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    • CommentAuthorPlHadfield
    • CommentTimeJan 11th 2018 edited
     
    Greetings from south Leicestershire, where we are hoping to avoid lock-in / sterilisation of our suspended timber sitting room floor. The floor is partly lifted and needs to be put back before we re-decorate the room ready for our July 20th pre-wedding party. We are hoping you people on this fantastic forum might have some thoughts about our potential overall air-tightness strategy amongst other things, which will inform what we do below those floorboards and floor at this stage.

    The floor is of 140mm x 18mm (5 ½” x ¾”) tongue-and-groove softwood boards. We lifted a few boards three years ago around the edge for electrical work prior to re-decoration, and that was the moment at which we thought we should consider what else to do while we have them up, in order to avoid lock-in of poor insulation and air-tightness down there. This would then be the first stage of the step-wise retrofit which we had been beginning to contemplate, to as high a level as can be justified by the likely-achievable whole-house air-tightness, and by the longer-term depth of our or future owners’ pockets. Those edge floorboards have remained up, and we have been without a sitting room, while we pondered the right way forward ever since.

    Given that we aren't sure whether we'll stay here for more than a year or two more, but may be here for forty years, we are hoping at this stage to take a sensible view ourselves about where the future air-tightness layer should be for the house as a whole, which will inform what we do in this sitting room floor void (and with the ceiling joists of the same room) in this first stage, to avoid lock-in. We’re hoping we can thereby avoid having to have a costly full retrofit plan drawn up professionally at this stage, in case we don’t stay and so don’t take the retrofit much further ourselves. The house is a detached, two-storey, 1955-ish cavity-walled construction, both external wall leaves being of brick, and with Rockwool mineral insulation blown into the approx. 65 mm (2 ½”) cavity between them by Miller Pattison 13 years ago. Including the internal garage (ripe for conversion to living space) it weighs in at approximately 140 m2 (1500 ft2). We are in a conservation village, but our brick is undistinguished, and the neighbouring property is rendered, so we believe there is a good chance that rendered External Wall Insulation (EWI) will be allowable. We are west facing, in a sheltered position but somewhat shaded (from at least the midwinter sun) by trees in almost all directions, especially (and from the summer sun too) by a very large and historic ash tree just outside our property at our south-east corner. Photos attached, I hope, showing amongst other things garage doors suffering from planning blight until we decide whether to convert the garage.

    Ideally we’d hope ultimately (if we stay) to insulate the perimeter down to the footings as part of a future EWI, sealing the airbricks, and bringing the 270 mm (10 ½”) underfloor void into the conditioned space of the house by heating it, and ventilating it into the interior. The suspended timber floor is to the sitting room and also the hallway, which are about half of the house’s total footprint, the rest being concrete slab on grade (garage plus kitchen/ dining area). Currently the suspended floor appears to be adequately ventilated via air bricks to the great outdoors.

    A plan for a future EWI is also attractive because the slab under the rest of the house, namely under the kitchen/dining room and the built-in garage, is we believe un-insulated, so the idea of cutting the thermal bridges at the perimeter of that slab with EWI down to the footings seems sensible there too, as well as saving the internal joinery work which would be required if we instead insulated on top of the slab. (We do have sufficient ceiling height at 2.44 m (8’) to do some of that perhaps if we had to, but hoping not). By insulating externally down to the footings we’d hope thereby to bring the subsoil beneath the house into the thermal mass, warming it up over several years. Since we’re on very heavy (Lias) clay with we hope no major granular intrusions, we’re hoping that that warmth will not be whipped away by water moving either vertically or horizontally to any significant extent in the ground below us (to paraphrase FosterTom in another post on this forum).

    But that may be a vain hope as we have a shallow perennial stream defining our garden boundary at the sitting room (southern, gable end) side of the house, which rises in a spring at our south-eastern corner. It runs the full length of that side of the house, only 1.5 m (five feet) or so away, at its nearest, from that gable wall. Its normal winter water level is 480 mm (1’7”) below the level of the ground adjacent to the wall (see attached ‘South wall and stream section’ detail), which makes it 600 mm (2’) below the lower surface of the 100mm (4”) thick concrete (rat pad?) which lies below the floor, 820 mm (2’8”) below the lower edge of the lowest of the five or so courses of blue bricks which seem to form the damp proofing of the outer leaf in that wall, and 980 mm (3’3”) below the internal wall leaf’s DPM. Flooding of this stream once or twice a year raises its level by 400 mm (16”) or so, due to inadequate culverting under the road outside, but it normally subsides within a day or so back to its normal level once the very heavy rainfall stops. It never gets higher because at that point it can escape over the top surface of the road, to its much lower stream bed on the far side of the road. When the stream is in spate in this way, the water level in a 0.6 m x 1.2 m (2’ x 4’) trial pit I have dug down through the concrete path, adjacent to the external face of the foundation wall, was just 370 mm (15“) below the lower surface of the concrete rat pad. But what the true water table level is under those conditions inside or indeed outside the foundation wall we have no clear idea, and the floodwaters were only inches from the edge of my trial pit, so that water didn’t have to travel far through the uppermost clay near the pit’s stream-ward side to pass into it. And the water level in the pit, after being so full, takes some time to subside back down to its normal water-table level of course. Probably I should bale out the trial pit as soon as the stream flood outside it has subsided, and leave it for a day or two to stabilise again, to assess what the true water table level is in there at that point. I will do so at the next flood event.

