Thanks for visiting our website. We want to give you some free advices to achieve high building standards for your home.
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.
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.
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.
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.
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
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?
WATER TIGHT FLASHINGS
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.
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.
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!
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.
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.
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.
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.
HEAT RECOVERY VENTILATION
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?
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.
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.