Well that's better!

We have a plasterboard tent with pretty much all the worst features documented by the draughtbusters website. Having come to terms with that reality we're now planning the remediation, starting in an ensuite and bedroom on the North side which have howling gales from under every skirting board.

The window reveals have been stripped, revealing cold bridges from brick cavity closures; these will be removed back to cavity width so an insulated closure can be installed. DPC look OK at jambs and cill. The cill and the jambs seem straightforward enough to insulate. The header with what I suspect is a box steel lintel less so; I have come across nothing online that offers clear solutions for dealing with the challenge these present in cold bridging terms. Advice and suggestions are very welcome; I do know the header window reveal is a condensation point (BIGTIME), and is pressed up tight against the mesh underside of the lintel. I haven't removed that plasterboard yet.

The floor adjacent to the wall has partially been lifted, showing up gaps between the joists and the blockwork I can get three fingers in. The whole floor will come up along the wall so these joist:wall gaps can be all be mortar-filled (any mix recommendations?), recessed to 12mm and generously sealed with silicone. Then 60mm of kooltherm will be applied to the outer wall between the joists. I'll seal the ground floor blobanddob gap at the same time.

The blobanddob plasterboarding to the walls will be stripped, the wall so exposed made good, electric and radiator tails chased in, and then sealed (not sure about product yet - have researched Soudal LQ and the windproofing paint from Elite - any further suggestions very welcome). Then directfix of 50mm aerothem plasterboard with VCL will be installed. We'll go 50cm back down the party wall with 20mm aerotherm board (which will be ~ the same depth as the existing plasterboard + blobsndobs)

We could use some advice on managing the junction between the top of these boards, the ceiling and the wall plate. Currently the blobanddob gap is open at the top to the loft because the ceiling plasterboard position varies; at some points it touches the wall plate; in others it's almost 20mm from it. This variability means that when the plasterboard is removed there will be a variable gap between the wall plate and the edge of the ceiling plasterboard. How effectively to deal with this has become a matter of some debate. Out dryliner expert (traditional) says trim the ceiling board back to a consistent distance from the wall plate - this should be the same as the thickness of the aerotherm insulation on the wall boards. Expose a 'tongue' of insulation on those wallboards by removing a plasterboard strip to match the thickness of the ceiling plasterboard (12.5mm), and insert this tongue into the gap.

I see the merits of this approach in removing the cold bridge between wall plate and ceiling plasterboard. But I don't like (a) the fact the aerotherm wall insulation 'tongue' is exposed into the loft nor (b) the exposed cut edge of the ceiling plasterboard right next to the eaves. Remediation for (a) could be that I can tape over the exposed insulation from the loft side. For (b), the cut edge could be sealed (e.g. Soudal LQ). The loft insulation being inadequate I am intending to beef up the insulation (PIR boards) across from the top of the wallplate to the ceiling noggin, but I still find myself uneasy with this approach - but frustratingly can't put my finger on why that is. It would be good to hear suggestions comments questions towards a resolution of this issue.

This is going on a bit - but one last question; elsewhere here I see 50mm ventilation gaps cited. My eaves have wholly unnecessary (the insulation doesn't currently come anywhere near to diminishing eaves ventilation) plastic vent fittings between all trusses. These provide only 25mm of depth for ventilation; no more could be arranged, since they are up (down, actually) against the outer face of the outer brickwall. Do I need some remediation of ventilation too?

Actually - another last question - has anyone experience of making their own door or window blower? As this project develops I can see the potential of blower tests to identify leaks but would baulk at repeatedly forking out for contractors - I need the funds for the project!

TIA, best regards

-- Mat

Actually - another last question - has anyone experience of making their own door or window blower? As this project develops I can see the potential of blower tests to identify leaks but would baulk at repeatedly forking out for contractors - I need the funds for the project!

JS Harris has posted about this a few times on the BuildHub site (actually maybe it was eBuild)... do a google for it. He used a car radiator fan IIRC. Actually measuring the permeability requires a bit more tech.

Hi Mat, and welcome. Sounds like a good project. Pardon me for asking more questions, but there's a few places where I think more detail would help. Firstly, what kind of dwelling is it? One floor, two floors or more? Detached, semi, or terraced? Cavity wall block and brick? What insulation does it have at present?

You're planning to change a thermal element, so you'll need to pay attention to building regs as regards levels of insulation etc.

There were a couple of mentions where a link would help, because a search didn't quickly turn up a definitive answer. For example, what draughtbusters site? And what is 50 mm aerotherm plaster? And the ceiling noggin?

