Air tightness membrane

have2flushtwice

I have a question re air tightness.
My builder said he was onna course which recommended that essentially to guarantee that airtightness was going to work the house had to be build in a balloon, with every surface covered and overlapping.

What material or membrane options are used to achieve this, I would like to see it before it gets installed.
Thanks

Dudda

Not often I say this but your builder is right.

Loads of different brands are available. Intello and Sika are probably the biggest and most common but lots are available. To put it simply it looks a bit like a roofing felt but you put it inside and pay a huge amount of attention to taping and sealing it everywhere. The tapes are expensive as they're designed to not deteriorate over time. If you ever come across old sellotape on a box in the attic you'll notice it's a strip of plastic with no stickiness. These tapes generally carry a 50 year guarantee. Airtightness is critical and one area I'd spend money. Ditch the granite worktop and get a laminate if required as you can upgrade later. Its very hard to improve airtightness later.

I'm worried as if you've a builder onsite and this is only now getting discussed who is looking after the build and why wasn't this specified earlier?

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Listen to this man /\

have2flushtwice

Thanks for the detailed response.
My "builder" is one who is pricing the job at present. The job hasn't started yet but I want to know what I'm paying for. There are no materials specified yet. The build hasn't commenced.

BryanF

have2flushtwice wrote: »

Thanks for the detailed response.
My "builder" is one who is pricing the job at present. The job hasn't started yet but I want to know what I'm paying for. There are no materials specified yet. The build hasn't commenced.

So what is the builder is pricing?

have2flushtwice

He is pricing the build of the house.

BryanF

Sorry I wasn’t clear, what documents is he pricing ? From what you’ve said he doesn’t have a spec to price, so it begs the question are you just wasting his time and yours?

Have you carried out a provisional BER assessment?
Have a specification, tender drawings, scope of work, engineers drawings, arch’s drawings etc

have2flushtwice

All of the above have been carried out and passed to builder.there is a comprehensive spec sheet.

My question is what options are there for the membrane.

BryanF

Best thing you can do is go on an air-tightness course. Last time I checked Siga and intello brands (between them market leaders) run day courses. If you have a spec/details, air-tightness i assume this already covered? What air-leakage/tightness value was set in the documents?

I’ve used intello (best IMO) and gerband (tears to easily) on my house with mainly the white contega, definitely the best.

Dudda

have2flushtwice wrote: »

There are no materials specified yet. The build hasn't commenced.

have2flushtwice wrote: »

All of the above have been carried out and passed to builder.there is a comprehensive spec sheet.

These statements kind of contradict each other. The 'comprehensive spec sheet' should give information on the airtightness. Can you find this section? The way specifications work is they might not specify a brand name but say things like it must have a tear rating of xxx and must have a vapour control of xxx and a guarantee of xxx and conform to xxx. That sets minimum standards so you wouldn't end up with the gerband BrianF mentioned above that tears easily but the builder can still chose among his preference for the better quality membranes.

My worry is if the builder is asking this question and recommending it then it sounds like airtightness isn't mentioned in this 'comprehensive spec sheet' which is why I'm asking can you find this section. Someplace it should also mention the overall airtightness rating the house is to achieve. Post this also if you can find it.

have2flushtwice wrote: »

My question is what options are there for the membrane.

To answer your question I'd tell him/her to use either Intello or Siga and it has to be reinforced. You can get intello that's not reinforced which is slightly cheaper and easier to tear. It's not common but is available.
If you go down to your local builder providers they'll have a roll in stock and let you have a look at it if you ask nicely. Alternatively you can ask your builder to provide a sample of what he intends to use. He might have off cuts on a site on another job he can give to you.

Wartburg

I´m wondering all the time if some guys here get paid for praising certain brands when it comes to air tightness. Or do they might have a business relationship to the mentioned brands?
I can just repeat what I´m stating almost every day: good air tightness is not dependend to a certain brand - it will be created by the diligence of the installer!
One day training courses are nice marketing strategies of the suppliers.Sitting in a fancy room and listening to a presentation does not make to a better air tightness installer in the most cases. I prefer on site trainings, to show tricky details and solutions in reality.
I´ve seen so many bad air tightness jobs where the praised brands have been used but would never blame the product for the bad result. It is lack of experience and understanding of how to use the products.
For example: all air tight tapes do lose bonding performance on lower temperatures. The weather conditions at the moment create a high risk of surface damp for air tightness membranes and other structural parts, like RSJ. No air tight tape will bond properly unless you have the room heated and the membrane totally dried upfront.
The people I like most are those "experts", peeling the liner of the tape and stick their finger into the adhesive layer, to judge how good the tape is. They just test the initial tack but not the overall bonding performance. Every air tight tape needs approx. 24 hours to develop its full bonding performance.

The key for a good air tightess is preparation and attention to details, not a certain brand. If you want, I can make your house air tight in a very good way, by using silage wrap or cardboard. But these materials are not the favourite ones for vapour control.