I like a lot of mass, more comfortable, smaller temperature swings, can absorb more solar heat. Stays cool during heatwaves

Need to fully wrap with an insulation barrier, don’t let heat out through the top of the walls or gables, mitigate downward heat loss. Move windows out into the insulation layer

Posted By: djhor just wait a while!

yes - can be a year, or even two heating seasons, to reach new equilibrium.

Posted By: lineweightThe scenario where it might not work so well is if it's a building that will only see occasional use, because each time you arrive it will take a while and quite a bit of energy to warm it up.

Indeed, I'd been assuming that the project was sensible - a residential project with continuous occupation. If not, then all bets are off!

Posted By: JulioSorry if this has been covered already, but had a look through and couldn't find anything.

I am looking at a project for a potential EWI job. The walls are 600mm wide, stone. I was wondering what effect the insulation would have on such massive walls, presumably over time the walls would heat up and maintain a steady (nearish 20^c temperature). Or would the huge amount mass of the wall negate the effectiveness of the insulation in some way? My concern is that the walls have so much mass that it would require quite alot of heat to just warm them up and keep them to near temperature.

Any thoughts appreciated.

Thanks

What was said above about occasional use +1
We have a holiday let with stone walls and stopped doing weekends after September because we would have to start heating on Wednesday to get it just acceptable by Friday evening.

I have another stone house (50cm stone / rubble walls) that I put on 100mm EWI. The difference was well worth the effort. The comfort level went up, the heating cost went down and black mould was banished from the not often used rooms.

Posted By: WillInAberdeenand the unresolved problem with the cold bridges where we cannot join the proposed EWI to the floor or loft insulation

I have no solution to this and just live with it with no apparent problems i.e. no mould at the edges.

Posted By: WillInAberdeenthe blockers are the current disproportionate building costs

The escalating cost of energy might alter this balance - if the wages don't race ahead of energy costs. I have done DIY for the insulation slabs and got a professional to do the rendering. This cut the labour cost by 1/3

At the present high energy prices and high building material prices, the simple financial payback on my potential EWI retrofit is ~20-30years. However, I don't have enough capital to hand (£30k+), so I would have to borrow it and pay interest, in which case it would never payback financially.

Over those 20+ years, the energy prices might come down (renewables) or go up (conflicts), I've given up making predictions since this year! If I was a gambling man, I could stake up my £30k as a bet that energy prices will go up, but I can't afford to make that bet!

I suspect it wouldn't payback in embodied carbon terms fast enough, before electric heating in Scotland becomes low-carbon, but who knows.

That's not to say I'm against wall insulation, I IWI'd our last house and am IWIing odd bits of this place DIY for extra comfort. Just that I have more pressing uses for the cash elsewhere! Heatpump and EV first.

It's like new windows, worth doing properly if the old ones are worn out, but probably not highest priority if the old ones are ok. We'll wait and see if EWI prices come back down.

We made some long-payback investments in our last house expecting it to be our 'forever home', but life changed, we had to move, and we lost that money. Being a bit more cautious this time!


On the cold bridges at the foundations, gables and eves: the default psi values in SAP10 are equivalent to adding an extra 0.1-0.2 on to the U value of our EWI, compared to using the same insulation thickness as IWI joined onto the loft and floor insulation. They do recommend using site-specific psi values, our walls and chimneys are quite thick, so the 'gap' in the insulation envelope would be quite wide. So not disastrous, but also not great if spending that much.money on low-U insulation.

The embodied lifecycle carbon of building an extra wind turbine is widely quoted as ~15g/kWhe (vs typical grid intensity 180 now and 400 a few years ago).

So low-carbon not zero-carbon, but so much closer to zero that previous assumptions require re-examination.

The carbon released in the manufacturing of 200mm of polystyrene, and some cement render, used to be negligible compared to the grid intensities of not very long ago, but not any more.

Unfortunately, grid intensity is complicated. Different people have widely different axes to grind - eg the Scottish government claim that Scotland already produces enough low-carbon electricity to cover all Scottish consumption, such that electricity in Scotland is already low-carbon. The UK National Grid and the CCC think that point would be around 2030, seems more reasonable. Once that point is reached, carbon invested in energy-saving cannot pay back anymore, so the EWI would have to payback its embodied carbon within a very few years.

An added complication is that the heat pump will produce 3 or 4 kWht of heat for each kWhe, so the effective carbon of the heat that might be saved by the EWI, is correspondingly less. But the heat pump itself embodies carbon.

And indeed, the logical endpoint is that the lowest carbon emissions will come from living in a tent, with a huge electric heater, which will take some thinking about.

So,

Posted By: WillInAberdeenwho knows

Posted By: WillInAberdeenthe lowest carbon emissions will come from living in a tent, with a huge electric heater

Bludyell, now you put it like that. I'll prob be dead, before out of a job.

Posted By: djha finite quantity of energy/power

Not really - or not within extremely capacious reason. Incident solar is orders of magnitude greater than our most extravagant usage, and there's nuclear (which I oppose totally, until it produces no life-on-earth endangering waste).

