tanneja

These have been out of stock for a while with BPC but seem to be back. Did you have to do anything special when fitting your 125mm pipe to ensure a good fit / no air leakage? Airtight tape around the junction?

I have obviously read a fair few posts on MVHR dos and don'ts on this forum, one of the critical pieces of advice being the 3m separation of inlet and outlet vent. I was surprised when going into the Paul Heat Recovery online shop for external grills, that their range comprises mainly of combination external vents as seen here: https://www.paulheatrecovery.co.uk/product-category/mvhr-ducting/terminals-external/ It is really surprising to me that these would be the online choice offered on their site. I appreciate vents can be obtained from any number of places online, but it has be rethinking, as one of these vent types would make my installation far simpler. I plan to call them tomorrow to discus what negatives there are to situating the vents in this way, but presumably it is a bad idea? Perhaps these are a product for where an end user simply has no choice but the penetrations to be in the same location, and there is an accepted level of airflow contamination based on the wind etc.

@TonyT my apologies, plasterboard at the end, so commit to the boxes ahead of that being offered up

Thanks Tony, would that mean PB at the end after having done that presumably? And is the ideal tape Tescon Vana?

What does anyone think of the instaaboxes? I am concerned by their depth eating significantly into our insulation depth on the external walls. https://www.phstore.co.uk/instaabox. Is there a better way?

That would work given my laymans understanding. My most problematic area is a cold flat roof ground floor extension. Had to be a cold roof to various reasons. Seems now the search is on for a slim profile, square housed, matt black, dimmable LED spot which needs minimal or no cavity behind it, is likely to be around in the long term for replacements, and doesn't cost a fortune. @Onoff is there anyone on the board who you follow or know of who has admirable aesthetic standards and found LEDs they were pleased with? Working my way through a labyrinth of lighting forum posts over the last 24 hours, and I am a slow reader

@TonyT that cable duct deal looks somewhat retrofittable to me, I offer my sincerest thanks for the assistance. @Onoff I have admired your room AVCL pics for a while now from other threads, you aren't my builder's favourite person. I can allow some room height loss with slim height LEDs, I just seem to read a lot on this site in the lighting section that GU10 is the way to go for best light effect and to ensure you can get bulbs in the future. Are the slim LEDs up to the task? I was following @MJNewton in his quest for best lighting and he ended up with GU10 LEDS. Would anyone have any recommendations for slim downlights that I won't regret? Can I avoid much if any cavity if I go for the slim LED spots and perhaps have a fire mat above (as seen on another thread)? I will at least need an Onoff style fit for the two deep speakers I have in the flat roof section. I won't have access from above as the roof membrane is already done.

@ToughButterCup is this still the advice you would give? We are likely to have FTTP delivered via pole top in the next 6 months, but that will be after our EWI firm has done their magic. I was searching threads here to see what wire they would use to embed behind the EWI, but take it you would suggest the pipe?

Hijacking my own thread, I also need to have a precise plan for the socket and switch back boxes in the timber extension, and the spot down lighters under the flat roof. It feels like the sockets for other internal studs and the solid externally rendered (and internally parged) brick external walls shouldn't be too tricky to overcome. For the external timber elements, as normal will have an AVCL layer just behind the plasterboard. My builder is accommodating of my views but sceptical as to airtightness measures. He says he would usually have the wires pulled to the general area, and just puncture the AVCL to get them through (the wiring has already been pulled, will be behind a final slim layer of PIR and the AVCL), not usually making a seal to the AVCL around the wires. He then offers up the plaster board with a small cut out for the rough socket / light exit. Then when done for all boards, get the lasers out and nicely micro manage the positions of the sockets and lights, then making the PB entry holes bigger to offer in the back box or light fittings (presumably causing more trauma to the already compromised AVCL), and wire up. This approach means I feel I would struggle for a retrospective airtightness, perhaps hoping for an inner backbox putty to attempt my airtightness, but the AVC wouldn't be bonded to the backbox housing in anyway, so would be PB achieved airtightness. Are the expensive and seemingly generous sized Instabox (https://www.phstore.co.uk/instaabox) and Optime (https://www.phstore.co.uk/optime-downlight-housing) housings the go to option for maintaining your airtightness recesses and so allow the builder to do their usual? Presumably the seemingly generous size of these units mean the builder can install these in the approx. position prior to the PB, then micromanage the penetration a bit as he planned with the laser, as long as he falls inside the generous boxes. Seems like an expensive but logical plan. Or, can you be a bit more cavalier and bunch up the AVCL in the penetration areas to provide slack for it to protrude back into a PIR cutout cavity? Then you would just need to grommet or tape the cable penetration through the AVCL. That might not be simple to achieve, but the cost of the back housings for lights and sockets is quickly adding up (probably 10 sockets, and 10 downlights), unsure what is the best way on balance.

