Free Advice to make your home more efficient

Thanks for visiting our website. We want to give you some free advice to achieve high building standards for your home.


Counter battens

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Wind tightness

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The right layout for roof window reveals

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Casement, Sash or Tilt-and-turn

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Preparation of the window opening

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The quality of window installation

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Appropriate fittings for windows

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Use the right product

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DPC is not the right product

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Building envelope walls require an air tightness strategy

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Timber joist ceilings create a high risk of air infiltration

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Sealing of wall areas above suspended ceilings

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Sealing of floor-to-wall junctions

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Close all access to the cavity

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Tell other trades about your aim for air tightness

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Chasings on cavity walls

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Where to place the ventilation unit

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Layout of ducting

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Layout of ducting, part 2

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Protect your mHRV System during the construction stage

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Keep mHRV extract ducts clean

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Prevent uninsulated parts of your building envelope

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External wall insulation

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Insulated plasterboard on external walls

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Installation of cables

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Lighting strategy

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Balancing of manifolds

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Locating external units of air-to-water heat pumps

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Are you looking for more advice for your project?

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Counter Battens
Counter Battens

Please consider the use of counter battens. They ensure a proper roof ventilation and prevent structural damages caused by moisture.

By having counter battens installed, you don´t need a ventilation layer between the breathable membrane and your rafter insulation. That means you can use thicker insulation to get better u-values and less cooling of the insulation through air infiltration.

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Taping of breather membranes
How to create a wind-tight roof ?

Slates and Roof Tiles are never 100% weather proof, neither against driving rain nor against draughts. Your breathable membrane is your protection layer against these elements.

We recommend to tape all overlaps and continue the membrane down to your wall area, to create a wind tight layer. This is the only strategy that secures the expected performance of your insulation material in the roof. 

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Roof Window Installation
It´s important to have the right reveal structure for roof windows

To prevent damages on the inside of your roof window, the right construction of the reveal is important.

When you build the reveal the wrong way, parts of your window won´t get heated and well ventilated in the winter and you´ll get soon or later condensation and mould in the corners.


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Tilt-and-turn windows are the best window option for Irish homes
Tilt-and-turn window with three gasket layers, where water won´t get access to the inside.

It´s a personal preference what type of window you select, but keep it mind that your decision should be made on more facts than the aesthetic. The most tightest window is always a tilt-and-turn window, because it has an all-round locking mechanism for the opening sash. Due to the opening to the inside, the sash is also more protected against weather in comparison to casement windows.

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Perfect Installation of DPC for Window Sills
Perfect prepared window sill

When using standard concrete window sills, a layer of DPC has to be wrapped around the window sill. This will prevent the ingress of dampness into the building structure, whenever the sill is saturated.  Ideally the DPC should be brought to the top of the sill, before the window frame is installed. This strategy will create the perfect loop for the DPC, which is impossible to achieve when the DPC has been left lose somewhere in the cavity or just close to the frame.

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Another great example for Munster Joinery´s installation work
Common window installation in Ireland

Your window supplier charges you the full amount for the installation of your windows. Do not accept any messy installation, caused by "speedy installers". Your new window should last for the next 30 years, hence it needs to be installed in a correct way. 

Bear in mind that the window need a proper air tightness strategy afterwards. How do you want to create this on a window as seen on the photo?

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Appropriate brackets instead of basic straps to hold a window
Basic inappropriate strap to the left, functional bracket on the right

The photo shows two types of window fixings.

The left strap was originally installed by the window supplier at the bottom of a room-height fixed glazing and will not carry the weight of the window. In coordination with the client, the window got additional appropriate brackets to prevent a drop.

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Archaic water-tight sealing made in Kerry
How do you want to ensure a water-tight sealing by using lead?

Lead and standard DPC are not suitable for water tightness in general.

