G and J

So if the proscribed procedure is followed then I can’t finalise the design of the heating system including ASHP size until my build is proven airtight (or otherwise). Crumbs. I had assumed my airtight test would be done after screeding.

Now I understand. I stupidly assumed you meant per year.

It’s very close to reality on our house and our summer house. That’s good to hear and I have assumed it was bang on, hence using it so much and relying on the output. So for our house, which is “not anywhere near” passive house insulation levels, Jeremy’s spreadsheet shows our heat loss at less than a third of @ChrisInKent’s. Methinks if Jeremy’s spreadsheet is as good as I think then the 7kW is rather suspect. So Chris, why not give Jeremy’s spreadsheet a go?

Perhaps they use a sun lamp at night to generate more. 😉

If I had to remove a vertical metal pipe safely (from my own land, naturally!) leaving it safe but with the minimum work I’d probably cut it off PDQ with a battery angle grinder, a bit proud of the ground, thence cutting four vertical cuts, thence two more horizontal cuts at ground level to leave two opposing bits sticking up that I’d then quickly hammer over. Might work best if the bits left standing for hammering were each a bit less than a quarter the circumference. A quick ‘polish’ with a grind wheel on said grinder would help make it safer. Maybe have an older, hi vis clad, overweight chap with a clipboard standing by to prove that it’s official. Oh and close the nearby road for 3 days, that really will make it look official. 😉

I’m thinking that either your numbers are wrong or mine are. Using Jeremy’s spreadsheet our not anywhere near PH 150m2 design looks to need just over 2kW to maintain 20C when it’s -3.5C outside. I am assuming 87% MVHR efficiency and 0.5AC/h. The air tightness and form factor (2.75) are the only PH ready things in the place really. I get the idea that an oversized heat pump lasts longer and is quieter but that’s still quite a difference.

I suspect it might prove easy to make a purely financial case for a battery system, but I’m with @JamesPa re the non existence of an environmental case. And I’m the absence of such a case I’m tempted to conclude that as it uses resources then such is likely to be environmentally negative. I might want one for battery backup (lights, internet, MVHR, freezer, etc) but that’ll be managed in a different way to a save money battery. So I’ll therefore accept that my battery system will be an indulgence. Not my only one either.

So the fish tank has electric eels and stingrays huh?

For home use battery weight isn’t an issue, so it sounds like I don’t need to worry about the using up of rare commodities. But how about the carbon footprint of the battery with associated bits? I appreciate by using the tariffs they can save money but will that reduce emissions?

I need a focal point in a relaxing room that isn’t a tv. We go to great lengths to hide our AV as it’s rude and ugly to my eyes (and that’s my job so I won’t live with competition on that one). I’ve been in way too many living rooms with no fire and a huge TV glaring down at me to accept such. And I think somewhere deep down in my DNA is the feeling that fire means safety and survival, so one can relax fir a bit as the dinosaurs won’t get me while the fires on. I did say it was irrational. We've looked hard at various electric faux fires and they are coming on, but they’re a way off yet.

So is it a good thing to evaluate battery purchase purely on financial payback? I have a nagging feeling that if we looked real hard at it all we might discover that the total number of tons of carbon who’s release into the atmosphere I’m responsible for between now and my demise will increase if I add a battery in. It might be that the world would be better served for those precious metals used in ‘my’ battery to be deployed in more electric vehicles. I’m going to cost building in the option of adding a battery in future by hubbing wiring to the key bits into my attached garage. If it’s not too much we’ll do it and thus maybe add a battery for power cut backup, rather than to save bills. When/if it’s proven that the new ecobatts (made from recycled pasta) actually reduce emissions overall including the battery production then it’ll be game on. But not until.

It won’t burn for a full evening Iceverge lol We are planning a pointless heavy metal contraption in our snug area. I will admit it’s more me that wants it than J. For many years we’ve had a fire each cold night so it’s kinda built into my psyche - having three wood burners and a couple of chainsaws does that to a man. But we are making so many über sensible decisions and being all grown up about the rest of the build that I’m ok with this irrational aberration. When we light it it will cause the ASHP to use less leccy (somehow!) and I’ve a cunning plan involving a spirit burner for when it’s not cold enough. And @MikeSharp01, I just knew there would be unexpected downsides to passive houses!

Agree with both of these!