We have been working our way around the house addressing airtightness, and feel we are doing our best, where this is now a best efforts approach since we are already half way through first fix when really appreciating the detail involved. We have already pulled data, alarm and audio cables through from the garage, via an uninsulated vented porch loft, to the main house. So we have a single bore hold that carries 20-30 cables. I can see on the internet airtightness products for cable pulls, but they are all intended to be in place before you pull a cable, where you then pierce the membrane as you pull each cable through. What if any chance do I have of making a suitably airtight fix for this? In addition, we have hot water pipes (plastic) making the same route via a parallel bore. These will likely expand and contract with hot water, so to simply silicone around the entry to the wall feels risky. Help!

Going around the house feeling for leaks is presumably a labour of love. Did you use additional devices to quantify the ACH and Pa when performing this exercise? Also super appreciate the external approach information. Fortunately where our joists go into wall plates, I think an internal parge ove rthe walls, with blowerproof around the edges of that wall plate should be really effective. If the joists were into the wall then that would presumably be much more work with ensuring airtightness around the joists.

This is really appreciated @Iceverge. Can I ask a nonsense question? Our house is part old construction (solid 215mm brick, with decent condition sand cement external render) and part new (300mm double medium density block skins with insulated cavity). The old build is to be covered with EWI (100mm EPS) and then both think coat render silicone silicate over top. Question is can the parge coat be applied externally for the old build under the EWI? Seems like it would still be behind the insulation. Presumably for the new build it needs to be on the inside to be on the inside of the insulation. Just wondering if, weather permitting, an external coat prior to EWI would be simpler to manage the joist joints. Maybe it wouldn't stand up to even a short duration in the elements.

Yes it is a best effort at this stage. I am minimal hands on due to injuries and lack of time with the kids and full WFH. That said the builder rates are very good for the quality I get due to them being family friends.

I'm trying to find the sweet spot between what will give us a reasonable attempt at airtightness, and simultaneously my builder can do without too much expense or heart ache on his side, when he would prefer to be getting on with the house in the way he knows best. -Plan to parge the external masonry walls (from the inside). -We have a poured ground floor and will take the parge down to ground, maybe needing a bit of foam or blowerproof in the corners, hoping for a simple and good result from that. -Then to sandwich an AVCL between the 1st floor double boarded ceiling plasterboard (as one layer of PB already done), where AVCL is lipped around the top room edges / corners, bonded in to seal those edge areas. An awkward area is the ground floor ceiling joist hangers which are hung onto timbers that are attached laid against the wall. A fair bit of first fix cabling and plumping is in the joist cavity areas, so unsure how well he would be able to trowl the parge up into the joist returns, and obviously cant get behind the main timber against the wall which the hangers are nailed to. It feels like the best attempt would be to trowl up in-between the joists where they are clean (no 1st fix elements) and instead using foam or blowerproof paint for the busy ones. I have one pot of blowerproof coming as a test. Am guessing where they can return the parge between joists, that a seal will be needed to manage the interaction between the page and wood. Then where that parge and block work is chased out for back boxes and cable runs, I guess blowerproof or re-parge over those cavities, including top and bottom of any conduit with silicone. Need to think about the two internal stud walls already in place on the first floor, I can't see how I can AVCL over the top of those, and so how to cut them off from the cold loft. I will change strategy for the future walls. It is a very busy crawlspace loft with diagonal timbers everywhere, but at least the rock wool isn't down, so potential to perhaps paint or sealant from above with the insulation put on afterwards. I could instead take off some plasterboard (not skimmed yet, so just unscrew) from the studs and tape or seal the stud to plasterboard joins from the inside. To confirm, what is the preference of persons here for airtightness of back boxes in studs or timber frame where the depth of the box is likely to require you punching through your VCL? We have already purchased regular metal back boxes for switches and sockets. Happy to adjust plan if there are obvious flaws that anyone can spot.