    Maybe the proximity of this stream is why the rest of the entire outer wall leaf of the house seems to be of what I suspect are Class B engineering bricks (red, very hard, and measuring unusually 225 mm x 108 mm x 70 mm or so (9” x 4.25” x 2.75“) except on the rear extension, where they are standard size).

    Our first thought for air-tightness was for the internal wet plaster layer to be the air-tightness layer, with attention to sealing and taping up all joists where they go into the inner leaf, and to sealing all other penetrations such as electrical sockets. In support of this, with some edge floorboards up we could see that the suspended timber ground floors have all their joists supported out, away from the supporting (inner leaf of the) walls by cantilevering them out from the inner leaf of the cavity walls, and from the internal structural walls, on blue engineering bricks. So these ground floor joists don’t penetrate the walls at all. So we would have fewer joist penetrations to seal, if we were going with this air-tightness plan, as only those at ceiling/ first floor level would need to be sealed. I find too that we can actually jack up each individual joist by a few mm, so could perhaps work a membrane underneath each one by one, and between them and the walls, We imagine that this cantilevering arrangement may have been used because of the proximity of the stream, in order to minimise the possibility of wet walls causing the joist ends to rot. (to be continued)…
    • CommentAuthorPlHadfield
    • CommentTimeJan 11th 2018 edited
     
    ....(Continued from first post) Would it be wishful thinking however to hope that rather than defining the internal plaster as the airtightness layer, the airtightness layer could be defined as a future layer of EWI adhesive over the outside of the cavity wall as discussed on this forum at
    http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14950&page=1 ? Or could a layer of a similar gunk there (Blowerproof for example - as seen at http://www.blowerproof.co.uk/blowerproof-airtight-membranes/) provide the air-tightness layer? At this current stage then we could leave the ceiling joists merrily leaking interior air into the cavity, in the hope that a later stage we will seal the external surface of the wall’s outer leaf (and seal the cavity at the top of the gables, and plaster or seal their inside walls in the loft). Even if current technology such as current EWI adhesives, or Blowerproof, doesn’t sound as if it will make the grade yet, perhaps we could be technological optimists and hope that future developments will make that feasible. That will save a lot of work now, and will get us back in business for the July wedding party. Bringing the underfloor void into the conditioned space of the house will also avoid the need to insulate the floor. Which means we can dismiss the idea of ripping it out and filling the whole underfloor void with concrete and insulation, as one or two potential passivehouse-minded advisers have suggested off-the-cuff as a possibility. That extra concrete and waste of a softwood floor seems like a lot of embodied carbon emissions, not to mention loss of the potential benefit of being plugged into the thermal mass of the earth below. Bags of Leca would be an alternative to concrete, but the same benefit would be lost.

    Our (wet) heating system is currently a re-purposed hospital system with galvanised pipes and cast iron radiators – the builder in the 1950s was a keen re-user of architectural and plumbing bygones it seems, which was good for his pocket no doubt (and will also creditably have reduced the house’s embodied carbon I suppose, if re-used materials can be given a measurable credit). A largely-uninsulated 50 mm (2”) galvanised steel heating return pipe passes for about 4.5 m (15’) through one corner of the underfloor void. With its residual insulation removed this might perhaps I suppose ultimately be enough heat in the void, with the perimeter well-insulated at that stage. We currently have a passive ventilation stack with a humidity-sensitive extract in our bathroom, and another planned for our kitchen. The accompanying humidity-sensitive intakes have been unnecessary while the house is still draughty, but we are planning to install at least one before sitting room floor replacement. (The distributors (BPD) of this Passivent iPSV system recommend just one humidity-controlled intake per habitable room). Our hope is that the gaps around the edge of the floor and skirting will provide sufficient passage of air from that intake below the floor up in to the sitting room above, precluding the need for us to install any floor ventilation grills. We have an enquiry pending with the distributors on this point.

    As mentioned, beneath said suspended timber floor is a 100 mm (4”) concrete slab (rat pad?) which I suspect may have no membrane below it and be saturated. I have dug a 25 mm (1”) diameter hole right through it, and couldn’t detect any sign of a membrane below, but may have dug straight through the membrane I suppose. Probing down to 400 mm (16”) below the pad with a 13 mm (½”) diameter agricultural core augur a year or two later revealed a surprising and somewhat disturbing amount of void space immediately below that hole. The augur came up mostly with small lengths of clay coated with a little sandy residue, this residue being I guessed from a sandy layer just below the slab. Between the lengths of clay were void sections on the augur. But the hole I had dug in the concrete may have been made use of by vermin in the interim, making burrows, and hence voids, below, I suppose. Any suggestions for investigating further the presence or absence of a membrane would be gratefully received – dig a bigger hole perhaps, large enough to put a hand in, then dig the earth (or hard core) away from beneath the slab just around the hole, and feel beneath it for a membrane perhaps? Certainly if there is one, it hasn’t been brought up to be continuous with the internal wall’s visible asphalt DPC three brick courses above, but then in the 1950s I guess that might well not have occurred to those involved. Or would the probes of an inexpensive moisture meter held in contact with the top surface of the concrete give me the answers I need? Perhaps I really need to dig a number of holes anyway to determine whether there are masses of voids everywhere beneath the pad, and also by probing in them during a flood event discover whether they fill with water. In which case it would probably be wise to give up on bringing the underfloor void into the conditioned space of the house, and just install insulation below the floor one way or another.

