Air Tightness, Internal Plasterboard, and Wall Sockets

[Gaf]

Have another active thread on wall insulation. This is somewhat related but this one's about air tightness so wanted to keep the focuses separate.

 

Short question is, if you have internal plasterboard (regardless of this being insulated or not), should there be taping (or alternative term) done around sockets / light switches for air tightness?

 

Reason for asking is a builder we're linked with said to expect to feel air / slight breeze from the sockets in the house if we put our hands down to the sockets. Said it was perfectly normal and happens because of air circulating behind the sockets and in the small cavity area behind the plasterboard. I thought sockets would be taped / sealed to prevent this happening, so the warm air in the house doesn't circulate behind the plasterboard.

[ProDave]

What is your relationship with this builder?  Is he doing any work for you?

 

If you are getting cold air out of a socket it is because of a failing in the building design or construction.  While sealing the "problem" might help it is not addressing the cause.  If he is about to do work for you and considers this normal, you might want to think again.

[Andehh]

Depends on your definition of normal, and what you're willing to pay for.

 

It's very normal for most new build homes, so is a default thing to expect from vast majority of builders... I have it (disappointingly so to a degree) and I was utterly fastidious over our block built bungalow. Still got a 'good' air tightness (good being 2.4 incl wood burner, not great for a buildhub standards admittedly)

 

To get a builder that will truly delivery a standard expected for buildhub will cost you noticably more.

 

Depends on your definition of acceptable and what you'll pay for it!

[joe90]

13 minutes ago, Andehh said:

To get a builder that will truly delivery a standard expected for buildhub will cost you noticably more.

I disagree only that my builder built to a fixed price and was meticulous, none of this “I have been doing it this way all my life”, yes perhaps I was lucky but when engaging with a builder/contractor make sure you spell out your expectations.

“expect to feel air / slight breeze from the sockets in the house if we put our hands down to the sockets. Said it was perfectly normal .”

 

 NO, get him to read this forum and tell him that is not what you want.

[TonyT]

What specification did the builder get?

[nod]

1 hour ago, Gaf said:

Have another active thread on wall insulation. This is somewhat related but this one's about air tightness so wanted to keep the focuses separate.

 

Short question is, if you have internal plasterboard (regardless of this being insulated or not), should there be taping (or alternative term) done around sockets / light switches for air tightness?

 

Reason for asking is a builder we're linked with said to expect to feel air / slight breeze from the sockets in the house if we put our hands down to the sockets. Said it was perfectly normal and happens because of air circulating behind the sockets and in the small cavity area behind the plasterboard. I thought sockets would be taped / sealed to prevent this happening, so the warm air in the house doesn't circulate behind the plasterboard.

Witch ever method of building that any of us decide to use 

Drafts of any sort arnt acceptable 

Some the mass produced homes are shocking But others are really good 

Define really good No drafts of any sort 

I wouldn’t use this builder At best he’s not on the same page as you 

More likely he’s not going to be living there and doesn’t give a F**k

[Gaf]

@ProDave @joe90 @TonyT @nod Just did a broad @ to cover everyone.

 

We hired a Royal Institute of Architects of Ireland (RIAI) Architect to complete the construction drawings and build specification for tender submissions. In the spec document supplied to the builders, it references that all construction works must accord with Building Regulations, and if there are any discrepancies between the drawings and the BRs, then the BRs take precedence. Some specific regulations were listed and some specific works were specified. This is the spec document that the builder in question had agreed to build the house to and he is aware that we have also hired a Charted Building Surveyor who will be doing periodic inspections on the build for submission to Building Control.

 

Some specifics in the spec re: air tightness:

• "Provide insulated cavity closures with d.p.c. Use appropriate joining tape to join the airtightness membrane with Partel Vara liquid airtightness membrane on block walls. in accordance with manufacturers instructions."
• "Internal wall finishes as per drawings. Wall plaster finish to be tight to screed and other junctions. The airtightness tapes to be used at floor and wall junctions and around any service pipes, to minimise air leakage and/or penetration."
• "All external floor, wall, door and window junctions and service penetrations to be made airtight"
• "The contractor is to include for carrying the tests on air permeability prior to completion. The procedure for testing is specified in I.S. EN 13829: 2000 “Thermal performance of buildings: determination of air permeability of buildings: fan pressurization method”."
• "All pipework in uninsulated roof voids are to be fully insulated with rigid polyflex insulation and taped at joints."

