gravelld

It can definitely be over-used. Cheaper foams don't deal well with movement. Look for the flexible ones, like Soudal Flexifoam. They allow some degree of compression and reshape. But think of it more of a gap filler for other measures than an air tightness provider, as such.

I meant that as a specific example - it might have affected the previous administration. The current one might be affected by unions, for example. Don't want to sound like a downer, just repeating what I've observed. I'd like to think you're right.

This is constantly done - review the select committees and various research committees investigations on the .gov.uk site. The issue is the annoying tendency of people ("stakeholders" i.e. including non humanoids like corporations etc) with different incentives and different goals also chipping in with quite different recommendations. Government, quite reasonably, cite the impact on economy and jobs as being as important, for example. Then, between a crusty self builder and a smart, well spoken, polished type flashing some credentials, who do you think gets called to give evidence and shape policy? For example, in a call-for-evidence on housing performance, we can all chip in with how we think all new homes should target Passivhaus levels of performance and give some good engineering and scientific evidence for our opinion, but all the Persimmon guy who employs thousands and donates to The Party needs to do is rub his fingers together. 🤌 It's the age-old story of lobbying.

Can you not get access to the eaves, to pour them in? 10:1 water:PVA was suggested here: http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13384

I don't know why there's such a fixation on the heating system for new build. If they were built properly it really wouldn't make much difference because the heat demand would be so low. It would be better to just fix the problem at source.

Do both, remove the bottom of the roof covering and and run the EWI over the top of the cavity to touch the loft insulation (assuming you have a cold roof). This also assumes enough overhang, but you can also kick out the bottom tiles to give you more space, and/or chamfer the top of the EWI. Remember you want that continuous insulation. Also consider plinth insulation. The only other thing you might consider is a different route to 'sticky and fixings' EWI and do something more like Larsen trussing, fixing an outer board and filling with loose fill instead. However this is much less done in the UK and will probably be consequently more expensive.

Sorry - what does this mean? 😕 Thanks for the advice - some wise words.

Given that the very nature of this forum is that of one for self builders of varying levels of experience, it might be best to describe why something is a "ludicrous idea". Not everyone understands all the steps and risks involved in what turns out to be a complex project.

Hmmm. Ok, that rings a bell. Looked at them many years ago.

Well... I don't know. But I do know that Nibe et al sell their exhaust air HPs as a combined solution. It might be the ventilation levels are not enough to satisy a tight build. Yeah, I assumed the ventilation must be continually provided whether or not the compressor is running. A bit like in a A2W HP the CH pump and the pump between the HP exchangers can keep running if the compressor is off... (AIUI)

I have my fabric first retrofit checklist and rooms in the roof makes for a low score! 😉 Best way of fixing those types of roof structures is to take the covering off, imo. Has to be done to make EWI continuous with loft insulation anyway (in a cold roof). Thanks!

Interesting idea. I want to make it as simple as possible. Although exhaust air heat pumps were originally about DHW I think they now also cover space heating. But am I trying to pump to much energy through the ducts when the "air cannae take it". I guess it's down to the heat loss eventually...

Really interesting thread. We're looking at a renovation project at the moment with a late 70s forced air heating system. First priority would be upgrading the building fabric (and likely removing a lot of asbestos). But after that, it would be interesting to use the existing ducting. If we achieve good levels of airtightness, would it be possible to use an exhaust air heat pump to also combine ventilation?

I've used a lot of Blowerproof - but it's not a decorating paint. As @Sparrowhawk says it's more like a liquid plastic/resin which cures semi-hard and is flexible to movement, unlike decorating paint. You can get it in white and it can be overpainted or plastered. It's ideal for narrower spaces and where taping might be difficult e.g. around pipe penetrations. It's a lot more forgiving to install.

I chanced across this place on Monday on a visit to London. It's interesting but is more aimed at the undergrad I think. The normal high minded thoughts and some parts have a focus on retrofit but nothing really practical, i.e. how we make it affordable to the 99%. There are a few exhibits from manufacturers. Probably the best thing about it is Store Street Espresso is just up the road.