    Over the days following my digging of my hole in this concrete pad, a dark ring of moisture further saturated the concrete just around the dug hole. But I am not clear whether this means that the rest of the pad is drier than the moist ring, which means that the hole itself was then a more major moisture penetration, and that there is indeed therefore likely to be a still-intact membrane under the rest. Maybe it just means that more moisture is rising into the air in the hole from the soil beneath, and thence into the surrounding ring of concrete, which implies that the paler surrounding concrete is less saturated than the dark ring, but may still be damp. If a concrete pad is somewhat damp, but not fully saturated, does that mean it is acting as a reasonably effective vapour barrier I wonder? I presume not. In the months following, this dark ring of moisture has disappeared.

    If the concrete rat pad (and its possible membrane, if any) is not acting as an effective vapour barrier then a vapour-impermeable membrane (thicker than 6 mil, and non-laminated, polyethylene perhaps, as suggested on this video https://www.youtube.com/watch?v=ypnhoM1BYvg) should presumably be put over the pad at this stage before we replace our lifted floorboards. So again any suggestions in this respect would be gratefully received. Further floorboard lifting will we hope be achieved without too much damage to them, as described by HandyAndy in the sixth or so reply of 6th March 2015 at https://community.screwfix.com/threads/lifting-floorboards-without-damaging-them.16635/ . By using a parallel punch to knock the nails through into the joists below, I seem to have avoided any significant damage to those boards removed so far. And for membrane installation I can just about slide around in the 270 mm void space on my back, with increasing feelings of claustrophobia, though working down there is certainly challenging.

    We are hoping that simply taping our membrane to the DPM of the internal leaf of the external (cavity) walls, and if necessary at any overlapped joins in the membrane, will be adequate (But with say 200mm (8”) overlaps do these overlaps even need taping I wonder? Perhaps not.) We won’t be trying to make it an air barrier after all, not even at the inner leaf of the external walls, if our technological optimism about an external air-tightness layer on the outside of the walls is tenable. But perhaps we should be taping it meticulously to keep any wayward radon out, even in our near-zero- (or at least negligible)-radon area (according to Public Health England’s map)? And in the interim our membrane will have to be worked around all the air-brick-related holes in the inner leaf, so as not to impede ventilation for the moment. But we just have to accept that this latter type of minor additional hassle is the inevitable consequence of a step-wise rather than an all-at-once retrofit.

    Should we bring the membrane up to the DPM at the top of the honeycombed pier walls, I wonder, in order to exclude any moisture which passes up from the concrete pad into those pier walls? Bringing the membrane up in this way would be a problem in the short term, in that it would prevent conditioned air from circulating from one pier-wall division of the underfloor void to the next, so we would then need to install a humidity-controlled intake in each of the three sections of the underfloor void created by the pier walls. We might also need a temporary additional heat source down there in each section, and until the external air-tightness and EWI is done I suppose.

    However three humidity-controlled intakes down there might be inappropriate in other ways, such as supplying too much external air into the sitting room above. Moreover the void beneath the suspended timber floor of the adjacent hallway currently benefits from air blown through from the air bricks, directly opposite its own, in the gable end wall of the sitting room underfloor void (via the honeycomb pier walls). This would no longer be possible if the membrane was taken up to the DPM of the pier walls, thus sealing the two outer underfloor voids from the inner third one, and from its adjoining hallway floor void.

    There is also the practical problem that the underfloor voids will in the interim (prior to EWI) probably lose so much heat laterally through their walls and through the foundations that they will potentially be cold, and thus temporarily liable to suffer from high relative humidity and concomitant moisture damage, even with the membrane in place and with the humidity-controlled intakes installed. And the under-hallway void will in the interim have no membrane, unless we start pulling that part of the house apart before the July wedding party too.

    We will in any case also need to arrange a well-insulated pipe to bring some combustion air across this void beneath the sitting room floor, in the meantime, to the cut-out in the concrete kitchen floor at its junction with the sitting room floor void. This is needed for our ancient open-flued Vulcan Continental gas boiler which sits in a large cupboard in the kitchen, just behind the adjoining wall. It currently draws its air supply via this cut-out from the sitting room underfloor void, prior to wastefully pushing out masses of exhaust heat through its flue. It has lasted at least 40 years, so against its deplorable inefficiency must be offset the embodied energy (not to mention the cost) of the alternative of a new condensing boiler every 13-15 years or less, which considerably limits the carbon balance benefit of these more efficient but shorter-lived appliances, I believe. Once the house has eventually been insulated and air-tightened well it will need much less heating, so until then we’ll just live with our ancient boiler and hope it lasts that long. Being a simple beast, spares are still readily available, and our 97-year-old neighbour five doors down has one too which is still going strong (in a house built and at one time lived in by the builder of our house, her brother-in-law).

    I guess that if we need to consult building control (?) about our proposed membrane, they may be nervous of the above-mentioned overall strategy. So I would hope just to stick to discussing the membrane with them, if necessary at all, and avoid going into any more details of future EWI etc at this stage. A sealable drain-with-flap from the underfloor void (above the membrane) to the exterior should presumably also be arranged, in case some mishap such as a major plumbing or roof leak causes bulk water to get into the void at any time in the future, and to pond in the membrane.