Edited January 24 by Gaf

[TonyT]

Item 1 Appropriate joint tape- sellotape?

Now mentions air tightness tape on item 2 but not item 1

item 3 no detail

item 4 just carry out a test no info on what to achieve

no thickness of insulation and no specification on tape

 
too vague a specification

 

 

[joth]

24 minutes ago, Gaf said:

Use appropriate joining tape to join the airtightness membrane with Partel Vara liquid airtightness membrane on block walls. in accordance with manufacturers instructions

This suggests there's a dedicated airtightness membrane somewhere behind the plasterboard? If so the project team want to put 99.99% of your effort into making that airtightness layer airtight, and not worry about applying airtightness products to layers of the wall build up that are not intended to be part of the airtightness layer.

Get this right, and the issue your builder mentions will only occur if there's inadequate insulation (so any air behind plasterboard gets too cold and convects), or there's a failure in the real airtightness layer. If either those happen it pays to address the root cause (insufficient insulation or failure of the real airtight layer) rather than paper it over.

Investing in multiple airtightness layers stacked atop each other does provide a degree of "defence in depth", but only really justified if the build has (much) more money than skills, or it's a retrofit.

 

If you have a detail drawing of wall cross section it will typically have the airtightness layer illustrated as a red line. And it should appear as a contiguous line on the plans.  This can answer a lot of questions! If not, ask the architect to provide it

 

Edited January 24 by joth

[Gaf]

18 minutes ago, TonyT said:

too vague a specification

Not good news.

 

8 minutes ago, joth said:

Investing in multiple airtightness layers stacked atop each other does provide a degree of "defence in depth", but only really justified if the build has (much) more money than skills, or it's a retrofit.

 

If you have a detail drawing of wall cross section it will typically have the airtightness layer illustrated as a red line. And it should appear as a contiguous line on the plans.  This can answer a lot of questions! If not, ask the architect to provide it

 

It's a new build.

 

Wall cross section with listed spec (no red line...)

 

 

[joth]

1 hour ago, Gaf said:

Not good news.

 

 

It's a new build.

 

Wall cross section with listed spec (no red line...)

 

 

So is the following text referring to inner or outer leaf block wall? And which side of it? And where does the membrane sit?

 

"Use appropriate joining tape to join the airtightness membrane with Partel Vara liquid airtightness membrane on block walls."

 

 

The problem you'll probably hit is 37mm plasterboard is not deep enough for a backbox so every single one is penetrating the assumed airtight layer. 

Edited January 24 by joth

[Gaf]

1 hour ago, joth said:

So is the following text referring to inner or outer leaf block wall? And which side of it? And where does the membrane sit?

 

"Use appropriate joining tape to join the airtightness membrane with Partel Vara liquid airtightness membrane on block walls."

 

Honestly I don't know. I sat into trusting the (quite expensive) architect knew what needed to be clarified in the spec.

 

1 hour ago, joth said:

The problem you'll probably hit is 37mm plasterboard is not deep enough for a backbox so every single one is penetrating the assumed airtight layer. 

 

Now that makes a lot of sense. So it's really looking like the builder was just communicating this potential issue to me. When meeting him we went through a lot of stuff and he did mention being surprised that the IWI was that thin and recommended increasing the thickness.

 

From my original understanding, the architect's selected IWI has a reference on the Kingspan spec stating "Resistant to the passage of water vapour", which I'm assuming isn't the same as air tightness.

 

Would it be fair to say the 'issue' here lies in the spec document and drawings, and not with the builder?

