Breather Membrane Tape.

[Watshot]

I'm supposed to use a double sided acrylic tape to seal the breathable membrane on my pitched warm roof. All I can find is really expensive stuff like Tyvec, around £25 for 25m. Is that about right, or would this sort of thing do, it's a fifth of the price:

http://www.screwfix.com/p/no-nonsense-double-sided-rough-surface-joint-tape-50mm-x-50m/27043#

Not trying to cut corners, but if it's anything like Tyvec membrane, it's dearer than most. Are there alternatives 'cause Google doesn't seem to know...

Cheers.

 

[freddiemercurystwin]

Why bother?

 

[noseall]

I have never seen it taped or been asked for the laps to be taped.

I don't see the point either. The whole point of breather membrane is to..er..breathe. Having open laps will only ensure more moist air will escape.

 

[Watshot]

Just going by what the manufacturers say. After all, Tyvec even make their 'plus' rolls pre-taped. Must be good reason for it.

I won't pretend to know the science behind it, but guessing as it doesn't require ventilation beneath the membrane, as it must be good enough at what it does, it's probably more to do with 'u' values etc. It's stated that draping achieves a slightly better value than flat on any sarking. But if the wind is blowing through the joins that will probably negate any benefit, and cause more wind flapping noise as well.

Agreed though, on a cold roof, there is no point. However, the question remains, to those that may have used it, is any double sided tape going to be as effective as the Tyvec stuff?

 

[freddiemercurystwin]

Its a waste of time and money.

 

[Watshot]

Its a waste of time and money.

Nice helpful reply, as always.

 

[freddiemercurystwin]

Prior to the popular use of breathable membranes when felt was the most common underlay, did they ever seal up the laps? And did they leak as a result?

Its just manufacturers covering themselves. It has nothing to do with U Values. A breathable membrane, if it is an effective one, offers no resistance to the passage of heat, it is breathable so lets air through.