Roger440

Thanks. That makes sense. So, as i suspected there still needs to be a mechanical fan somewhere. Interesting though. Until i see where i get to with air tightness, cant really make any decisions.

Thanks. All the blurb i can fins suggests there needs to be a fan somewhere, you a PIV for them to work. But it seems they are a mystery product, theres just no info beyond the basic website description. Im attracted to the concept as, essentially theres nothing to go wrong, and doesnt use any power. Which seems to good to be true. And we all know what normally means!

Just be aware post october 23, much has been tightened up in BCO land. They do now bear at least a small amount of responsibility for what they sign off, where, previously, they didnt. You may find they now want "evidence" from a qualified professional to support your assertions, even though your proposals are pretty conventional. That means paying for reports, such as WUFI, for example. But they might not. No way of knowing until they are involved. I know what id do, but thats very different to Redbeard. Clearly he has encounterd sensible BCO's to date. Do let us know how you get on though. Ill be doing similar in another year or so.

Where are the battery costs in your numbers?

Its far from clear how these work. Google not much help either. What causes the air to move when they are open, as it says you need 20ps air pressure difference?

Starting from a position of no heating yes. Doesnt add up if you have a nearly new gas system already. Obviously if you go DIY as you have done, then that skews the figures, but for most, who are just paying, (probably grossly inflated prices) its makes no economic sense. Just wait for the boiler to die, then do it. Im in the same position, albeit with oil. And i would DIY it. But it still makes no economic sense. I have some re-cofiguring of the heating to do, so i will provision for an ASHP. But i wont be fitting one until i have to or the economics swing in its favour.

Thats interesting. I need to buy more for my workshop. The previous part i did in 100mm (seconds) with 100 x 50 battens. Was going to do 50 +50 this time to reduce the bridging effect of the battens. Though the saving on timber by using 50x50 studs might offset the PIR increase? Plus of course depends what seconds and Co have available at the time.

Ed on another tangent. So, Rachel says they are getting rid of the ECO4 scheme to reduce bills, and Ed says he is going to load gas with extra cost and increase them. Left hand and right hand and all that. Not that it stacks up anyway, as 13bn, is less than £500 per household. Thats not going to buy you much, and certainly not at grossly inflated grant harvesting prices. Maybe it just for labour party members or some other select group?

As others have said, you have not indicated your motivations. So rather a difficult question to answer. As you ask, id just leave it until it breaks. Put the money you would have spent to good use elsewhere.

Where is this cheap PIR you speak of?

Ive found this very difficult to use on the thicker boards. PIR at least. Works great at 50mm. Useless at 100mm. Better off with a cheap normal saw.

It is the lack of clarity, and ultimately, the judgement of the BCO, that i would not involve then unless its unavoidable. If BCO doesnt agree, tough on you. There is no "appeal" process even if they are wrong. On some of the old house groups, theres been a couple of people running into quite some difficulty with BCO's that seem to be unwilling to relax standards based on it being an older building etc etc. Which the clause that Redbeard highlights specifically allows for. But if the BCO says no, then its no. To the point that one person couldnt insulate his roof to current standard, the BCO just said replace the entire roof structure so you can. All while roof is stripped. Sadly, as the old school BCO's retire and the new breed of box tickers comes in, i cant see it getting any better. OP, hope yours goes smoothly.

Doesnt building control use 15 years as its guide as to insisting on stuff, at least in a retrofit situation?

Now thats a bit of a minefield if ever there was one...............

Or you could not bother and just crack on and fit the insulation. How will anyone ever know? As always, aside from cost, what will the BCO add to this simple excercise? Bear in mind, they may not agree with your proposal and you may need to do more/something different to comply. Once they know work is happening, they know. You cannot have them "unknow".