Unfortunately the most builders & home owners are looking nowadays for the cheapest price only.
Especially when it comes to the construction business, this selection criteria can be totally wrong.
When you´re buying the cheapest food and it doesn´t taste, you can correct this wrong decision mostly without any problem instantly. But when you did the wrong
decision for your long-lasting building structure, it is much harder (and fierce expensive) to correct it afterwards.
"Experience is simply the name we give our mistakes."
Just have a look on the two following graphics, to understand how important it is, to have the right building construction.
The graphic on the left shows a traditional roof construction as used in plenty of Irish buildings. The condensation still increases significantly, by using the popular (black) felt instead of an breathable roof membrane.
The right graphic shows clearly how the same construction is sustainably improved. This happens only by installing a vapour membrane on the internal side.
Many spray foam insulation companies offering a "special" spray foam, which is already airtight and without the need of a separate vapour membrane beneath the spray foam on the inside of the roof or ceiling.
Unfortunately the most companies are not right when they do these "irresistible offers". The truth is, that they mostly use an open cell foam for domestic spray foam insulations and this kind of foam requires a separate vapour membrane. You can find the details about the proper installation in the official certs (e.g. NSAI Certification) of the foam manufacturer. We would highly recommend to check these certs instead of trusting false promises.
Because of the high density of polystyrene insulation boards (and similar materials), you´ll need a vapour barrier for the internal sealing of your window joints.
If you just use a vapour retarder, a certain amount of dampness will pass the sealing but can´t escape to the outside because the external polystyrene boards will block it. This can cause
damages inside of the building structure due to dampness and condensation.
Please ask for details before you choose your sealing tape. The sd-value of the most available competitor tapes is definitely too low whenever you want to use an ETICS.
This calculation was done by a mineral wool supplier. There must be a hidden spot somewhere in Cork, where they never get
freezing temperatures during winter (nights).
Whenever you want to calculate the risk of dampness in your prefered building structure, please do not operate on average monthly temperatures.
Everyone knows that we´ll get freezing temperature over a few nights every winter here in the South of Ireland as well.
The result of "No condensation" will change very fast in those nights.
The most Irish timber frame house builders are using OSB boards for the external cladding of the timber structure. Unfortunately OSB has such a high sd value that dampness will be blocked on the inside of the boards (or in other words: inside of the insulation layer). By using the wrong internal vapour barriers, a certain amount of dampness will pass the vapour permeable membranes and gets stuck inside of the construction. Not good, especially when you´re using an low-density insulation material like mineral wool.
There´s a huge difference between a best-built window and a best installed window.
On the photos below, the "expert" totally "forgot" a proper insulation and sealing around the steel post of a corner window system. You´ll probably never take notice about except you´re doing
an airtight test and remove the cover afterwards because of poor values around the window.
But in one point the window fitters were very progressive thinking: By leaving the carrying loops on the windows it probably makes the replacement easier in some decades.
I´m getting sick of sealing solutions as seen on the photo beside. Lead is definitely one of the worst options for permanent water-tight sealing under doors. First, you mostly have at least one overlapping where the water easily penetrates and second: the lead is not properly connected to the structure. Tradition is nice and worth to preserve but not when it comes to water-tight sealings.
The most engineers and architects want to have humidity variable membranes like pro clima Intello or Isover Vario installed in the new buildings.
Have you ever come across with their installation manual? The manufacturer(s) recommend(s) to prevent almost every dust during the construction stage.
The left photo shows a standard vapour control membrane after the site just got a small tidying up including sweeping. As you can see, there´s a visible amount of dirt & dust on the membrane.
Fresh (and clean) air is important in air tight buildings.
The most people opt for a conventional HRV System to get the demanded air supplied.
It´s essential to keep the entire ducting system free of dust and dirt during the installation and the entire construction stage. Unfortunately there are still companies around without a particular interest of a neath installation. As a result, the occupiers get a supply of germs and bacterias beside the fresh air.
... to be continued