    Or instead of a PE membrane, should we be considering a spray-on moisture-proofing of some sort for the concrete slab? That might be easier than trying to manhandle large pieces of a thick-ish polyethylene membrane down through a 30”wide space between floorboards and wall into the underfloor void, between 100 mm x 50 mm (4” x 2”) joists spaced at 420 mm (16 ½”) centres. Or should we invest in a ‘smart membrane’ which will pull moisture through to its underside? And would it be worth put in some more comprehensive underfloor heating pipes while we are down there I wonder? And instead of insulating externally down to the base of the foundations, should we just break up the full width of the concrete path which goes all the way round the house (and doesn’t subside on the other three sides) and put a skirt of insulation under its replacement? That would almost certainly be worthwhile along half of the north side of the house, where our neighbours have built a solid floor right up to our fence, which is only 1320 mm (4’4”) from our own house wall. So we could probably thereby plug into their warmer underfloor mass there, to reduce heat loss further in that direction.

    With apologies for the lengthy explanations, hoping we are on the right lines, and welcoming any suggestions or thoughts from the assembled expertise on this forum. FosterTom according to my note you kindly offered a drawing in your forum post of Oct 28th 2016 about sealing and insulating crawlspace perimeters. I cannot immediately find that post at present, as I didn’t note which category or topic it was in. If your offer is still available, and you could let us have your email address again through this forum, or direct me to the topic and category of that post, I should be grateful.
    • CommentAuthorPlHadfield
    • CommentTimeJan 11th 2018
     
    Will attach photos when I have found out how to do so. Not 2 MB jpgs it seems.
    •  
      CommentAuthordjh
    • CommentTimeJan 11th 2018
     
    Posted By: PlHadfieldwe are hoping to avoid lock-in / sterilisation

    What do you mean by 'lock-in / sterilisation'?

    Using the internal plaster as the basis of the airtightness sounds like a good plan.

    Your stream doesn't sound to be too much of a problem, in fact it may be a help. You might think about a French drain when you install the EWI, but you will need a place for the French drain to drain to and that sounds like it might be difficult to find.

    The concrete pad under your floor is below the DPM/DPC and so potentially damp. You'll need to think carefully about what to do in that space; how deep is it?

    It might be worth making or hiring a blower fan to get an idea of existing airtightness and where the major leaks are.
    • CommentAuthorPlHadfield
    • CommentTimeJan 11th 2018 edited
     
    Thanks DJH.

    Posted By: djhWhat do you mean by 'lock-in / sterilisation'?


    Apologies, I should have explained that I meant 'lock-in" of poor quality air-tightness and insulation below the floor once it is replaced, never (or not for many decades) to be disturbed again, as we and future occupants probably won't want to disrupt any decoration (and possible hardwood floor over the softwood boards) for a considerable time once we have put it back this time. In other words that part of the building's fabric will be "sterilised" with regards to retrofit measures for a long time.

    If you mean how deep is the underfloor void space, it is only ten and a half inches deep from the bottom of the floor joists to the concrete pad. The concrete pad itself is 4" thick. See the attached detail with my original post for a roughly scale drawing.

    Posted By: djhUsing the internal plaster as the basis of the airtightness sounds like a good plan.


    Our main question really is: can we ditch the idea of using the internal plaster as the air-tightness layer, in the hope that it will be easier to use a layer of applied EWI adhesive, or other gunk, for that purpose at a later stage. That will enable us to forget about plastering the internal walls of the underfloor void at this stage, and to forget about trying to seal the sitting room ceiling joist wall penetrations. That will enable us to get on quickly with getting a vapour membrane down (if necessary?), getting our floor boards put back, and getting our sitting room decorated for July.

    Do you have any ideas on how I can convert jpg photos for attaching?
    •  
      CommentAuthordjh
    • CommentTimeJan 11th 2018
     
    Posted By: PlHadfieldDo you have any ideas on how I can convert jpg photos for attaching?

    You need to edit them. I run linux and would use gimp or ffmpeg. Typically, find a photo editor and save the photo with reduced resolution.

    PS If you want quotes to come out in blue, choose Html formatting. Choose Text formatting if you want links to work. You can edit a post to change the formatting.
    •  
      CommentAuthordjh
    • CommentTimeJan 11th 2018
     
    Posted By: PlHadfieldOur main question really is: can we ditch the idea of using the internal plaster as the air-tightness layer, in the hope that it will be easier to use a layer of applied EWI adhesive, or other gunk, for that purpose at a later stage. That will enable us to forget about plastering the internal walls of the underfloor void at this stage, and to forget about trying to seal the sitting room ceiling joist wall penetrations. That will enable us to get on quickly with getting a vapour membrane down (if necessary?), getting our floor boards put back, and getting our sitting room decorated for July.

    It is possible to use either the inside or the outside as the primary air barrier, but frequently it is best to use the inside despite some awkwardnesses like joist ends.

    If you put a vapour barrier down at ground floor level then that is almost always an air barrier too, so you won't need to plaster the underfloor void in that case. The ease of connecting such a vapour membrane to the internal plaster is one reason internal plaster is a good choice. A downside is the need to deal with the first floor joist ends, as you say.

    You will need to decide, plan and install your underfloor insulation before putting in a vapour barrier, of course.
    • CommentAuthorPlHadfield
    • CommentTimeJan 11th 2018 edited
     
    Posted By: Nick ParsonsOnly if you are completely in control (and I really do mean 'completely' and 'in control'!) of the EWI could you hope for (even if not guarantee) there to be sufficient coverage of adhesive for it to function as an air barrier.

