Sparrowhawk

Which do you have? I am sorely tempted, moreso than by a pizza oven. I used to hot smoke fish and chicken in an adapted wok but haven't done any for years.

"Just make one model that follows the green line, not 3 models where I have to work out which to use when and on which settings, and guess which will be more token efficient..."

Wish you could transfer any you don't use to me! I'm doing open source work on a large 20+ year old C codebase, and designing something that will improve CPU and memory efficiency. Fable is significantly better at planning that than Opus, which leaves holes that I can spot at a glance. Fable still leaves holes, and I have to review it with GPT and have back and forth to find and fix them all, but it's a clear improvement. I've got access to GPT-5.6 Sol this morning and that may be doing a better job planning on this codebase than Fable is. I've also got a lot more OpenAI tokens to burn than Anthropic, and I have to ration my Fable usage. More new toys... There's software that will do that and estimate the tokens per conversation (can't remember the name of the programs). That hasn't been of interest to me, so on macOS I use https://github.com/steipete/CodexBar to keep an eye on how my usage is going.

I'm finding Sonnet 5 works out more expensive than Opus due to the number of tokens it's using (for coding). Not impressed with it TBH. Now Fable, that really is something else!

@hauntedicecreamvan Which door did you go with? I'm currently looking for a fully glazed door.

Do these help? https://usceiling.com/wp-content/uploads/2018/11/AeroBarrier-X1-Sealant-Datasheet-and-SDS.pdf https://www.arcat.com/datasheets/aeroseal/AeroBarrier_X1_Sealant_Datasheet_and_SDS.pdf

I'm assuming only bottom horizontal surfaces because it's not sticking to vertical surfaces, so it's not sticking but settling out onto the floor. It sounds great but I wouldn't want to risk it in a furnished house!

Do you have more than one HeatGeek installer in your area? They come with a premium, but there was a 50% difference between the two quotes I got. Some are just taking the mick with their prices (and if people will pay, who can blame them).

Consider going to a HeatGeek accredited installer, because they know their stuff and will install outside MCS or may be able to get a reasonable system design through MCS. And a HeatGeek installer will appreciate that you've already done a basic heat loss calculation to size up the previous system design!

Nice, I had an 1898 house for 7 years which had the original plaster mouldings and they added real character to the place. You've answered your question Rads it is!

Welcome @woodstream! Parts of my house are built into the roof like this. The 45 degree bits have badly fitted PIR insulation where the cold air goes both sides of it(!); we've decided the payoff from tearing down the ceilings to redo it isn't worth it, so I've focused on the vertical walls. If you need to crawl in the tight space, treat yourself to the recycled plastic bottle insulation, it's a lot more pleasant to work with. I put 100mm of this in the 1m high vertical wall on one side of our bathroom, and that alone raised the temperature by 2C in winter, so it's worth doing. Where you can get to the 45 degree rafters, pop mineral wool batts between them (remember it needs supporting, with netting, plasterboard, whatever - it will sag without) leaving a 50mm gap for ventilation. It can be easier to put wooden battens along the joist to enforce this gap. And then make it as airtight as possible, because draughts going round your insulation will undo much of the indoor comfort that your insulation brings. If you're up for it, put an air and moisture tight membrane on; otherwise plasterboard and seal all cracks carefully.

My experience is you won't get a standard installer to do anything else and will have to either do it yourself or let them do the install and then do whatever you can for airtightness on the internal side.

Welcome @jc212. I've spent years since moving into this house (rubbish buildered and rubbish shelf-buildered) tracking down air leaks and fixing them, usually by taking the floor above up and doing it from there. You've a fun but ultimately satisfying journey ahead of you. Do you have buy-in to take the ceiling down, or take down at least for 50cm around the edge of the room? If you don't (and I can never get buy-in for this from SWMBO) then we need to think of a different approach. @Big Jimbo has posted good instructions above, though I find I have tiny air leaks around or through expanding foam when I use it to stick or seal PIR in place and which defeats the object. What I would add is get yourself a tub of Soudal Soudatight. Or Passive Purple, or Blowerproof, or any other brand. These are thick airtightness paints and really help to seal the leaks. Back to it, I would expect there's 1-3mm gaps around your joists if they sit into the wall, and air is coming in here. Pack these with something, mortar, caulk etc, and when dry paint with the airtightness paint. Then carry on with Jimbo's instructions re sticking PIR in place, or fill the whole ceiling between the rafters with insulation. Some of us have built our own blower doors to depressurise rooms in the house and make it easier to find leaks. Another approach is on a windy day when the wind is hitting your extension, to open a window on the opposite side of the house. This naturally creates a path for air to flow and you'll find the places that leak are quite noticeable.

