Airtightness

brendan_donegal

Guys/Ladies,
I have been advised to complete a scratch coat on all external walls before we apply the drylining as Blocks are very porous and the scratch coat is excellent in regards to airtightness. Any opinions?

Also Tape around windows was mentioned, anyone know what this tape is and is it needed? All they knew was it was very expensive....isn't everything...!!

MicktheMan

brendan_donegal wrote: »

Guys/Ladies,
I have been advised to complete a scratch coat on all external walls before we apply the drylining as Blocks are very porous and the scratch coat is excellent in regards to airtightness. Any opinions?QUOTE]

This is good advice. Ensure that the scratch coat is complete, goes all that way to floor. Tape between wall and floor. If 2 storey have you thought about how to seal 1st floor joists etc. Same goes for wall to roof/ceiling upstairs.
If you are serious about airtightness I would advise you to consult an air tightness tester for advise. Often, the detailing of wall/floor, wall/roof, wall/opes junctions and service penetrations is where the mistakes are made.

BryanF

pm sent on air-tightness

MicktheMan

brendan_donegal wrote: »

Also Tape around windows was mentioned, anyone know what this tape is and is it needed? All they knew was it was very expensive....isn't everything...!!

Yes it is. Ensure it is proper airtightness tape. It might be expensive, but will pay for itself in no time in fuel savings.

One such tape is made in Switzerland and the company sounds like Liga. They run a one day course once a month which you may benefit from given your questions on here.

BryanF

MicktheMan wrote: »

Yes it is. Ensure it is proper airtightness tape. It might be expensive, but will pay for itself in no time in fuel savings.

One such tape is made in Switzerland and the company sounds like Liga. They run a one day course once a month which you may benefit from given your questions on here.

snap (in my pm)

john_cappa

can i get the PM aswell?

Trying to increase my knowledge. Is a certain air tightness required in the regulation or is it just something to focus in for your own best interest for keeping the house warm.

owenmclove

I was going to create a thread for this question but I think it may be relevant to this discussion.

What are peoples thoughts on the need to scratch coat under insulated plaster board if the cavity is being pumped? I think I read on Construct Ireland that the pumped silver bead acts as a good air-tightness layer on its own making me wonder if the scratch coat is needed. Does anyone have experience with this?

sas

owenmclove wrote: »

I was going to create a thread for this question but I think it may be relevant to this discussion.

What are peoples thoughts on the need to scratch coat under insulated plaster board if the cavity is being pumped? I think I read on Construct Ireland that the pumped silver bead acts as a good air-tightness layer on its own making me wonder if the scratch coat is needed. Does anyone have experience with this?

I don't believe for a second that the bead contributes to Airtightness. The installers struggle at times to not leave voids in the wall, let alone to get it densely packed. Sheets of polystyrene aren't even airtight!

In summary, scratch coat is needed.

Carlow52

brendan_donegal wrote: »

Guys/Ladies,
I have been advised to complete a scratch coat on all external walls before we apply the drylining as Blocks are very porous and the scratch coat is excellent in regards to airtightness. Any opinions?

Also Tape around windows was mentioned, anyone know what this tape is and is it needed? All they knew was it was very expensive....isn't everything...!!

earlier today u were asked not to create a new thread for similar questions.

In the other thread u are also covering A/T + tape etc which is at the very minimum, disingenuous to the folk here.

BryanF

Carlow52 wrote: »

earlier today u were asked not to create a new thread for similar questions.

In the other thread u are also covering A/T + tape etc which is at the very minimum, disingenuous to the folk here.

don't worry about it, its his home he's building:D

MicktheMan

owenmclove wrote: »

What are peoples thoughts on the need to scratch coat under insulated plaster board if the cavity is being pumped? I think I read on Construct Ireland that the pumped silver bead acts as a good air-tightness layer on its own making me wonder if the scratch coat is needed. Does anyone have experience with this?

From my experince as an air tightness tester, pumping the cavity has a negligable, if any, air tightness improvement effect. How could it?

MicktheMan

john_cappa wrote: »

Is a certain air tightness required in the regulation or is it just something to focus in for your own best interest for keeping the house warm.

Yes, the regulations call for a level less that 7m3/hr/m2. However, this is still very loose and imo, anyone building should really be aiming for a level of at least less than 2 with proper ventilation. I find most people are insulating to the nth degree but take no notice of airtightness and thermal bridging. Madness!

No6

owenmclove wrote: »

I was going to create a thread for this question but I think it may be relevant to this discussion.

What are peoples thoughts on the need to scratch coat under insulated plaster board if the cavity is being pumped? I think I read on Construct Ireland that the pumped silver bead acts as a good air-tightness layer on its own making me wonder if the scratch coat is needed. Does anyone have experience with this?

I think anecdotally people who live in older draughty houses have found that pumping the walls improves the airtightness or at least reduces the draughts, this is possibly what you are referring to, in a new house trying to achieve a good airtightness result scratch coat the walls and tape the windows at a bare minimum!!.

brendan_donegal

No6 wrote: »

I think anecdotally people who live in older draughty houses have found that pumping the walls improves the airtightness or at least reduces the draughts, this is possibly what you are referring to, in a new house trying to achieve a good airtightness result scratch coat the walls and tape the windows at a bare minimum!!.

What would you suggest are other standard/generic steps that should be taken to increase airtightness?

brendan_donegal

BryanF wrote: »

pm sent on air-tightness

Very good document, with pictures, with all this technical jargon, good to see it visually for a change.
Thank you for that

beyondpassive

Pumped bead is not airtight.

Scratch coat is not airtight. There are different levels of airtight. Part L airtight 7h at 50 pascals), MHRV airtightness 1.5m3/hr/m2, passive levels 0.6 m3/hr/m3. (Q50=N50 assuming volume and envelope area are the same)

back boxes and conduits have to be sealed and cross walls/ partitioned sealed from external walls.

EWI isnt airtight either, its windtight which is a seperate matter.

brendan_donegal

beyondpassive wrote: »

Pumped bead is not airtight.

Scratch coat is not airtight. There are different levels of airtight. Part L airtight 7h at 50 pascals), MHRV airtightness 1.5m3/hr/m2, passive levels 0.6 m3/hr/m3. (Q50=N50 assuming volume and envelope area are the same)

back boxes and conduits have to be sealed and cross walls/ partitioned sealed from external walls.

EWI isnt airtight either, its windtight which is a seperate matter.

So are you recommending the scratch coat then or is it a waist of time?