Airtightness Question

thunderRoad

Hi guys,
Am thinking of using the wall construction in the sketch, my question is;

Is there a way of fixing the plasterboard to the walls without using the 'mushroom' fixings, i.e. without making holes in the airtight membrane?

Also, anybody see any problems with this kind of construction?

Thanks guys...

Wall Sketch.JPG

Retro-Fit

Its an out dated detail.

1. Cold bridging. Your inner leaf is a massive cold bridge, there is no insulation between it and perimeter ground level. Window reveals are massive cold bridges.

2. Airtightness. How many trades are involved here. The sparks and plumbers will tear holes in your membrane which should be protected by a services cavity. How do you continue this membrane at eaves level. Each person produces 7 litres of water per day through respiration, showers etc. Warm air laden with vapour will condense inside the barrier, mould loves it there. You'd be better off without it.

3. The wall is only a component. what is your ventilation and moisture management strategy? You need to look at your build in an integrated manner. What permiability, what heat load are you trying to achieve. what heating bills can you afford in 2020.

4. Concrete blocks have little or no thermal capacity. The concrete industry sells us a notion of thermal mass which is blatent lies. Double plasterboard gives as much thermal mas as solid concrete in irish houses.

thunderRoad

Hi retro-fit,

am going to use the details here,

http://www.environ.ie/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,18749,en.pdf

http://www.environ.ie/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,18751,en.pdf

sinnerboy posted them for me a while back,

will be using a hrv system,
215mm quinnlite on inside leaf,
sorry prob should have stated this in original post

just tryin to figure out the best way to get the house as airtight as possible, maybe i should abandon the insulation on the inside of the inner leaf and use wet plaster as an airtight barrier...

thanks for reply

by construction above i was refering to insulation+airtight membrane+plasterboard

GoneShootin

thunderRoad wrote: »

inner leaf

Question - what the hell is an "inner leaf"

thunderRoad

GoneShootin wrote: »

Question - what the hell is an "inner leaf"

the inside row of blockwork


By construction above i was refering to the insulation+airtight membrane+plasterboard

sinnerboy

thunderRoad wrote: »

maybe i should abandon the insulation on the inside of the inner leaf and use wet plaster as an airtight barrier...

you got it .

plaster even to concealed places eg between your floor joists

BoozyBabe

Okay, here's the completely clueless girl coming out in me again, but I've a question Re: Airtightness.

We are building a traditional block built house & will have 2 open chimneys, so we're never going to achieve 100% airtightness, or anything close.
For that reason, I don't think there's any point in spending a fortune on airtightness materials, if we're never going to reap the full benefits from them.

But, at the same time, I want to minimise air escaping from all other parts of the house. 2 large gaping holes in the house is more than enough for me, so I'd like to eliminate the rest.

Seeing as I'm never going to have a true airtight house, what is the most economical way for me to seal up the rest of the house?
& possibly a real stupid question:- is this done as standard by the builders anyway (my economical way, that is), or do I need to push them on it to do.

Like, I don't want to be harping on about membrane this & that if it's industry standard anyway.

Appreciate any advice
Thanks,
BB

RKQ

IMO Airtightness is about slowing the natural movement of air. Slowing the loss of heat from a structure. Airtightness does not mean you will turn your house into a submarine. There will always be some air movement no matter how slow.

Open chimneys aren't great for airtightness or BER rating but you could easily install a chimney balloon, a stove or a fire front to seal them. These could be reto-fitted whereas airtightness should be done prior to slabbing and plastering, during construction

Airtightness is a Building Regulation requirement - its the Law. So it can not be avoided or ignored. It is a proven technology on the Continent and should be embraced by the self-builder.

Plastered walls or plastic vapour barriers may provide elements of airtightness but IMHO you should use a certified membrane from Siga, ProClima or Moy. Many of these manufacturers provide 1 day training courses. It is possible to install these membranes yourself.

sinnerboy

BoozyBabe wrote: »

what is the most economical way for me to seal up the rest of the house?

Wet plaster direct to internal block work - everywhere including between upper floor joists ...... even if you then dry line over

Tape seal around windows and external doors before plastering

Keep elecs off external walls where possible . Where unavoidable seal cable entries to boxes using fire rated silicone .

Seal around drain pipes through walls and floors

.