So far, raw heat dumped into the biosphere (as distinct from GHG effects) by entropy-squandering present energy-use has not of itself contributed significantly to Earth's temperature-equilibrium with outer space, but it might become so. Or wind and tide harvesting, increasing surface friction between solid Earth and its atmosphere, might slow Earth's rotation.

Aiui, carbon emissions are causing heating of the atmosphere thus threatening the survival of many species including us. Whereas running out of power is rather inconvenient.

So carbon reduction is very much the gold standard, as far as I'm concerned! Including embodied carbon. Not claiming that I always meet the gold standard of course, but good to know how to measure it.

In due course (2040?) we will probably be able to manufacture polystyrene and render without emitting any carbon, at which point we can all move out of the tents and start EWI-ing again. (Or some other materials).

I agree with Tom that we haven't scratched the surface of renewables yet - floating offshore/oceanic wind is going to be a(nother) game changer. But a renewably-powered tent-heater causes (exactly) no more raw-heat-dumping than if the same sunshine had fallen onto Earth and squandered all its negative entropy on impact.

Radical population reduction is baked-in now, no generation since the Boomers have reproduced themselves at the replacement rate. Humankind is going to get older, and then fewer, this century. After that,

who knows?

Jeff, I hope that's what happens, but it's rather a gamble so Im not counting on it .. !

Talk about EWI again now? Sorry Julio..

Thanks for all the comments and debate, the building is in need of alot of work and retrofitting anyhow, so whilst doing that it makes sense to try and improve the thermal efficiency as much as possible.
Good to hear that the mass will warm up in the end, even if it is a bit alarming to hear that it might take 2 years with current energy prices! Also the thickness that the wall is going to end up is going to be a bit ridiculous!

Yes the junction as floor and eaves is tricky in retrofit, also there may be at least 1 wall IWI'd, so the external facade can be retained... So trying to think about the junction between EWI and IWI. Anyone got any smart ideas/ details of how to make these junctions as cold bridge free as possible.
Retrofitting in a course of foam glass blocks at the floor slab to wall (with EWI) junction is too much to think about, but would a layer of IWI's insulation up to a height of say 1100mm, help stop the cold bridge on this junction? Just an idea...

Posted By: Peter_in_HungaryI have found that tenants usually don't care about running costs

Hmm, but what does that mean? In this country, tenants are so relieved at having secured a place to live that they don't think about running costs, they'll deal with that tomorrow. OTOH, [mostly social] tenants that are fortunate enough to be moved into a PH-certified development are so pleased to be blessed by a pleasing environment and low running costs that they don't ever want to move anywhere else. So methinks it's a case of lack of education (or lack of educational opportunities).

Posted By: fostertomThe inevitability of accelerating incidence of exotic diseases, given human interference with ecosystem stabilities and forced proximity with (e.g. eating) wild animals will, like Covid (and flu before it) disproportionately lay un-naturally longevid older generations gently to rest - so tho pop is set to shrink, it won't necessarily carry on the present trend of getting older (as in, a burden on shrinking workforce).

A remarkably blinkered and shortsighted view, Tom, IMHO, I'm afraid.

Posted By: JulioGood to hear that the mass will warm up in the end, even if it is a bit alarming to hear that it might take 2 years with current energy prices! Also the thickness that the wall is going to end up is going to be a bit ridiculous!

I can't see the walls taking much time to reach temperature equilibrium inside after EWI. In my experience you won't notice the warm up once the heating season starts as the heating will be gradual as the temp outside slowly drops. The building will be wonderfully stable in temp. cool in summer and warm in winter. Run the heating continuously on low rather than big set-backs and then blasting with heat.

Ridiculously thick walls are nice. You get a wonderfully wide window sill that makes a attractive feature (IMO) and kids love sitting in it to look out.

Posted By: JulioSo trying to think about the junction between EWI and IWI. Anyone got any smart ideas/ details of how to make these junctions as cold bridge free as possible.

Usually solved by having a return of the IWI onto the EWI wall

Posted By: JulioRetrofitting in a course of foam glass blocks at the floor slab to wall (with EWI) junction is too much to think about, but would a layer of IWI's insulation up to a height of say 1100mm, help stop the cold bridge on this junction? Just an idea...

If you have any foundations (or the wall goes down any depth in to the ground) then carrying down the EWI into the ground will help mitigate the floor to wall cold bridge. Otherwise as I said above I put up with it and haven't had any problems.

Posted By: Julio
Retrofitting in a course of foam glass blocks at the floor slab to wall (with EWI) junction is too much to think about, but would a layer of IWI's insulation up to a height of say 1100mm, help stop the cold bridge on this junction? Just an idea...

I'm not quite clear what you are trying to insulate from what here.

Or are you intending to insulate the floor slab, on top of it? In that case, effectively you are suggesting turning that insulation layer upwards at the edges, so it overlaps with the EWI, in a similar way as has been suggested for the corners of the buildings where there's a transition from EWI to IWI. That makes sense to me. I think you should consider extending the EWI downwards us much as possible (potentially underground) in addition - as already suggested above.