I'm not clear what problems you anticipate from exposing the insulation into the loft nor from the cut edges of plasterboard?

The simplest way to overcome the problem of the lintel is likely to be EWI, but I have no idea whether you have any thoughts about that.

I think some sectional drawings of the wall and ceiling would help to clarify your plans for airtightness and insulation. Also don't forget that once the rooms are airtight, you should plan for some ventilation - it may be worth installing some ducting if you plan mechanical ventilation.

I built a blower fan that works, but never needed to use it in anger. You just need an electric car fan, an adjustable voltage power supply that can supply enough current, and a pressure sensor for 50 Pa. Oh and a piece of board and some wire. Cut the board a little larger than the fan and fasten them together. You need to seal them together and you want four holes in the corner of the board so you can fasten it to a larger piece cut to fit whichever window or door you choose to mount it through. Oh and a smoke pencil will be useful if you're trying to find leaks. Let me know if you want more details.

Draughtbusters is Tony (of this site)'s project to help people address these and other fuel poverty issues. I had not heard of Aerotherm plaster (board), but Google suggests it is a mixture of plaster and aerogel, of which the latter has a lambda value of 0.014W/mK.

I understand the resolution to make the gap between ceiling and wall plate consistent,but the tongue idea seems overcomplicated... Why is this suggested?

I would consider pest proofing too, do mice like aerogel as much as PUR? Expensive tastes these rodents...

Posted By: cc64@djh; terrace, gnd and fst floors; cavity wall; 102 outer brick veneer; 60 mm cavity full fill blow fibre; 10mm block wall (medium density is my guess since it's definitely neither dense nor aircrete); all finished with a gloriously leaky blob and dob job; ~17.5 mm of blobs, 12.5mm pf plasterboard (~30mm in total).

If you have 60mm cavity of full fill of blown fiber - where does the gale behind the plaster board come from ?

@peterinHungary; the blobanddob plasterboard is open to the eaves; the gap varies from 20mm to a mere sliver - all more than enough to disrupt the air control layer

@Nick, yes I do mean spaceTherm, thanks for the clarity. Proctor no longer bond Aerogel to Fermacell, at least for the directFix product; its name indicated the installation method, which is 'shot fired nails' (Proctor's phrase) into the underlying wall. I would guess the gun gun settings required adequately to penetrate that wall threaten to overwhelm the strength of the facing Fermacell. This product now consists of the insulant layer, a 6mm ply reinforcement layer, then 9.5mm plasterboard. The ply bonded layer serves both to distribute the installation forces and also to some extent as a VCL The plasterboard is also available in foil face if a VB is required.

Thanks for the link/ref to Damon - I'll follow that up.

Out of interest how does the Proctor MgOboard + 10mm aerogel fall short in bldg reg terms?
Mat

Posted By: cc64This is going on a bit - but one last question; elsewhere here I see 50mm ventilation gaps cited. My eaves have wholly unnecessary (the insulation doesn't currently come anywhere near to diminishing eaves ventilation) plastic vent fittings between all trusses. These provide only 25mm of depth for ventilation; no more could be arranged, since they are up (down, actually) against the outer face of the outer brickwall. Do I need some remediation of ventilation too?

Some guidance here..

https://www.swishbp.co.uk/design/building-regulations/

If you have a pitched roof with insulation at joist level they recommend the equivalent of a 10mm wide gap the whole length of the eaves both sides.

Typically this gets blocked either by insulation (yours sounds ok if you have 25mm gaps) or when the fascias are overboarded or replaced with uPVC.

You can get plastic trays that maintain an air gap allowing you to stuff insulation down into the eaves.

You can buy round eaves vents at places like screwfix but you need a lot. A rectangular slot 10mm wide provides 10,000 square mm of area per meter. A typical 70mm round vent provides about 2100 square mm so you need 10,000/2100 = 5 vents per meter.

Posted By: cc64The insulation 'tongue' idea is specifically to ensure continuity of insulation at the wall:ceiling junction; without the tongue there is at the top of each wall board an uninsulated gap the height of (the thickness of) the ceiling plasterboard. Something comparable is done vertically at the wall corner junctions for the same reason.

I think we understand that. My question was what problems do you foresee from it? (subtext: you're probably worrying about nothing in this respect, but we need to know what you're worrying about before we can loftily dismiss it. )

@ Nick; Proctor now assert lambda of 0.015 for aerogel. That allows me to match 50mm of aerogel with 60mm of Kooltherm 100 series between floor and ceiling below, which should save a few bob.

