Free advices for high building standards



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


Counter Battens
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 an air layer between the breathable membrane and your rafter insulation. That means you can use thicker insulation and you´ll get better u-values.

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

Weather Tight Sealing


Slates and Roof Tiles are never 100% weather proof. Your breathable membrane protects your roof structure against wind and driving rain.

Please seal (mostly by using special tape) all overlappings, penetrations and connections to roof windows. This is the

only way to make your roof structure completely wind tight.

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

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.



Perfect Installation of DPC for Window Sills
Perfect prepared window sill

DPC on Window Sills


The DPC should be wrapped around the window sill and the window frame goes on top of the DPC. This is the only way to prevent the ingress of dampness through the concrete of the window sill.

Another great example for MJ window installation
Typical window installation

No compromises regarding Window Installation


Your window supplier charged you a full amount for the installation of your windows. Do not accept a messy installation, caused by "speedy installers".

Bear in mind that the window need a proper airtight sealing afterwards. How do you want to achieve this on a window as seen on the photo?


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

Lead and DPC are poor sealings


A permanent working water tight sealing can´t be made of lead or DPC.

Please have a look here for the right solutions.


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

External walls need to be plastered internally


The internal plaster creates an airtight layer for masonry. No matter if you want to use insulated plasterboard or just a hard wall finish in your house, you need to plaster all external walls of your house on the inside. The blocks are too porous on their own and missing pieces of mortar joints will cause draughts as well.

Plaster around joists for timber ceilings creates airtightness
Whereever ceiling joists reach into the cavity, they have to sealed

Don´t forget to seal the joist for the timber ceilings


Many existing houses are struggling with draughts, coming straight out of the ceiling. Please ensure a proper

sealing around all joistes and beams which reach into the cavity. Cavity wall insulation does not create airtightness!

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

Suspended Ceilings are in need of plaster as well


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

MF suspended ceiling and the concrete slab need to be plastered as well, to prevent air leakages.

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

The perimeter should get an airtight sealing


When you´re using screed for restoration purposes or underfloor heating, please seal at least the joints to the masonry around the external walls.

The photo beside shows the difference between the sealed external and the plain internal wall. It was taken during an air tight pre-test in a new building.

Airtight sealing for cavity walls
The most forgotten seailing regarding airtightness

Cavity walls require an airtight sealing


Whenever cavity walls get access to the inner area of the house, the cavity need an airtight sealing too. Typical building situations are sun rooms and ground level extensions, having an external gable on the first floor straight above the beginning of 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 prevent draughts.

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

Other trades can dramatically lower the air tight performance


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 air tight performance of your building.


HRV Unit installation
Out of sight, out of mind.

The right place to install a HRV Unit


The most efficient system is pointless in case you install the main unit in an uninsulated void inside of your roof. How do you want to achieve good heat recovery values when the unit and the ducts are not properly protected against cold?

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

Think ahead regarding duct installation


Please keep in mind that your ducts shouldn´t weaken your insulation. Also please don´t forget that they need a proper airtight sealing afterwards, whereever they penetrate your vapour control layer.

In some cases it could make sense to think about a Decentralised HRV System.


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.

Prevent uninsulated parts in your building shell


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 applied into the eve area because of missing counter battens under the slates. The actual detail will definitely cause a cold spot on the inner leaf which will end in dampness and mould.

Are you looking for more advices?

Please feel free to get in contact with us.