lookseehear

Not that I can see. I think I'm just going to give up on trying to find medium density blocks for a sensible price that can deliver and go with the standard dense at £1.25 each.

I've applied for a cash account, but the prices I'm seeing online don't go lower than £2.08 inc VAT for dense blocks and not many options either in Radstock or Bristol. Pretty frustrating - it isn't like we're in the middle of nowhere!

I was looking for something like this recently, but struggled to find anything I could get locally for a good price. I'm paying £1.25 + VAT for dense blocks and any thermal aggregate seem to end up closer to £3/block!

In practise how low should mineral wool go within the cavity - right down to the base or would you stand it off the bottom of the cavity somehow?

Everything you say is correct other than the vapour won't condense because a cold roof space must be ventilated. Assuming this is a pitched roof the eaves of the roof typically have 50mm clear of any insulation to allow free air flow, and it's this ventilation which prevents moisture buildup. In terms of different types of membranes there are a lot! Typically you'll have a VCL on the warm side of the insulation which can also be an airtightness layer, but its primary purpose is to reduce moist air from living spaces moving into cold spaces. VCLs can permit a small amount of vapour through, but not enough to cause a build up of moisture in a properly ventilated loft. VCLs are not the same as breather membranes which are designed to allow vapour through but not liquid water, and are normally placed on the cold side of the insulation to allow any excess water vapour within insulation to pass through.

I hadn't heard of gypframe and just looked it up. What do you do if you need a strong wall fixing? The appeal of timber battens is that you can at least screw into it if you need to.

It's hard to tell but the most important thing with the loft insulation is to make sure you retain ventilation at the eaves - it looks suspiciously like the loft roll is pushed up against the underside of the roof.

Ideally you would have your insulation layer with a membrane, then more battens to create a void where you can run services (pipes, wires) to avoid having them puncture your vapour control membrane, then plasterboard over the top (or dense WF and lime plaster).

Welcome! You'll find lots of people doing similar things to you on here - I'm one of them. Definitely have a read through this thread when you get a minute. I, too, am confused by the membrane on the cold side - I think the idea is that because wood fibre insulation is very hygroscopic (will absorb moisture), it will act like a bit of a sponge making your walls stay relatively dry but your insulation becomes wet. This goes against the idea that wood fibre should be able to buffer moisture in the walls, and will inevitably create air gaps between the membrane and the wall. Seems unnecessary to me! "Knowing nothing of your building I'd guess that 100mm maximum" - I'm fairly sure this is referencing how much insulation you can use. If you are insulating internally you are limited on how much you can use, because the more insulation you put in, the warmer your house but the colder the stone walls become which increases risks of condensation within the structure. I think that what Redbeard was saying is that 100mm of insulation might be on the edge of being too much internally for a solid walled property. If you are familiar with U values, it would seem sensible to aim for something in the region of 0.4-0.5 rather than trying to get to modern standards (below 0.2) with internal wall insulation. "What about the window reveals?" - I'm probably going to use something like a thin layer of wood fibre or mineral wool to take up the unevenness of the stonework, then a thin layer of modern PIR insulation on top, all fully taped to the windows and any airtightness/vapour control membranes but this is open to critique. Low thickness is important here to avoid impacting window size. "Don't forget to ensure the wall ins touches the roof ins too." - this means that your wall insulation should be continuous with roof insulation to avoid any cold gaps or bridges. It looks like you're wanting to retain the cornice detail from your photos so not exactly sure what you'll do here but probably just careful attention to detail around the edges to avoid gaps.

Does anyone know what the norm is if you aren't able to order all your windows up front because you don't have finalised measurements? My builder is getting on to me about ordering windows for the extension which is fair enough, but we will also be replacing the windows for the rest of the house over the coming year (somewhere in the region of 25 windows overall) and some of the openings are going to be extended in width and or height from existing. This makes ordering all of them at once a challenge, but I don't want to buy a few then be over a barrel when it comes to ordering the next tranche because we want them to match the existing so can't shop around. One option is to buy the windows for the extension and accept that these may be different to the rest of the house, then try to get ourselves in a position in the spring to bulk order windows for the rest of the house as a whole, but ideally we'd agree some kind of price based on an estimate up front then tweak as necessary, or do suppliers ever offer a price per m2 or similar? Second question is about fitting. I assume for best results the glazing supplier will need to also do the fitting, or can I get my builder to do this? We're looking at triple glazed alu clad timber ideally.

Are these common? Do I just ask the window manufacturer for them? Not sure I follow how this works - lets say I get in the shower with the door closed (as you do) therefore the fan in the 'wet' room ramps up to maximum, but the 'dry' rooms are still dry meaning trickle vents will be closed. Where is the air coming from in this instance? Our kitchen/diner/living space is quite large (65m2) - would you put two in? I'm pretty sold on this I think. It does seem a shame though when you have lovely warm air after a shower only to dump it all outside!

It took me a minute to see what you're getting at - I guess I didn't quite realise how low the air flow rates of MVHR systems are, but at 20-30m3/hr to a typical living space there's not really much 'redistribution' of heat going on other than keeping it within the overall thermal envelope. I probably need to take a serious look at the cost and disruption of ducted MVHR vs decentralised systems with heat recovery because I had assumed one of the benefits of a centralised system is that you are putting warmer air back into living spaces.

I often see distemper mentioned in the breathable paints discusssions.

I read through this earlier in horror - so pleased you got it sorted. I can't imagine what the last couple of days have been like!

I agree, but if you take an example where you have 21 degree warm air (could be warmer than this when extracted close to the ridge of the vaulted ceiling) and 8 degree fresh air incoming, with 80% efficiency then you could reasonably expect the air being pushed to living spaces being above above 18 degrees (18.4 degrees would be 80% efficiency assuming it's linear). Bear in mind that we currently tend to have bedrooms at 17 degrees around the clock currently. I'm not expecting it to 'heat' the rooms but to reduce the number of days we use the oil boiler by making those rooms more comfortable during the milder months in spring and autumn.