    (Edit: The above quote was part of a whisper from Nick Parsons, which I hadn't realised was a whisper, so replied publicly. Moreover neither Nick nor djh had seen the second, lengthy original posting at the time they made their comments above, as I had mistakenly whispered it. I am a beginner, but learning now.)
    Thanks for this Nick. Indeed if we sell the house in a few years time then inevitably we won't be in control at all of what happens to it. But we will have no further direct interest at that point. I didn't meant that we were expecting to leave it and still retain an interest.

    We aren't contemplating an all-at-once, whole-house, retrofit, for all the reasons that the 'Europhit' project gives, including that it is probably most economic to upgrade elements of the building as they wear out. So I believe that step-wise retrofits are well-regarded now, and inevitably people will sell and leave houses when these step-wise retrofits are part-way complete.

    There doesn't seem to me to be any way of avoiding that. The only ray of hope which I see, to mitigating the problem of handing over which you rightly point out, is to have the sort of national database of addresses, and the measures taken there, such as is proposed by the Bonfield report (if I understand it correctly). Then new owners would have the benefit of high quality advice about the measures taken on the building to date, and the potential future measures, including access to the entire retrofit plan for the house, such as it is. Hopefully they would also by that means have access to advice about which expert practitioners, such as qualified retrofit coordinators and other expert AECB members (including yourself), will know enough about retrofit to advise on the next steps.

    It seems to me that we each have to do what we can, in the situation in which we find ourselves and in the face of climate change, even if we aren't sure how long we it will be before we sell a house and move on. And it seems to me that when we are upgrading parts of the fabric for other reasons than energy upgrades we should do our best to avoid locking in poor air-tightness and insulation. Do you think I am correct in these respects?


    Posted By: djhPS If you want quotes to come out in blue, choose Html formatting. Choose Text formatting if you want links to work. You can edit a post to change the formatting..... Typically, find a photo editor and save the photo with reduced resolution.

    Thanks djh, I have converted my previous comment to html now. And I will have a go at editing my photos as you suggest.


    Posted By: djhYou will need to decide, plan and install your underfloor insulation before putting in a vapour barrier, of course.

    (Edit: djh hadn't seen the second (part of the) original posting at the time he made his quoted comment). What we are proposing is not to insulate the floor at all in fact, but to insulate the perimeter instead, and to bring the underfloor void into the conditioned space of the house by closing all but a humidity-sensitive intake ventilator (or three) and then ventilating that void to the room above. The vapour barrier, if appropriate, would just be on top of the underfloor concrete rat pad (or 'oversite' as I believe it is sometimes referred to), to reduce the amount of moisture evaporating from it into the void space and thence into the house.
  1.  
    ''I didn't mean that we were expecting to leave it and still retain an interest.''. No, I realise that, but I got the impression that you were wanting to be able to 'pass the baton' having achieved whatever result from what you'd already done. The point I was making is that if you say: 'There is an external a/t layer because we've had EWI done' it's hard to be certain of that unless you have been right on top of the process.

    ''It seems to me that we each have to do what we can, in the situation in which we find ourselves and in the face of climate change, even if we aren't sure how long we it will be before we sell a house and move on. And it seems to me that when we are upgrading parts of the fabric for other reasons than energy upgrades we should do our best to avoid locking in poor air-tightness and insulation. Do you think I am correct in these respects?''

    I agree wholeheartedly.
    • CommentAuthorgravelld
    • CommentTimeJan 11th 2018
     
    Russel Hayden is relying on the EWI adhesive on his project:

    https://thebox-haus.weebly.com/posts/more-tape-please
    https://thebox-haus.weebly.com/posts/rockwool-redart

    (Note my comment... have to say I get a tad annoyed with blogs that leave the comments open and no-one ever responds... anyway it's an interesting blog).

    As Nick implies, continuous beds of adhesive is not standard practice. Indeed, I've heard it can make things more difficult in certain cases, with less even walls. No chance of S+C parge coat before the EWI?

    Good to hear of another Leicestershire member! There aren't many of us. I'm near Melton. Sounds like we have a lot of similarities - 1950s CW build, lots of clay! At least our floors are solid :wink:
    •  
      CommentAuthordjh
    • CommentTimeJan 12th 2018 edited
     
    Posted By: gravelldRussel Hayden is relying on the EWI adhesive on his project

    Ooh! PH porn. Thanks for that; I've just wasted an hour reading it. :cool:

    Looks like a well-run project.
    • CommentAuthorbhommels
    • CommentTimeJan 12th 2018
     
    Hi, I am in a very similar situation to you: extending and thermally upgrading a 1945 (very early ) cavity wall build. Living room: suspended wood floor. Kitchen: concrete on hardcore on clay soil, not comfortable at any time of year.
    Although it was quite expensive, we decided to have the kitchen floor dug up, have a new load bearing floor, 300mm XPS and 75mm screed (with UFH) floor on top put down. Absolutely no regrets of spending the hard earned cash on this, even with the UFH still not connected it is quite comfortable already! I very much doubt whether you get the same with putting EWI down to footings level (if you can achieve that neatly without destabilising the walls), as it will remain a massive heat sink. In fact, we are thinking of not trying to insulate the suspended wooden floor but doing away with it completely and give the living room the same treatment.