Right, but as Nick has also asked, what exactly is Aerotherm?

@djh & Peter_in_Hungary; EWI probably wouldn't go down too well; this is terrace house, and I strongly suspect it would be tricky to implement in isolation (my neighbours would not be interested).

It's a lot more awkward, but they probably suffer from the same problems as you and might be interested in a cure (or their landlords might, if they're renting).

@djh; terrace, gnd and fst floors; cavity wall; 102 outer brick veneer; 60 mm cavity full fill blow fibre; 10mm block wall (medium density is my guess since it's definitely neither dense nor aircrete); all finished with a gloriously leaky blob and dob job; ~17.5 mm of blobs, 12.5mm pf plasterboard (~30mm in total).

Thanks. It helps to know for sure.

Thanks for your suggestion re sectional drawings - I've got one on the go... my erasor is getting a workout, but plans are maturing; it's clear that the loft needs to be included in the grand design if the control layers are to line up continuously.

Good and thanks.

Re: blower fan - a car fan is enough? I'm surprised - the commercial units are rated at 6000cfm IIRC; in that case I can better see a way forward - but details of your own proven approach would be very welcome, esp the regulator and the manometer. Thanks.

Sorry for the delay, I got distracted whilst checking the details :( Car radiator fan, yes it should be. I used Paul Jennings for our airtest; he has two fans and was relieved to be able to bring the smaller one, by train, to our house! I also asked a local airtightness company for a quote to check the price but they declined because they didn't have a small enough fan. It doesn't say a lot about the average standard of house construction in this country.

I picked up a car radiator fan on ebay or somewhere and a 12 V, 200W adjustable power supply (Fusion PS200ADJ but any equivalent is fine) The pressure sensor is a Dwyer Mark II manometer type(M-700PA I think)

Today I made some "discoveries" - as I suppose must be routine in this field of endeavour; the first was that our host here is none other than Keith Hall of AECB and the Passivhaus Trust! Realising this made me feel very silly, but also cheered me up no end about the scale of the endeavours ahead;

Indeed, and much kudos to Keith for keeping this site running.

The second discovery was... window header structures.. and why mine are condensers. Were someone to propose structuring the envelope around a window like this I would say it was a (very thermally bad) joke; I'm set for a life of comedy, since I've got 8 of them. Structure from inside to outside at the bathroom window header (which has a dormer) is (vertically)
1. 12.5mm plasterboard (always dripping condensation in the winter)
2. ~10mm of dry-lining adhesive (I think - but does seem to be slightly more dense than the stuff used on the adjacent drylining)
3. STEEL BOX LINTEL! OMG that's cold; small mercy on the first floor is that this is inner blockwork only, since the winodw has terminated the cavity and there is no outer veneer brickwork above; I dread to think what I'll find on the ground floor, where that outer brick facing needs support.
4. a plywood sheet - all of 4mm
5. The cold void of the dormer.
That's not a lot of thermal isolation from the outside world.

I'm shocked at this construction. And not at all surprised that is it cold. So now I have another endeavour added to my collection ... figuring out how to deal with this structure; this project seems to be expanding

Ouch! That sounds awful. From the sound of it there's no reason for the box lintel since it's not supporting anything? So stripping it out and replacing it with a simple insulation-filled timber structure shouldn't be too hard.

http://m.earth.org.uk/aerogel-on-the-north-face.html

Damon learned a lot about how to work with/around aerogel and shared it on his blog

Thanks all for your comments.

@djh

- my concern about the insulation 'tongue' exposure into the loft void are ill-formed, nebulous anxieties supported by nothing substantial i can get my head around. Having chased my various control layers through a sectional drawing as suggested I've concluded that the air and vapour barrier established on the inner face of the blockwork by sealing it will mean that the aerotherm insulation is FLANKED by air & vapour control layers (since its bonding to a sheet first of 6mmply, and then foil-faced plasterboard. That being the case I think the insulation exposure into the loft space could be an advantage in forming an outlet for any condensation that does form within the insulation. Calculations done by Proctor do not suggest any should be expected. So no lofty dismissal, rather a lofty benefit.