GoneShootin

sinnerboy wrote: »

Wet plaster direct to internal block work - everywhere including between upper floor joists ...... even if you then dry line over

Tape seal around windows and external doors before plastering

Keep elecs off external walls where possible . Where unavoidable seal cable entries to boxes using fire rated silicone .

Seal around drain pipes through walls and floors

.

This is the kind of practical advice that should be gospel to any builder!

thunderRoad

Lads,

asuming all the best practice details are strictly adhered to, and using plaster on the blockwork rather than airtight membrane, is a hrv system still feasible?,

wont have fireplaces, and will have membrane roof and ceilings, service ducts

maybe this is not a question that can be easily answered,

thanks for ur replies

sinnerboy

Yes is the simple answer . Get Q50/5 - which you will if you follow deatils and HRV makes sense

GoneShootin

sinnerboy wrote: »

Get Q50/5 - which you will if you follow deatils

hah?

sinnerboy

http://www.bsria.co.uk/documents/airtightness-dwellings.pdf

Q50 is "short hand" reference to level of air tightness

Q50 - 10 b regs min

Q 50 - 5 min for HRV

Q 50 - 3 UK "best practice"

Q 50 - 0.6 - passiv house standard

Slates

I bought all the kit for a 253m² storey and a half house yesterday, this came to €1200 inc vat

sinnerboy

what kit slates ? testing equipment- or air tight membranes and tapes etc ?

Slates

sinnerboy wrote: »

what kit slates ? testing equipment- or air tight membranes and tapes etc ?

Tapes and membranes, I'll be putting them on myself over the coming month

thunderRoad

Slates wrote: »

Tapes and membranes, I'll be putting them on myself over the coming month

hi slates,
did you do the airtightness course?

Slates

thunderRoad wrote: »

hi slates,
did you do the airtightness course?

sure did, and it was very good

sinnerboy

Fair play Slates . Lets know how the Q50 test goes when you do it

thunderRoad

slates,
any chance you'd pm me the details of the course provider if you still have them?
cheers

thanks lads...

Slates

thunderRoad wrote: »

slates,
any chance you'd pm me the details of the course provider if you still have them?
cheers

thanks lads...

PM Sent

RKQ

Most Air tight membrane Manufacturers run regular installation courses (at least 66.6% do)
Well worth doing a course. Good luck.:D

Wally Runs

Upgrading an existing home for insulation HRV and air tightness.

The project:

I am in the process of engaging a builder to extend and renovate a 1970’s hollow block semi-d. The project includes the upgrade of the existing structures insulation through ‘dry-lining’ the external walls with composite plaster boards, insulation below the suspended timer floors and the attic is to be converted along with a single story extension to the rear. In the specifications I have indicted that I wish to install HRV, thus I require the final building to be airtight to the current standards or better?

Now, in my limited understanding, I reckon that making the new structure and converted attic air tight should be relativity straight forward with the use of the current rage of products (vapour control films and tapes etc) along with quality workmanship. This goes for the pipe work, electrics etc. and as the ground floor floorboards are to be lifted for the insulation, I assume vapour control can used here too to create the envelope.

With regards to the external walls, it is my understanding the insulation with the built in vapour control will take care of it here. Now, I know may have some issues with the existing windows (PVC double glazed, with 12 mm gap but poorly installed – previous owner) and I plan to have these repaired as best as possible or replaced if beyond economic means.

So my question: assuming that the builders use quality products and install them correctly, can I expect to get the level of air tightness to make HRV worthwhile? Am I expecting too much?

ardara1

Slates wrote: »

I bought all the kit for a 253m² storey and a half house yesterday, this came to €1200 inc vat

Slates - what do you hope to achieve with the 1200 Euro you spent?

I've asked the question a number of times from similar posts - but no results came back.

thunderRoad

RKQ wrote: »

Most Air tight membrane Manufacturers run regular installation courses (at least 66.6% do)
Well worth doing a course. Good luck.:D

thanks RKQ,
i'll give them a shout also and see...

sinnerboy

Wally Runs wrote: »

So my question: assuming that the builders use quality products and install them correctly, can I expect to get the level of air tightness to make HRV worthwhile?

yes . follow these details. have the works tested - look for air tightness of Q50 - 5 or better for HRV

http://www.environ.ie/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,18753,en.pdf

Wally Runs wrote: »

Am I expecting too much?

no - it can be done