    For the airtightness layer we were advised to go for the inside (render/plaster) layer. Given the poor detailing of our cavities and their terminations around (historic, bricked up) doors and windows, I think it would have been very hard to achieve an airtighness layer on the outside. Even though our 50mm cavity is filled (blown) with mineral wool, it is by no means airtight. Admittedly it is finicky to get a good continuous airtightness layer between ceiling and floor, this is where I have to take it room by room. And since it is not visible I can slap on the parge coat myself :-)
    Good luck! Bart
    • CommentAuthorPlHadfield
    • CommentTimeJan 13th 2018 edited
     
    It looks as if by whispering the second part of my original post to Fostertom, it has not been seen by the whole list, as I had hoped it would (as well as being whispered). I have now gone back and unwhispered it. No wonder you were confused about our intentions if you hadn't seen that second, and even lengthier part.

    Apologies for that. Please look back to the second post in this topic if you previously just read one longish post - there are two I am afraid. I hope it now makes more sense, having, I hope, been revealed to all, and if you manage to wade your way through it all.
    •  
      CommentAuthordjh
    • CommentTimeJan 13th 2018 edited
     
    The whole point of a whisper is that nobody else hears it :)

    Thanks for making it public; I was wondering why there was only one part!

    edit: you might want to fix the broken blowerproof link.
    •  
      CommentAuthordjh
    • CommentTimeJan 13th 2018
     
    Note that blowerproof is vapour tight as well as airtight, so you need to consider where to use it. One reason that the internal surface is often preferred for the airtight layer is that many materials strategies also require a vapour barrier there as well.
    •  
      CommentAuthordjh
    • CommentTimeJan 13th 2018
     
    I don't think there's any chance of a membrane underneath your rat pad. 1"-2" of sand blinding maybe. The voids in the clay may be due to the clay shrinking as it has dried out through the years, after having been built on when wet and expanded. Hopefully you're not anywhere it could be subsidence?

    You've come up with a bunch of fairly complex possible proposals and some fairly fundamental questions. Given that, I think you're likely to experience a fairly steep learning curve over the next few months, and likely to change your thoughts as to the best plan. So my advice would be to put your floor boards back down and get your sitting room back for your pre-wedding party. Spend the time up to then learning more and planning but not doing anything to the house yet, oh and planning for your wedding! The alternative would be to hire a professional that you trust and follow their guidance as to what to do, but finding such a paragon might be difficult.
    • CommentAuthorPlHadfield
    • CommentTimeJan 15th 2018 edited
     
    Posted By: gravelldNo chance of S+C parge coat before the EWI?

    Thanks gravelld. Yes, that sounds like an excellent idea. I wonder what the cost would be compared to heavy horizontal strips of EWI adhesive. Quite a lot more perhaps, but anyway we can cross that bridge when we come to it, if we do. The key point is that, thanks to your additional suggestion, it looks to me as if there will be several possibilities for an air barrier on the outside of the existing masonry. That indicates that we could proceed with our basic strategy for the underfloor void work now, on the basis that such an air-tightness strategy for the whole house is feasible, albeit bearing in mind the caveats mentioned by bhommels about external air-tightness.



    Posted By: bhommelsI very much doubt whether you get the same with putting EWI down to footings level (if you can achieve that neatly without destabilising the walls), as it will remain a massive heat sink.

    I am hoping that by plugging into the thermal mass of the ground below it will not in fact be a heat sink but a source of thermal mass, along the lines championed by FosterTom on this forum. It is also the approach taken by the hugely respected Building Science Corporation in the USA, and of their legendary Joe Lstiburek in particular, who says 'don't insulate the floor, insulate the perimeter, and bring the underfloor void into the conditioned space of the house.' That is the approach I have been favouring. In other words I am hoping that the soil mass beneath our own floor is sufficiently impermeable to water that a warm column will build up over several years between the warm earth 10 metres down and our warm building above. The question in our particular circumstances is whether that warm column will be disturbed and cooled excessively by the horizontal passage of water below whipping the heat away. Not easy to quantify, but I wondered whether, given the levels of the water table and of the adjacent stream, and my observations on the nature of the soil, anyone cared to hazard an opinion on this forum. Yours is certainly appreciated. I am hoping that Wednesday night's predicted heavy rain might give us a good flood event, during which to probe the hole through and beneath the rat pad to determine whether liquid water is present in the voids there. After the next such event I will also immediately bale out my trial pit in order to make the best possible assessment of the change in height of the water table adjacent to that outside (south, gable end) wall.



    Posted By: bhommelsIn fact, we are thinking of not trying to insulate the suspended wooden floor but doing away with it completely and give the living room the same treatment.

    I do take the point. My preference to avoid this is due to a) the very large quantity of embodied carbon in the alternative concrete floor, and b) the loss of what could be the benefit of the warm column of soil and subsoil below, if little or no horizontal movement of water is occurring.



    Posted By: gravelldGood to hear of another Leicestershire member!

    Likewise, very good to hear. I have spoken to one or two members of the Institute of Sustainable Development at De Montfort University in Leicester about the possibility of getting together a retrofit group for the east midlands, along the lines of the excellent Manchester-based Carbon Coop of which I am a member. The sticking point seems to be that there are few experienced AECB members, or retrofit designers, coordinators or contractors in the area, and none in Leicestershire as far as I can determine. Nottingham, nearer to you than to us, has one or two, but that is rather at the northern end of the East Midlands area. We need to crank up the 'Midlands Engine' (our equivalent of the 'Northern Powerhouse'), in this respect.



