellings. With over 20 years experience in construction and a particular interest in the emerging renewable "green" technologies, Clive is well placed to advise on how best to make the cost effective improvements to your property which will save you money. Sales and marketing are handled by Eithne Dalby. Enrate is fully accredited and registered with SEI, and a member of the BER Assessors Association of Ireland.

We are committed to providing a quality impartial service which will address the individual requirements of each client.

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