 

It's like the spec. and the drawings aren't exactly aligning because there is no air tightness membrane listed on the drawings. On the Kingspan K18 page, it does state (under 'Finishing'): "To avoid air leakage, any penetrations through the insulation (electrical sockets, plumbing and wiring etc) should be sealed with flexible sealant or equivalent, or a combination of flexible polyurethane foam and flexible sealant or equivalent. Any remaining gaps between boards / sheets of insulation should be filled with flexible sealant or equivalent, or a combination of flexible polyurethane foam and flexible sealant or equivalent." Should that be something specifically referenced in the spec?

 

Can I ask, based on the fact I'm somewhat locked into 100mm blocks with 150mm cavity, what should be the makeup of the external walls? Something like the below (from outside to inside):

1. Sand/Cement Render
2. Concrete Block (100mm) Outer Leaf
3. 150mm Cavity with Pumped Bead Insulation
4. Concrete Block (100mm) Inner Leaf
5. Air Tightness Member (Same thing as a vapour control membrane?)
6. Battens
7. Plasterboard

 

[Iceverge]

1 hour ago, Gaf said:

Can I ask, based on the fact I'm somewhat locked into 100mm blocks with 150mm cavity, what should be the makeup of the external walls? Something like the below (from outside to inside):

1. Sand/Cement Render
2. Concrete Block (100mm) Outer Leaf
3. 150mm Cavity with Pumped Bead Insulation
4. Concrete Block (100mm) Inner Leaf
5. Air Tightness Member (Same thing as a vapour control membrane?)
6. Battens
7. Plasterboard

 

( Airtightness membrane is the same thing as vapour control membrane in this case) 

 

That build up would be fine. It would probably be the one I would pick as there would be no chasing of walls or routing tracks out of the back of insulation for electrical conduit. You'll loose some more internal space mind you. 

 

You could substitute the airtightness membrane for a parge coat of sand+cement if you wanted but it might be more work. 

 

You could put mineral wool batts between the battens for added insulation too.

 

[joth]

7 hours ago, Gaf said:

To avoid air leakage, any penetrations through the insulation [...]

There's the problem. There is no airtightness layer as such specified. Just insulation, and a vague hand-waving wishful thought that it might stop drafts too.

 

Do you have an overall airtightness goal? What did your SAP or MCS or PHPP heat loss calcs use?

Are you installing trickle vents or MVHR? This determines if your ACH goal is a min or a max allowable value.

 

7 hours ago, Gaf said:

I sat into trusting the (quite expensive) architect knew what needed to be clarified in the spec.

Don't beat yourself up on this one. Truth is the vast majority of architects have bugger all idea about this stuff. As a client with your head screwed on, your both more motivated and more likely to chase these details than they are. Sad but true.

 

[Gaf]

7 hours ago, Iceverge said:

( Airtightness membrane is the same thing as vapour control membrane in this case)

Ah OK, so they're one and the same thing in this situation.

 

Are there any brands/makes that are generally recognised as good quality that I should at least be making sure is used? Any typical spec. values? Don't mean to have you do my homework on this, only curious if you may know off hand.

 

7 hours ago, Iceverge said:

You'll loose some more internal space mind you.

 

With this being a new build, I really thought the architect factored the IWI into the internal floor areas to prevent loss of space. It's a while ago now but I've a memory of a phone conversation where I asked about the internal wet/dry plastering and the architect said you'd need to leave a cavity for services so wasn't advising wet plastering - I assumed he developed the drawings to accommodate the method of 'attaching' the plasterboard. But it doesn't look like he's specified how the cavity is achieved behind the plasterboard (dot-dab, battens), and hasn't specified an airtight/vapour control membrane.

 

1 hour ago, joth said:

Do you have an overall airtightness goal? What did your SAP or MCS or PHPP heat loss calcs use?

 

Are you installing trickle vents or MVHR? This determines if your ACH goal is a min or a max allowable value.

 

Airtightness: To be honest again, I was relying on the architects references to the building regulations for what was required on this. From my reading this morning, the Irish building regulations are only 5m3/hr/m2 which, if the blogs/articles I've read are accurate, isn't a particularly difficult standard to achieve and, to quote an article, this new standard "doesn’t go far enough".