- re the box lintel; not sure I want to go down the rip it out route (there's only so much disruption that can be tolerated... luck is already being firmly pushed); and the inner blockwork it supports does have a couple of roof trusses above.
The structure context of the excavated window includes a dormer, as mentioned (the measly 4mm ply forms its exposed base, and is in direct contact with the top of the window frame: and here I found another chilling constructional 'feature' : that contact is variable and in no way sealed; at one end I can slide a stainlessteel ruler through to the outside world; at the other a whole pencil). Given the vertical alignment of that ply with the lintel I think I can use something like kingspan K5 wall board in a suitable thickness to insulate the lintel externally, with that insulation visually hidden from the exterior within the dormer window structure. Happy to hear responses thoughts suggestions for that dormer. Which will also influence the treatment of a.n. other bigger dormer on the other side of the house (later)

For the remainder of the window lintels (5) I've just come across a possibility; has anyone here experience of https://keystonelintels.com ?? They have a product 'keyslip lightweight brick headers' which sits on the outer lintel leaf and consists of a 70mm-deep insulated box (magnesium bldg board filled with an unspecified insulant) faced externally with a veneer cut from bricks. These are custom made per building and using the same bricks as the external veneer facing. The structure of these headers is sufficiently robust that they support the weight of brickwork courses above. Has to be worth a query or two to their tech bods. That of course is for the outer face of the lintels in place of the existing brick courses.

For the inwards-facing lintel faces (window reveal header and wall above, I'm inclined to remove entirely the plaster keys - so I can install a greater thickness of insulation - and use a suitable adhesive to secure the header window reveal board. Currently I'm undecided if this will be a lesser spec aerogel or Kooltherm K10* series. Instastik is recommended for aerogel to plaster; need to research what might adhere robustly resiliently to a galvanized steel lintel undergoing periodic thermal movement.

Thanks for the details re:diy air testing; all sounds simple enough; I even have a sheet of kitchen countertop made up to block off a window opening I can use to accommodate a fan. I have noticed many refurb projects START with a (baseline) airflow test; given the size of some of the holes I've been patching up I think I'd have needed a fan on an industrial scale to get such a baseline test. I look forward to the day a mere car rad fan is enough. Satisfyingly, in one room the sealing put in place to sockets, switches and the ceiling rose (the hole for which was apparently made using a hammer) now means it is no longer possible to slam the room's door, which was an unanticipated effect of airtightness... (-:

re aerogel; installation does seem to include its own unique challenges; I read (and noted down) somewhere that (presumably blunt, hence hot) drill bits 'grabbed' when their heat melted the synthetic core of the insulation. Blunt drill bits like blunt kitchen knives are a hazard. Using sharp ones should sort that issue.
Those handling the aerogel are recommended to use PPE.

- re EWI and roping the neighbours in too; I discovered the horrors lurking in my house pretty much at the same time they had contractors in 'doing the bathrooms'; I popped by to let them know what I'd discovered so they could potentially leverage the contractor-on-site advantage to address some of the issues that their house most probably shares. But I was just a tad too late, the work had progressed too far; they were now completing essentially superficial cosmetic 'improvements' to a house with deeply flawed fabric. They replaced their windows last year. My guess is that having spend those sums they're probably locked-in for the duration of their occupancy. I consider myself fortunate to have a research-everythibng-in-detail-and-tehn-some -more mindset and so will remediate the fabric first.

@ Nick Parsons

Thanks for your backof the envelope calcs. I agree that the outcome of those would fall short; but I'll be using 50mm of aerogel not 10mm, which should deliver something around 0.2 (R5.3).
Do you happen to know what was the budget for the victorian terrace project you linked? and what they ended up spending? This field is used to the peformance gap between predicted and actual in building energy terms. The predicted versus actual £ terms can be as eye-opening.

@ RobL

Thanks for the diy air test link; I'll follow that up; I agree that finding the leaks and sealing them takes priority over getting any airleakage figure; neg press and the sensitivity of the back of a wetted hand will progress that discovery.

Has anyone found a source of good sealed backboxes for switches and sockets? I'll have a dual socket and a pair of switches on this insulated wall, and I'm keen to ensure the penetrations these make through the foil faced plasterboard VB are made good; otherwise the aerogel would mop up any vapour leaking in.

Just this evening's research session I discovered the resources at http://www.zerocarbonhub.org/ - fabulous; where would we all be without the generosity of those that make thee resources available.

Matt

Posted By: cc64re the box lintel; not sure I want to go down the rip it out route (there's only so much disruption that can be tolerated... luck is already being firmly pushed); and the inner blockwork it supports does have a couple of roof trusses above.

Ah, the situation is clearly more complex than your description had led me to think. Perhaps a diagram, or photo, or two would help.

'keyslip lightweight brick headers'

https://keystonelintels.com/keyslip/#lfgbh

I'd be very sceptical about using them. No information about what the insulation is, nor U nor psi values for the product is worrying. But a steel lintel is going to be a major problem thermally, unless of the thermally broken type.