jayc89

Yeah, exactly. Some is behind and some is in front of the metal frame. Presumably the one behind is on the external wall, so acting as a breather membrane (i.e. not allowing wind to directly reach the insulation), and I'd assume the one in front is an AVCL (Airtight Vapour Control Layer) but I'm not sure why that would only be needed on internal walls.

What's the deal with the membrane detail? It looks like some is behind the MF and some is on top of it? I realise all my questions might come across like the Spanish Inquisition. I'm generally interested as Internal Wall Insulation is next on my list of jobs to tackle.

https://www.thermafleece.com/product/thermafleece-natrahemp It doesn't look a million miles off. Is the insulation using the metal framing to hold it up, or are there additional fixings too? Would love to know how they got your cornice down in one piece!

Is that Thermafleece NatraHemp or similar?

We're in a similar position (minus the smells). What's the current building fabric like? Trickle vents? Letter boxes? Wet plaster/dot&dab PB? Unless the house is already reasonably airtight, it's likely the smells will make their way in one way or another.

So for a 126m3/h house it's best to look for a unit that can support 420m3/h? Which means it runs ~ 30% capacity on trickle?

A financial advisor recently recommended that we only consider fixed and tracker mortgages. Fixed are fixed, so you know what you pay each month and trackers are a fixed percentage above the base rate, so is transparent whereas variable/discounted deals are at the entire discretion of the lender. They can pick and choose when and by how much they change their interest rates by.

Is this true even if you don't plan to feed back to the grid?

Yes, that was the PIR debate I was referencing. Everything but PIR would be breathable, fitting PIR essentially nullifies the permeability of the other materials. I'm willing to take that risk, but should the worst happens (i.e. damp became a problem), I'd need to strip back to remove the PIR.

I live in a solid brick wall house. The ground floor has been insulated; 100mm PIR with 25mm PIR up stands. Two of the external walls are 220mm thick, the other two are 330mm thick. The two thicker walls are always, approx 15% warmer than the thinner walls. The majority of the walls are pointed in lime, where they've been pointed in cement over the years, I'm slowly repointing with lime again. Internally, there's lime plaster throughout. There's approx 200mm rock wool in the loft, but it's looking pretty sorry for itself. I suspect historic roof leaks have had their lasting impact on it. Generally, the ground floor holds heat pretty well, but upstairs leaks like a sieve. My ultimate goal is to have an airtight and reasonably well insulated house. With emphasis on "reasonably", I'm not going for PassivHaus/EnerPhit standards. In an ideal world, I'd strip everything back to brick, including the removal of the first floor joists, which are pocketed into the walls, and start again. However, the reality is we need to live in the house now, so I need to tackle rooms one by one, or at most a couple of rooms at a time. My current thinking is; - Use Passive Purple External (brush) to seal the floor void inc. around the existing joists pockets in the walls, and a 100mm strip above/below the joists. (Passive Purple External vs Internal as it's breathable) - Breather membrane from top joists to bottom joists (or floor slab), overlapping the Passive Purple and taped appropriately. (This should mean any air leakage shouldn't reach the insulation.) - Batten over the breather membrane with 50mm timber on the 220mm walls and 25mm timber on the 330mm walls, using concrete screws, straight through to the brick work, penetrating the breather membrane, sealed with appropriate acrylic sealant. - Infill with 50/25mm PIR - Cross batten with 25mm timber (to prevent cold bridges) - Infill with 25mm PIR - Staple and tape AVCL over the cross-battens - Further 25mm cross-battens as service void - Run electrics, 35mm back boxes. - (First first floor) continue AVCL across bottom of roof joists, tapped to 100mm strip of Passive Purple applied to perimeter of each room (ultimately hidden behind the coving) - Plasterboard (walls and ceiling) and skim - 300mm blown cellulose loft insulation - Further loose cellulose within floor void extending 500mm from perimeter. (Main objective here is to keep the insulation surrounding the joist ends breathable) I'll install MVHR at the same time. This will be located in the cold-loft space, so insulated ducting from the unit to the manifold, which will be buried in the 300mm cellulose insulation. A couple of deeper service voids will allow me to route the ducting from the loft to the ground floor. I appreciate the use of PIR in a solid wall building is somewhat controversial, It's a risk I'm willing to take and should the worst happen, I could remove the PIR without having to rip out the battens and breather membrane, meaning we it should still be relatively air tight. Baring the PIR debate, I'd appreciate all and any feedback on my plan of attack. Be brutally honest.