 

SAP/MCS/PHPP: Might be showing my unintended ignorance (again) but the only thing referenced to us in Ireland was a provisional Building Energy Rating (BER) assessment which would give us an estimated energy rating in kWh/m²/yr and an estimated CO2 emissions indicator in kgCO2/m2/yr. If you build your own house in Ireland you're only required to get one if you want to sell the house in the future (which we won't be doing) and when discussing it with the architect he was adamant that, if the house is built to the specification he provided, then it will meet the required "A2" rating which is 25-50kWh/m²/yr. Again, probably overly trusting here, but we planned to get one done once the house was completed only as it allows us to access lower interest rate mortgages.

 

We are going with MVHR.

 

1 hour ago, joth said:

Don't beat yourself up on this one. Truth is the vast majority of architects have bugger all idea about this stuff. As a client with your head screwed on, your both more motivated and more likely to chase these details than they are. Sad but true.

 

Yeah, have to say it's been a frustrating learning curve. We thought we were doing things reasonably 'correctly' by paying up for professional services during the various stages so far.

 

[Gaf]

Meant to clarify that the "A2" rating is the Building Regulations requirement now and is one rating below the highest "A1" BER rating - though this is still below passive house standards.

[ProDave]

What is your plan with this house?  Full turn key build, i.e, you get a house ready to move into?  If so you need to work out all the finer details with the builder before continuing.

 

A very common self build method is pay a builder to build a wind and watertight shell, so you get the basic structure, roof, windows, doors external finishes, and you just finish off the interior.  If that is your plan, just let the builder carry on, and you can detail the air tightness properly, this forum will guide you.  but factor in losing about 25mm off each external wall, i.e. to do it properly the rooms will be about 25mm smaller than you expect as it has not been allowed for.

[Gaf]

55 minutes ago, ProDave said:

..you just finish off the interior.  If that is your plan, just let the builder carry on, and you can detail the air tightness properly, this forum will guide you.  but factor in losing about 25mm off each external wall, i.e. to do it properly the rooms will be about 25mm smaller than you expect as it has not been allowed for.

 

That's the plan.

 

Only things the builder isn't doing is the internal painting, kitchen and utility units, and we're debating whether I'll lay the click-together laminate flooring or paying him to do it when the time comes (skirting is included in tender quote).

 

Where I'm at with this is to contact the architect to check about the airtight/vapour membrane and the battens, and really if they weren't accounted for I'm really thinking of requesting an updated set of drawings to include these with appropriate changes to the foundations to accommodate the lost internal space. We paid a premium for those drawings and he's RIAI so I'm of the opinion we should have as good as they get construction drawings. The architect we went with didn't say this but two other RIAI architects we linked with for quotes on the construction drawings were a bit belittling of drawings from engineers and/or architectural technologists and indicated they'd be substandard.

Edited January 25 by Gaf

[Gaf]

@ProDave Just realised I misread your question. We're not just doing the main structure and looking after the whole interior ourselves, the builder will be doing all interal work bar painting and laying laminte floors. So, as you said, we need to nail down these points now before starting.

 

@joth @Iceverge Curious if you think the architect is following something like this approach to airtightness, where it looks like only the ceiling is done?

 

I've Googled and am not just finding an exact answer. How is the taping like this attached to the block work? How then are the battens added in a way that they don't pierce the airtight/vapour barrier?

 

 

 

 

[saveasteading]

1 hour ago, Gaf said:

How then are the battens added in a way that they don't pierce the airtight/vapour barrier?

If you screw a batten through the membrane into another timber, the leak potential is between zero and negligible, because the hole is filled and all pulled tight, even when multiplied by hundreds.

I guess, if it was a concern, you could put some double sided sticky tape over the membrane.

[Redbeard]

As @saveasteading said, 

"If you screw a batten through the membrane into another timber, the leak potential is between zero and negligible, because the hole is filled and all pulled tight, even when multiplied by hundreds."