A permanent water tight sealing can´t be made of a material, which is applied lose to the substrate. The capillary action of water will allow the water to seep into the building right underneath the DPC or lead


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DPC is not a water tight sealing layer for door thresholds
Loose DPC creates more moisture ingress than it prevents

As the name insists, DPC was originally made as damp-proof course. It works in walls, because it´s squeezed in between blocks and mortar.

It doesn´t work when the DPC is losely applied to the substrate. Black fabric absorbs heat during the day but cools down very fast at night. That leads to interstitial condensation


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Only plastered walls are airtight
Perfect preparation for the installation of insulated plasterboards

Never leave the inside of external walls without an air tightness layer. Concrete blocks are porous and every mortar joint is a potential risk for air infiltration as well. That´s why every square meter of building envelope walls with access to the habitable space has to be covered with an air tightness layer (usually plaster coat or air tight paint). If you´re doing an extension or retrofit and prefer the the use of plaster board instead of plaster finish, please ensure an air tightness layer prior the installation of the plaster boards. 

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Plaster around joists for timber ceilings creates the required air tightness
The complete joist area of timber joist ceilings requires an air tightness strategy

Many existing houses with timber joist ceilings do struggle with draughts at ceiling (downstairs) and floor level (upstairs). The reason is a missing air tightness strategy for the joist level. New houses with timber joist ceilings require an air tightness strategy for this floor level. Standard cavity wall insulation is not doing any benefit for air tightness.

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How to ensure airtightness above mf ceilings
MF Ceilings need attention regarding airtightness

It´s the same principle as shown on the timber joist ceilings above. The small piece of external wall area between the

suspended ceiling and the main floor level (e.g. timber joist or pre-fab concrete slab)  needs to get covered with an air tightness layer as well. Air Tight Paint is a serious alternative to plaster.

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Proof of necessity for perimeter air tight sealing
Perimeter Sealing on external walls

When pouring floor, please take attention to the potential air infiltration at the floor-to-wall junction. There are two options:

No. 1 - the complete air tight sealing of the floor height at all exterior walls

No. 2 - all floor-to-wall junctions have to be sealed at the final floor level

The photo beside shows the difference between the sealed external and the exposed internal wall. It was taken during a preliminary air tightness test in a new building.

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Airtight sealing for cavity walls
The most forgotten seailing regarding airtightness

Whenever internal walls have been built as cavity walls with access to the main cavity, they need an airtight sealing too. Typical building situations are sun rooms and ground level extensions, having an external gable on the first floor right above the entrance to the extension. We recommend to close the cavity first by using insulation boards, as used around the doors and windows. Than you should use an airtight tape or membrane to have the air tightness permanently secured.

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All trades at the building site should take care regarding air tightness
Sometimes they don´t know what they do

Please take care that following trades do not destroy the air tight installation. Especially electricians and plumbers are great in doing

unexpected modifications afterwards. Please remind that the easiest way for their purpose could end in the worst solution for the overall air tightness performance of your building.

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Chasings on exterior walls need to be sealed air tight
Air Tight Sealing of chasings

It´s a common problem for cavity wall buildings here in Ireland. Even by having the conduit sealed, there is a noticable draught coming through the sockets and switches. The reason is the untreated surface in the chasing, where air infiltrates through the block and streams up or down along the outside of the conduit. If you want to create a house with low air changes, you´ll need to seal the chasing before installing the conduits.

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the most inappropriate HRV unit installation
When every filter change turns into nightmare...

Keep in mind that your hrv unit requires constant access for changing the filters and further maintenance work. 

Placing the unit in a cold surrounding (cold attic) will increase the risk of condensation and decreases the efficiency.

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HRV Ducts lowering insulation values
HRV Ducts are not made for insulation purposes.

Try to keep all ducts within the thermal building envelope. Also, please don´t forget that they need a proper air tight sealing, wherever they penetrate your air tight & vapour control layer.

Especially for retrofit it could make sense to think about a Ductless HRV System.