Definitely the way to go....in a very small way we did something similar. We bought a very tired bungalow, which was a probate sale. Our plan to demolish and build a house on footprint with similarities to house next door. We shared design ideas with the immediate neighbours before planning, and then just before planning went in we did a letter drop to the road "we are......we're planning to.....doing it to become our home.....appreciate will cause you disruption.......contact no.s" etc The reaction was mixed, inc. no reaction from some and did generate some subjective objections, but also was a great way to get to know the new neighbours, had coffee with a number, on chatting terms with more way before actually starting (we still haven't demolished) so was definitely a positive. The other thing we learnt is that the "quiet ones" are sometimes the most vociferous in their WRITTEN objections and whilst welcoming feedback its' best not to position your plans in terms of it all being open to change (you will have some basics that are red lines for you and you won't necessarily be able to please everyone......at one point each if our neighbours were pushing for the ASHP to be on the other boundary!) Finally don't take it personally, whatever the reaction now, when the dust settles people will respect you for having done it. Hope it goes well

Not sure but I think that means it’s circa £16/m2 (exc.) at 140mm which is the same as I found nyrock frame slab for, and that has no installation costs (as a little old and round bald guy will be running round fitting the nyrock for free!). I'm guessing the shredded stuff would be good for deeper frames but looks like the bats will work well for me. Next question though is what do I use for the 50mm inboard of the frame. I’m assuming rolls would be better to reduce gaps. Is there a clear market leader?

Materials. The insulation and VCL and maybe the inner layer of OSB we will be doing. Understood - but we are prepared to invest the time (2 retired types here) so that does change things, but it is a point well made. We built in '91 in 5 months when we were both working full time and still found the time to do stuff ourselves (some including labouring, electrics, plumbing, roofing, painting) and whilst we don't want to take forever we aren't going to push it through as quickly this time as we are older and we don't have to. (We had two mortgages going at once back then - v stressful!).

On the face of it it looks like the same lambda but only 75% of the price. - So, thank you.

Will investigate. Ta.

Is there an easy rule of thumb for the cost per area/volume of this and will I need more than the VCL to contain it while it sets, as if it needs another layer of OSB inboard then it will hurt.

If I have a wall build up with Frametherm that hits u=0.18, changing to a mineral wool which has a lambda of 0.035 changes that into a wall u=0.19! Ouch. I think that's another 15mm of mineral wool to compensate. But I do like to save cash so will look into it.

OK, that's good to know, thank you.

So to be clear @sgt_woulds, what heating should I build into my new house when I install it next year? We have close neighbours either side, gas is already at the bungalow we are demolishing, and low running costs is an important factor or us.

In the beginning there was plan A; and plan A was marmite because plan A used PIR and thus got us a decent average wall u-value (circa 0.15W/km2) for a thin-ish wall and at a sensible cost and lo, we thought it was good - but there are those who though of PIR was the anticrust. And behold, the heathen (G&J in this case) listened and paid homage to the almighty (Jeremy) spreadsheet and asked it for guidance. At which point we realised that given how airtight we were going to be and the insulation levels in floor and attics the precise wall insulation level didn't really make that much difference, within reason. So, that means we could contemplate relaxing to a wall u value of circa 0.18. Which means we can contemplate mineral wool instead of PIR. (Plan A is: 120mm foil backed PIR in frame 25mm PIR layer VCL 20mm service void OSB, then finally plasterboard and skim.) Off to Ubakus we went to play with 140 Frametherm32 in the timber frame plus..... what exactly? We could do as plan A but with a thicker PIR layer inboard of the frame. But how about we put yet more mineral wool inboard? Something like: 140 Frametherm32 in frame VCL (is this condensation I see before me?) 50mm battens with 50mm mineral wall between, then OSB, Plasterboard and skim. Is this a good plan? Will we get a wet VCL? Will the service void be OK filled with wool? Is it better to do the 50mm battens horizontally to reduce bridging? Is there a better alternative to mineral wool for the inboard layer? (I probably should apologise for coming back to the forum for yet more help with our wall build ups, but in reality it is the cumulative affect of BH groans at my planning to use PIR that has driven this, so in a way, it's BH's own bloody fault lol) Responses and thoughts gratefully received.....

Oh dear. So after a few months my new neighbours won’t like my noise one bit - once they’ve got to know me.

Ah then that’s the answer. My ASHP is going half way down the garden. My man cave is at the bottom of the garden, and will have a nice big sound bar connected to my smart tv. So I solve the ASHP noise issue by getting to enjoy some serious beats to exercise too. Brilliant. 😉