 

but some are pessimists, so his 2nd point:

 

("I guess, if it was a concern, you could put some double sided sticky tape over the membrane.") is also valid. To that end you may find the double-sided butyl tape used in some basement waterproofing systems to be useful, or you could pre-drill holes and gunge in a squirt of silicone or air-tight 'gunge' like Orcon-F before you drive each screw. I have done the latter *and* lost the will to live.

 

I may have misunderstood an earlier part of the discussion, but is the archo suggesting a service void *between the main wall and the insulated plasterboard*?

[Gaf]

I've just realised that @Iceverge already showed me how to build up this process with the diagram - apologies for missing that.

 

So with the vapour membrane stuck onto the blocks, with the battens screwed into the blocks, this does the job with the battens themselves acting as a seal for the piercings.

 

2 hours ago, saveasteading said:

If you screw a batten through the membrane into another timber, the leak potential is between zero and negligible, because the hole is filled and all pulled tight, even when multiplied by hundreds.

I guess, if it was a concern, you could put some double sided sticky tape over the membrane.

 

This would mean two battens with the VCL between them?

 

1 hour ago, Redbeard said:

I may have misunderstood an earlier part of the discussion, but is the archo suggesting a service void *between the main wall and the insulated plasterboard*?

 

I think that's what's suggested but only from reading through the K18 spec document, it only details mechanically fixing K18 with timber or metal studding/channels (no reference to dot-dab). The spec received from the architect hasn't specified anything on this from what I can see - I'll have to read it again to check has he just said "to manufacturers specifications" or something which I assume would indicate to the builder to follow the K18 document.

 

Battens and/or a service void are not shown on the drawings for the walls (below). The construction drawings show the plasterboard flush against the inner block leaf. A void is shown for the ceilings though - not sure why it's not shown on the walls.

 

 

From reading more about the K18, it seems to be the case that the VCL incorporated into each board is viewed as sufficient but requires detailing to ensure it's correctly sealed: "Kingspan Kooltherm® K18 contains an integral vapour control layer and, when installed correctly, with appropriate detailing at joints between sheets, penetrations and wall perimeters, can provide the necessary vapour resistance. If required, the vapour resistance of the wall lining can be increased by the application of two coats of Gyproc Drywall Sealer."

 

What started this whole thing was my attempt to understand why the builder said to expect to feel a breeze coming out of the sockets. As best as I can tell, this indicates that when the K18 is punctured to place the sockets, he doesn't seal around the sockets to maintain the VCL even though the K18 spec document states: "To avoid air leakage, any penetrations through the insulation (electrical sockets, plumbing and wiring etc) should be sealed with flexible sealant or equivalent, or a combination of flexible polyurethane foam and flexible sealant or equivalent."

 

Is there any definition of "appropriate detailing" or is this generally understood to mean vapour barrier foil tape?

 

As best I can tell, the below is the proposed make-up of the wall even though the studs aren't shown on the construction drawings.

 

 

 

 

 

 

 

 

Edited January 26 by Gaf

[Iceverge]

Not quite, the insulated plasterboards are normally stuck directly to the internal leaf with special adhesive. It should be continuous along the perimeter of each and the back of the board divided into sections to avoid any air circulating there. 

 

However in reality it gets 4 lumps of adhesive per board and shoved against the walls. 

 

Unplastered blocks are very leaky ( you can pour a bottle of water through them). The air literally blows through the blocks and freezes your house. 

 

 

In the detail with airtighess membrane inside the blocks it's normally fixed to the wall and taped. Then a 47*42mm batten is nailed/screwed though it into the blocks. Typically when you pinch an A/T membrane with a screw it's good enough to stop leaks. 

 

 

[Mr Punter]

I would not go with insulated plasterboard.  It is almost impossible to recycle.  Use 2"x2" battens and mineral wool batts.  Parge the blockwork with sand:cement:lime.  Again, if the place is later demolished it can easily be crushed and reused.

[Iceverge]

Half of the insulated plasterboard you buy ends up in the skip too.

 

Parging is a good idea i think. You can air test and solve leaks before boarding out.