Thanks @marshian for the mention and welcome @Rocket Ron. Edwardian, nice - does it have original fireplaces and plasterwork inside? A friend installed UFH downstairs in his open plan 1950s house, with 50mm PIR between the joists (fitted by a builder so not airtight), and then the tray system you describe on top. The slightly warm floor feels wonderful underfoot, as is the lack of radiators, but it's not been as economical to run as he expected. Here in my 1920s house I've kept with radiators as the joists themselves are close together and going to provide cold bridges through the floor. My flow temperatures are considerably higher than @marshian - about 45C when it's 1-5 degree outside last week. Doing a heat loss calculation, I wouldn't call the process easy, but I may have been too anal with getting the construction details right (there are contradictory U-values for most building materials). It was worth doing though. If I had a more standard house I'd try HeatGeek's tool to do one first. Where it pays off is working out if an improvement is going to be worth doing or not. In many cases, it showed that adding extra insulation wasn't worth the cost or disruption. But it gave me numbers for how much heat was lost via draughts, and stopping those has made the biggest increase in comfort inside the house. So my point is that the choice between underfloor heating or radiators probably won't matter in the long run, compared with nailing airtightness. But I'd do UFH because it's going to look better, and the extra heating cost would be worth it for me.

Good thread, here's the ones I can remember using. I've had a number of different sealants because I've usually needed them at short notice and had to grab one from a local shop. Keep in mind I'm using on renovations not new build, so I'm working on poor substrates. Foams Illbruck FM330 expanding foam - good, but when filling gaps with sharp corners (broken bricks etc) doesn't expand into the corner to make it fully airtight, even with lots of wetting of the surfaces. Keep getting air leaks through or around a line of this foam in the 10mm gap between masonry and PIR. Soudafoam Gun Win. & Door SWS - less dense and flexible foam, but a bit better gap filling. Blue in colour and the blue stains (got some on the floor the second time I used it, oops) Soudal Gap Filling Foam Hand-Held 750ml - used these twice, stick nozzle in hole and empty can. Does what it says on the tin. Bonus item: bottle of acetone. Wipe nozzle of foam gun with acetone after use, stops build-up of set foam. Sealants and adhesives Geocel Contractors Decorators Caulk - smooths like a dream, cracks like an arse. Avoid. CT1 - strong adhesion, difficult to tool smooth, with water + washing up liquid or spittle. I saw a tip on here to use it first then pop white silicone over the top to keep it white - it's also easier to tool down doing it that way. Not hugely flexible once set - I wouldn't use around windows, doors etc. Everbuild Everflex 335 Premium Construction Silicone Sealant (Clear) - smooths easily, sealed the car roof well and has stayed stuck down for 12m+ Everbuild Everflex 450+ Builders Silicone - it stays white and flexible. Didn't smooth down particularly well, and the entire tube went off. I won't be getting it again. Everbuild Everflex AC50 Contract Acoustic Sealant and Adhesive - bought for a through-ceiling acoustic sealant. Would get Everbuild AC95 Acoustic Sealant next time as AC95 contains safer chemicals. Soudal Fix All High Tack - bought to stick on skirting board and it does that brilliantly. It also smooths well as caulking - but it's an absolute BEAST as it's so thick to squeeze out a fine bead. Still looking for a favourite caulk. Bonus item: No Nonsense Multi Nozzle Pack - when the nozzle goes solid the tube is generally still liquid. Bang on a new nozzle and give your tube a second (or third, or fourth) life. Bonus shout-out to Silicone grease which when popped in the cap has kept some nozzles from setting. Airtightness paints Soudatight LQ - brilliant stuff and sticks well even in dusty corners. Buy cheap brushes and chuck after use.