@Levo do you mind me asking what unit / features you settled on?

@Iceverge what was your strategy with the back boxes? Im torn between putty pads or airtight paint. I dont want to materially reduce the available internal depth of my backboxes as plan for zwave modules to permit automations. Not bought a putty pad yet to see how bulky it is.

Maybe fit a net a few inches above the roof surface somehow, to stop them from landing https://birdbarrier.com/stealthnet-bird-netting.html

You hear polar views on the effectiveness of fake birds of prey / cats, but willing to try something. Scaffolding comes down in a few weeks so simplest to get something up there (1st floor roof) now. Perhaps a second layer of rubber over the main open part of the flat roof would be some insurance in case of a pecked hole, we have some left over. AstroTurf is interesting, wondering if it might negatively impact rain drainage. At the very least it is disturbing when it happens while my partner sleeps after a night shift, so a deterrent would be good. Could affix reflective tape to the chimney too, although if that is effective, I would imagine it would need somewhat frequent replacing as it gets weathered.

What is the most effective and cost effective 5mm process to the external blockwork to attempt an airtight later out of a parge coat (or parge plus), vs a layer of bonding (the stuff is super sticky, surely it is air tight). I think the builder would rather dot and dab over either approach.

Thanks for the advice. I think for the plastered room we will double board the ceiling with an AVCL between the boards, then remove the top 4 inches of plaster board from the walls, have this AVCL lip into that cavity, attach slim batons over the AVCL in that cavity to hold in place and give something for wet plaster / bonding to hold on to, filling in that top 4 inches with this wet plaster / bonding. I didn't recall but at my request the builder internally rendered the brick walls prior to dot a dab at my request in the hope of some sound performance, so hopefully with this ceiling approach the leakage from the room could be ok.

Our builder has just finished installing rubber flat roof sections. Before now we had a more complex roof structure without any flat roof. Some mornings, and right now, we have a handful of crows going nuts up there, either fighting or mashing up their food. Very concerned about the rubber if they continue to use the handy area for their hangout. Can anything be done to deter them (scare crows / other devices / natural deterrent), or protect roof in some way?

I've found myself looking at https://www.ecomerchant.co.uk/pro-clima-contega-solido-sl.html tape for our already plastered upstairs rooms which I would like to have some airtightness. Rooms are already boarded directed onto the ceiling joists so no chance to fit a membrane there. I can double board with a sheet membrane on the ceiling, but don't have the space to double board the walls, so would likely need a tape for all other PB joins in the room / the room corners. I guess we will have a plasterboard based airtightness. Is this tape any good? Likely to need 2-3 rolls per room at around £40 a go.

I have provisioned for a 1m wide x 1m deep x 2m tall cupboard as a airing cupboard for damp clothes that cant be tumbled. We have the opportunity to put some forms of heating in there to assist with gentle drying. Thinking of a T off from the central heating to a tiny radiator on the floor in there. Could I get a conventional very small rad in there but lay it on it's side? An alternative would be to snake some pipe hoping that has output, and have it on a TRV of some kind to call fro heat when open. I would want to stay away from electric heater due to the moisture. There will be airflow through the curboard to recycle the air.

@MikeGrahamT21 did you go ahead with the wood clad ceiling in the end? If yes, what approach did you take (sourcing pressure treated wood vs a fire rated coating, and then boarding option too)?

When one looks at the PHI database, when it has columns for airflow range, why is the upper bound (the "To" column) seemingly stated a s a flow number far below the max airflow in the unit literatures? Is it the PHI test max airflow attempted, and for some reason that is never max unit airflow? While I am not PH project, I want to discount having to apply relevance to these PHI test flow numbers to help size my system.