    Posted By: Nick Parsons''I didn't mean that we were expecting to leave it and still retain an interest.''. No, I realise that, but I got the impression that you were wanting to be able to 'pass the baton' having achieved whatever result from what you'd already done. The point I was making is that if you say: 'There is an external a/t layer because we've had EWI done' it's hard to be certain of that unless you have been right on top of the process.

    Yes, I had been thinking that the EWI installation would be towards the end of the retrofit process, probably along with improved windows and doors. So I had imagined that the EWI air-tightness would therefore be verifiable at that stage by means of a blower door test, whenever that was. That test result would then also be available, potentially, to subsequent owners and occupiers. However what you say makes me think deeper, and to wonder about the sealing of the top of the wall cavity at the eaves. If that has not been sealed well at the stage of the EWI and blower door test, then the test will give a poor result for that reason alone. If the existing original roof is still in good condition generally at that stage, the roof and eaves might therefore remain to be given the full passivhouse style treatment, as the very last step perhaps of the step-wise retrofit. I wonder how feasible it would be to seal the cavity at the eaves however in advance of that, at the time of the EWI. In other words will it be feasible to seal the top of the cavity before, and separate from, the full roof treatment some years or decades later. Can we hope to make the top of the cavity wall airtight simply by stripping the eaves tiles and felt, and sealing whatever is nominally closing the cavity at that point (gappy slates I suspect, which could just have a parge coat too perhaps)? I probably need to investigate the construction there by stripping some tiles and felt, and having a look. I will do so when the rain stops.



    Posted By: djhyou might want to fix the broken blowerproof link.

    Fixed now I hope.



    Posted By: djhNote that blowerproof is vapour tight as well as airtight, so you need to consider where to use it. One reason that the internal surface is often preferred for the airtight layer is that many materials strategies also require a vapour barrier there as well.

    Thank you. Of course, whoever eventually drew up the whole-house plan for us (or a subsequent owner) would need to be careful about the Blowerproof, if used, being a vapour barrier, or at least a vapour retarder. That hadn't occured to me. I'm interested to hear what you say about some materials strategies requiring an internal vapour barrier, as in my ignorance I thought that in general vapour retarders and barriers were largely unnecessary in walls in our maritime UK climate.
    We are envisaging that before going to the extent of EWI, if we go that far, we would at that stage get properly qualified advice on the whole project. We were simply hoping to avoid the expense of it at this stage, given that we may not stay in the house for long.



    Posted By: djhI don't think there's any chance of a membrane underneath your rat pad. 1"-2" of sand blinding maybe. The voids in the clay may be due to the clay shrinking as it has dried out through the years, after having been built on when wet and expanded.

    Thank you very much for this, and that's just the sort of thing it is good to hear, namely that the sand on my soil augur was probably from that likely sand blinding. That makes a lot of sense. And also as you say, voids in the clay could be from shrinkage and drying out now that that clay has the house over it, so drying it out of course and keeping it dry ever since the house was built. Lets hope that those voids are not vented to the open air anywhere outside the house, or heat from the hoped-for warm column may be in danger of being whipped away in the interim. Once we (or potentially future owners) make the foundations air-tight, when the EWI is done there, such danger should I hope be mitigated anyway.



    Posted By: djhHopefully you're not anywhere it could be subsidence?
    I am not aware of any subsidence at this end of the village. Fingers crossed not. The large ash tree just outside the south-eastern corner of our plot is on the far side(on the far bank) of the stream, so my hope has always been that it will have been reluctant to put any roots across, under the stream where the soil would be permanently waterlogged and anaerobic. Not a favourable environment for growing roots I have always hoped. We are keeping our eye on it in case it shows signs of the ash die-back which I believe around 95% of our ash trees are predicted to die from over the next decade or two. If it does come down it will be a great shame for the garden bird-life and because we enjoy its cooling shade on the hottest summer days. But it will give our plot the benefit of a great deal of extra incident solar radiation to play pv games with.



    Posted By: djhI think you're likely to experience a fairly steep learning curve over the next few months, and likely to change your thoughts as to the best plan

    Yes, but then again we've given it more than three years already, and don't need to have the whole plan worked out at this stage, just a decision as to whether the idea of an eventual external air-tightness layer over the whole house is feasible (which it sounds as if it is, from gravelld's suggestion of a parge coat, failing all else) and whether a vapour barrier of any sort over the underfloor void’s concrete pad and over the sub-DPM walls in that void is sensible, which also sounds as if it probably is. Those two answers will we hope be the basis for what we now do below the floor, prior to replacing it.
    If a vapour barrier in the void is sensible, then I am thinking that a layer of spray-on vapour barrier over the honeycomb pier walls, including over the internal surface of the gaps in them if that can be done, could mean that the pier walls could remain gappy (no membrane over them), which would allow desirable ventilation through between the three voids. Yet the underfloor void space could by that means be reasonably protected against evaporation of moisture from those walls, which was being drawn up into them from the concrete pad below. Then the main question is whether a poly membrane is best over the horizontal surface of the concrete, and over the non-gappy, internal surfaces of the outside walls, or whether the same spray-on vapour barrier would be best there too.


