YodhrinForge

I'm hoping that my planned collection system and DIY filter box will mean airborne particulates will be minimal enough that I'll get a decent lifespan out of the ventilation filters, but yeah every time I look around a corner on this project there's another bugger sucking his teeth, tutting, and holding out his hand for more money

Thanks for the link and to everyone for responding. Dearie me though, 380 bob is three times the price of the induction hob that'll be going underneath it lol. Still it seems like a poor place to try skimping to save money so I'll have to suck it up I suppose. A bit more of a headscratcher than it seems as I'm intending to run an occasionally somewhat business-esque woodworking shop inside, meaning A; I need to think about managing sound so I don't end up with neighbours on the warpath, and B; I need to consider the pattern of air movement inside the space to maximise the efficiency of airborne particulate filtration. I think I'll probably need to bite the bullet and get a small ducted unit.

As I go down the list of Stuff I Need To Know, I keep running into little niggles like this where the info I can find through searching is unsatisfying. I'm aiming for an EnerPHit-ish retrofit of an old stone cottage, obviously that will include MVHR and equally obviously that means Extract Hood Bad...at least from a temperature/air balance perspective. The alternatives seem to be either picking an MVHR unit with an extra port for a cooker hood and some kind of boosting compensation mode for when it's running, but I'm toiling to find a reasonably priced one that also has the other features I'd like - and honestly I'm not all that comfortable directing even pre-filtered greasy air into my whole house ventilation system - or a recirculating hood which has implications for air quality. I've seen several compact MVHR units when researching options for ventilating my garage workshop, but am I right in assuming nobody has thought to combine something like that with a cooker hood to provide a self-contained extracting-heat-recovery-cooker-hood-thingumy? Or are my hesitations about the usual methods unjustified and I should just go with the typical wisdom?

I hadn't considered the alkalinity factor Mike that's really interesting thanks. I had wanted the clay due to it being really effective at transporting moisture as a defence against possible short periods of penetrating damp(the cottage is in the central belt of Scotland with exposed stonework on the south and west, the west also being the gable, and it's a conservation area so there's no prospect of changing that with a render system - I had considered applying a masonry creme once I've had the wall checked for cement-based repairs or mortars to be raked out and replaced with lime if found, as I had heard that more modern iterations are actually as vapour open as they claim, but I've found it difficult to find definitive information on that as there are so many complaints and warnings about the old style ones) to help draw any moisture through into the wood fiber where the internal warmth can get it back to vapour quicker, but I think I do remember seeing a hybrid product that had both lime and clay so I'll look further into that. My internal finishes were all going to be pigmented clay plaster topcoats like the ones Russel mentioned or clay based paints so that at least shouldn't prove an issue. There will be a void at ceiling level as I was already planning to lower the ceiling ~30cm to run MVHR ducting and make plumbing up the new bathroom easier, but it shouldn't be an issue regardless as there's an existing attic conversion so once I settle on an appropriate method the insulation will continue up into the roof space with only the joists/rafters to impede it. I had planned to carry the vapour retarding membrane the roof probably will require down onto the walls just below the rafter level, tape them off there, and then use adhesive-backed coir or hemp strips over that so they'll take plaster which should link the roof and wall airtight layers. I'll have a read at your thread cheers. Another issue I'm encountering is how to deal with the interface at the rear of the house since it had a block cavity-walled extension added at the same time as the roof conversion some time pre-2000 and I also intend to replace an existing small pointless conservatory(it's north facing and only has two actual "walls", leaning against the existing stonework on one side and the block extension on the other) with a utility room extension which will be timber frame(specifically engineered timber I-beams because I can build the whole thing myself and save a bunch of money), so any suggestions there would be helpful.

As well as my roofing questions which the forum has been very helpful with, I'm considering how to approach the insulation of the internal walls of my late 1800's semi-detached stone walled cottage. My initial instinct was to go for a solid mass buildup using clay plaster to level the wall and also to bond wood fibre boards to it, then a reinforcing layer of the same clay plaster with mesh, and a final topcoat of a finer grade of clay plaster. This leaves the wall completely vapour open and relies on the combination of MVHR and the properties of the clay & wood fiber boards to manage humidity and condensation(any windows will be triple glazed insulated-aluclad timber, but tbh there aren't that many windows so most of the walls will be taking insulation). However I've recently been put on to "more modern" techniques by a builder pal, exemplified by BackToEarth's "NatureWall" system that has a much more layered buildup of bonded wood fiber as previous but instead of a reinforcing coat they specify a vapour open airtightness membrane with taped seams, then a battened service cavity with the floppy wood fiber to infil, then what seems to be a clayboard type product as your internal surface to then skimcoat. The notion of running services in a cavity rather than having to chase out paths in the insulation is appealing, but honestly I'm not completely sold on all these membranes and tapes that get pushed these days - am I just being a snobby Luddite or is there something to the modern approach?

Oh nice one thanks man, that does look interesting, I'll give it a watch over lunch.

Aye but as I said in the OP, I can't alter the dimensions of the existing roofing as it's a conservation area, and it would be awkward anyway given the property's shape. I'll just have to stay with room-in-roof and try to boost the thickness internally without losing too much space or introducing moisture issues. Something to chat to the architect about anyway. Thanks folks.

Obviously the rafter section is different since the space has already been converted, but that's how traditional roofs are done up here; basically no eaves, slate over felt nailed through directly to the sarking. But it seems Russel has answered my question definitively - if they can't take a nail securely they're not an adequate substitute for the boards in this case. A shame but it is what it is, I'll just have to shrink the internal space a little to fit adequate insulation and put vents in

Ahoy. So, I'm about(*touch wood*, the offer's accepted but you never know) to be moving into a late 1800's stone built semi-detached cottage with a traditional Scottish slate roof, ie, slates nailed through felt directly to sarking boards in turn nailed to the rafters, no battens/counter-battens. I'm planning to retrofit the property to radically increase its efficiency and comfort, but that obviously has to be done sensitively to avoid future issues. There's an existing velux conversion of the roof space that appears to have been done inside-out without disturbing the existing roof excessively, but it was done pre-2000 and the insulation appears pretty minimal. I'd like to increase the insulation & thermal mass, but ideally without having to pay for big honking dormers on the rear elevation or stealing too much of the internal space. Given the roof needs a good once over and potentially a complete strip-and-reslate anyway, modern insulating wood-fibre sarking panels such as from Steico are appealing since they would allow the creation of a full warm roof rather than the present room-in-roof construction, but as I've never done this sort of thing before I'm wondering whether that kind of panel is suitable for nailing into? Every example of its use I can find online is in a battened/counter-battened construction. The current exterior dimensions of the roof cannot be significantly altered, both because the house is in a conservation area and because of the somewhat unusual construction(rather than a typical abutting-rectangles approach, it's more like two interlocking L-shapes with one cottage biased to the front and the other the rear - this includes the roof space). Any advice or experience would be welcome.

Market economics is why we are where we are, but okay let's get government out of things. Including rigging the prices to subsidise gas, grid connection charges based on the time when coal fired stations were the only source of electricity, and gas disconnect charges that are more than strictly the cost of labour & materials required to do the work. If we were paying what electricity actually costs to generate and distribute up here in Scotland, you could run an ASHP for the leakiest old Victorian tenement flat and it would still be slightly cheaper than a gas-fired system, but instead with prices pegged to gas and connector fees passed on to customers you need a near-passive level of eco retrofit and a very well designed heat pump system competently installed to hit break even and a home battery with solar to start getting ahead. If you just take away subsidies and incentives without also fundamentally changing how the energy market works in the UK it won't take several years, it'll take several decades.