£30 is the cheapest I've been quoted for the L-angled lintels.

£5k but still non-structural. The company want an engineer's report prior to quoting anything structural. Structural won't work for us anyway as we're wanting splayed heads, where the bottom is the same width as the window, however the companies I've spoke with have said even splayed heads need a 150mm bearing at either side, which would just look odd. So we're looking at lintels + dry cast, I think.

That's ludicrously cheap. They're at least double, from what I can see, here. And not much more than an L-angled Catnic.

Builder is recommended a Solid Wall Lintel to the external face and then an L-angle lintel to the internal face. Whereas Catnic are recommending a Solid Wall Lintel to the external face and a box lintel to the internal face. The difference is the loading figures to the internal face; L-angle supports up to 19kN whereas the box lintel supports up to 47kN. What's typically spec'd on a 1.5 brick thick wall? Are Catnic just being over cautious, or is their valid reason to go for such a stronger lintel? Standard 9" clay brick wall.

I can't imagine that to be true. Trickle vents are generally a flimsy piece of plastic I wouldn't have thought they provide a suitable airtight seal.

Our house is like a blood sieve at the moment. Whilst the stat doesn't seem to drop that quickly, it feels noticeably cooler when it's windy. I hope this is rectified once we install wall insulation, which in-turn should make it air tighter too.

Extremely selfish, but good news for me. We plan to kick off our renovation in anger next year.

I have a pet hate of rods, especially cheap ones from Toolstation etc. A section got detached 5m down our drains and we had to get someone in to jet them back out again. So Jet every time for me, unless you have a decent set of rods.

Unfortunately that moisture still needs to go somewhere. I'd decouple the problems; heat loss - insulation humidity - ventilation

£10k for stone window heads. £1.2k for pre-cast ones. 10x more expensive

I'm looking to board out our loft, joists are approx 150mm deep at 400 centres. There's a couple of king post trusses up there so not much of a clear run. Right now there's around 200mm of rock wool insulation, but I plan to have 300mm blown cellulose installed next year. This means anything I do needs to be at least 150mm above the current joists. I've seen systems like LoftZone and LoftLegs which look useful, but quite expensive for the size of our loft, (approx 11m x 7m - but I'd likely leave a 1m perimeter to allow for ventilation - probably in-line with a couple of chimney stacks come through the roof void) I looked at using something twist strap or strong ties, but 1) getting 150mm battens up there would be a PITA and 2) be expensive. Twist straps and timber legs looks to be approx. half the price of any bought-in "solution." Are there any other, cheaper, alternatives?

In order to apply a blanket dT across all radiators, doesn't it assume that each radiator is perfectly sized for the room it's fitted in? Similar to UFH pipe spacing etc. Otherwise won't you risk having a dT 4 or 7, depending on the flow temp, but that not resulting in a comfortable room temp?

If you fancy a couple of hour jaunt, Mike Wye stocks it. https://www.mikewye.co.uk/product/geotextile-membrane/ I used this stuff when laying a Limecrete floor.

I don't think there is a one size fits all answer to that question. There are so many variables; is your house pointed using lime? Has it been rendered? If so, with what? Are the ground levels suitably low? Are your drains and gutters functioning correctly? There are so many sources of damp that need to be controlled before it becomes a problem internally. IMO, and I'm only a novice DIYer, moisture only gets "trapped" if it there's an excess of it (i.e. raised ground levels, broken drains/gutters) and/or it can't escape from either side (i.e. the external face is pointed and/or rendered using cement.

That could work. We're not putting in the 2x new showers until the extension is up, but we are fitting IWI to the existing rooms prior to that so I could fit the ducting in the floor void just leaving an up-stand to join beneath where that stud wall will eventually be fitted.