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Flexible ducts should be kept short and without kinks
Please do not install the ducts as seen on the photo

In general - try to place your hrv unit somewhere in the centre of the house, to keep the runs for the ducts as short as possible. The longer they are, the more resistance they create and the hrv unit has to work harder. Never get terminals connected as seen on the photo. These kinks do lower the performance and increase the noise.

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Prevent to get your HRV ducts contaminated with dust and dirt during the building stage
Supply of germs and bacterias included

Your mHRV System is designed to supply you with fresh clean air. Please treat the system carefully during the construction stage and block all plenums and accesses to prevent the contamination of the system. There´s plenty of dust and dirt involved whilst your house is been built and you do not want to have your mHRV system contaminated before you have your air supply started.

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There is a high risk of contamination for every extract duct of mHRV
Is this looking healthy???

The extract circuit of your mHRV is running permanently in all of your wet rooms. It´s a fact that not only air will be extracted, because of an existing amount of dirt and dust in the air.

You´ll see the traces of this pollution clearly around your extract vents and inside of the extract ducts in a certain while. The solution to prevent this situation is already available - you just need to get in contact with us.

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The 200mm wide cavity is worthless in the top area where the wall plate is.
The 200mm wide cavity is worthless in the top area where the wall plate is.

The plan was, to use beads for pumping the cavity walls and spray foam for the roof area. Unfortunately there is a triangle which will not be covered by the proposed insulation materials. The cavity needs to get blocked on top for fire safety reasons and the spray foam can not be applied into the cavity area above, because of lack of access.

The actual detail will definitely cause a cold spot on the inner leaf which will probably end in thermal bridging and mould.

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bad detail of finishing external wall insulation at ground level
wrong detail - the plinth insulation has been left exposed at the bottom

Do not watch out for grants - select real professionals with proven reputation instead. An external wall insulation system is the perfect insulation for new and existing buildings but the performance depends to details and the experience of the installer. Attention is needed to prevent thermal bridging and never ever put on the finishing coat in the winter!

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insulated slab on perimeter wall
typical detail of perimeter wall insulation with an insulated slab

Please consider the following facts before installing an insulated plasterboard to the exterior wall of your building:

1. Risk of interstitial condensation

2. Lowering of thermal mass

3. Cold bridging through metal mushroom fixings

If this is your preferred insulation strategy still, please make sure you have the wall covered with an air tight layer (plaster or air tight paint) prior to the installation of the slabs.

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The difference between a poor and a good installation of cables
Which installation would you prefer?

Some day it can happen, that you might need to detect a faulty cable. Especially when the cables have been laid up and down above your metal frame ceiling, you´re increasing the risk of damaging the cable sheathing. This can happen because of the movement in the structure, which allows the cable to rub on the sharp metal edges.

It´s always better to have the cables installed to the underside of the ceiling in neat and clear runs.

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Is the installation of recess lights still up-to-date?
We counted a total of 28 recess lights on the photo

Recess lights do have more disadvantages than advantages. Every recess light is costing you a good amount of money during the installation process. It creates weak spots for the air tightness and insulation. The beam angle is pretty low in comparison to pendants or ceiling mounted lights, which leads to a certain quantity to brighten the complete room. But the more recess lights you have installed and running, the more you´ll be affected by shadowing and higher energy consumption.

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heating manifold with adjustable flow meters
The glass tubes at the top of the manifold are flow meters, which have to be adjusted individually for every circuit

No matter if you have radiators or underfloor heating installed - every sophisticated heating system requires a hydraulic balancing of the system, to ensure that every part of the building will be supplied with the required amount of heat. Not more or less.

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It´s not the best idea to install the external unit of an air-to-water system facing windwards. If you have not other option, consider the installation of a barrier in an appropriate distance, to prevent that the wind affects the performance of your heat pump.

Do not place the unit to close to your house as well, otherwise you are in risk of condensation at your external walls in the winter.

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