    Posted By: djhSo my advice would be to put your floor boards back down and get your sitting room back for your pre-wedding party. Spend the time up to then learning more and planning but not doing anything to the house yet, oh and planning for your wedding! The alternative would be to hire a professional that you trust and follow their guidance as to what to do, but finding such a paragon might be difficult. The alternative would be to hire a professional that you trust and follow their guidance as to what to do, but finding such a paragon might be difficult.

    Unfortunately we have promised ourselves that we will have the floor down for the wedding, never to be lifted again, especially if we put a hardwood floor over the top as we may do (before the wedding). Our promise to ourselves is particularly as we have lived for more than three years without a sitting room already, so the idea of taking it up and being without it again is not really psychologically tenable. But I do appreciate the point. I liked the answer I understand Bill Butcher of the Green Building Store reputedly gave, when asked if there was anything he would do differently if building a passive house again. (Or was it an early major retrofit?) Anyway he apparently said “Yes, spend longer thinking about it”. So I do appreciate the point. But I had been hoping that the three-plus years of thinking and investigating would have got us, even as relative beginners, as far as we needed to be at this stage. That would hopefully be to know enough to ask sensible questions of this forum. And to get one or two answers which would enable us to get the underfloor void treated in the way we need to over the next month or two and the floor back down. As I say, we are envisaging that after the wedding, and certainly before getting as far as the EWI stage, if we go that far, we would get properly qualified advice from a professional paragon on the whole project. We imagine getting some PHPP package input and probably also some pure architectural input for the garage conversion aspect at that stage. Most of the wedding planning is ably in the hands of the bride and groom in fact, in the way of many modern weddings, and seems to be fairly well advanced (he says hopefully) having already been under way for six months or so and with six months to go.
    • CommentAuthorgravelld
    • CommentTimeJan 15th 2018 edited
     
    Posted By: PlHadfieldI am hoping that by plugging into the thermal mass of the ground below it will not in fact be a heat sink but a source of thermal mass, along the lines championed by FosterTom on this forum. It is also the approach taken by the hugely respected Building Science Corporation in the USA, and of their legendary Joe Lstiburek in particular, who says 'don't insulate the floor, insulate the perimeter, and bring the underfloor void into the conditioned space of the house.' That is the approach I have been favouring.
    I don't think perimeter insulation is the ivory-tower disruption-irrelevant money-no-object ideal solution, but it is a solution good enough to achieve Ph levels of performance, therefore it's good enough in my project. It seems like it should be default for retrofits where disruption is to be kept to a minimum.

    Posted By: PlHadfieldLikewise, very good to hear. I have spoken to one or two members of the Institute of Sustainable Development at De Montfort University in Leicester about the possibility of getting together a retrofit group for the east midlands, along the lines of the excellent Manchester-based Carbon Coop of which I am a member. The sticking point seems to be that there are few experienced AECB members, or retrofit designers, coordinators or contractors in the area, and none in Leicestershire as far as I can determine. Nottingham, nearer to you than to us, has one or two, but that is rather at the northern end of the East Midlands area. We need to crank up the 'Midlands Engine' (our equivalent of the 'Northern Powerhouse'), in this respect.
    Yes, plenty going on in Nottingham which is most definitely East Midlands, although to an extent it feels like it has lost momentum somewhat.

    I too have been mightily impressed with what Carbon Coop are doing - the grants they appear to be finding, excellent practical training (it looks like). Not decided to become a member due to the fact I'm not in Manchester!

    There are some Leicestershire practitioners on the design side, but not many. There's a Ph in Rutland, a self build by the architect. A high performance build in Pickwell, not Ph as far as I know. Not so much on the retrofit side.

    Posted By: PlHadfieldI wonder how feasible it would be to seal the cavity at the eaves however in advance of that, at the time of the EWI. In other words will it be feasible to seal the top of the cavity before, and separate from, the full roof treatment some years or decades later. Can we hope to make the top of the cavity wall airtight simply by stripping the eaves tiles and felt, and sealing whatever is nominally closing the cavity at that point (gappy slates I suspect, which could just have a parge coat too perhaps)?
    Is it filled? I think you can get most of the way there if so, but sealing the top is also important. See my eaves detail thread. http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15484&page=1 .

    Also https://thebox-haus.weebly.com/posts/the-zen-art-of-taping
    •  
      CommentAuthordjh
    • CommentTimeJan 15th 2018
     
    Posted By: PlHadfieldto get one or two answers which would enable us to get the underfloor void treated in the way we need to over the next month or two and the floor back down. As I say, we are envisaging that after the wedding, and certainly before getting as far as the EWI stage, if we go that far, we would get properly qualified advice from a professional paragon on the whole project. We imagine getting some PHPP package input and probably also some pure architectural input for the garage conversion aspect at that stage.

    I think that's backwards. You need the advice first. You're assuming that because it is feasible to make the external surface serve as an air barrier, that's going to be a sensible choice backed by the professional. I know of projects that tried to make their external surface serve as the air barrier and where they failed to meet their target. Feasibility is not the same as a recommendation. Until the whole plan is in place, you can't know.

    I don't know why you kept the floor up for three years to the point where you wish to see the back of the issue, but that is history - a sunk cost. If it was me, I would put the boards back down, perhaps put some cheap carpet over it for the immediate future (coir or suchlike if you're concerned about carbon) and think again after getting the advice and agreeing a broad plan.
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